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Home My WebLink AboutEAST SIDE GREEN RIVER WATERSHED PROJECT 1 1 ' t Y. �- AW .� ,may �/� -�a �}^ -," J � �.�+6►'r :'F .,•�� -tip � �4�1.- . _ A, -- s � � j CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT PLAN AND ENVIRONMENTAL IMPACT STATEMENT 1997 CITY COUNCIL Daniel F. Clawson Randy Corman Bob Edwards Kathy Keolker-Wheeler Toni Nelson King Parker Timothy J. Schlitzer MAYOR Jesse Tanner PLANNING/BUILDING/PUBLIC WORKS ADMINISTRATOR Gregg Zimmerman PLANNING/BUILDING/PUBLIC WORKS AND COMMUNITY SERVICES STAFF Ron Olson Leslie Betlach (Community Services) Jack Crumley Lenora Blauman Ron Straka Glen Kost (Community Services) John Thompson Bob Mahn Scott Woodbury Mark Pywell Technical and Funding Assistance Provided by U. S. D. A. Natural Resources Conservation Service Rod Den Herder Larry Johnson Gary Conaway Larry Cooke Prepared by R. W. BECK, INC. in association with Jones & Stokes Associates, Incorporated Northwest Hydraulic Consultants Herrera Environmental Consultants City of Renton East Side Green River Watershed Project Final Plan and Environmental Impact Statement Page 2 REVIEW PROCESS: Concurrent with publication of the FEIS, the City is also issuing a separately bound Mitigation Document, which addresses impacts anticipated from the preferred project action. Following issuance of the Mitigation Document, there will be a thirty (30) day appeal period during which the adequacy of the FEIS and the Mitigation Document may be appealed, pursuant to SEPA Rules (WAC 197-11) and the City of Renton's Environmental Review Ordinance (4-6). QUESTIONS OR ADDITIONAL INFORMATION: If you have any questions, or would like additional information, please contact Mark Pywell, City of Renton Development Services Division, at (425) 277-5586 or Scott Woodbury, City of Renton Surface Water Utility, at (425) 277-5547. Sincerely, Gregg A. Z4e66-a--n, Administrator Planning/Building/Public Works Department P L A N CERTIFICATE OF ENGINEER EAST SIDE GREEN RIVER WATERSHED PROJECT PLAN The technical material and data contained in this report were prepared under the supervision and direction of the undersigned, whose seal as a registered professional engineer licensed to practice as such in the State of Washington is affixed below. Michael S. Gi urt r ss�on� �:�` Project Manager EXPIRES: 1 Z- y -`18 CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT PLAN TABLE OF CONTENTS VOLUME 1 AGENCY LETTER CERTIFICATE OF ENGINEER TABLE OF CONTENTS LIST OF ACRONYMS SECTION 1 EXECUTIVE SUMMARY................................................................. 1-1 1.1 INTRODUCTION AND PROJECT NEED................................................. 1-1 1 .2 PLAN ELEMENTS .................................................................................... 1-2 1 .3 PROJECT GOALS.................................................................................... 1-3 1 .4 STUDY FINDINGS .................................................................................. 1-4 1 .5 ALTERNATIVE FLOOD CONTROL MEASURES....................................... 1-6 1 .6 SELECTION OF PREFERRED ALTERNATIVES .......................................... 1-7 SECTION 2 INTRODUCTION ......................................................................... 2-1 2.1 PROJECT NEED ...................................................................................... 2-1 2.2 PURPOSE AND AUTHORIZATION ........................................................ 2-2 2.3 PROJECT GOALS.................................................................................... 2-3 SECTION 3 BACKGROUND AND PLANNING HISTORY................................ 3-1 3.1 BACKGROUND..................................................................................... 3-1 3.2 PLANNING HISTORY ............................................................................. 3-1 3.2.1 1950s ............................................................................................... 3-2 3.2.2 1960s ............................................................................................... 3-2 3.2.3 1970s ............................................................................................... 3-3 3.2.4 1980s ............................................................................................... 3-3 3.2.5 1990s ............................................................................................... 3-4 SECTION 4 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS ................................................................... 4-1 4.1 RELEVANT CITY OF RENTON REGULATIONS, POLICIES, ANDPLANS............................................................................................ 4-1 4.1 .1 City of Renton Drainage Standards................................................... 4-1 4.1 .2 Wetlands Management Ordinance (WMO) ...................................... 4-1 4.1 .3 Shoreline Master Program (SMP) ...................................................... 4-1 X0011592.112 TABLE OF CONTENTS 4.1 .4 Mosquito Abatement Program ..........................................................4-2 4.1 .5 Master Trails Program ........................................................................4-3 4.1 .6 Transportation Improvement Program and Oakesdale Avenue Extension Project...............................................................................4-3 4.1 .7 Surface Water Utility Comprehensive Plan, Draft (HDR Engineering, 1995) ..................................................................4-4 4.1 .8 Comprehensive Land Use Plan (Renton, 1995).................................4-5 4.1 .9 Flood Insurance Study.......................................................................4-5 4.1 .10 Critical Areas Inventory, 1991, and Inventory Updates, 1992 and 1996 ...............................................................................4-6 4.1 .11 Black River Water Quality Management Plan ..................................4-7 4.2 OTHER RELEVANT REGULATIONS, POLICIES, AND PLANS...................4-7 4.2.1 Growth Management Act..................................................................4-7 4.2.2 Washington State Department of Ecology (DOE) Water Quality Standards for Surface Waters.............................................................4-9 4.2.3 State Environmental Policy Act (SEPA)/National Environmental Policy Act (NEPA)...............................................................................4-9 4.2.4 Washington State Department of Fish and Wildlife/Hydraulic ProjectApproval..............................................................................4-10 4.2.5 Federal Clean Water Act..................................................................4-10 4.2.6 East Side Green River Watershed Project Environmental Mitigation Agreement and Program.................................................4-11 4.2.7 Plans Directly Governing Operation of the Black River Pump Station (BRPS) .................................................................................4-13 4.2.8 Renton/Tukwila Interlocal Agreement..............................................4-13 4.2.9 East Side Green River Watershed Plan.............................................4-14 4.2.10 East Side Green River Watershed Project Final EIS and Amplification of Final EIS...............................................................4-14 4.2.11 Green-Duwamish Nonpoint Action Plan (GDWNAP)....................4-14 4.2.12 King County Flood Hazard Reduction Plan ...................................4-15 4.2.13 Comprehensive Fisheries Assessment of the Mill Creek, Garrison Creek, and Springbrook System ......................................4-15 4.2.14 City of Kent Drainage Plans...........................................................4-16 4.2.15 Puget Sound Water Quality Management Plan..............................4-16 4.2.16 City of Tukwila Drainage Plans ......................................................4-17 4.2.17 Operation and Maintenance Programs and Obligations................4-17 4.2.18 King County Drainage District No. 1 Comprehensive Plan............4-18 SECTION 5 PROJECT COORDINATION..........................................................5-1 5.1 CITY PROJECT DESIGN TEAM.................................................................5-1 5.2 PUBLIC PARTICIPATION/WORKSHOPS..................................................5-1 5.3 AGENCY COORDINATION.....................................................................5-2 ii R. W. Beck X0011592.112 CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT PLAN SECTION 6 CURRENT CONDITIONS............................................................. 6-1 6.1 GENERAL................................................................................................ 6-1 6.2 PROJECT AREA....................................................................................... 6-1 6.3 EXISTING LAND USE.............................................................................. 6-2 6.4 EXISTING VALLEY AREA DRAINAGE SYSTEM......................................... 6-3 6.4.1 Springbrook Creek............................................................................ 6-3 6.4.2 Panther Creek................................................................................... 6-3 6.4.3 Rolling Hills Creek............................................................................ 6-4 6.4.4 Black River Pump Station.................................................................. 6-5 6.4.5 Valley Wetlands ................................................................................ 6-6 6.4.6 SW 23rd Street Drainage Channel.................................................... 6-6 6.4.7 Other Drainage Systems................................................................... 6-6 6.5 FLOODING............................................................................................. 6-7 6.5.1 Hydrologic/Hydraulic Modeling Approach ....................................... 6-7 6.5.2 Hydrologic/Hydraulic Analysis Results ............................................ 6-12 6.5.2.1 SPRINGBROOK CREEK WATER SURFACE ELEVATIONS AND STREAM CHANNEL VELOCITIES............................................. 6-13 6.5.2.2 SIMULATED FLOODING PROBLEMS OF DRAINAGE SYSTEMS TRIBUTARY TO SPRINGBROOK CREEK.................................. 6-13 6.5.2.3 VALLEY AREA WETLANDS ...................................................... 6-14 6.5.2.4 BLACK RIVER PUMP STATION................................................ 6-14 6.5.3 Flooding Problems.......................................................................... 6-15 6.6 WATER QUALITY.................................................................................. 6-16 6.6.1 Water Quality Investigations........................................................... 6-16 6.6.2 Water Quality Problems ................................................................. 6-16 6.6.2.1 LAND USE AND POPULATION DENSITY............................... 6-17 6.6.2.2 WATER AND SEDIMENT QUALITY......................................... 6-17 6.6.2.3 SEDIMENTATION AND EROSION .......................................... 6-20 6.6.2.4 FLOOD-RELATED WATER QUALITY PROBLEMS.................... 6-20 6.7 WETLANDS .......................................................................................... 6-21 6.7.1 City-Coordinated Wetland Investigations........................................ 6-21 6.7.2 Wetland Functional Values.............................................................. 6-21 6.7.2.1 GROUNDWATER DISCHARGE AND RECHARGE................... 6-22 6.7.2.2 FLOOD STORAGE................................................................... 6-22 6.7.2.3 SHORELINE ANCHORING...................................................... 6-22 6.7.2.4 WATER PURIFICATION........................................................... 6-22 6.7.2.5 FOOD CHAIN SUPPORT........................................................ 6-23 6.7.2.6 WILDLIFE HABITAT................................................................. 6-23 6.7.2.7 FISH HABITAT......................................................................... 6-23 6.7.2.8 ACTIVE AND PASSIVE RECREATION, HERITAGE, AND EDUCATION ........................................................................... 6-23 6.7.3 Wetland Management Ordinance Categories................................. 6-23 6.7.3.1 CATEGORY 1 WETLANDS....................................................... 6-24 X0011592.112 R. W. Beck iii TABLE OF CONTENTS 6.7.3.2 CATEGORY 2 WETLANDS .......................................................6-24 6.7.3.3 CATEGORY 3 WETLANDS .......................................................6-24 6.7.4 City Wetland Ownership.................................................................6-25 6.8 FISH AND WILDLIFE.............................................................................6-25 6.8.1 Fish and Wildlife Investigations........................................................6-25 6.8.2 Fish .................................................................................................6-25 6.8.2.1 SPRINGBROOK CREEK............................................................6-25 6.8.2.2 PANTHER CREEK.....................................................................6-28 6.8.2.3 ROLLING HILLS CREEK ...........................................................6-29 6.8.3 Wildlife ...........................................................................................6-30 SECTION 7 FUTURE CONDITIONS.................................................................7-1 7.1 GENERAL ................................................................................................7-1 7.2 FUTURE LAND USE ................................................................................7-1 7.3 FLOODING .............................................................................................7-2 7.3.1 Analysis.............................................................................................7-2 7.3.2 Hydrologic/Hydraulic Analysis Results...............................................7-3 7.3.2.1 SPRINGBROOK CREEK WATER SURFACE ELEVATIONS AND STREAM CHANNEL VELOCITIES................................................7-3 7.3.2.2 SIMULATED FLOODING PROBLEMS OF DRAINAGE SYSTEMS TRIBUTARY TO SPRINGBROOK CREEK.....................................7-5 7.3.2.3 VALLEY AREA WETLANDS.........................................................7-6 7.3.2.4 BLACK RIVER PUMP STATION .................................................7-6 7.3.3 Flooding Problems ............................................................................7-6 7.4 ENVIRONMENTAL RESOURCES.............................................................7-7 7.4.1 Water Quality....................................................................................7-7 7.4.2 Fish and Wildlife ...............................................................................7-8 7.4.3 Wetlands...........................................................................................7-9 SECTION 8 ALTERNATIVE SOLUTIONS AND EVALUATION ...........................8-1 8.1 GENERAL ................................................................................................8-1 8.2 ALTERNATIVES DEFINITION PROCESS...................................................8-1 8.3 DESCRIPTION OF FLOOD CONTROL SOLUTIONS...............................8-4 8.3.1 SPRINGB ROOK CREEK ALTERNATIVES............................................8-5 SPRINGBROOK CREEK ALTERNATIVE 1 (SC1) — NO ACTION.............8-5 Flooding Problems Along the Main Stem of Springbrook Creek..........8-6 SPRINGBROOK CREEK ALTERNATIVE 2 (SC2) — LOCALIZED IMPROVEMENTS TO SPRINGBROOK CREEK........................................8-6 SPRINGBROOK CREEK ALTERNATIVE 3 (SC3) — SPRINGBROOK CREEK GREENWAY IMPROVEMENTS .............................................................8-11 8.3.2 PANTHER CREEK ALTERNATIVES ..................................................8-13 PANTHER CREEK ALTERNATIVE 1 (PC1) — NO ACTION....................8-14 PANTHER CREEK ALTERNATIVE 2 (PC2) — HIGH FLOW BYPASS TO PANTHER CREEK WETLAND ...............................................................8-15 iv R. W. Beck X0011592.112 CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT PLAN PANTHER CREEK ALTERNATIVE 3 (PC3) — MAINTAIN EXISTING FLOW INTO SW 34TH STREET SYSTEM......................................................... 8-15 8.3.3 SW 23RD STREET DRAINAGE CHANNEL ALTERNATIVES............. 8-17 SW 23RD STREET ALTERNATIVE 1 (23ST1) — NO ACTION............... 8-17 SW 23RD STREET ALTERNATIVE 2 (23ST2) — MINOR CONVEYANCE IMPROVEMENTS................................................................................. 8-18 SW 23RD STREET ALTERNATIVE 3 (23ST3) — MAJOR CONVEYANCE IMPROVEMENTS................................................................................. 8-20 8.3.4 WETLAND MITIGATION BANK AND WETLAND HYDRAULIC MODIFICATIONS........................................................................... 8-21 WETLAND 12 — EXISTING CONDITIONS ......................................... 8-21 WETLAND 12 —ALTERNATIVE 1, NO ACTION................................. 8-22 WETLAND 12 —ALTERNATIVE 2, CULVERT REPLACEMENT............. 8-22 WETLAND 32 (WETLAND MITIGATION BANK SITE) - EXISTING CONDITIONS ..................................................................................... 8-23 WETLAND 32 —ALTERNATIVE 1, NO ACTION................................. 8-23 WETLAND 32 —ALTERNATIVE 2, MITIGATION BANK/EXCAVATE LARGE OFF-CHANNEL STORAGE................................................................... 8-23 WETLAND 7N — EXISTING CONDITIONS......................................... 8-24 WETLAND 7N —ALTERNATIVE 1, NO ACTION ................................ 8-24 WETLAND 7N —ALTERNATIVE 2, CULVERT REPLACEMENT............ 8-25 8.3.5 PIPE SYSTEM IMPROVEMENTS...................................................... 8-25 PIPE SYSTEM IMPROVEMENTS ALTERNATIVE 1 (PS1) — NO ACTION8-25 PIPE SYSTEM IMPROVEMENTS ALTERNATIVE 2 (PS2) — PIPE SYSTEM IMPROVEMENTS........................................................... 8-25 8.4 ALTERNATIVE EVALUATION................................................................. 8-26 8.4.1 Alternative Evaluation Process ........................................................ 8-26 8.4.2 Evaluation Factors........................................................................... 8-27 8.4.2.1 HYDRAULIC CONSIDERATIONS ............................................ 8-27 8.4.2.2 WETLANDS............................................................................. 8-27 8.4.2.3 WATER QUALITY/SEDIMENT QUALITY.................................. 8-28 8.4.2.4 FISH RESOURCES ................................................................... 8-28 8.4.2.5 WILDLIFE HABITAT/VEGETATION .......................................... 8-29 8.4.2.6 COST....................................................................................... 8-29 8.4.2.7 AESTHETICS............................................................................ 8-30 8.4.2.8 LAND USE............................................................................... 8-30 8.4.2.9 OPERATIONS AND MAINTENANCE....................................... 8-30 8.4.2.10 IMPLEMENTATION AND FINANCING.................................. 8-30 8.4.2.11 UTILITIES............................................................................... 8-30 8.4.2.12 TRANSPORTATION............................................................... 8-31 8.4.2.13 GROUNDWATER.................................................................. 8-31 8.4.2.14 RECREATION ........................................................................ 8-31 8.4.3 Summary Matrix Evaluation............................................................ 8-32 X0011592.112 R. W. Beck V TABLE OF CONTENTS SECTION 9 RECOMMENDED PLAN ................................................. .9-1 9.1 INTRODUCTION ....................................................................................9-1 9.2 PROJECT ELEMENT SUMMARY AND POTENTIAL CONTRIBUTORS .....9-1 9.3 PROJECT IMPLEMENTATION AND PHASING ........................................9-2 SECTION 10 REFERENCES..............................................................................10-1 LIST OF TABLES TABLE 1-1 SUMMARY OF ALTERNATIVES TABLE 1-2 SUMMARY OF PREFERRED ALTERNATIVES, COSTS AND POTENTIAL CONTRIBUTORS TABLE 6-1 BLACK RIVER PUMP STATION CAPACITIES TABLE 6-2 BLACK RIVER PUMP STATION — ALLOWABLE PUMPING RATES— PUMP OPERATIONS AND PROCEDURES PLAN TABLE 6-3 SUMMARY OF PEAK FLOWS AND WATER SURFACE ELEVATIONS — CURRENT LAND USE CONDITIONS — FEQ HYDRAULIC ANALYSIS TABLE 6-4 SUMMARY OF MAXIMUM ELEVATIONS AND DURATIONS VALLEY WETLANDS — 2-YEAR EVENT TABLE 6-5 SUMMARY OF WATER QUALITY PROBLEMS — SPRINGBROOK CREEK, PANTHER CREEK AND ROLLING HILLS CREEK TABLE 6-6 MAINSTREAM SPRINGBROOK CREEK — UPSTREAM/DOWNSTREAM WATER QUALITY TABLE 6-7 NUMBER OF SALMONIDS PASSING BLACK RIVER PUMPING STATION — 1983-1994 TABLE 6-8 PANTHER CREEK (WRIA 09-0006) ELECTROFISHING SUMMARY TABLE 7-1 APPROXIMATE CONTRIBUTING IMPERVIOUS AREA BY JURISDICTION — EAST SIDE GREEN RIVER WATERSHED TABLE 7-2 SUMMARY OF PEAK FLOWS AND WATER SURFACE ELEVATIONS — FUTURE LAND USE CONDITIONS — FEQ HYDRAULIC ANALYSIS TABLE 7-3 COMPARISON OF PEAK FLOWS AND WATER SURFACE ELEVATIONS — FEQ AND FEMA TABLE 7-4 SUMMARY OF MAXIMUM ELEVATIONS AND DURATIONS VALLEY WETLANDS —2 YEAR FLOOD TABLE 8-1 PRELIMINARY FLOOD CONTROL SOLUTIONS ELIMINATED FROM FURTHER CONSIDERATION TABLE 8-2 SUMMARY OF HYDRAULIC MODELING RESULTS - FLOOD CONTROL ALTERNATIVE TABLE 8-3 SUMMARY OF HYDRAULIC MODELING RESULTS TO VALLEY WETLANDS - FLOOD CONTROL ALTERNATIVES vi R. W.Beck x0011592.112 CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT PLAN TABLE 8-4 SUMMARY OF IMPACTS FOR HYDRAULICS BY ALTERNATIVE TABLE 8-5 SUMMARY OF IMPACTS FOR WETLANDS BY ALTERNATIVE TABLE 8-6 SUMMARY OF IMPACTS FOR SURFACE WATER AND SEDIMENT QUALITY BY ALTERNATIVE TABLE 8-7 SUMMARY OF IMPACT FOR FISHERIES BY ALTERNATIVE TABLE 8-8 SUMMARY OF IMPACTS FOR VEGETATION AND WILDLIFE BY ALTERNATIVE TABLE 8-9 SUMMARY OF COST ESTIMATES BY ALTERNATIVE TABLE 8-10 SUMMARY OF IMPACTS FOR AESTHETICS BY ALTERNATIVE TABLE 8-11 SUMMARY OF IMPACTS FOR LAND USE BY ALTERNATIVE TABLE 8-12 SUMMARY OF IMPACTS FOR OPERATION AND MAINTENANCE BY ALTERNATIVE TABLE 8-13 SUMMARY OF IMPACTS FOR IMPLEMENTATION AND FINANCING BY ALTERNATIVE TABLE 8-14 SUMMARY OF IMPACTS FOR UTILITIES BY ALTERNATIVE TABLE 8-15 SUMMARY OF IMPACTS FOR TRANSPORTATION BY ALTERNATIVE TABLE 8-16 SUMMARY OF IMPACTS FOR GROUNDWATER BY ALTERNATIVE TABLE 8-17 SUMMARY OF IMPACTS FOR RECREATION BY ALTERNATIVE TABLE 8-18 MATRIX EVALUATION SUMMARY TABLE 9-1 SUMMARY OF PROJECT ELEMENTS WITH POTENTIAL CONTRIBUTORS LIST OF FIGURES FIGURE 6-1 PROJECT AREA (ESGRW) FIGURE 6-2 RENTON VALLEY - EXISTING DRAINAGE SYSTEM FIGURE 6-3 EXISTING LAND USE - ESGRW FIGURE 6-4 MAJOR DRAINAGE SYSTEM MODELED BY FEQ FIGURE 6-5 FLOOD AREAS CURRENT CONDITIONS FIGURE 6-6A PHOTOGRAPHS OF SELECTED REACHES FIGURE 6-613 PHOTOGRAPHS OF PROBLEM AREAS FIGURE 6-7 WETLANDS FIGURE 7-1 FUTURE LAND USE - ESGWP FIGURE 7-2 SPRINGBROOK CREEK WATER SURFACE PROFILE FIGURE 8-1 COMBINED PROJECT ALTERNATIVES FIGURE 8-2 SPRINGBROOK CREEK ALTERNATIVES X0011592.112 R. W. Beck vii TABLE OF CONTENTS FIGURE 8-3 SPRINGBROOK CREEK ALTERNATIVE 2 TYPICAL CROSS SECTION FIGURE 8-4 SPRINGBROOK CREEK ALTERNATIVE 2 - ELEMENT 3/ ALTERNATIVE 3 - ELEMENT 3 FIGURE 8-5 SPRINGBROOK CREEK ALTERNATIVE 3 TYPICAL CROSS SECTIONS (TWO SECTIONS) FIGURE 8-6 PANTHER CREEK AND SW 23RD STREET DRAINAGE CHANNEL ALTERNATIVES FIGURE 8-7 SW 23 STREET ALTERNATIVE 2 SCHEMATIC PLAN AND PROFILE FIGURE 8-8 SW 23RD STREET ALTERNATIVE 3 SCHEMATIC PLAN AND PROFILE FIGURE 8-9 SW 23RD STREET ALTERNATIVE 3 TYPICAL CROSS SECTION FIGURE 8-10 WETLAND MITIGATION BANK AND WETLAND HYDRAULIC MODIFICATIONS FIGURE 8-11 PIPE SYSTEM IMPROVEMENTS VOLUME 2 - APPENDICES (BOUND SEPARATELY AND ISSUED WITH DRAFT PLAN AND EIS IN DECEMBER 1996) APPENDIX A ESGRWP ALTERNATIVE EVALUATION TECHNICAL MEMORANDA APPENDIX A-1 HYDRAULIC CONSIDERATIONS APPENDIX A-2 WETLANDS APPENDIX A-3 SURFACE WATER AND SEDIMENT QUALITY CONSIDERATIONS APPENDIX A-4 FISH RESOURCES APPENDIX A-5 VEGETATION/WILDLIFE HABITAT APPENDIX A-6 AESTHETICS APPENDIX A-7 LAND USE APPENDIX A-8 OPERATIONS AND MAINTENANCE APPENDIX A-9 IMPLEMENTATION AND FINANCING APPENDIX A-10 UTILITIES APPENDIX A-11 TRANSPORTATION APPENDIX A-12 GROUNDWATER APPENDIX A-13 RECREATION APPENDIX B PUBLIC/AGENCY COORDINATION APPENDIX C COST ESTIMATES APPENDIX D ESGRWP FEQ MODELING OF ALTERNATIVES, CLARIFICATION OF DESIGN CRITERIA AND ALTERNATIVE DEFINITIONS. JUNE 29, 1995. APPENDIX E ENVIRONMENTAL MITIGATION AGREEMENT viii R. W. Beck X0011592.112 CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT PLAN This report has been prepared for the use of the client for the specific purposes identified in the report. The conclusions, observations, and recommendations contained herein attributed to R. W. Beck, Inc., ("R. W. Beck") constitute the opinions of R. W. Beck. To the extent that statements, information, and opinions provided by the client or others have been used in the preparation of this report, R. W. Beck has relied upon the same to be accurate, and for which no assurances are intended and no representations or warranties are made. R. W. Beck makes no certification and gives no assurances except as explicitly set forth in this report. Copyright 1997, R. W. Beck, Inc. All rights reserved. X0011592.112 R. W Beck ix LIST OF ACRONYMS 23ST SW 23rd Street Alternatives BRPS Black River Pump Station BRWQMP Black River Water Quality Management Plan °C Degrees Centigrade cfs Cubic Feet Per Second CMP Corrugated Metal Pipe Corps U.S. Army Corps of Engineers CSTC Boeing Customer Service Training Center CWA Clean Water Act DD No. 1 King County Drainage District No. 1 DEIS Draft Environmental Impact Statement DNS Determination of Non-Significance DS Determination of Significance DU Dwelling Unit EIS Environmental Impact Statement EMA Environmental Mitigation Agreement EMP Environmental Mitigation Program ESGRW East Side Green River Watershed ESGRWP East Side Green River Watershed Project EVR East Valley Road FEMA Federal Emergency Management Agency FEQ Full Equations (Computer Model) FHRP Flood Hazard Reduction Plan FIS Flood Insurance Study fps Feet Per Second GDWNAP Green-Duwamish Watershed Nonpoint Action Plan GMA Growth Management Act GRBP Green River Basin Program GRFCZD Green River Flood Control Zone District GRIA Green River Interlocal Agreement X011592.112 AUGUST 1997 LIST OF ACRONYMS HOV High Occupancy Vehicle HPA Hydraulic Project Approval HSPF Hydrologic Simulation Program FORTRAN KCSWDM King County Surface Water Design Manual Metro Municipality of Metropolitan Seattle mg/1 milligrams per liter NEPA National Environmental Policy Act NFIP National Flood Insurance Program NGVD National Geodetic Vertical Datum (1929) NHC Northwest Hydraulic Consultants,Incorporated NRCS Natural Resources Conservation Service NTU Nephelometric Turbidity Units NWP National Wide Permit PC Panther Creek Alternatives PCW Panther Creek Wetland POPP Pump Operations and Procedures Plan PS Pipe System Improvement Alternatives RCC Renton City Code RCW Revised Code of Washington RM River Mile SC Springbrook Creek Alternatives SCS Soil Conservation Service (now called Natural Resources Conservation Service) SEPA State Environmental Policy Act SMP Shoreline Master Program SR State Route SWU City of Renton Surface Water Utility WAC Washington Administrative Code WDFW Washington State Department of Fish and Wildlife WDNR Washington Department of Natural Resources WMO Wetland Management Ordinance WSDOT Washington State Department of Transportation 2 R. W Beck AUGUST 1997 X011592.112 SECTION 1 EXECUTIVE SUMMARY 1 1 - . 1 SECTION 1 EXECUTIVE SUMMARY 1.1 INTRODUCTION AND PROJECT NEED The East Side Green River Watershed (ESGRW), also known as the Black River Basin, encompasses approximately 24 square miles and includes the cities of Renton, Kent, and Tukwila, and portions of unincorporated King County. The boundaries of the ESGRW are shown in Figure 6.1. The Renton Valley area, hereafter referred to as the Valley area, is an approximately 1,400-acre area lying in the downstream portion of the ESGRW. Runoff within the ESGRW drains to Springbrook Creek, the dominant drainage system in the Renton Valley area. Springbrook Creek extends to the Black River Pump Station (BRPS). Creek flows at the BRPS are pumped into the last remaining reach of the Black River, which drains into the Green River. The Renton Valley area, an area generally bounded by I-405 to the north, Talbot Road S to the east, SW 43rd Street to the south, and the Renton city limits to the west, is subject to recurrent flooding problems. During five floods in the last seven years (January 9, 1990; November 24, 1990; April 5, 1991; February 8-9, 1996; and December 1996-January 1997), Valley area streets and adjacent properties were under several feet of water, damaging private and public property, congesting traffic, impacting business operations, and raising safety concerns. The City of Renton has a long history of flood control planning in the Valley area. Since the early 1960s, the City of Renton has worked with the Soil Conservation Service (SCS), now called the Natural Resources Conservation Service (NRCS)', to reduce flood hazards. Channel and structural improvements that have been completed with NRCS assistance include the BRPS (1972), the Black River channel from the pump station to the Green River (1980), the BRPS Storage Pond (1984), a widened and realigned reach of Springbrook Creek (P-1 Channel) from the pond to SW Grady Way (1987), and a second widened and realigned reach of Springbrook Creek from SW Grady Way to SW 16th Street (1995). While these major flood control projects have been completed, they have not extended far enough upstream to solve the Valley area flooding problems. Some of the Valley area streets that remain subject to recurrent flooding include SW 43rd Street between Oakesdale Avenue and East Valley Road (EVR), EVR between SW 43rd Street and SW 23rd Street, and Lind Avenue SW between SW 43rd Street and SW 41st Street. Several properties along these streets are also flooded and subject to flood damage. Figure 6-5 at the end of Section 6 illustrates ' SCS changed their name to NRCS in 1995. The terms NRCS and SCS are considered synonymous. However, for consistency,the term NRCS is used throughout,except in Section 3.2,Project History, and in citations to documents produced by SCS prior to when the agency changed its name. X0011592.112 SECTION 1 areas subject to flooding problems. Figure 6-6B includes several photographs taken during past floods. While flooding is presently a severe problem, it will become worse if no action is taken. Future development in the watershed will be significant. Based on land use as it existed in 1989, growth within the Valley area itself is estimated at 590 acres of future industrial and commercial development, an increase of more than 100 percent. Within the entire ESGRW, the estimated amount of impervious surfaces such as roads, roofs, and driveways is estimated to increase by 45 to 50 percent above current conditions based on full buildout in accordance with adopted land use plans. Impervious surfaces produce the majority of stormwater runoff volume. Unless the program for flood control improvements continues, future development will increase the frequency and depths of flooding well above current conditions. This plan is needed to identify flood control measures that, when implemented, correct current flooding and prevent future flooding in the Valley area. To identify flood control measures that will achieve flood protection goals, can be permitted, and can be supported by the area property owners, a comprehensive plan with several elements is necessary. The plan elements are discussed below. 1.2 PLAN ELEMENTS This plan reflects a continuation of past flood control planning efforts. The primary purpose of this plan is to develop a multi-benefit, affordable, comprehensive surface water improvement plan that minimizes impacts to environmental resources and, if possible, enhances these resources while providing flood protection. The plan is comprehensive and integrates an extensive understanding of the drainage system, obtained through several environmental and technical work efforts, with public and agency input on project focus and environmental concerns. The extensive technical and environmental efforts ensure that flood control measures will achieve flood protection goals and that environmental enhancements, as well as any resulting impacts requiring mitigation from flood control measures, can be well defined. Input from the Valley area property owners and interested regulatory agencies was incorporated to ensure that recommended plan elements will have local support and can be permitted. NRCS is participating by providing funding support and technical assistance under the Watershed Protection and Flood Prevention Act (PL-566). Major elements of the planning effort include: ■ Development of hydrologic (HSPF) and hydraulic (FEQ) computer models to analyze the existing drainage system response to current and future storm events and evaluate flood control measures. ■ Pump testing of the Black River Pump Station. 1-2 R. W. Beck X0011592.112 EXECUTIVE SUMMARY ■ Public and agency coordination through a series of workshops and coordination with the Technical Committee of the Green River Basin Program, an organization comprised of several area cities and King County that is responsible for coordinated management of the Green River and its tributaries. ■ Integration of information collected through prior studies and plans, including: ■ Streamflow monitoring program and crest stage monitoring program ■ Black River Water Quality Management Plan (R. W. Beck, 1993; see Section 4.1.11) ■ City Wetland Inventory Update (Jones & Stokes, 1996; see Section 4.1.10) ■ Coinprehensive Fisheries Assessinent of the Mill Creek, Garrison Creek, and Springbrook System (Harza, 1995; see Section 4.2.13) ■ Identification and evaluation of flood control measures. ■ Development of a concurrent ESGRW Plan Environmental Impact Statement (EIS) to fulfill the requirements of the State Environmental Policy Act (SEPA). 1 .3 PROJECT GOALS Goals for the project were defined by the project team with input from the public and interested regulatory agencies. Public and agency workshops were held on May 16 and May 18, 1995, respectively, to discuss the planning effort, project goals, and flood control measures. The goals are summarized here and defined in greater detail in Section 2. ■ Reduce Flood Hazards. Provide flood protection considering design criteria consistent with City drainage standards under anticipated future land use development conditions. ■ Preserve the Technical Assistance and Funding Relationship with the NRCS. Continuing funding assistance could significantly reduce the financial impact of flood control improvements on City resources. ■ Mitigate Project Impacts. Incorporate measures into the plan to mitigate impacts resulting from project actions after first avoiding, then minimizing, the impacts when possible. For example, limit construction through existing wetlands and replace existing riparian habitat impacted by construction on an equal or better level. ■ Minimize Drainage System Maintenance Requirements. ■ Improve Riparian Habitat. Attain and maintain diverse and self-sustaining habitats that support aquatic and terrestrial species by improving fish rearing habitat, reducing erosive flows and stabilizing eroding banks, reducing solar insolation of the water through riparian plantings, and enhancing wetlands. X0011592.112 R. W. Beck 1-3 SECTION 1 ■ Design for Multiple Benefits. In addition to flood reduction and improving riparian habitat, the ESGRW project should be designed to allow for multiple uses whenever feasible. Other desired benefits include improving water quality, recreational, educational, and/or open space uses. Where possible, the project should incorporate design features to reduce mosquito breeding in the Panther Creek Wetland. ■ Seek Grants and Other Funding Options in addition to maintaining funding assistance from NRCS. ■ Coordinate plan recommendations with other City and Agency projects/ programs to maximize the use of public funds. 1.4 STUDY FINDINGS As indicated above, the frequency and depths of flooding will increase as the watershed continues to develop. Based on the hydrologic/hydraulic modeling effort, Springbrook Creek water levels could increase as much as 3 feet for the 10-year flood' between current and future land use conditions. Springbrook Creek is predicted to overtop SW 34th Street and Oakesdale Avenue during the future land-use conditions 10-year flood. High water surface elevations in Springbrook Creek is a major cause of flooding of tributary systems such as the SW 43rd Street system and East Valley Road system. High Springbrook Creek water levels cause water to back up in these tributary systems, and thus can substantially reduce their capacity, resulting in ponding of excess water in the roadways or on adjacent properties. Future increases in Springbrook Creek water levels will be a major factor causing these systems to flood more frequently and severely. In some areas, street surfaces 3,000 to 4,000 feet away from Springbrook Creek are about the same elevation as high Springbrook Creek water surface elevations. For example, the Springbrook Creek water elevation rose to 17.2 feet at the upstream side of the crossing of Oakesdale Avenue (overtopping the road) during the February 8-9, 1996, flood. The roadway surface elevation 3,500 feet east of Springbrook Creek, near the intersection of SW 43rd Street and Lind Avenue SW is 16.7 feet. The study concluded that high Springbrook Creek flood levels near the south end of the City are due to a combination of restrictions at roadway crossings, namely SW 27th Street, SW 34th Street, and Oakesdale Avenue, plus inadequate stream channel capacity, such as in the reach between approximately SW 16th Street and SW 23rd Street. In order to provide flood control for future stream flows, it was determined that a combination of Springbrook Creek channel improvements with improvements to tributary systems is necessary. '-The 10-year flood is defined as a flood having a 1 in 10 chance(10%)of being equaled or exceeded in any given year. 1-4 R. W.Beck x0011592.112 EXECUTIVE SUMMARY In addition to flooding problems, current environmental conditions in the Valley area are a major concern to the City. Springbrook Creek has been identified as a Class A water under the water quality standards established by the State of Washington (WAC 173-201A). However, water quality data indicate that Springbrook Creek, the dominant drainage system in the Valley, is severely degraded and has exceeded Department of Ecology water quality standards or guidelines for metals, temperature, phosphorus, dissolved oxygen, turbidity, and fecal coliform bacteria (R. W. Beck, 1993; Harza 1995). As required by Section 303(d) of the Federal Clean Water Act, the Department of Ecology has identified Springbrook Creek on its listing of threatened and impaired waterbodies. It is important to recognize that water quality in Springbrook Creek is a multi- jurisdiction problem, as the City of Kent and King County make up the majority of the basin. Measures to improve water quality can be integrated into the Valley area flood control measures. However, because the Valley area makes up a very small portion of the overall watershed, such improvements to water quality should be considered relatively minor. To achieve a more significant water quality improve- ment, correcting existing water quality problems in the upstream portion of the watershed, including Renton, Kent, and King County, will be necessary. Measures to correct water quality are defined in the Black River Water Quality Management Plan (R. W. Beck, 1993) and the City of Kent Five-Year Water Quality Program, 1992-1996 (Resource Planning Associates, 1991). The City of Kent is working on an updated water quality study for lower Mill Creek, with a draft report pending issuance. Improving water quality within the ESGRW will need to be a cooperative interlocal effort. Recent studies of the Springbrook Creek, Mill Creek (Kent), and Garrison Creek (Kent) watersheds have also demonstrated that temperature, dissolved oxygen, and metals concentration can exceed lethal limits for salmonids. Poor water quality is likely one of the factors limiting the ESGRW fish resource (Harza, 1995). The lower reaches of Springbrook Creek (in Renton and Kent) are not suitable spawning habitat due to the low channel gradient and the resulting sedimentation of the streambed with fine-grained material. Upstream of Renton, however, the upper reaches of Springbrook Creek and its tributaries, Mill Creek and Garrison Creek, contain habitat conditions suitable for salmonid spawning and rearing. In that respect, it is critical that Lower Springbrook Creek serve as an essential link between the Green River and headwater spawning grounds. Although there are still numerous wetlands in the Valley, landfilling and development in the Valley area have resulted in the loss of wetlands. Wetlands are valuable resources offering environmental benefits, such as groundwater recharge, water quality enhancements, flood storage, and aquatic and terrestrial wildlife habitats, as well as providing educational opportunities and recreational uses. Based upon the hydrologic/hydraulic modeling done as a part of this study, the remaining Valley area wetlands provide significant flood flow attenuation. For the 100-year event under future condition land use without any x0011592.112 R. W. Beck 1-5 SECTION 1 of the conveyance improvement proposed by this project, the combined flood storage volume provided by the wetlands is estimated to be over 750 acre-feet. 1 .5 ALTERNATIVE FLOOD CONTROL MEASURES Flood control alternatives for solving current and future flooding problems and improving environmental resources in the Valley area were identified by the project team with public and agency input. Alternatives were, in general, developed to work together to meet the City's project goals. For example, to reduce flooding, both improvements to Springbrook Creek as well as improvements to tributary pipe systems are necessary. The alternatives were presented in the categories listed below. For each category, a no-action alternative was also evaluated. Table 1-1 provides a summary of these alternatives within each category. Several of the alternatives are made up of several improvements, defined as elements. Figure 8-1, at the end of Section 8, illustrates a summary of all alternative elements. ■ Springbrook Creek Alternatives (SC)— The Springbrook Creek alternatives were focused on reducing Springbrook Creek water levels through a combination of widening selected reaches and improving roadway crossings. Lowering the water levels will correct roadway overtopping problems and reduce the presence of high water levels that lead to flooding of tributary systems. The Springbrook Creek alterna- tives also included consideration for habitat improvements and channel maintenance. ■ Panther Creek Alternatives (PC)— The Panther Creek alternatives were identified to correct the flooding of East Valley Road near SW 34th Street, in the area of Nendels Hotel. ■ SW 23rd Street Drainage Channel Alternatives (23ST)— The SW 23rd Street Drainage Channel alternatives were identified to correct flooding of East Valley Road south of SW 23rd Street as well as to replace existing, difficult to access culverts that outlet water from the Panther Creek Wetland. ■ Wetland Mitigation Bank and Wetland Hydraulic Modifications (W)— The proposed 14-acre Wetland Mitigation Bank (City Wetland No. 32) site is located along Springbrook Creek on the east side of Oakesdale Avenue between approximately SW 34th Street and SW 40th Street. This element includes enhancing and expanding Wetland No. 32 to create mitigation credits for use in compensating off-site wetland impacts from other projects occurring in the same drainage basin. Expansion of the wetland would also provide additional flood storage volume, create off-channel habitat, and enhance the downstream system by attenuating flows and improving water quality. A second 31-acre site located west of Oakesdale Avenue between 1-6 R. W. Beck X0011592.112 EXECUTIVE SUMMARY approximately SW 30th Street and SW 33rd Street that the City proposes to develop as a wetland bank is not included in this ESGRWP partially because of its limited benefit on reducing downstream Springbrook Creek flows and water levels. Additional information on the City's wetland mitigation banking proposal will be documented in the Wetland Mitigation Bank Program and Plan (Renton, 1997 pending) soon to be released. The other wetland hydraulic modifications (City Wetland No. 12 and 7N) generally include improving their connections to the drainage system, thereby allowing them to provide additional flood storage. The additional storage will offset, in part, the loss of flood storage provided by wetlands that would result from the lowering of Springbrook Creek water levels, as proposed under the Springbrook Creek alternatives. ■ Pipe System Improvements (PS)— The pipe system improvements were generally identified to work together with the Springbrook Creek alternatives to solve localized flooding problems. 1.6 SELECTION OF PREFERRED ALTERNATIVES As a part of the ESGRWP plan and accompanying EIS, the alternatives were evaluated in detail using several evaluation criteria, including; ■ Hydraulic Considerations ■ Wetlands ■ Water Quality/Sediment Quality ■ Fish Resources ■ Wildlife Habitat/Vegetation ■ Cost ■ Aesthetics ■ Land Use ■ Operations and Maintenance ■ Implementation and Financing ■ Utilities ■ Transportation ■ Groundwater ■ Recreation X0011592.112 R. W. Beck 1-7 SECTION 1 The results for each evaluation criterion are summarized in Tables 8-4 through 8-17 at the end of Section 8. Table 8-18 integrates the results of all these tables into one abbreviated table. Table 1-1 provides a further abbreviated version of Table 8-18, in which the alternatives are described and evaluated in terms of flood control, environmental considerations, and cost. The following paragraphs provide an abbreviated discussion outlining the primary factors influencing the preferred alternative recommendations. A summary of the preferred alternatives is given in Table 1-2. Table 1-2 gives the estimated project costs as well as potential contributors for implementation of project elements. Table 1-2 is an abbreviated version of Table 9-1. The form of participation for the potential contributors listed in these tables could vary significantly and range from providing volunteer assistance in planting projects to cost sharing on large capital improvements. The selection of the preferred alternative incorporates input received on the Draft ESGRWP Plan and EIS from NRCS, the City's interdepartmental design team, Valley area property owners, regulatory agencies, and others. Springbrook Creek Alternative 3 (SC3)-This alternative is preferred over Alternative SC2 because it goes the farthest in achieving the environmental restoration goals of the project while still achieving the desired flood protection goals. Alternative SO is more costly than SC2 because of a greater length of channel would be widened, a new road crossing structure would be installed at the Oakesdale Avenue crossing of Springbrook Creek at SW 41st Street, and the riparian plantings would be more extensive. The higher cost is justified because of the greater environmental and public benefit, the reduced need for maintenance, and the broad support for this alternative from the commentors on the Draft Plan and EIS, permitting agencies, and others. Also, a large portion of the additional channel widening from SW 30th Street to SW 40th Street is along the City's wetland mitigation banking site (Alternative W32-2) and fits well with the conceptual plans for the bank site. Depending upon available funding, its advantages to widen the channel adjacent to the bank site at the same time the bank site is constructed. In this way, reduced unit costs for earthwork and other construction items may be realized because of the larger scale of the combined project. Thus, the cost difference between alternative SO and SC2 may be less than projected. NRCS supports Alternative SO and the implementation of some of the elements of Alternative SO depends in a large degree upon the availability of NRCS funding. If NRCS financial assistance or other grant funding sources are not available, the City may instead need to revert to Alternative SC2 which is less costly, but also provides a lesser degree of environmental benefit. 1-8 R. W. Beck X0011592.112 EXECUTIVE SUMMARY Panther Creek Alternative 2 (PC2)-PC2 is preferred over PC3 primarily because it is possible for Panther Creek to divert into the Panther Creek Wetland over time on its own. Therefore, if the City were to implement PC3, there would be some risk that over time the creek would naturally be redirected to the Panther Creek Wetland, and consequently, the new more expensive pipe system under PC3 would not be fully utilized. Also, combined with SW 23rd Street Alternative 3, the diversion of additional water into the Panther Creek Wetland is considered a benefit to the City's mosquito abatement program because of the reduced stagnation in the wetland made possible by the greater flow of water through the wetland. As a change from the description of PC2 in the Draft ESGRWP Plan and EIS, it is recommended that the required mitigation for PC2 include the State Department of Fish and Wildlife's suggestion for vegetative maintenance and plantings along the overflow path from the Panther Creek high flow bypass structure to the standing water areas in the Panther Creek Wetland. This measure will help ensure that outmigrating salmonids and other fish that may overflow out of the creek at the diversion structure are able to reach standing pools of water in the wetland and eventually pass into the downstream system through the new SR- 167 culvert proposed under the SW 23rd Street Alternative 23ST3. SW 23rd Street Alternative 3(23ST3)-This alternative is preferred over 23ST2 because the addition of the deepened and widened channel will create positive drainage over the length of the channel, increasing channel capacity and the capacity of the drainage systems outfalling into the channel while reducing maintenance needs and reducing stagnation that negatively impacts the quality of water in the channel. With regard to the new culvert proposed across SR-167 at SW 23rd Street, the Draft Plan and EIS proposed that the culvert not be designed to accommodate future adult fish passage into the Panther Creek Wetland. This was primarily because fish would be entrapped in the wetland unless a channel was excavated through the wetland, and it was considered highly unlikely that wetland regulatory agencies would ever permit such a channel because of wetland impact issues. However, the State Department of Fish and Wildlife commented that the culvert should not preclude adult fish migration into and through the Panther Creek at some future time. It is therefore recommended that the culvert be designed as requested by Fish and Wildlife. The Washington State Department of Transportation has committed to funding the culvert installation. It important to note that NRCS supports Alternative 23ST3. However, the implementation of the deepened and widened channel depends in a large degree upon the availability of NRCS funding. If NRCS financial assistance or other grant funding sources are not available, the City may instead need to revert to Alternative 23ST2,which is less costly,but also has lesser benefits. X0011592.112 R. W Beck 1-9 SECTION 1 Wetland Mitigation Bank And Wetland Hydraulic Modifications Alternative 2 and Pipe System Improvements Alternative 2 (PS2)-The proposed Alternative 2 actions for both of these alternative categories are preferred over no action because of the benefits to be provided. 1-10 R. W. Beck X0011592.112 Table 1 -1 Summary of Alternatives Alternative Summary Description Flood Environmental Cost$ Control Considerations (Thousands) Springbrook Creek Alternatives SC1-No Action No changes to existing drainage system as development continues in the watershed. Major Flooding Impaired See Note 1 Remove bridge north of 27th,new box culverts at 27th and 34th,sliplinning existing culverts and SC2-Localized Improvements add 2 new culverts at Oakesdale,channel improvements 16th to 23rd,channel maintenance,and Major Benefit Improved $5,900 habitat improvements SC3-Springbrook Creek Remove bridge north of 27th,new box culverts at 27th,34th,and Oakesdale,channel Greenway Improvements improvements 16th to 23rd and 30th to 40th,channel maintenance,and more extensive habitat Major Benefit Improved more than SC2 $7,320 improvements than SC2 Panther Creek Alternatives PC -No Action No changes to existing drainage system as development continues in the watershed. Local Flooding Impaired See Note 1 PC2-High Flow Bypass to New diversion structure at SR-167 culverts to divert flow>5 cfs to wetland to reduce flows in Benefit No Significant Change $980 Panther Creek Wetland EVR/34th system. Also includes minor improvements along 34th PC3-Maintain Existing Flow to No changes to SR-167 crossings. Pipe replacements and minor channel improvements along EVR Benefit No Significant Change $1,660 SW 34th Street System and 34th between SR-167 and Springbrook Creek SW 23rd Street Drainage Channel Alternatives 23ST1-No Action No changes to existing drainage system as development continues in the watershed Local Flooding Impaired See Note 1 23ST2-Minor Conveyance Replace SR-167 culverts with new crossing at 23rd. Olympic petroleum line relocation or culvert Benefit Improved $610 Improvements replacement 23ST3-Major Conveyance Provides slightly more Improved,but requiring Improvements 23ST-2 improvements plus channel widening and deepening. benefit than 23ST2 more mitigation than $1,410 23ST2 Wetland Mitigation Bank and Wetland Hydraulic Modifications W12 Alternative 1-No Action No changes to existing drainage system as development continues in the watershed No Significant Change No Significant Change See Note 1 W12 Alternative 2-Culvert Culvert replacement to increase flow capacity connection between wetland and Springbrook Benefit No Significant Change $10 Replacement W32 Alternative 1-No Action No changes to existing drainage system as development continues in the watershed No Significant Change No Significant Change See Note 1 W32 Alternative 2-Wetland Expand and enhance existing wetland to provide wetland mitigation bank site Benefit Major Benefits $1,990 Mitigation Bank W7 Alternative 1-No Action No changes to existing drainage system as development continues in the watershed No Significant Change No Significant Change See Note 1 W7 Alternative 2-Culvert Culvert replacement to increase flow capacity connection between wetland and 19th system Minor Benefit No Significant Change $34 Replacement (Rolling Hills Creek) Pipe System Improvements P1-No Action No changes to existing drainage system as development continues in the watershed Major Flooding No Significant Change See Note 1 P2-Pipe System Improvements Pipe improvements to 43rd system,EVR system(south of 23rd),and removing Rolling Hills Culvert Major Benefit No Significant Change $4,210 at Springbrook Creek Note 1: Although not estimated,there is a negative cost impact associated with flooding and the greater level of maintenance under the no action alternatives. TABLE 1-2 SUMMARY OF PREFERRED ALTERNATIVES,COSTS AND POTENTIAL CONTRIBUTORS Alternative and Alternative Elements Total Cost Potential Contributors (Planning through Construction) (See Legend) Springbrook Creek Alternative 3(SC3)—Greenway Improvements SC3-Element 1 - Improvements at Roadway A. Remove Bridge North of SW 27th Street $50,000 City SWU;DD41 B. SW 27th Street Culvert Improvements $992,000 City SWU; DD#1 C. SW 34th Street Culvert Improvements $954,000 City SWU; DD#1 D. Oakesdale Avenue SW Culvert Improvements $1,035,000 City SWU; DD#l;City of Kent SC3-Element 2 -Channel Improvements A. Channel Improvements from SW 16th Street to SW 23rd Street $2,809,000 City SWU, Parks;NRCS; DD#l; KCD; Friends of BR B Channel Improvements from SW 30th Street to SW 41st Street $1,002,000 City SWU;NRCS; DD#1; KCD; Friends of BR SC3-Element 3 -Channel Maintenance Program $188,000 City SWU; Kent; King Co;Tukwila; DD#l; KCD; Friends of BR SC3-Element 4- Improve Riparian Habitat/Extensive Plantings $294,000 City SWU, Parks;NRCS; DD#1; KCD; Friends of BR SC3 Total $7,324,000 PANTHER CREEK ALTERNATIVE 2(PC2)-HIGH FLOW BYPASS PC2-Element 1 -Modify Existing Flow Split at SR-167 with New Structure $62,000 WSDOT; City SWU PC2-Element 2- SW 34th Street Drainage Improvements $921,000 City SWU PC2 Total $983,000 SW 23RD ST ALTERNATIVE 3 (23ST3)- MAJOR CONVEYANCE IMPROVEMENTS 23ST3-Element 1 - Replace SR-167 Culvert Crossings with New Crossing at SW 23rd $511,000 WSDOT;City SWU 23ST3-Element 2-Olympic Pipeline Relocation/Culvert Improvements $97,000 Olympic Pipeline Co.;City SWU 23ST3-Element 3 -Channel Widening and Deepening $797,000 City SWU;NRCS; KCD; Friends of BR 23ST3 Total $1,405,000 WETLAND MITIGATION BANK AND WETLAND HYDRAULIC MODIFICATIONS(W) Wetland 12 Alternative 2 -Culvert Replacement $10,000 City SWU Wetland 7N Alternative 2 -Culvert Replacement $34,000 City SWU Wetland 32 Alternative 2- Mitigation Bank/Excavate Large Off-Channel Storage $1,988,000 City SWU and other City funds; Bank Participants W Total $2,032,000 PIPE SYSTEM IMPROVEMENTS ALTERNATIVE 2 (PS2) Element 1 - SW 43rd Street System Improvements $3,089,000 City SWU;City of Kent Element 2- East Valley Road(South of SW 23rd Street) $1,096,000 City SWU Element 3 -Remove Rolling Hills Creek Culvert at Springbrook Creek $25,000 City SWU PS2 Total $4,210,000 Preferred Alternative Combined Total $15,954,000 Legend: SWU - Renton Surface Water Utility; NRCS - Natural Resources Conservation Service; Parks - Renton Parks Department; WSDOT - Washington State Department of Transportation; DD#1 -Drainage District No. l; KCD- King Conservation District; Friends of BR- Friends of Black River Note: The form of participation for the potential contributors could vary significantly and range from providing volunteer assistance in planting projects to cost sharing on large capital improvements. Possible funding options for the City SWU include: grants, loans, local improvement districts, basin surcharges, utility rates, and others. Cost sharing of road crossing improvements may be made with the City's Transportation System Division. N Z Z O O � ~ V cWn � O H Z SECTION 2 INTRODUCTION 2.1 PROJECT NEED The Renton Valley area, an area generally bounded by I-405 to the north, Talbot Road S to the east, SW 43rd Street to the south, and the Renton city limits to the west, is subject to recurrent flooding problems. The watershed tributary to the Valley area, known as the East Side Green River Watershed (ESGRW), including areas of Renton, Kent, King County, and a small area of Tukwila, has been highly developed into residential, commercial, and industrial land uses. The conversion of natural, vegetated land area to developed impervious areas has resulted in increased volumes of runoff entering the Valley area drainage system. For example, five floods in the last seven years (January 9, 1990; November 24, 1990; April 5, 1991; February 8-9, 1996; and December 1996-January 1997) inundated many city streets and private properties with several feet of water. The negative impacts of such flooding include: ■ Interruption of business. ■ Damage to public and private property. ■ Habitat and water quality degradation. ■ Channel erosion and sedimentation problems. ■ Traffic disruption, including the impairment of access for emergency vehicles. ■ Health and safety concerns. Some of the affected streets and areas include SW 43rd Street between Oakesdale Avenue and East Valley Road (EVR); East Valley Road between SW 43rd Street and SW 23rd Street; and Lind Avenue SW between SW 43rd Street and SW 34th Street. Figure 6-5 at the end of Section 6 illustrates the areas subject to flooding problems. Figure 6-6B includes several photographs taken during past floods. In addition to flooding problems, current environmental conditions in the Valley area are also a major concern to the City. Water quality data indicate that Springbrook Creek, the dominant drainage system in the Valley, is severely degraded. The fish resource is limited in part due to poor water quality and sedimentation problems. Many valley wetlands have been lost or negatively affected due to landfilling and development activities. While flooding is presently a severe problem, it will become worse if no action is taken. Future development in the watershed will be significant. Based on land use as it existed in 1989, growth within the Valley area itself is estimated at 590 acres of future industrial and commercial development, an increase of more than 100 percent. Within the entire ESGRW, the estimated amount of impervious surfaces such as roads, roofs, and driveways is estimated to increase by 45 to X0011592.112 SECTION 2 50 percent above current conditions based on full buildout in accordance with adopted land use plans. Impervious surfaces produce the majority of stormwater runoff volume. Unless the program for flood control improvements continues, the amount of future development will increase the frequency and depths of flooding well above current conditions. This plan is needed to identify flood control measures that, when implemented, correct current flooding and prevent future flooding in the Valley area. 2.2 PURPOSE AND AUTHORIZATION The primary purpose of this project is to develop a multi-benefit, affordable, comprehensive surface water plan that minimizes impacts to environmental resources and, if possible, enhances these resources while providing flood protection. Implementation of plan recommendations will help ensure protection of existing private and public property, infrastructure, and environmental resources. It will also provide protection for these resources under future development conditions consistent with the City's land use plan and land use plans of other jurisdictions within the watershed boundaries. In fulfilling the purpose of a multi-benefit comprehensive plan, the plan integrates an extensive understanding of the system, obtained through several environmental and technical work efforts, with public and agency input on project focus and environmental concerns. The extensive technical and environmental efforts ensure that flood control measures will work and that environmental enhancements as well as any resulting impacts requiring mitigation from flood control measures can be well defined. Input from the Valley area property owners and interested regulatory agencies was incorporated to ensure that recommended plan elements will have local support and can be permitted. Major elements of the planning effort include: ■ Development of hydrologic (HSPF) and hydraulic (FEQ) computer models that were used to analyze the existing drainage system response to current and future storm events and evaluate flood control measures. ■ Implementation of a streamflow monitoring program and crest stage monitoring program. ■ Pump testing of the Black River Pump Station. ■ Development of the Black River Water Quality Management Plan (R. W. Beck, 1993), which includes a water quality and sediment quality sampling program and habitat inventories (see summary description of this study in Section 4.1.11). ■ City Wetland Inventory Update (Jones & Stokes, 1996). ■ Identification and evaluation of flood control measures. 2-2 R. W. Beck X0011592.112 INTRODUCTION ■ Public and agency coordination through a series of workshops and coordination with the Technical Committee of the Green River Basin Program, an organization comprised of several area cities and King County that is responsible for coordinated management of the Green River and its tributaries. ■ Development of a concurrent East Side Green River Watershed Project (ESGRWP) Environmental Impact Statement (EIS) to fulfill the requirements of the State Environmental Policy Act (SEPA). This study was authorized by the City of Renton through an engineering agreement with R. W. Beck dated June 6, 1994. 2.3 PROJECT GOALS The ESGRW Project has eight principal goals: Goal No. 1 Reduce Flood Hazards. Protect the main stem of Springbrook Creek and major tributary systems from flooding up to a 100-year flood' to be consistent with the King County Surface Water Design Manual (KCSWDM) design criteria as adopted by the City in Section 4-22 of the Renton City Code (RCC), the City's flood hazards ordinance (4-31-31, RCC), and the Natural Resources Conservation Service (NRCS) standards defined in Goal 2 below. Goal No. 2 Preserve the Technical Assistance and Funding Relationship of the Natural Resources Conservation Service. Since the early 1960s, the City of Renton has worked with the NRCS to reduce flooding hazards within the ESGRW. Channel and structural improvements that have been completed with NRCS assistance include the Black River Pump Station (1972), the Black River channel from the pump station to the Green River (1980), the Black River Pump Station Storage Pond (1984), and the P-1 Channel from the pond to SW Grady Way (1987). In 1995, the City completed a segment of P 1 Channel from SW Grady Way to SW 16th Street with NRCS assistance. The City wishes to continue its funding relationship with the NRCS. For the project to be eligible for NRCS funding, new channel and related improvements must be designed in accordance with NRCS channel sizing criteria and other applicable standards. ' The 100-year flood is defined a flood having a one percent probability of being equaled or exceeded in any given year. x0011592.112 R. W. Beck 2-3 SECTION 2 Goal No. 3 Mitigate Project Impacts. Incorporate measures into the design to mitigate impacts resulting from project actions after first avoiding, then minimizing, the impacts when possible. For example, limit construction through existing wetlands and replace existing riparian habitat impacted by construction on an equal or better level. Goal No. 4 Minimize Drainage Maintenance Requirements. Minimize the extent and frequency of maintenance by designing for sedimentation to occur at defined locations where suitable and sizing channel improvements to minimize the need for sediment and vegetation management. Goal No. 5 Improve Riparian Habitat. Attain and maintain diverse and self- sustaining habitats that support aquatic and terrestrial species by: a) Improving fish rearing habitat in accordance with Washington State Department of Fish and Wildlife (WDFW), KCSWDM, and Tribal standards and guidelines. b) Reducing erosive flows and/or stabilizing eroding banks in accordance with WDFW and KCSWDM criteria, utilizing biostabilization measures where feasible. c) Reducing solar insolation of the water through riparian plantings. d) Protecting and enhancing wetlands through acquisition, plantings, or modifying wetland hydrology in accordance with local, state, and federal regulations and Puget Sound Wetlands and Stormwater Management Research Program guidelines. Goal No. 6 Design for Multiple Benefits. In addition to flood reduction and improving riparian habitat, the ESGRW project should be designed to allow for multiple uses whenever feasible by: a) Providing for recreational, educational, and/or open space uses by including recreational trails, interpretive signing, and other such measures in the project design; b) Incorporating design features, where possible, to reduce mosquito breeding in the Panther Creek Wetland; and c) Incorporating measures to protect and improve water quality. Goal No. 7 Seek Grants and Other Funding Options. In addition to maintaining funding assistance from NRCS, the City should pursue grants and other financial support to implement project elements and minimize cost impacts to the City, its residents, and rate payers. 2-4 R. W. Beck x0011592.112 INTRODUCTION Goal No. 8 Coordinate with Other City and Agency Projects. To maximize the use of public funds, it is important that the plan is consistent with ongoing and planned City projects and coordinated with ongoing and planned projects of other agencies, jurisdictions, and private entities. X0011592.112 R. W. Beck 2-5 ' SECTION 3 BACKGROUND AND PLANNING HISTORY 1 1 1 1 SECTION 3 BACKGROUND AND PLANNING HISTORY 3.1 BACKGROUND The current ESGRWP effort re-examines past ESGRW studies primarily developed by the United States Department of Agriculture, Soil Conservation Service [now called Natural Resources Conservation Service (NRCS)I, beginning in the 1960s. Initial flood control planning efforts began after the cities of Auburn, Kent, Renton, and Tukwila, along with King County, and the King Conservation District' passed a resolution requesting flood protection from the federal government under the Watershed Protection and Flood Prevention Act (Public Law 566). This initial effort led to the construction of the Black River Pump Station (BRPS), the first component of the recommended flood control system. The City of Renton assumed lead-agency responsibility for the project within Renton in 1982. The City, with assistance from the NRCS, coordinated the construction of the BRPS storage pond (forebay), the P-1 Channel from the BRPS pond to SW 16th Street, the Grady Way Box Culvert, and the Interstate 405 Box Culvert. In 1988, the City initiated a process for further construction of the P-1 Channel south of SW 16th Street. In response to public and agency comments, the City conducted an Adequacy Determination Study of the ESGRWP planning and environmental review information (Jones & Stokes, 1988). The Adequacy Determination Study identified specific deficiencies in the previous planning efforts with respect to impacts on wetlands, streams, wildlife habitat, fisheries, and water quality south of SW 16th Street. The identification of these deficiencies led to the current ESGRWP. A more detailed history of planning in the ESGRW is provided in the following paragraphs. 3.2 PLANNING HISTORY This section provides a chronology of planning efforts and construction activities in the ESGRW relating to the current project. The ESGRW, also known as the Black River Basin, encompasses approximately 24 square miles and includes portions of the cities of Renton, Kent, Tukwila, and unincorporated King County. The ESGRW is illustrated in Figure 6-1. The current project area in which flood control measures are being considered is the Renton Valley area, an area ' King Conservation District was called the King County Soil&Water Conservation District prior to 1973. After 1973, and prior to 1992, the District was called the King County Conservation District. X0011592.112 SECTION 3 generally bounded by I-405 to the north, Talbot Road S to the east, SW 43rd Street to the south, and the Renton city limits to the west. The Valley area is illustrated on Figure 6-2 and is within the downstream portion of the ESGRW. 3.2.1 1950s By the late 1950s, levees had been constructed along much of the Green River. The levee system included a flood gate located near the confluence of the Black River and the Green River. This system allowed the Black River to flow into the Green River during low Green River flow and prevented the Green River from flowing back into the Black River during periods of high Green River flows that would flood the Valley area. The levee system could not adequately prevent floods because floodwaters from the Black River could not be discharged from the Valley area whenever the flood gate was closed due to high flows in the Green River. This resulted in flooding inside the dikes within the Valley interior. 3.2.2 1960s To address this problem, in 1960 the cities of Auburn, Kent, Renton, and Tukwila, along with King County and the King Conservation District, passed a resolution agreeing to participate as local sponsors to request federal assistance under the Watershed Protection and Flood Prevention Act (PL-566) administered by the SCS. In 1962, SCS completed preliminary planning work for solving the interior Valley flooding problems. During the same year, the Howard Hanson Dam was completed. The dam helped prevent major valley flooding from the Green River; however, it did not solve the interior Valley flooding problems from the Black River when high Green River flows closed the flood gate. In 1965, SCS developed the East Side Green River Watershed Work Plan (SCS, 1965), which recommended land treatment and structural measures to manage stormwater runoff and solve the interior Valley flooding. The land treatment measures consisted of cropland management practices, wildlife habitat preservation and enhancement, and recreational opportunity improvements to prevent damage to lands changing from agricultural to urban uses. The struc- tural improvements consisted of new or improved drainage channels for the collection and conveyance of runoff, discharge works (i.e., BRPS), and an improved outlet channel to discharge runoff into the Green River from the BRPS. The total planned channel improvements consisted of 28.2 miles of channels. The P-1 Channel was the proposed primary receiving channel and was planned to extend 8.5 miles from the discharge works (BRPS) through Renton and into Kent. The work plans were approved by Congress in 1966, and construction of the BRPS began shortly thereafter. The pump station lifts the interior Valley drainage so it can flow by gravity into the Green River during high flow periods (see Section 6.4.4). 3-2 R. W. Beck X0011592.112 BACKGROUND AND PLANNING HISTORY 3.2.3 1970s The BRPS was completed in 1972. Further construction of other plan elements was postponed after it was determined that an Environmental Impact Statement (EIS) would have to be prepared under the then recently enacted National Environmental Policy Act (NEPA). In 1979, the final NEPA project EIS was reviewed and approved at the federal level(SCS, 1979). A related program began in 1978, when King County and the Valley cities signed an interlocal agreement initiating the Green River Basin Program, a cooperative local effort created to address a variety of surface water-related resource problems and to coordinate Green River management activities. King County, with funding through the Green River Basin Program, provides for operation and maintenance of the BRPS. 3.2.4 1980s During the late 1970s and early 1980s, additional technical studies were performed, which recommended modifying the project design with an alternative channel alignment, reducing channel size, and adding two proposed flood storage ponds (the BRPS floodwater storage pond and the Panther Creek Wetland). These changes were reflected in the Revised Watershed Plan prepared by SCS (SCS, 1978) and as supplemented in a 1981 amplification to the 1979 NEPA EIS (SCS, 1981). A Revised Watershed Plan Agreement was signed by local sponsors to the plan and NRCS in early 1980 (Renton File No. CAG-80-009). Under the Revised Watershed Plan and EIS amplification, structural measures included enlarging and realigning approximately 11.1 miles of stream channel (i.e., the P-1, P-2, and P-9 channels) to provide storage and convey flood flows to the constructed BRPS and outlet channel to the Green River. The two channels to be located in the City of Renton were designated as the P-1 and P 9 channels. The P-1 Channel was defined as the primary channel to begin in the City of Kent and extend through Renton to the BRPS. The P-9 Channel was to be a tributary of the P-1 Channel along SW 23rd Street between the Panther Creek Wetland and the P-1 Channel. The typical bottom width of the P-1 Channel within the City of Renton ranged from 70 to 80 feet, with the top width ranging from 200 to 210 feet. This configuration reflected a reduction in channel size (from a 120- to 165-foot bottom width) that was allowable with the creation of the BRPS floodwater storage pond to provide flood storage when the BRPS has to restrict pumping rates during periods of high Green River flows [in accordance with the Green River Interlocal Agreement (GRIA), the BRPS must reduce pumping rates when the flows in the Green River at the Auburn gage exceed 9,500 cfs]. The BRPS floodwater storage pond was also intended to provide wildlife habitat. The P 9 Channel was proposed to have a bottom width of 30 feet, a top channel width of 150 feet, and a length of approximately 3,500 feet. The amplification (supplement) to the EIS was issued in May of 1981 as a result of these changes. X0011592.112 R. W. Beck 3-3 SECTION 3 In 1982, the local sponsors placed the project on hold due to the lack of community support resulting from the high cost of the proposed capital projects and the sponsors' failure to agree on an equitable funding mechanism to implement the plan. Because the City of Renton is located at the downstream end of the watershed, it is the jurisdiction most seriously affected by increases in runoff. To maintain the efforts of the flood control program, the City of Renton acquired lead-agency responsibilities for the ESGRWP from King County in 1982, with designation as lead sponsor being formally authorized at a June 7, 1983 meeting of the Green River Basin Executive Committee. Between 1984 and 1990, the City of Renton, with assistance from the SCS, coordinated the construction of the BRPS floodwater storage pond, the P-1 Channel from the BRPS Forebay to SW Grady Way, the Grady Way Box Culvert, the P-1 Channel East Side Retaining Wall, the I-405 Box Culvert, and the SW 16th Bridge Replacement. In March 1988, the City conducted an Adequacy Determination Study of the East Side Green River Watershed planning and environmental review information (Jones & Stokes, 1988). As mentioned above in Section 3.1, the Adequacy Determination Study identified specific deficiencies in the previous planning efforts with respect to impacts on wetlands, streams, wildlife habitat, fisheries, and water quality south of SW 16th Street. The identification of these deficiencies led to the current ESGRWP. 3.2.5 19905 In 1990, the City began work on the current ESGRWP. Since 1990, the City has conducted several technical and environmental studies to support the current planning effort. Some of the major studies include the Black River Water Quality Management Plan (R. W. Beck, 1993), the City of Renton Wetlands Inventory Update (Jones & Stokes, 1996), the ESGRWP Hydraulic Analysis Report - Existing Drainage Systein (R. W. Beck, 1996a),and the ESGRWP Hydrologic Analysis (NFIC, 1996). The City, with NRCS assistance, also completed Springbrook Creek(P 1 Channel) improvements between Grady Way and SW 16th Street in 1995. The improve- ments included a parallel channel along this reach that passes through the previously constructed I-405 box culvert. 3-4 R. W. Beck X0011592.112 SECTION 4 CONSISTENCY WITH REGULATIONS AND OTHER ' RELEVANT POLICIES AND PLANS i7l. 1 1 1 . . 1 1 1 1 SECTION 4 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS 4.1 RELEVANT CITY OF RENTON REGULATIONS, POLICIES, AND PLANS 4.1.1 CITY OF RENTON DRAINAGE STANDARDS Adopted and formally proposed draft policies for storm and surface water are listed in the City's Comprehensive Land Use Plan or in Appendix A of the draft Surface Water Utility (SWU) Comprehensive Plan (HDR Engineering, 1995). The ESGRWP is consistent with and implements many of these policies. A substantial portion of the City's drainage standards are found in Chapters 4-22, Storm and Surface Water Drainage, and 4-31, Flood Hazards, of the Renton City Code (RCC). The City has also adopted the 1990 King County Surface Water Design Manual (KCSWDM). Other drainage requirements and policies may also be found in separate sections of the RCC, such as Chapter 4-19, Shoreline Master Program, and Chapter 4-10, Mining, Excavating, and Grading. The ESGRWP's flood control measure design criteria are consistent with the KCSWDM. 4.1.2 WETLANDS MANAGEMENT ORDINANCE (WMO) The City's regulations and policies pertaining to wetland resources are found in the WMO, Section 4-32 of the RCC. The ordinance is based on a "no net loss" policy of wetland resources. The WMO includes definitions of wetlands, allowed and regulated activities in a wetland and/or wetland buffer, and review procedures and permitting requirements for projects affecting wetlands. Many of the ESGRWP improvements may affect wetlands and/or their buffers. Therefore, the ESGRWP must comply with the WMO requirements. 4.1.3 SHORELINE MASTER PROGRAM (SMP) Because the mean annual flow of Springbrook Creek north of about SW 43rd Street has been determined by the Department of Ecology (Washington State, 1991) to exceed 20 cfs, the entire length within Renton from its mouth to SW 43rd Street is designated a Shoreline of Statewide Significance and is under the jurisdiction of the Shoreline Management Act of 1971. Wetlands determined to be associated with this area of Springbrook Creek are also considered Shorelines of Statewide Significance. In compliance with the Shoreline Management Act, the City has adopted a Shoreline Master Program (SMP; Chapter 4-19 of the RCC) for regulating activities within shoreline areas. Much of the ESGRWP proposed X0011592.112 SECTION 4 improvements are within the shoreline of Springbrook Creek and must comply and be consistent with SMP requirements and policies. Two shoreline designations—urban and conservancy—affect the Springbrook Creek system where Project actions are proposed. The conservancy designation is generally tied to previously identified wetlands or riparian habitat and significantly limits the allowable land uses within its boundaries. Areas within the urban designation have much fewer restrictions on allowable land uses. 4.1 .4 MOSQUITO ABATEMENT PROGRAM The Panther Creek Wetland is an approximately 60-acre complex located in the City of Renton east of State Route (SR) 167, west of Talbot Road, north of SW 43rd Street, and south of Interstate 405. The City of Renton initiated the Panther Creek Wetland Mosquito Abatement Program, administered by the Parks Department, in the mid-1970s in response to complaints received from residents living adjacent to the wetland. Early treatments included treatment methods such as aerial sprayings. However, increasing environmental information available in the mid-1980s led to the consideration of a program that balanced citizen demand for a Mosquito Abatement Program with environmental regulations and concerns. Under continued citizen advocacy for mosquito control, the City applied for a State Environmental Policy Act (SEPA) determination for a 5-year program (1989-1993). A Determination of Non-Significance (DNS) was issued by the City of Renton and upheld by the Hearing Examiner following an appeal of the DNS. The DNS specified methods and types of treatment and monitoring, requirements for notification to citizens and agencies, and provisions for reconsideration of the suitability of the proposed treatment. The Examiner required that a wildlife census be conducted prior to treatment of the wetland each year. The mosquito control treatment methods used from 1989-1993 consisted of both land and water treatments. The water treatment utilized a biological insecticide called Altosid (methoprene) in dissolvable briquette form. The Altosid was placed in the water once or twice a season to prevent mosquito larvae from maturing into adults by inhibiting their growth. The land treatment utilized ultra low volume insecticide application for the control of adult mosquitoes and was typically conducted from May through the mosquito season Quly/August). The 1989-1993 Mosquito Abatement Program was administered according to the program requirements of the SEPA determination and Hearing Examiner. In 1990, the program administration was transferred to the Surface Water Utility, which has since managed the program. 4-2 R. W.Beck x0011592.112 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS In 1994, the City applied for a SEPA determination for a land treatment (fogging) program between June and August 1994 utilizing synthetic pyrethroid products. A DNS was issued by the City of Renton (File No. LUA-94-066, ECF) for the proposed program. The program was then implemented in accordance with the SEPA proposal and determination. Continued recurrence of mosquito populations in the Panther Creek Wetland resulted in citizen requests for continued mosquito control efforts. In order to provide relief from the nuisance and discomfort caused by the mosquitoes, the City conducted environmental review for a proposed 5-year mosquito abatement program from 1995 to 1999 similar in scope to that conducted in 1994 (LUA-95-038, ECF). The current program area is adjacent to and upland of the eastern edge of the Panther Creek Wetland generally located between SR-167 on the west and Lake Avenue South/Talbot Road South on the east and extending from SW 41st Street on the south to I-405 on the north. Fogging was conducted in 1995 and for the 1996 program through the end of the mosquito season. A primary goal of the ESGRWP is to design project improvements for multiple benefit. Where possible, the ESGRWP will incorporate features to reduce mosquito breeding in the Panther Creek Wetland to lessen the need for the application of insecticides. 4.1.5 MASTER TRAILS PROGRAM The Master Trails Program (Renton, 1990) is an element of the City's Cornprehensive Park, Recreation, and Open Space Plan (Renton, 1992). These documents identify existing facilities and future plans for expanding the City's existing network of parks, recreation, and open space facilities. A primary goal of the ESGRWP is to design project improvements for multiple benefit. Where feasible, the ESGRWP will provide for recreational, educational, and/or open space uses by including recreational trails, interpretive signs, and other such measures in the project design. 4.1.6 TRANSPORTATION IMPROVEMENT PROGRAM AND OAKESDALE AVENUE EXTENSION PROJECT The City's 6-Year Transportation Improvement Program is an element of the City's Capital Improvement Program and identifies future projects for improvement of the City's transportation systems. Future transportation facilities planned by the City of Renton where ESGRWP improvements are proposed include: ■ The extension of Oakesdale Avenue from its existing terminus at SW 16th Street to SW 31st Street(LUA-95-024, ECF). X0011592.112 R. W. Beck 4-3 SECTION 4 ■ A high occupancy vehicle (HOV) facility along the south side of SW 27th Street between the new Oakesdale Avenue facility and SR-167. This HOV facility would be adjacent to, but separate from, SW 27th Street and would cross Springbrook Creek. The City's planned extension of Oakesdale Avenue would cross Springbrook Creek. Two alternative locations for this crossing were considered in a draft Environmental Impact Statement (EIS) prepared by the City and issued in April 1997. One alternative Springbrook Creek crossing would be located approximately 400 feet south of SW 16th Street and the other would be located approximately 700 feet south of SW 16th Street. Both crossings would involve a bridge structure with a 56-foot-wide roadway with curbs and sidewalk on both sides. The final EIS issued in July 1997 presents the alignment crossing the creek closest to SW 16th Street as the preferred alignment. Minor alignment changes discussed in the final EIS shift the crossing slightly north to approximately 300 feet south of SW 16th Street. In accordance with the City's drainage regulations, the new bridge, would be designed to prevent an increase in upstream water levels. Coordination of the ESGRWP with the proposed transportation improvements is ongoing. 4.1.7 SURFACE WATER UTILITY COMPREHENSIVE PLAN, DRAFT (HDR ENGINEERING, 1995) The first comprehensive plan for the Surface Water Utility since its creation in 1987 is currently in draft form. The plan is intended to: ■ Guide the Utility's Capital Improvement needs for the next 6 years. ■ Identify operations and maintenance needs of the Utility. ■ Identify existing and future regulatory mandates with which the Utility must comply. ■ Identify longer term stormwater management issues and concerns. The Surface Water Utility Coinprehensive Plan identifies existing and future capital improvement, operations, and maintenance needs within the entire City, coordinates those needs with potential funding sources, and ranks and schedules each element identified in the plan for funding and implementation over a six- year period. The six-year capital improvement program and other recommendations of the plan are reviewed annually as part of the City's normal annual budget process and are used as guidance in the determination of the annual program and budget. Following any necessary revisions, the first year of the six-year plan is incorporated into the citywide budget and is thus adopted as the annual Surface Water Utility program for that year. The improvements identified in the ESGRWP Plan will be implemented over a 5- to 15-year period through the six-year capital improvement program and annual budget process, depending upon available funding. 4-4 R. W. Beck X0011592.112 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS 4.1.8 COMPREHENSIVE LAND USE PLAN (RENTON,. 1995) In general, requirements and policies regarding land use within the watershed are defined in the comprehensive land use plans of King County and the cities of Kent, Tukwila, and Renton. Flood control measures identified under the ESGRWP are based on future flows determined assuming full development in the watershed in accordance with the future land use plans for these jurisdictions. All of the improvements outlined in this ESGRWP Plan are within the City of Renton and, therefore, must be consistent with the land use policies and regulations of Renton's Comprehensive Plan. Some of the environmental policies identified in the City of Renton s Compre- hensive Land Use Plan with which the ESGRWP is consistent include: ■ Manage water resources for multiple uses including recreation, fish and wildlife, flood protection, erosion control, water supply, energy production, and open space (EN-3). ■ Rehabilitate degraded channels and banks through public programs and new development (EN-7). ■ Maintain and enhance natural drainage systems to protect water quality, reduce public costs, and prevent environmental degradation (EN-23). ■ Use, maintain, and enhance the natural stormwater storage capacity provided in existing significant wetlands (EN-31). ■ Manage the cumulative effects of stormwater through a combination of engineering and preservation of natural systems (EN-36). ■ Identify and preserve corridors connecting habitat through acquisition, regulation of development proposals, and other means (EN-47). ■ Re-establish self-sustaining fisheries resources in appropriate rivers and creeks through encouragement of hatcheries and salmonid use (EN-49). 4.1.9 FLOOD INSURANCE STUDY The Federal Emergency Management Agency (FEMA) is the agency responsible for administering the National Flood Insurance Program (NFIP) and sponsors hydrologic and hydraulic analyses to determine flood risks in communities throughout the United States. These analyses are conducted following FEMA guidelines and yield the flood risk information shown on the NFIP maps, such as the 100-year floodplain and floodway. The information on the NFIP maps is used by participating communities to design and adopt floodplain management measures, such as those in the City of Renton Drainage Standards (see Section 4.1.1). FEMA, in turn, makes flood insurance available to property owners within that community. X0011592.112 R. W Beck 4-5 SECTION 4 The first Flood Insurance Study (FIS) performed for the City of Renton was published by FEMA in 1980 (FEMA, 1980). The hydrologic and hydraulic analyses, on which the FIS was based, were completed in July 1979 by Tudor Engineering. The FIS for the City of Renton was subsequently updated in 1989 using hydraulic analyses from June 1987 studies by CH2M Hill (FEMA, 1989). For Springbrook Creek, CH2M Hill used hydrology from the prior FIS in the update. The revised areas along Springbrook Creek and its tributaries within Renton included: ■ Springbrook Creek from the Black River Pump Station to SW 16th Street ■ Rolling Hills Creek from I-405 to the outfall of the pipe system passing through the Renton Village. The effective maps for Renton were reissued and are now dated May 16, 1995 (FEMA, 1995). The FIS for Renton was last issued May 20, 1996 (FEMA, 1996). No changes to the flood elevations were made in the 1995 map reissuance or 1996 FIS update. Any improvements within the flood hazard areas mapped by FEMA must be consistent with FEMA requirements for a participating community, such as the City, to continue to be eligible under the NFIP. The ESGRWP improvements are consistent with FEMA requirements and will greatly reduce flooding hazards within the study area. 4.1.10 CRITICAL AREAS INVENTORY, 1991, AND INVENTORY UPDATES, 1992 AND 1996 Wetlands within the study area were originally mapped and subsequently updated as a part of separate inventory projects. The initial mapping was done in 1991 (Jones & Stokes, 1991). The study catalogued information about each wetland, such as wetland type, size, dominant species, habitat quality, whether the wetland is inundated year-round or seasonal, flow pattern, and hydrologic connection. The inventory also provided an evaluation of wetland functions and values. These functions and values are important when considering potential impacts to wetlands from proposed flood reduction alternatives and when developing appropriate mitigation strategies. Since the original wetland inventory was completed, the City has made two updates in the mapping and inventory information in 1992 (R. W. Beck, 1993) and 1996 (Jones & Stokes, 1996). The updates were done to incorporate new or updated information, such as site- specific wetland delineations. The ESGRWP study has incorporated the most recent 1996 wetland information. 4.1.11 BLACK RIVER WATER QUALITY MANAGEMENT PLAN The BRWQMP, completed in May 1993 by R. W. Beck, et al, was developed to identify existing and future surface water quality problems in the Renton and northerly King County portion of the Black River Basin (also ESGRW) and 4-6 R. W. Beck x0011592.112 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS formulate solutions to these problems. The BRWQMP included a water quality and sediment sampling program; a review of historical data collected by Metro, Green River Community College, Washington State Department of Ecology, and others; a review of industrial and commercial area discharges and hazardous material spills; and an analysis of sediment loading through the drainage system. The plan also included an evaluation of wetlands, habitat, and aquatic resources; development of a recommended public education and involvement program; an evaluation of stormwater management practices; and an analysis of preliminary ESGRWP alternatives. Much of the environmental information developed from the BRWQMP is used to evaluate the benefits and impacts of the ESGRWP flood control measures. Chapter 3 of the BRWQMP, Volume 1, includes a discussion of the relationship of the BRWQMP and the ESGRWP and a summary of preliminary ESGRWP alternatives. For several reasons, as outlined in the ESGRWP Hydraulic Analysis report (R. W. Beck, 1996a), the alternatives have been redefined for evaluation in the ESGRWP environmental impact statement. Recommendations of the BRWQMP will be implemented through the City of Renton Surface Water Utility Comprehensive Plan. 4.2 OTHER RELEVANT REGULATIONS, POLICIES, AND PLANS 4.2.1 GROWTH MANAGEMENT ACT A general discussion of the Growth Management Act (GMA) is provided in this section because it contains land use planning requirements for designating and protecting critical environmental areas such as wetlands and fish habitat areas. Enacted on July 1, 1990, the GMA's goal is to manage growth in Washington State's fastest growing counties through the adoption of local comprehensive land use plans and development regulations. The GMA requires the following jurisdictions to adopt comprehensive land use plans: ■ Counties with population of 50,000 or greater and an increase in population of more than 10 percent in the last 10 years and any cities in such a county. ■ Counties that have a population increase of more than 20 percent in the last 10 years and any cities in such a county. ■ Counties that elect to conform with the Act. x0011592.112 R. W. Beck 4-7 SECTION 4 The GMA includes comprehensive land use plan advisory goals and requirements, as well as development regulations. Eleven counties in Washington, including King County, must adopt comprehensive plans under the Act. Those required to adopt comprehensive land use plans needed to do so on or before July 1, 1994. Renton, as a city in King County, must comply with this Act. Comprehensive Plans—Advisory Goals. The GMA has at least 13 advisory goals aimed solely at guiding the development of local comprehensive plans, including: encouraging urban growth where reasonable, reducing urban sprawl, encouraging efficient transportation systems based on regional priorities, encouraging the availability and variety of affordable housing, encouraging the retention of open space and recreational opportunities, and protecting the environment. Comprehensive Plans—Requirements. Comprehensive plans must contain elements for land use, housing, capital facilities, utilities, and transportation. In addition, the land use element must: ■ Review drainage, flooding, and stormwater runoff in the area and nearby jurisdiction. ■ Provide guidance for corrective actions to mitigate or cleanse those discharges that pollute waters of the state. ■ Be consistent with plans of neighboring jurisdictions. ■ Plan for infrastructure to be implemented concurrently with planned development. The ESGRWP is consistent with GMA requirements by providing flood protection and long-term water quality improvement. The plan is also consistent with plans of neighboring jurisdictions by evaluating flood control measures based on the most recent land use information for jurisdictions within the watershed and by considering large upstream flood control facilities, such as the Kent Lagoons project, in predicting future runoff rates and volumes. Development Regulations—Natural Resource Lands and Critical Areas. Cities and counties subject to the Act must: ■ Inventory and designate natural resource lands and critical areas on or before September 1, 1991. ■ Adopt development regulations on or before September 1, 1991, to ensure the conservation of agricultural, forest, and mineral resource lands. ■ Adopt development regulations on or before September 1, 1991, precluding land uses or development that are incompatible with designated "critical areas," which include the following areas and ecosystems: ■ Wetlands ■ Areas with a critical recharging effect on aquifers used for potable water ■ Fish and wildlife habitat conservation 4-8 R. W. Beck X0011592.112 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS ■ Frequently flooded areas ■ Geologically hazardous areas The City has completed all the development regulation requirements pertaining to Natural Resource Lands and Critical Areas. Implementation. Within 1 year of the adoption of its comprehensive plan, counties and cities must enact development regulations, such as zoning ordinances, official controls, and planned unit development ordinances, that are consistent with and implement the comprehensive plan. Each county and city that adopts a comprehensive plan under the Act is required to report to the Department of Community Development annually for a period of 5 years, beginning on January 1, 1991, and each 5 years thereafter, on the progress made by that county or city in implementing the requirements of the GMA. 4.2.2 WASHINGTON STATE DEPARTMENT OF ECOLOGY (DOE) WATER QUALITY STANDARDS FOR SURFACE WATERS Water quality standards have been established by the State of Washington (WAC 173-201A) for surface waters. These standards are designed to protect and promote the survival and longevity of aquatic organisms. The applicable standards are based on the class of water under consideration. Springbrook Creek has been identified as a Class A water and, therefore, is expected to meet those Class A standards. A summary of Class A standards in provided in Table WTl in the Surface Water and Sediment Quality Technical Memorandum in Volume 2 - Appendix A of the Draft Plan and EIS (Renton, 1996). Springbrook Creek has exceeded the Class A standards on many occasions for dissolved oxygen, fecal coliform bacteria, turbidity, temperature, and metals. A primary goal of the ESGRWP is to design project improvements for multiple benefits. The ESGRWP measures are intended to improve long-term water quality. 4.2.3 STATE ENVIRONMENTAL POLICY ACT (SEPA)/NATIONAL ENVIRONMENTAL POLICY ACT (NEPA) The ESGRWP must comply with the State Environmental Policy Act(SEPA) (WAC 197-11-360). On January 29, 1996, the City issued a determination of significance for the project based on a finding that the proposed project may cause significant adverse impacts to the environment (RCW 43.21C.020{2}) unless mitigation measures are identified. In accordance with SEPA, the determination of significance requires the City to prepare an environmental impact statement (EIS) for the project. The EIS developed for the project is consistent with SEPA requirements. X0011592.112 R. W. Beck 4-9 SECTION 4 Compliance with the National Environmental Policy Act (NEPA) is required for any federally funded project. Past ESGRW plan efforts have been funded by NRCS, and NEPA requirements have been satisfied. A NEPA EIS was completed for past project activities (see Section 4.2.10). For future project activities, a primary project goal is to maintain NRCS funding support. Any future project with federal funding support would also need to comply with NEPA requirements. It is most likely that NEPA compliance would be in the form of NEPA Environmental Assessments (EA) specific to project elements as they are implemented. Because the adoption of this project's Final SEPA EIS would precede implementation of project elements, the NEPA EAs can be developed to be consistent with the mitigation measures described in the current ESGRWP SEPA EIS. 4.2.4 WASHINGTON STATE DEPARTMENT OF FISH AND WILDLIFE/HYDRAULIC PROJECT APPROVAL The Washington State Department of Fish and Wildlife (WDFW) requires a Hydraulic Project Approval (HPA) for construction activities that use, divert, obstruct, or change the natural flow or bed of any of the waters of the state (RCW 75.20.100). The purpose of the requirements is to protect fisheries habitat in stream channels and prevent erosion, and to protect freshwater and near-shore marine aquatic life. The requirements would be administered through the HPA permit process. ESGRWP project elements likely to fall under the HPA permit requirements include any construction activities within the ordinary high water of Springbrook Creek and Panther Creek and other channels, such as channel widening and culvert improvements. 4.2.5 FEDERAL CLEAN WATER ACT Implementation of any of the project flood control measures that require work in waters of the U.S. will likely be subject to Section 404 of the Clean Water Act (CWA). Waters of the U.S. include Springbrook Creek, Panther Creek, Rolling Hills Creek, and connecting channels, intermittent streams, and wetlands. Under Section 404 of the CWA, the U.S. Army Corps of Engineers (Corps) has been given the responsibility and authority to regulate the discharge of dredged or fill materials into waters and adjacent wetlands of the United States (Federal Register, 1986). Section 404 permitting is commonly applicable to freshwater wetlands. Two kinds of permits are issued by the Corps, General and Individual. General permits (also known as Nationwide permits or NWPs) cover proposals that would have minimal adverse impacts on the environment. The most commonly used NWP for wetland alterations is NWP 26; this NWP specifically addresses wetlands that are (1) above the headwaters of a river or stream (i.e., that point in the watercourse at which the mean annual discharge is less than 5 cubic feet per second), or (2) hydrologically isolated. Such permits apply to fills and other 440 R. W. Beck X0011592.112 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS impacts of less than one-third of an acre, although current regional conditions may allow impacts of up to 2 acres to be covered by a General Permit. Proposed impacts from one-third of an acre to 2 acres may require a Water Quality Certification under Section 401 of the CWA from the Department of Ecology. Other NWPs allow impacts to wetlands for specific purposes. For example, an NWP 12 is used for wetland impacts caused by utility installation and maintenance. Unless covered by one of the NWPs, projects with wetlands impacts require Individual permits. The Corps evaluates Individual permits based on the probable impacts of a project on environmental quality and on a determination of whether or not the project is in the public interest. Actions seeking Individual permits must comply with Section 404(b)(1) guidelines, which require that an applicant prove there are no other practicable alternatives to the proposed project and that the project has avoided and/or minimized impacts to wetlands to the maximum extent practicable. Section 401 of the CWA also mandates that federally permitted activities in wetlands comply with the CWA and state water quality standards. Section 303(d) of the CWA requires the identification of impaired and threatened waterbodies. Every two years, the state is required to identify waterbodies not expected to meet state surface water quality standards after using technology- based controls. These waters are referred to as "Water Quality Limited" and the report where this information can be found is called the Section 303(d) List. This section of the CWA also requires states to develop a priority ranking and establish Total Maximum Daily Loads in accordance with the ranking. In other words, Section 303(d) requires states to develop a list of waterbodies that need additional work beyond existing controls to achieve or maintain surface water quality standards. The Washington State Department of Ecology has listed Springbrook Creek as not meeting state surface water quality standards (see Section 6.6.2.2). 4.2.6 EAST SIDE GREEN RIVER WATERSHED PROJECT ENVIRONMENTAL MITIGATION AGREEMENT AND PROGRAM The Environmental Mitigation Agreement (EMA; SCS, 1974) and Environmental Mitigation Program (EMP; Green River Basin Program, 1980) were agreements approved by the original ESGRWP participating jurisdictions that detailed both land use policy and environmental habitat improvements. The EMP was formulated to mitigate anticipated impacts of the overall ESGRWP improvements contained in the ESGRWP Final Environmental Impact Statement (SCS, 1979) described in Section 4.2.10 and to implement the provisions of the EMA, a copy of which is included in Volume 2, Appendix E of the draft Plan and EIS (Renton, 1996). Many of the impacts from past ESGRWP improvements were mitigated following this document. X0011592.112 R. W. Beck 4-11 SECTION 4 As the current ESGRWP improvements are being re-evaluated within Renton, the EMP mitigation conditions imposed on the earlier project configuration are no longer applicable. The mitigation conditions will be redefined through the current ESGRWP EIS and mitigation document and may or may not include elements from the 1980 EMP. Prior to or concurrent with the development of the mitigation document for the ESGRWP EIS, an agreement superseding or amending the EMA should be executed between the City of Renton and NRCS to accomplish the following: ■ With regard to Section 1 of the EMA, affirm that the City acquisition of the Panther Creek Wetland and a portion of the City of Renton Wetland (approximately 20 acres of Wetland W-12) satisfies Section 1 obligations for the East Side Green River Watershed. The City has acquired over 72 acres of the Panther Creek Wetland to date, but only up to 40 acres of the Panther Creek Wetland acquisition may apply in accordance with the EMP. ■ With regard to Section 2 of the EMA, affirm that the requirements (2 percent of project area for wildlife habitat, submittal of landscape development plans, and management of unused land for wildlife open-space) no longer need to be applied because the East Side project has been scaled down and because these requirements have been implemented to date for the projects that have been completed. ■ Affirm that Sections 3 and 4 of the EMA have been implemented since the agreement's inception. These actions will be continued in the future as any activity affecting stream channels is by statue under the jurisdiction and permit authority of WDFW, which consistently requires such actions (see Section 4.2.4). ■ Affirm that compliance with Section 5 was achieved. Certification that compliance was achieved is documented in Appendix 15 of the EMP. These changes are considered appropriate and necessary for the following reasons: ■ The EMA was to address the East and West Side Green River Watershed Plans. Only the P-17 pump station has been implemented for the entire West Side Plan and only a portion of the original East Side Plan has been constructed. ■ The EMA does not have any sunset clause or other provisions to define how long and under what conditions the provisions of the EMA must continue to be applied. Therefore, a new or supplemental agreement is needed to establish such provisions. ■ East Side Green River Watershed improvements constructed to date with the assistance of the NRCS have been mitigated appropriately in accordance with the EMA and other specific mitigation that may have been required through local environmental and permit review processes. 4-12 R. W. Beck x0011592.112 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS i As noted above, the EMA mitigation conditions and implementing provisions of ' the EMP imposed on the earlier project configuration are no longer applicable for future ESGRWP improvements which are being re-evaluated within Renton. ' 4.2.7 PLANS DIRECTLY GOVERNING OPERATION OF THE BLACK RIVER PUMP STATION (BRPS) iGreen River Basin Program and Interlocal Agreement. Members of the Green River Basin Program signed an Interlocal Agreement (GRIA; Green River Basin ' Program, 1992), dated June 30, 1992, which sets forth policies and regulations to coordinate Green River management activities. The members of the Green River Basin Program include King County and the cities of Auburn, Kent, Renton, and Tukwila. The GRIA sets forth pumping limitations for all existing stations discharging to the Green River by adopting and incorporating by reference the Pump Operations and Procedures Plan (POPP; Green River Basin Program, 1986). In accordance with the POPP,, the BRPS must begin to limit pumping rates when the flows in the Green River at the Auburn gage exceed 9,500 cfs. The GRIA also sets forth guidelines for future pumped discharges into the Green River and for levee improvements, interior drainage responsibilities, technical leadership, public safety and welfare through a levee monitoring system, emergency operations and a flood warning system, and cost sharing. The ' agreement also calls for updating the POPP and includes a recommendation to revise the rating curve for the BRPS to incorporate the results of pump tests performed as a part of the ESGRWP. ' Activities of the Green River Basin Program are funded by revenues generated by the Green River Flood Control Zone District. BRPS Operations and Maintenance Manual. Another document that describes the operation of the BRPS is the Black River Pumping Plant, Operation and ' Maintenance Manual (SCS, 1972). Maintenance of the BRPS is the responsibility of King County through the Green River Basin Program. The County is required to operate and maintain the pump station in accordance with this manual as a ' condition of receiving construction funding from the federal sponsor for the project, NRCS. ' 4.2.8 RENTON/TUKWILA INTERLOCALAGREEMENT The cities of Renton and Tukwila executed a reciprocal annexation agreement in ' 1986 (Renton File No. CAG-86-046). Section 4 of the agreement requires that Renton assume Tukwila's share of the cost of the construction and maintenance of the P-1 Channel that would be located in the reciprocal annexation area. ' Tukwila reserved the right to connect to and use the P-1 Channel. The flood control measures evaluated as a part of the ESGRWP include the assumption that the Tukwila area affected by this agreement drains to Springbrook Creek. ' x0011592.112 R. W.Beck 4-13 SECTION 4 4.2.9 EAST SIDE GREEN RIVER WATERSHED PLAN The East Side Green River Revised Watershed Plan (ESGRW Plan)(SCS, 1978) included a recommended program of flood control improvements along the east , side of the Green River within portions of Renton, Kent, and the City of Tukwila. As described under the project history (Section 3.2), the ESGRW Plan was , developed to revise previous ESGRW work plans (SCS, 1965) as a result of the enactment of NEPA. The flood control measures recommended in this plan were subsequently revised through the ESGRW Plan Final EIS (SCS, 1979) and the ESGRW Plan Amplification of Final EIS (SCS, 1981) described below. 4.2.10 EAST SIDE GREEN RIVER WATERSHED PROJECT FINAL EIS AND t AMPLIFICATION OF FINAL EIS The 1979 Final EIS (SCS, 1979) was developed for the ESGRWP to comply with NEPA. It contained an analysis of the project purpose and goals, an evaluation of alternatives, a selection of the preferred flood control alternative, and summary of environmental impacts. The general project objective was to provide a 25-year ' level of protection from flooding in the Valley, which includes portions of Renton, Kent, and Tukwila. The recommended program included the widening and realignment of 11.1 miles of stream channels(the P-1, P-9, and P-2 channels). ' The 1979 Final EIS was supplemented by the ESGRW Plan Amplification of Final EIS (SCS, 1981). The amplification was prepared because engineering and ' hydrologic analysis completed after the 1979 Final EIS led to some modifications of the recommended flood control measures. The modifications included the reduction of channel widths by creating the BRPS floodwater storage pond and ' utilizing flood storage provided by the Panther Creek Wetland. Maintaining continued NRCS support is a primary project goal. This support requires that the flood control measures must be consistent, in terms of project goals and area benefited, with this work plan as it forms the basis under which federal funding may be provided. NRCS has been involved with the planning ' effort and flood control measures considered in the current ESGRWP are consistent with the original project goals. 4.2.11 GREEN-DUWAMISH NON POINT ACTION PLAN (GDWNAP) The GDWNAP, dated January 28, 1991, was developed to minimize nonpoint ' source water pollution, protect beneficial uses, and enhance water quality in the Green-Duwamish watershed. GDWNAP Action 51 (Recommendation 52) identified the need for developing a water quality management plan for the ' Black River Basin. With funding assistance through the Centennial Clean Water Fund, the BRWQMP was completed in May 1993 (R. W. Beck, 1993). The ' relationship of the BRWQMP to the ESGRWP is described in Section 4.1.11. Other GDWNAP actions have already been implemented or are not applicable to the ESGRWP. 4-14 R. W. Beck x0011592.112 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS 4.2.12 KING COUNTY FLOOD HAZARD REDUCTION PLAN The King County Flood Hazard Reduction Plan (FHRP; King County, 1993) was adopted by King County in 1993. GMA requires that local regulations and policies be consistent with adjacent jurisdictions. The FHRP established policies that are directly applicable to the ESGRWP, including: ■ Jurisdictions in King County should seek to reduce the risk of severe flood hazards and damages experienced by existing public and private developments (G-4). ■ The existing flood storage and conveyance functions and ecological values of floodplains, wetlands, and riparian corridors should be protected and, where possible, enhanced or restored (G-7). ■ Floodplains, rivers, streams, and other water resources should be managed for multiple uses, including flood and erosion hazard reduction, fish and wildlife habitat, agriculture, open space, recreation, and, where appropriate, water supply and hydropower (G-8). ■ New flood hazard reduction projects, whether protecting new or existing development, should seek to provide protection from the 100-year, future conditions flood, plus a margin of safety. When new projects are being built to protect existing development, lesser protection may be provided where 100-year protection is not practical. Existing flood hazard reduction projects protecting existing developments should be maintained at their current level of protection unless the alternatives evaluation shows that a different level of protection is warranted (FHR-7). ■ Wherever reasonable, design flood hazard reduction projects to include preservation or creation of wetlands and fish habitat areas, and to be compatible with open space and recreation opportunities (FHR-8). ■ Wherever possible, design projects in ways that require minimal or no maintenance over the long term (FHR-9). 4.2.13 COMPREHENSIVE FISHERIES ASSESSMENT OF THE MILL CREEK, GARRISON CREEK, AND SPRINGBROOK SYSTEM The purpose of this study was to characterize the status of the system fishery resource and assess environmental factors likely to control fish production in the watershed. The study, prepared for the City of Kent (Harza, 1995), included an analysis of fish habitat, including physical aspects of the stream systems, riparian habitat, water quality, and fish passage. The study also included an analysis of fish population, including species composition and distribution, salmonid spawning abundance and distribution, and production of downstream migrating salmonids. The report recommends a comprehensive approach to improving the X0011592.112 R. W. Beck 4-15 SECTION 4 fishery resource. Some of the study's general recommendations that pertain to the ESGRWP include: ■ Stabilize stream channels and create instream or side channel pool habitat. ■ Minimize dredging in the low gradient portion of the watershed to decrease turbidity. ■ Improve water quality for the entire watershed with emphasis on dissolved oxygen, temperature, high turbidity, and particular heavy metal concentra- tions. The flood control measures proposed under the ESGRWP are consistent with the recommendations in this report and are intended to improve riparian habitat and long-term water quality. 4.2.14 CITY OF KENT DRAINAGE PLANS The City of Kent makes up the majority of the area within the ESGRW, and its surface water management program affects the downstream system in Renton. The most comprehensive surface water plan for the City of Kent that defines projected stormwater management facilities as well as project stream flow rates is the draft Mill Creek Storrnwater Management Analysis (R. W. Beck, 1994). The City of Kent is proceeding with many of the improvements identified in the plan, including the Kent Lagoons project, a major stormwater detention and habitat enhancement project, and many road crossing culvert improvements. The analysis of flood control measures under the ESGRWP (e.g., prediction of future flow rates) assumes that several of the planned improvements will be implemented. Specific improvements assumed to be in place under future land use conditions are listed in Section 7.3. 4.2.15 PUGET SOUND WATER QUALITY MANAGEMENT PLAN The Puget Sound Water Quality Authority was established by the state legislature in 1985. The authority completed the first Puget Sound Water Quality Management Plan in 1987, with the fourth and current plan issued in 1994. Policies in the plan with which the ESGRWP is consistent include: ■ All governmental actions will lead toward eliminating the presence of sediments in the Puget Sound basin that cause adverse effects to biological resources or pose a significant health risk to humans (S-1.a). ■ Control erosion and manage the quantity and quality of stormwater runoff from public and private activities and protect stream channels, aquatic habitat, wetlands, fish, shellfish, and other aquatic resources (SW-2.1.1). ■ Protect and enhance water quality, and achieve water quality and sediment quality standards (SW-2.1.2). 4-16 R. W. Beck X0011592.112 CONSISTENCY WITH REGULATIONS AND OTHER RELEVANT POLICIES AND PLANS ■ Protect beneficial uses, as described in Washington State's water quality standards, 173-201 WAC (SW-2.1.4). 4.2.16 CITY OF TUKWILA DRAINAGE PLANS The City of Tukwila makes up a small portion of the ESGRW along the Green River west of the Renton city limits. The City of Tukwila has developed three studies to evaluate drainage patterns and parameters in this area, including: ■ City of Tukwila Nelson Place/McLeod/Boeing CSTC Storm Drainage Technical Report by Hammond, Collier &Wade-Livingstone Associates, Inc. (1992). ■ City of Tukwila Nelson Place/Longacres Way Storm Drainage System Preliminary Design Report by Kramer Chin and Mayo (1988). ■ City of Tukwila Southeast Central Business District Drainage Study by Gardner Consultants (1992). By ensuring a reduction in flooding levels, the ESGRWP benefits the City of Tukwila's SE Central Business District basin. Drainage improvements on and tributary to Springbrook Creek that benefit the Nelson Place Basin are already in place, with the last segment of Springbrook Creek improvements downstream of the Nelson Place outfall completed in summer 1995. 4.2.1 7 OPERATION AND MAINTENANCE PROGRAMS AND OBLIGATIONS Normal operations and maintenance of drainage systems is generally determined by who owns the system, unless this responsibility has by an agreement been transferred to some other party. Practically all systems within public right-of-way are maintained by the City. An exception would be the 48-inch storm drain for the City of Tukwila in SW 16th Street that outfalls into Springbrook Creek just downstream of the SW 16th Street bridge. For the constructed channel and structures (except the BRPS) downstream of SW 16th Street (P-1 Channel), the City was required to acquire the necessary right-of-way and execute operation and maintenance agreements as a condition of receiving construction funding from the federal sponsor for the project, NRCS. Maintenance activities identified in the agreements include sediment and debris removal, vegetation management, keeping access berms in useable condition, and rehabilitating eroded areas or other damage to the channel and related improvements. Detailed information on agreements and easements under which the City assumed stormwater maintenance responsibilities for systems along Springbrook Creek is contained within the City's Surface Water Utility and Property Management section files. X0011592.112 R. W. Beck 4-17 SECTION 4 4.2.18 KING COUNTY DRAINAGE DISTRICT NO. 1 COMPREHENSIVE PLAN The District was formed around 1906 to provided drainage and flood control for the properties in the District. The District's boundaries and right-of-way were established by condemnation per King County Superior Court Cause No. 32912. The boundary of the District includes the ESGRWP area and extends from the foot of the hills on the east of the valley to the Green River on the west, and from approximately James Street in the City of Kent on the south to the Black River outlet into the Green River on the north. The District has broad powers as authorized in RCW Title 85, including the taxing of benefited properties within the District and the condemnation of land for District purposes. The District collects money from the properties on the valley floor within the District's boundary and uses these funds for regular maintenance activities primarily upstream of the City of Renton. In 1994, the District completed a comprehensive plan (King County Drainage District No. 1, 1994) which identifies capital improvements to reduce flooding on Springbrook Creek and Mill Creek, including recommendations for improvements within the City of Renton. However, the ESGRWP Plan supersedes the District's plan for the implementation of surface water capital improvements within the City of Renton. 4-18 R. W. Beck x0011592.112 SECTION 5 PROJECT COORDINATION 1 1 SECTION 5 PROJECT COORDINATION 5.1 CITY PROJECT DESIGN TEAM To ensure a coordinated approach in planning the ESGRWP with other ongoing City activities, the City uses a Project Design Team. The City's Project Design Team includes representatives from the Development Services, Long-Range Planning, and Transportation Divisions, Community Services Department, and the Surface Water Utility (SWU). Approximately four meetings have been held with the entire Project Design Team; numerous smaller meetings between the SWU and the other individual departments have been held. Two major City activities in the Valley area relevant to the ESGRWP discussed on numerous occasions include the Oakesdale Avenue Extension Project and the City's Master Trails Program (see Section 4.1). In addition, the Project Design Team has also provided technical review of major decisions made during the planning effort and also reviewed the draft Plan and EIS (Renton, 1996). 5.2 PUBLIC PARTICIPATION/WORKSHOPS A public meeting/workshop was held on May 16, 1995, at the City of Renton Community Center. The purpose of this meeting was to inform interested citizens about the planning effort and solicit input on the flood control measures being considered to solve current and future flooding problems and improve aquatic resources in the Valley area. A copy of the agenda, handout materials, and summary of the meeting minutes are included in Appendix B of the draft Plan and EIS (Renton, 1996). Notice of the meeting was published in the "Renton Reporter" and announcements were sent to all property owners in the Valley area. Several jurisdictions were also invited to the meeting, including King County Surface Water Management, cities of Kent and Tukwila, King County Drainage District No. 1, Puget Sound Water Quality Authority, Washington State Department of Transportation, Seattle Audubon Society, Seattle Water Department, King County Conservation District, Municipality of Metropolitan Seattle (Metro), and NRCS. In addition to the public meeting/workshop, the City conducted an extensive public involvement program as a part of the BRWQMP. As described in Section 4, the BRWQMP is closely related to the ESGRWP and addresses much of the same study area. While the focus of the public involvement under the BRWQMP was on water quality and environmental resources, information about the ESGRWP and the City's program for flood control was also included. The program included a mailer/questionnaire, five meetings with a citizen task force, and two public meetings in 1991 and 1992. A detailed summary of this public X0011592.112 SECTION 5 involvement program can be found in Volume 3, Appendix D, of the BRWQMP (R. W. Beck, 1993). 5.3 AGENCY COORDINATION The City of Renton has worked directly with NRCS since the City took lead agency status on the ESGRWP in 1982. Under the Watershed Protection and Flood Prevention Act (Public Law 566), the City of Renton and NRCS entered into an agreement to continue the flood control program (Renton File No. CAG-80-009 and Addenda). The current plan reflects a continuation of this agreement, and NRCS is providing funding and technical assistance. The City has worked closely with NRCS throughout the planning study. NRCS has reviewed the technical approach and resulting products. NRCS representatives have also participated in consultant team meetings and public and agency workshops. An agency meeting/workshop was held on May 18, 1995, at the City of Renton Community Center. Similar to the public meeting/workshop, the agency workshop was held to inform affected agencies about the planning effort and solicit input on the flood control measures being considered. A copy of the agenda, handout materials, and summary of the meeting minutes are included in Appendix B of the draft Plan and EIS (Renton, 1996). The agencies invited to the workshop included the Washington State Department of Ecology (Ecology), Muckleshoot and Duwamish Indian Tribes, the U.S. Environmental Protection Agency, Washington State Department of Fish and Wildlife (WDFW), U.S. Army Corps of Engineers (Corps), National Marine Fisheries Service, U.S. Fish and Wildlife Service, and NRCS. The workshop was very informative, with several agencies attending and providing input. The consulting team used the information collected during the agency workshop and the May 16 public workshop to modify some of the approaches for flood control and the flood control alternatives (see Section 8). Neighboring jurisdictions were also involved through the Green River Basin Program (see Section 4.2.7), including King County and the cities of Renton, Kent, Tukwila, and Auburn. As a part of this program, the Green River Basin Program Technical Committee meets on a monthly basis to coordinate flood management activities along the Green River. The City of Renton has made two presentations to the committee regarding the project. The purpose of the first meeting, held on February 23, 1995, was to discuss the results of the City's BRPS pump test and the pumping limitations during high Green River flows. The purpose of the second meeting, held on February 22, 1996, was to inform the committee that the EIS scoping notice had been issued. 5-2 R. W. Beck X0011592.112 PROJECT COORDINATION Individual agencies were also contacted to inquire about specific issues. This consultation was done mainly through telephone conversations. In addition, the City conducted agency coordination as a part of the BRWQMP. The BRWQMP held three meetings with a technical advisory committee, which was composed of state and federal agencies, adjacent jurisdictions, and environmental interest groups. While the focus of the BRWQMP was on water quality and environmental resources, information about the ESGRWP and the City's program for flood control was also discussed. A detailed summary of the technical advisory committee meetings can be found in Volume 3,Appendix E,of the BRWQMP. x0011592.112 R. W. Beck 5-3 SECTION 6 CURRENT CONDITIONS 1 1 1 1 SECTION 6 CURRENT CONDITIONS 6.1 GENERAL The Valley area is subject to recurrent flooding problems. During five floods in the last seven years (January 9, 1990; November 24; 1990, April 5, 1991; February 8-9, 1996; and December 1996-January 1997), area streets were under several feet of water, causing damage to private and public property, congesting traffic, impacting business operations, and raising safety concerns. In addition to flooding problems, current environmental conditions in the Valley area are also a major concern to the City. Water quality data indicate that Springbrook Creek, the dominant drainage system in the Valley, has severely degraded water quality. The fish resource is limited in part because of this poor water quality and sedimentation problems. Many Valley wetlands have been lost or negatively affected due to landfilling and development activities. This section describes current conditions in the Valley area surface water management system and summarizes known problems relating to flooding, water quality, and environmental resources such as wetlands, fish, and wildlife. 6.2 PROJECT AREA There are three study areas referred to in this document. The primary study area is referred to as the Valley area (see Figure 6-1). The Valley area within the City of Renton is of special concern because of recurrent flooding, water quality problems, and the need to protect remaining wetlands. The Valley area is also shown in Figure 6-2 and generally bounded by 1-405 to the north, Talbot Road South to the east, SW 43rd Street to the south (Renton city limits), and the Renton city limits to the west. The ESGRWP focuses on correcting problems in this area. The second area is the East Side Green River Watershed (ESGRW), also known as the Black River Basin, which encompasses approximately 24 square miles, including the cities of Renton, Kent, Tukwila, and unincorporated King County (see Figure 6-1). The ESGRW generally extends from the confluence of the Black and Green rivers at Tukwila, south along the east side of the Green River to the City of Kent downtown area, and east to the western edge of the Covington drift plain. The Valley area is located within the ESGRW. The ESGRW is important because all stormwater runoff generated in this area is conveyed to the Valley area drainage system. This study area is, therefore, the focus of the hydrologic analysis conducted as part of this plan. X0011592.112 SECTION 6 The third area is the BRWQMP study area, which includes the Valley area plus the contributing watershed lying within the City of Renton and the northern portion of the watershed lying within unincorporated King County (see Figure 6-1). The BRWQM Plan was described in Section 4.1. The geology of the ESGWP study area is dominated by two different zones: the Covington drift plain, a rolling upland plateau in the eastern portion of the watershed underlain by glacial deposits, and the Green River Valley (King County, 1987). The Covington drift plain is covered with basal till, with small outwash deposits. Most of the plain's soils belong to the Alderwood Association (NHC, 1996). The Green River Valley is relatively flat and of alluvial origin. Soils in the Valley are predominantly silt loams with some silty clay loams, fine sandy loams, peat, and fill (Harza, 1996). The majority of peat soils are within the Valley area and located primarily between Springbrook Creek and SR-167 from SW 19th Street to SW 41st Street. Soils in the Valley area are generally poorly drained and produce considerable runoff. 6.3 EXISTING LAND USE Existing land use in the Valley area is dominated by light and heavy industrial and commercial sites with some large undeveloped areas, some of which are existing wetlands. Existing land use in the Valley area and the ESGWW is illustrated on Figure 6-3 and is based on the Hydrologic Analysis Report (NHC, 1996). For the hydrologic analysis, existing land use was categorized based on aerial photographs (April 1988 and September 1989). Land use was divided into eight different categories: upland forested; upland cleared; lowland undeveloped; low-, medium-, and high-density residential; multifamily residential; and commercial/ industrial. Low-density residential is defined as 0.2-1 dwelling unit (DU)/acre, medium-density residential is defined as 1-2-DU/acre, and high-density residential is defined as 2-4 DU/acre. Land use can have a dramatic effect on surface runoff in urban areas because of the amount of impervious surfaces created by buildings or pavement. The pavement channels stormwater, which would otherwise be soaked up by soil and vegetation, and carries it into streams and rivers causing bank erosion, flooding, and sedimentation. Peak rates of runoff in undeveloped areas can increase several times after these areas become urbanized. Reducing the amount of water that would otherwise soak into the soil reduces groundwater recharge, which can affect streams by lowering summer base flows. Land use also affects the quality of surface runoff. During dry periods, dirt and pollutants accumulate on surfaces. Stormwater washes off these contaminants and carries them to urban waterways. Water quality is degraded with solids, oil, and grease from streets and parking lots; nutrients from over-fertilized lawns and gardens; and bacteriological and viral contaminants from human and animal waste. Impacts of land use on water quality are also discussed in Section 6.6.2. 6-2 R. W. Beck X0011592.112 CURRENT CONDITIONS 6.4 EXISTING VALLEY AREA DRAINAGE SYSTEM 6.4.1 SPRINGBROOK CREEK The existing Valley area surface water conveyance system is illustrated on Figure 6-2. The primary drainage system in the Valley area is Springbrook Creek, which extends north from the City of Kent to the Black River Pump Station (BRPS). Figure 6-6A includes photographs of selected reaches. Tributary to Springbrook Creek are Mill and Garrison creeks (Kent), Panther Creek, and Rolling Hills Creek. These streams originate on the plateaus east of the Green River Valley and are supplemented by localized inflow within the Valley. Springbrook Creek flows north along the Valley floor to the BRPS, which discharges through the last remaining reach of the Black River into the Green River. The Black River today is a small remnant of the old Black River that drained Lake Washington before construction of the Lake Washington Ship Canal and Ballard Locks, which lowered Lake Washington and diverted flows from the Black River. Several of the main drainage features along Springbrook Creek downstream of SW 16th Street were constructed as part of past ESGRWP improvements that have been largely funded by the NRCS (formerly SCS). These features include the BRPS, a large storage pond known as the BRPS floodwater storage pond, the Grady Way and I-405 box culverts, retaining walls along Oakesdale Avenue and the SW 16th Street Bridge, and widened and realigned portions of Springbrook Creek between the BRPS and SW 16th Street. A construction project to improve the SW Grady Way to SW 16th Street reach by constructing a parallel channel that flows through the 1-405 box culvert was completed in summer 1995. This project is referred to as the Connecting Channel Project, and its location is illustrated on Figure 6-2. Upstream of SW 16th Street, Springbrook Creek is much narrower, but has been deepened and widened in past years by farmers, local jurisdictions, and King County Drainage District No. 1 (DD No. 1). Tributary drainage systems have also been revised over the years as land uses have changed. Open ditches used when portions of the valley were farmed have been replaced by closed pipe systems to accommodate construction of roads and private development. 6.4.2 PANTHER CREEK Panther Creek originates in the plateau area in the eastern portion of the basin and drains an approximately 2-square-mile basin. Panther Creek originates at Panther Lake in unincorporated King County and flows in a northwesterly direction toward the City of Renton (see Figure 6-1). Panther Creek enters the Valley area at the base of Talbot Hills just west of Talbot Road. In this area, the creek flows through an alluvial fan and the creek channel becomes braided. Low flows enter two culverts under SR-167, which are the southernmost culverts between 1-405 and SW 43rd Street. The two culverts are shown on Figure 6-2 in x0011592.112 R. W. Beck 6-3 SECTION 6 SR-167 between SW 34th Street and SW 39th Street. These culverts discharge to a short drainage channel that connects to an approximately 3,000-foot-long pipe system along the East Valley Road (EVR) and SW 34th Street. This pipe system discharges to Springbrook Creek. Moderate and high Panther Creek flows split where the channel becomes braided. Some of the flow enters the two culverts under SR-167 and some is directed north into the Panther Creek Wetland. Panther Creek flows also exceed the capacity of the two southernmost SR-167 culverts during large storms, and excess flows travel north into the Panther Creek Wetland. Flows entering the wetland are temporarily stored and/or discharged to the west under SR-167 through a series of existing culverts ranging from 12 to 48 inches in diameter as well as a 36-inch-high by 48-inch-wide box culvert at the north end of the wetland near I-405. With the exception of the 36-inch by 48-inch box culvert, many of these culverts are severely plugged, limiting their capacity. The Panther Creek Wetland outflows from the SR-167 culvert crossings between approximately SW 23rd Street and SW 34th Street enter a ditch/wetland system (Wetland W-48e) located along the west side of SR-167. This system drains to a pipe system in EVR through an open ditch at approximately SW 29th Street. The EVR pipe system extends north and discharges to an existing channel along SW 23rd Street that flows west to Springbrook Creek. According to staff with the Washington Department of Transportation, the SR-167 culverts were located to coordinate with drainage systems in place at the time SR-167 was built, but these drainages have since been revised as a result of changes in land use downstream of the culverts. During flooding conditions, Panther Creek flows that pass through the two southernmost SR-167 culverts can exceed the capacity of the 3,000-foot-long pipe system along EVR/SW 34th Street. As a result, flooding of private property and EVR occurs. In addition, the system also overflows to the north to enter the ditch/wetland that runs along the west side of SR-167. 6.4.3 ROLLING HILLS CREEK Rolling Hills Creek originates on a plateau area in the northeastern portion of the basin and drains an approximate 1.4-square-mile drainage basin. Rolling Hills Creek enters a pipe system within the Renton Shopping Center on the north side of I-405. The pipe system discharges to a short section of channel running west along the north side of I-405 (see Figure 6-2). The creek then runs south under I-405 through 48-inch-diameter and 132-inch-diameter culvert crossings. From the I-405 crossing, a low-flow channel carries runoff along the east side of SR-167 to a 36-inch-high by 48-inch-wide box culvert that crosses west underneath SR-167. This culvert connects to a 60-inch-diameter system that flows west to Springbrook Creek. During intense storms, the capacity of the 36-inch-high by 48-inch-wide box culvert is exceeded, causing water to be stored in the Panther Creek Wetland. During periods of extreme flows, flows from both Panther Creek 6-4 R. W. Beck X0011592.112 CURRENT CONDITIONS and Rolling Hills Creek become interconnected as the entire Panther Creek Wetland area is flooded. Following a major storm event, this stored runoff is released from the wetland and flows return to their respective low-flow channels. 6.4.4 BLACK RIVER PUMP STATION The BRPS is located north of I-405 near where Monster Road crosses the Black River. As discussed previously, the BRPS lifts water from the pump station forebay to the Black River channel, which flows by gravity to the Green River. The BRPS was constructed in 1972 as a part of the original ESGRW Project. The pump station is maintained and operated by King County. The BRPS is equipped with eight vertical propeller pumps that discharge through flap gates. Characteristics of the pumps are shown in Table 6-1. The operation of the BRPS is dictated by the terms of the Pump Operations and Procedures Plan (POPP; Green River Basin Program, 1986), the Green River Interlocal Agreement (GRIA; Green River Basin Program, 1992), and the Pump Operation Manual (USDA SCS, 1972). These documents specify pumping rates for various forebay water levels, as well as limits on maximum allowable pumped discharge when flows in the Green River are high. The BRPS is required to reduce pumping rates when the Green River reaches flows in excess of 9,500 cfs at the Auburn gaging station and may have to completely stop pumping when flows reach 12,000 cfs. The pumping restrictions are summarized in Table 6-2. The GRIA was described in Section 4.2. The original intended nominal capacity was 2,945 cfs. Currently, however, two of the largest pumps (P-5 and P-7) are not operational, leaving a total nominal capacity of 1,917 cfs. If the actual pumping rate is less than that allowed (per the GRIA) under high Green River flow conditions, more water must be stored in the ESGRW drainage system to prevent flooding. For example, at a Green River flow rate of 11,500, the BRPS must reduce pumping to 900 cfs. If there has been a 25 percent efficiency loss in the rated capacity of the pumps (e.g., due to wear on the pump impellers or speed of the pumps running lower than the design speed), the actual pumping rate of two large pumps may be only 675 cfs. For extreme Green River floods, such as the 1975 event in which flows were close to or above 11,500 cfs for 20 hours, this reduced pumping would create the need for an additional 372 acre-feet of storage in the ESGRW system. Because of the importance of understanding the actual pump capacities versus the rated pump capacities, the City, with the approval of King County, performed a series of pump tests. The pump tests are documented in the Black River Pump Station Performance Tests on P-3 and P-8 (NHC, 1995) and the Technical Memorandum Black River Pump Station Performance Test (NHC, 1992), which included testing of Pumps P-3 and P 6. The pump test results and analysis of the BRPS operation are also described in the ESGRWP Hydrologic Analysis (NHC, 1996). X0011592.112 R. W. Beck 6-5 SECTION 6 In summary, the pumps that have been tested were found not to be operating at their design capacity. Therefore, pumping rates used for computer simulations are based upon the tested capacities and other factors, such as assumptions regarding future maintenance of the pumps by King County. Detailed discussions of the methodology used for modeling the pump station operation are included in the ESGRWP Hydrologic Analysis and the ESGWP Hydraulic Analysis (R. W. Beck, 1996a). 6.4.5 VALLEY WETLANDS The Valley area wetlands are an integral component of the existing drainage system. Wetlands provide naturally occurring flood storage by temporarily storing flood waters and attenuating downstream flows. Wetlands also provide significant water quality and habitat benefits. The Valley area wetlands are discussed in more detail in Section 6.7. 6.4.6 SW 23RD STREET DRAINAGE CHANNEL The SW 23rd Street drainage channel is an existing channel between SR-167 and Springbrook Creek along the SW 23rd Street right-of-way. Local runoff as well as outflows from the Panther Creek Wetland from the poorly functioning SR-167 culvert crossings between SW 23rd Street and SW 34th Street (see Section 6.4.2) are conveyed through this channel to Springbrook Creek. Portions of the existing channel system along SW 23rd Street were designed and built assuming that the P-1/P-9 channels would be built according to the previous NRCS work plans (SCS, 1965 and 1978). These include the Lind Avenue culvert crossing, the EVR culvert crossing, and local pipe systems draining to this channel (particularly from the south). These systems were built very low, whereas the existing channel bottom was never lowered to the design grades. As a result, the existing low systems accumulate sediment and are a maintenance problem for the City. 6.4.7 OTHER DRAINAGE SYSTEMS Other localized drainage systems in the Valley area are characterized by low- gradient channels and pipe systems that are subject to backwater conditions when there are high water levels in Springbrook Creek. Backwater conditions severely restrict the conveyance capacity of many systems and can lead to street ponding and flooding. Some of the major pipe systems in the Valley area are shown on Figure 6-2. 6-6 R. W. Beck X0011592.112 CURRENT CONDITIONS 6.5 FLOODING 6.5.1 HYDROLOGIC/HYDRAULIC MODELING APPROACH Detailed hydrologic and hydraulic studies of the ESGRW drainage system were previously undertaken by the NRCS in the 1960s and 1970s; however, changes in the system, changes in regulations relative to environmental issues, and advances in hydraulic and hydrologic modeling techniques have all prompted a detailed re-examination of hydrologic and hydraulic conditions within the ESGRW. As part of the current ESGRWP, a comprehensive examination of the drainage system's response to flood events was conducted. This examination consisted of two components. The first component included the ESGRWP Hydrologic Analysis. The purpose of the hydrologic analysis was to evaluate the hydrologic response of the ESGRW drainage system, establish flood flow frequencies (i.e., 2-, 10-, 25-, and 100-year), and develop hydrographs that could be input to a hydraulic model and routed through the Valley area drainage system. The second component consisted of the ESGRWP Hydraulic Analysis. The hydraulic analysis consisted of developing a hydraulic computer model to simulate the hydraulic response of the Valley area drainage system to identify the cause of flooding problems. The hydraulic model was also used to evaluate alternative flood control improvements. The hydraulic modeling of flood control alternatives is described in the ESGRWP Hydraulic Modeling of Flood Control Alternatives (R. W. Beck, 1995a). The following paragraphs provide a general description of the hydrologic and hydraulic analysis. As discussed above, the first component of the modeling approach is the hydrologic analysis that was described in the ESGRW Hydrologic Analysis report. A variety of hydrologic models was considered. Hydrologic models produce hydrographs for the watershed that describe how runoff flows change over time in response to precipitation events. The U.S. Environmental Protection Agency's Hydrologic Simulation Program—FORTRAN (HSPF; USEPA, 1988)—was used. HSPF is a continuous hydrologic model that produces runoff hydrographs for an extended period in response to actual rainfall records. Continuous hydrologic modeling is of particular value when studying a system such as the ESGRW because it allows detailed examination of the interrelationships between flows in the Green River and local runoff from the ESGRW. Stormwater generated in the ESGRW is conveyed to the BRPS where it is pumped into the Green River. Maximum allowable pumping rates from the BRPS into the Green River are regulated by the terms of the Green River Interlocal Agreement (GRBP, 1992). The simultaneous occurrence of high flows in the Green River and the Valley area drainage system can result in flooding problems because there are limits to the amount of water that can be pumped into the Green River under these conditions. X0011592.112 R. W. Beck 6-7 SECTION 6 HSPF was used to predict flow rates at specific locations in the Valley area drainage system for varying flood-flow frequencies. These events included the 2-, 10-, 25-, and 100-year flood-flow frequencies for existing land use as well as future land-use conditions (see Section 7.3). The second component of the study is the hydraulic analysis. Hydraulic computer modeling was necessary because the HSPF hydrologic computer program can only develop approximate water surface elevations on complex drainage systems such as in the Valley area. The Valley area drainage system involves several complex hydraulic features, including pumping (with and without pumping restrictions resulting from high Green River flows), backwater effects (due to the flatness of the Valley and highly variable downstream water elevations at the BRPS), and flood-flow storage occurring in several major wetlands. A hydraulic model called FEQ (Franz, 1994) was selected for the hydraulic analysis because it has the ability to simulate the complex drainage system of the Valley area. FEQ performs a one-dimensional analysis of flow hydraulics using St. Venant equations. The FEQ model is a non-steady state model that can simulate varying water surface elevations over time in the different components of the conveyance system, such as channels, culverts, and under bridges. FEQ can also simulate water surface elevations in storage ponds such as BRPS floodwater storage pond and model their effect on backwater conditions in Springbrook Creek. In addition, FEQ can simulate the hydraulic connections between the larger Valley wetlands and the conveyance system, which can provide helpful information (e.g., maximum water levels and durations of inundation) when considering potential impacts to wetlands from proposed system improvements. FEQ can also directly model the simulation of the BRPS and its pumping limitations as set forth under the GRIA. The hydraulic analysis consisted of using the FEQ hydraulic computer model to simulate the hydraulic response of the major conveyance systems in the Valley area. This was done by routing hydrographs (developed as a part of the hydrologic analysis) through the Valley area's major drainage system compo- nents. HSPF-generated hydrographs were imported into the FEQ model at points that represent key locations within the Valley area drainage system. FEQ then routes these hydrographs through the Valley area major conveyance system until flows are pumped into the Green River by the BRPS. While routing flows, the FEQ model simulates the time history of flows and water surface elevations throughout the drainage system. It is important to note that the focus of the FEQ hydraulic analysis is on the major drainage conveyance systems in the Valley; smaller local conveyance systems were not modeled. The major systems included in the FEQ model are described below and shown on Figure 6-4. 6-8 R. W. Beck x0011592.112 CURRENT CONDITIONS ■ Springbrook Creek. Springbrook Creek is included in the model from its confluence with Mill Creek, located a few hundred feet south of SW 43rd Street, to the BRPS. The Connecting Channel Project, which includes a parallel channel from SW 16th Street through the I-405 box culvert to SW Grady Way, is also included in the model. This project was constructed in 1995. ■ Rolling Hills Creek. Rolling Hills Creek is included in the model from a point 675 feet upstream of I-405 to its confluence with Springbrook Creek. As previously discussed, the Creek crosses 1-405 with 48-inch- and 132-inch-diameter culverts. The 132-inch-diameter culvert has a weir control at its inlet and is used for high flows. The FEQ model representation includes both crossings in addition to the weir inlet control for the 132-inch-diameter culvert. ■ Panther Creek System. Panther Creek enters the Valley area east of SR-167 near Valley General Hospital. Panther Creek's low and moderate flows enter the two southernmost SR-167 culvert crossings and discharge to a short section of open channel. Flows then enter a 24-inch- and 36-inch-diameter system, which flows north along East Valley Road (EVR). At SW 34th Street, the system turns west, increases to a 60-inch-diameter pipe system at Lind Avenue SW, and continues west to Springbrook Creek. High Panther Creek flows that exceed the capacity of the two southernmost SR-167 culvert crossings travel north into the Panther Creek Wetland. Although some flows may exit Panther Creek Wetland through a series of partially functioning SR-167 culvert crossings between SW 27th Street and SW 34th Street, the model incorporates a simplified representation of the system. This simplified representation includes the assumption that the SR-167 crossings between SW 23rd and SW 34th do not function such that high Panther Creek flows entering the Panther Creek Wetland flow north to eventually exit the wetland through the 36-inch by 48-inch box culvert located in the northern third of the wetland. A detailed description of the modeling approach to the Panther Creek Wetland system can be found in the ESGRWP Hydraulic Analysis (R. W. Beck, 1996a). ■ SW 23rd Street Drainage. The existing drainage channel located along the SW 23rd Street right-of-way between Springbrook Creek and EVR was also included in the FEQ model. Under the existing channel system configuration, it is assumed that this channel system only conveys local runoff from Subbasin S10 shown in Figure 6-4. ■ FEQ Wetlands. Wetlands modeled using FEQ are shown in Figure 6-4. It is important to note the distinction between the wetlands modeled using FEQ and the existing wetlands mapped in the City's wetlands inventory (Figure 6-7). The areas defined as wetlands in the FEQ model, termed FEQ wetlands, were used because of their potential for storing floodwaters during extreme floods and not because they meet the classification of a wetland. Therefore, as part of the FEQ model, they should be thought of as off-channel x0011592.112 R. W. Beck 6-9 SECTION 6 flood storage areas rather than wetlands. These storage areas were identified based on a review of Corps of Engineers 1980 topography and available knowledge about Springbrook Creek flood elevations (primarily FEMA). By comparing topography with FEMA base flood elevations, Valley areas that were thought to provide significant off-channel storage volume were identified as FEQ wetlands. In some instances, the FEQ-modeled wetland areas closely match the City's inventoried wetlands (e.g., FEQ Wetland No. 3 on Figure 6-4 and Wetland No. W-8N on Figure 6-7). In other instances, an area designated as an FEQ wetland was not considered a wetland under the City's inventory (e.g., FEQ Wetland No. 8). It should also be noted that the numbering system used to identify FEQ wetlands differs from the City's inventory because the original FEQ model development was completed prior to the wetland inventory. The Valley area wetlands were defined in FEQ by elevation-area curves and hydraulic connections to the system. An elevation-area curve consists of a relationship between water surface elevation and the corresponding water surface area. FEQ internally computes the storage volume contained within the wetland at any given elevation based on the elevation-area curves. A defined hydraulic connection (i.e., either weir flow over an embankment or culverts) between the wetlands and the drainage system is needed for the model to simulate wetland inflows and outflows. ■ Black River Pump Station. An important assumption of the FEQ analysis relates to the simulation of the Black River Pump Station (BRPS) operation. Testing of the pump station indicates that the pumps are operating somewhat below their design capacity. Assumed pump capacities for model simulations are based largely on the results of BRPS pump tests. The ESGRWP Hydrologic Analysis (NHC, 1996) report provides a detailed description of the approach for representing the BRPS pumping rates. As part of the hydrologic hydraulic analyses, a model run of the January 9, 1990, flood was simulated to validate the model results. The results of these simulations are presented in both the ESGRWP Hydrologic Analysis and the ESGRWP Hydraulic Analysis. While there are limited field observations of water surface elevations during this flood, the simulation (in terms of peak flows at the BRPS forebay) provided reasonable results. Simulated peak flows at the BRPS were within 13 percent of the best estimate of the actual flows. Because the field observations were limited during the 1990 event, recommendations were made to begin stream flow and crest gage monitoring programs. The City has since engaged in an extensive stream flow and water level monitoring program. The stream flow and water level monitoring program is described in both the ESGRWP Hydrologic Analysis and the ESGRWP Hydraulic Analysis. The interrelationship between the ESGRW drainage system and Green River was also evaluated in the hydrologic/hydraulic modeling approach. As discussed previously, maximum allowable pumped discharges from the ESGRW system into the Green River via the BRPS are constrained by the terms of the GRIA 6-10 R. W. Beck X0011592.112 CURRENT CONDITIONS (GRBP, 1992). Allowable pumped discharges are reduced progressively from approximately 3,000 cfs to 0 cfs as flows in the Green River at Auburn increase from 9,500 cfs to 12,000 cfs. The simultaneous occurrence of high flows in the Green River and high flows in the ESGRW is of critical interest in determining the amount of flood control storage required in the Valley area drainage system and the level of protection provided by the existing drainage system. High flows in the Green River are controlled by Corps of Engineers' flood-control operations at Howard Hanson Dam, which was constructed in 1961. The Corps operates this dam to restrict flow at Auburn to a maximum of 12,000 cfs. Recorded flows in the Green River at Auburn are available since 1936. By simulating local flow in the ESGRW system on a continuous basis for the period of time since the dam was constructed, it is possible to examine directly the simultaneous occurrence of high flows in the Green River and the ESGRW system. To address this issue, two different flood simulations have been developed for the 25- and 100-year frequency floods, both of which can be used for planning and design of future system improvements. One of the flood simulations reflects a severe local precipitation event without BRPS pumping restrictions. This simulation, referred to as the "conveyance" simulation, was needed to ensure that Springbrook Creek will have sufficient hydraulic capacity to convey peak flows to the BRPS. The second flood simulation reflects a severe Green River flood that causes the pump station to restrict its pumping rates. This simulation, referred to as the "storage" simulation, was needed to ensure that the Springbrook Creek system and the BRPS forebay have sufficient storage capacity (during periods of high Green River flow and subsequent restricted BRPS pumping rates) to temporarily hold flood waters without causing flood damage to structures, roadways, and other areas. Only the conveyance simulation was needed to determine the effects of 2-year and 10-year frequency storms on system capacity. The storage simulation for the 2-year and 10-year events (as determined by frequency analysis of peak annual storage volumes at BRPS forebay; see NHC, 1996) was not a concern because it was determined that these events would cause negligible build-ups of storage at the forebay during high Green River flows. Another important item to note in the hydrologic/hydraulic model simulations relates to the presence of large stormwater detention facilities in the basin. The City of Kent Lagoons Project, a regional stormwater detention and water quality facility, is assumed to be constructed and in operation for both current and future condition simulations. Construction of this facility was substantially completed in the summer of 1996. In addition to the hydraulic modeling of the major conveyance systems with the FEQ hydraulic model, several other pipe systems were modeled using the BWPIPE backwater model (King County, 1990). These systems were modeled to evaluate the capacity of the tributaries and to establish design criteria by identifying necessary downstream water levels in Springbrook Creek to correct flooding. The tributary systems include: X0011592.112 R. W. Beck 6-11 SECTION 6 ■ SW 43rd Street System, by R. W. Beck — documented in R. W. Beck's March 27, 1995, design criteria memorandum (R. W. Beck, 1995b). ■ East Valley Road/SW 34th Street System, by City of Renton — documented in April 6, 1995, Draft Design Goals memorandum. ■ East Valley Road System(SW 23rd Street to SW 34th Street), by City of Renton —documented in April 6, 1995, Draft Design Goals memorandum. ■ Rolling Hills Creek (through the Renton Shopping Center), by City of Renton—documented in April 6, 1995, Draft Design Goals memorandum. 6.5.2 HYDROLOGIC/HYDRAULIC ANALYSIS RESULTS The HSPF simulations of the Valley area drainage system were conducted to help evaluate the magnitude of rare flood events, establish specific flood-flow frequencies, and generate runoff hydrographs that could be routed by the hydraulic FEQ computer model. The results presented in this section are taken from the hydraulic FEQ modeling. The detailed hydraulic modeling of the Valley area drainage system using the FEQ computer model is described in the ESGRWP Hydraulic Analysis report (R. W. Beck, 1996a). Results of the existing drainage system simulations, including peak flows and corresponding water surface elevations, are summarized for current land use conditions in Table 6-3. The following paragraphs provide an analysis of results for current land use conditions. The analysis is divided into four sections: ■ Springbrook Creek water surface elevations and stream channel velocities. ■ Simulated flooding problems of drainage systems tributary to Springbrook Creek. ■ Valley area wetlands. ■ BRPS. One item to note about the results presented in Table 6-3 is that the peak flows for the "conveyance" event are based upon a frequency analysis of the simulated Springbrook Creek annual maximum inflows to the BRPS forebay for the period of record. The peak flows for the "storage" event are based upon a frequency analysis of the simulated annual maximum storage in the BRPS forebay for the period of record. The frequency analyses are the basis by which the storm frequency flood flows (i.e., 100-year, etc.) are selected. It is important to recognize that the peak flows for Rolling Hills and Panther creeks given in Table 6-3 are based upon a frequency analyses of Springbrook Creek and do not represent the true flood flow frequencies for these systems. Rolling Hills and Panther creek flood flows for different storm frequencies that are based upon frequency analyses of these systems are contained in the ESGRWP Hydraulic Analysis (NHC, 1996). 6-12 R. W. Beck x0011592.112 CURRENT CONDITIONS 6.5.2.1 SPRINGBROOK CREEK WATER SURFACE ELEVATIONS AND STREAM CHANNEL VELOCITIES For current land use conditions, the "storage" 100-year flood simulation resulted in the highest Springbrook Creek water surface elevations between the BRPS and a few hundred feet upstream of SW 16th Street. Upstream of SW 16th Street, the "conveyance" 100-year flood simulation resulted in the highest water surface elevations. Under the current conditions simulation, the SW 34th Street crossing and the Oakesdale Avenue crossing are overtopped for the "conveyance" 100-year floods. No overtopping was predicted by the model for any of the "storage" events. While overtopping at these culvert crossings can lead to localized flooding, high Springbrook Creek water surface elevations can also cause tributary systems to flood. This is discussed in the following section. The simulation results can also be used to predict the average stream channel velocities corresponding to the peak flow through any channel reach. This information is helpful for identifying channel erosion problems. Channels that have good vegetative cover along their banks can generally accommodate flow velocities of 4 to 5 feet per second (fps) without being susceptible to significant erosion. This allowable flow velocity can be lower, however, depending on soil conditions, amount/character of vegetation, and channel configuration such as bends and bank side slopes. In any case, some degree of minor erosion is common in natural channels and should be anticipated. For the 2-year event, maximum simulated velocities ranged from 1 to 3 fps. One exception to this is a short reach upstream of SW 16th Street (Branch 10), which was simulated to have a velocity of 7.7 fps. For the 100-year conveyance event, flow velocities generally ranged from 2 to 4 fps. Again, the reach upstream of SW 16th street was an exception, having a maximum simulated velocity of 9.7 fps. High velocities occur here in part because this branch forms the transition between the large improved channel downstream of SW 16th Street and a narrower unimproved channel upstream. This reach could be subject to significant erosion problems during moderate floods. Such erosion problems through this reach were confirmed during field observations. 6.5.2.2 SIMULATED FLOODING PROBLEMS OF DRAINAGE SYSTEMS TRIBUTARY TO SPRINGBROOK CREEK As previously discussed, major conveyance systems tributary to Springbrook Creek were analyzed using either the FEQ computer model or the BWPIPE model. Under existing land use conditions, the following systems were predicted to have surface ponding: ■ The East Valley Road system along SW 34th Street and where Panther Creek enters the system. ■ The East Valley Road system south of SW 23rd Street. X0011592.112 R. W. Beck 6-13 SECTION 6 ■ The SW 43rd Street system in the vicinity of Lind Avenue SW. ■ The SW 7th Street system (this problem is being addressed under a separate City study). The analyses generally show these systems to flood at the 10-year event. The primary cause of this flooding in these systems (excluding SW 7th Street) is high Springbrook Creek water surface elevations. High water surface elevations in Springbrook Creek cause water to back up in these tributary systems and can substantially reduce their capacity, resulting in ponding of excess water in the roadways or on adjacent properties. In some areas, street surfaces 3,000 to 4,000 feet away from Springbrook Creek are about the same elevation as high Springbrook Creek water surface elevations. For example, the Springbrook Creek water elevation rose to 17.2 feet at the upstream side of the crossing of Oakesdale Avenue (overtopping the road) during the February 8-9, 1996, flood. The roadway surface elevation 3,500 feet east of Springbrook Creek, near the intersection of SW 43rd Street and Lind Avenue SW is 16.7 feet. 6.5.2.3 VALLEY AREA WETLANDS The Valley area wetlands provide a significant volume of flood storage. Overall, the Valley area wetlands are simulated to provide 639 acre-feet of storage for the 100-year current condition"conveyance" flood. Water surface elevations and periods of inundation for the more frequent 2-year flood simulation are shown in Table 6-4. This table shows that Springbrook Creek 2-year flows do not inundate many of the Valley area wetlands, such as FEQ Wetland Nos. 4, 5, 6, 8, 9, and 10. Using the City wetland inventory numbers, these wetlands include 10, 11, 14, 16, 32, and 51. This indicates that several wetlands are not directly connected hydrologically to or affected by backwater from Springbrook Creek during the more frequent storm events. 6.5.2.4 BLACK RIVER PUMP STATION For current land use simulations, the maximum pumping rates of the BRPS vary from 532 cfs to 1,360 cfs for the different flood frequencies (see Table 6-3). A maximum of 1,360 cfs is simulated for the 100-year "storage" flood, which reflects the use of three large pumps to evacuate water that had been stored upstream of the BRPS when high flows in the Green River forced a reduction of pumping rates. This 1,300 cfs occurs after the Green River flows drop to a level where increased pumping is allowed. This same event results in the maximum simulated elevation at the BRPS forebay of 8.4 feet. Pump station outflow is a function of the number and type of pumps that are assumed to be operating in the simulation in accordance with the Pump Operations and Maintenance Manual (SCS, 1972). Modeled outflows will not always exactly match any specific pump combination, in which case the outflow is determined by interpolation. 6-14 R. W. Beck X0011592.112 CURRENT CONDITIONS 6.5.3 FLOODING PROBLEMS The flooding problems simulated by the FEQ modeling are validated by observations made during floods. For example, five floods in the last seven years (January 9, 1990; November 24, 1990; April 5, 1991; February 8-9, 1996; and December 1996-January 1997) resulted in many City streets and private properties being covered by several feet of water, causing property damage, traffic congestion, impacting business operations, and safety concerns related to impairment of emergency vehicle access. The affected streets and areas include the following: ■ SW 43rd Street between Oakesdale Avenue and East Valley Road. ■ East Valley Road between SW 43rd Street and SW 23rd Street. ■ Lind Avenue between SW 43rd Street and SW 34th Street. ■ Springbrook Creek crossing of SW 34th Street. ■ Springbrook Creek crossing of Oakesdale Avenue. ■ SW 7th Street System. ■ Renton Shopping Center. Valley areas subject to significant recurrent flooding are illustrated in Figure 6-5. These areas were defined by reviewing computer modeling results, conducting field observations, and documented drainage problems by City staff. Several photographs of these flooded locations are shown on Figure 6-6B. In the case of the SW 43rd Street system, significant flow is contributed by the drainage system serving the City of Kent, which connects to the SW 43rd Street system near Lind Avenue. During flood events, when Springbrook Creek is high, the SW 43rd Street system does not have the capacity to carry the street drainage plus the flow from Kent. As a result, street ponding occurs at depths of 1 to 3 feet (see Figure 6-613). The frequency of the flooding problems far exceeds the City's storm drainage objective for providing a 100-year level of protection (Policy EN-G). In addition, the City has adopted portions of the King County Surface Water Management (KCSWM) Design Manual, which set forth design criteria for new storm drainage systems. Although the Valley area drainage system is not new, the City uses these criteria as a goal for existing systems. These criteria stipulate that during the 25-year design storm event, storm drainage systems shall not rise any higher than 0.5 foot below the grate of any drainage structure. For a 100-year design storm event, a storm drainage system must be designed to prevent overtopping roadway crowns and flooding building structures. The Renton Shopping Center was flooded during the January 9, 1990; November 24, 1990; and February 8-9, 1996, events. Based on discussions with City staff, the stream from the Rolling Hills basin discharging into the two culvert inlets on the north side of I-405 and downstream of the shopping center was not X0011592.112 R. W Beck 6-15 SECTION 6 bank full at the same time areas in the shopping center were being flooded. Based on this information, capacity problems upstream of this point internal to the shopping center are suspected to have caused the flooding. This particular problem area, as well as the SW 7th Street flooding problem, is within the ESGRW; however, it is outside the Valley study area and will not be addressed in the ESGRWP. A detailed analysis of the SW 7th Street system is currently being done as part of the draft City of Renton SW 7th Avenue, Hardie Avenue, and Lake Avenue Drainage Investigations (R. W. Beck, 1996b). High stream velocities and channel erosion caused by flooding can also be a problem. Based upon the hydrologic/hydraulic analysis and field observations, the Springbrook Creek reach upstream of SW 16th Street is subject to erosion during flood conditions. 6.6 WATER QUALITY 6.6.1 WATER QUALITY INVESTIGATIONS The most in-depth study of water quality within the area is the BRWQMP (R. W. Beck, 1993). The BRWQMP included a water quality and sediment sampling program; a review of historical data collected by Metro, Green River Community College, Washington State Department of Ecology, and others; a review of industrial and commercial area discharges and hazardous material spills; and an analysis of sediment loading through the drainage system. Since the completion of the BRWQMP, some additional water quality monitoring (primarily temperature and dissolved oxygen) was completed within the Valley area as part of the Comprehensive Fisheries Assessment of Mill Creek, Garrison Creek, and Springbrook Creek System (Harza, 1995). This was done primarily to evaluate water quality suitability for fish. In addition, the Renton draft Surface Water Utility (SWU) Comprehensive Plan (HDR Engineering, 1995) also included an abbreviated analysis that evaluated water quality in the context of the overall City drainage system. The SWU Comprehensive Plan provides a good summary of water quality in the area. 6.6.2 WATER QUALITY PROBLEMS Water quality conditions within the ESGRW are primarily a function of past and ongoing human activities and practices within the watershed. The analysis of water quality problems in this plan focuses on the following: ■ Land use and population density. ■ Water and sediment quality. ■ Sediment and erosion. ■ Flood-related water quality problems. 6-16 R. W. Beck x0011592.112 CURRENT CONDITIONS A summary of water quality problems for Springbrook, Panther, and Rolling Hills creeks is shown in Table 6-5. 6.6.2.1 LAND USE AND POPULATION DENSITY Current land use was discussed in Section 6.3. Land use relates directly to the quality of urban runoff generated within a given basin or subbasin. Urban and commercial uses result in an increase in impervious area yielding higher runoff during storm events. In addition, urban and commercial land uses result in an increase in pollutant loading, which is carried via stormwater runoff to receiving waters such as Springbrook and Panther creeks. Within the ESGRW, degraded water quality conditions may, at least in part, be attributed to the urban and commercial land uses present. Various commercial and light industrial operations located within the Valley are believed to contribute pollutants to Springbrook Creek via surface water runoff. These operations include auto wrecking yards and several light manufacturing firms. Runoff from SR-167 is another source that can contribute high metals loadings. As a part of the BRWQMP, potential industrial and commercial sources were identified based on their standard industrial classification (SIC) designation. Priority rankings were then assigned to each facility based on its potential to discharge pollutants. High priority industries include manufacturers (e.g., steel, chemicals), metal finishers and fabricators, auto repair shops, and junkyards. At the time of the BRWQMP study, there were 83 businesses falling under the high- priority industry ranking in the BRWQMP study area, 58 of which are automotive repair or service stations. Pollutants typically associated with these facilities include petroleum hydrocarbons, solvents (cleaning and degreasing agents), and metals. Poor housekeeping practices, such as improper storage and disposal of waste materials, are also a problem with industrial uses. In addition to surface water, groundwater may also be adversely affected at these facilities. Improper disposal of chemical wastes and accidental spills of chemicals at these facilities can result in contaminated soils and groundwater. The BRWQMP also contains a listing of known contamination sites and businesses falling under NPDES regulation requirements. Other urban and rural residential activities that occur within the ESGRW and can potentially impact water quality include hobby farming (fertilizers, fecal coliform bacteria), gardening and lawn maintenance (fertilizers, pesticides), on-site wastewater disposal (nutrients, fecal coliform bacteria), and improper disposal of wastes (paint, antifreeze, petroleum products, pet wastes). 6.6.2.2 WATER AND SEDIMENT QUALITY The general water and sediment quality problems in the Valley area and tributary watershed include: ■ High levels of metals, fecal coliform bacteria, nutrients, and turbidity in storm flows in most streams. X0011592.112 R. W Beck 6-17 SECTION 6 ■ High levels of fecal coliform bacteria, elevated temperatures, and low levels of dissolved oxygen in base flows in most streams. ■ Stream bank erosion and sediment deposition. ■ The introduction of low-oxygen groundwater into the Valley area streams contributes to the low levels of dissolved oxygen (Yake, 1985). Metro has collected Springbrook Creek water quality data (Station 0317) near SW 16th Street since 1977. Of 44 streams surveyed during base flow by Metro in the Puget Sound area, Springbrook Creek consistently has had one of the most degraded water quality conditions (Metro, 1989). When compared to the other streams monitored, Springbrook Creek had the lowest dissolved oxygen and third highest level of fecal coliform. Turbidity, conductivity, total phosphorus, solids, and ammonia values also were very high. The SWU Comprehensive Plan indicates that Springbrook Creek is the most severely polluted water body in the City and degraded during both dry and wet weather conditions. However, it is important to recognize that water quality is severely degraded as Springbrook Creek enters the City of Renton from the City of Kent. Water quality does not appear to change significantly as Springbrook Creek flows through the Valley area. The lack of further degradation may be due to the treatment of stormwater provided by the Panther Creek Wetland (HDR, 1995). In compliance with Section 303(d) of the Clean Water Act, Washington State DOE has listed Springbrook Creek as not meeting state surface water quality standards for the following: ■ Fecal Coliform. ■ Temperature. ■ Dissolved Oxygen. ■ Sediment Bioassay. ■ Cadmium. ■ Copper. ■ Mercury. ■ Zinc. Recent studies of the Springbrook Creek, Mill Creek (Kent), and Garrison Creek (Kent) watersheds have also demonstrated that temperature, dissolved oxygen, and metals concentrations can exceed lethal limits for salmonids. Additionally, aquatic insect numbers and their species diversity are low throughout the lower reaches of these stream systems (Harza, 1995). Table 6-6 (excerpted from the SWU Comprehensive Plan, HDR, 1995) provides a summary of Springbrook Creek water quality upstream of the Valley area (as measured in Kent near the City limits) and the Metro station at the SW 16th Street bridge. Four parameters consistently do not meet the Department of Ecology water quality standards or guidelines: phosphorus, dissolved oxygen, 6-18 R. W. Beck X0011592.112 CURRENT CONDITIONS turbidity, and fecal coliform bacteria. Although the temperature standard was exceeded only a few times during the 6 years of record, the City of Kent collected samples at the station noted early in the morning. Since water temperatures are cooler in the morning than later in the day, it is likely that the temperature standard may have been exceeded more frequently than was observed. Table 6-6 also suggests that the water quality standards are exceeded for zinc, copper, and lead. However, a comparison of historic data with standards is misleading in that the standard is for dissolved metal, whereas the historic data consist of tests for total metals (HDR, 1995). Studies by the Department of Ecology suggest that some of the low dissolved oxygen problems may be due to the influx of low-oxygen groundwater (Yake, 1985). In addition, the lack of gradient, low velocities, and lack of instream structure (i.e., woody debris) in the constructed channel sections inhibit re-aeration. Lack of riparian cover contributes to the temperature problem (R. W. Beck, 1993). Metro data also show consistently high levels of turbidity, conductivity, total phosphorus, solids, ammonia, and metals contamination in Springbrook Creek. The annual baseflow ammonia loading from Springbrook Creek to the Green River was the highest of all Metro sites monitored (Metro, 1989). Zinc concentrations (126 ppm) in sediment samples taken from Springbrook Creek in 1987 were the second highest of all 20 samples taken by Metro in its annual stream survey (Metro, 1989). In 1986, the sediment concentration of cadmium (2.6 ppm) was six times higher than that in any of the other 19 stream samples. The major historical source of zinc appears to have been sediments that have since been removed from the creek at the upstream Western Processing site in Kent (HDR, 1995). The Western Processing site is located upstream on Mill Creek in Kent. This site has been designated as an EPA Superfund site and will be cleaned up over several years. Recent data have documented high levels of zinc and cadmium contamination in sediments in Mill Creek (Converse, 1989). Mill Creek is a tributary of Springbrook Creek, representing approximately two-fifths of the entire ESGRW. These high levels of upstream contamination represent a significant source of concern for the basin. An additional problem for Springbrook Creek is the hydrologic disconnection of some Valley wetlands from the channelized portions of the stream system. This disconnection means that pollutants entering the stream channels are not being adsorbed and/or biofiltered by the remaining wetlands as would have occurred in an undisturbed system. Some sediment sampling within the Valley area has been conducted. The sampling done indicates that sediments can be contaminated. Sampling along Springbrook Creek channel suggests that total petroleum hydrocarbons (TPH) concentrations exceed soil cleanup levels, thus requiring treatment (e.g. on-site bioremediation) or restricting disposal of these sediments, if dredged, to an approved landfill (R. W. Beck, 1993). Compared with 22 sediment sampling x0011592.112 R. W. Beck 6-19 SECTION 6 stations in western King County, Metro's Springbrook Creek sampling location at SW 16th Street was sixth highest for copper, had less than average for lead, but was the highest for zinc. However, the Metro station may not properly reflect overall sediment conditions in Springbrook Creek because the percentage of fines at SW 16th Street sediment sampling station is lower than other sampled locations (Renton/Kent city limits and BRPS floodwater storage pond entrance) and there appears to be a general relationship between the percentage of fines and sediment quality (HDR, 1995). Fine sediments tend to adsorb more pollutants because of their large surface area. 6.6.2.3 SEDIMENTATION AND EROSION Water quality in the ESGRW reflects the rapid conversion from predominantly rural, forest, and agricultural land uses to urban, industrial, and commercial development. Residential construction in the Valley hillside and plateau areas is thought to have accelerated erosion and sedimentation in essentially all tributaries. Downcutting is evident in the upper 1 to 1.5 miles of Panther Creek where stream gradients reach as high as 15 percent. Similar conditions exist in the upper Springbrook Creek channel where channel gradients also exceed 15 percent. Localized erosion problems have also occurred at some storm drain outfalls and along portions of Springbrook Creek having high velocities, particularly in the area upstream of SW 16th Street. Current sediment loads generated within the BRWQMP study area were estimated as part of the BRWQMP. Based on current land use, existing sediment loading due to soil erosion and washoff is estimated at approximately 750 tons per year (R. W. Beck, 1993). 6.6.2.4 FLOOD-RELATED WATER QUALITY PROBLEMS As previously mentioned, recurrent flooding in the Valley area is extensive. Water quality problems arising from frequent flooding are related to various circumstances, such as the inundation of stored materials, including toxicants, that may be released and enter into flood flows. Flood waters may also carry away contaminated soil from commercial or industrial activities or from improperly stored waste products. Other flood-related impacts to water quality that occur within the basin include those associated with stream channel vertical erosion (incision) combined with lateral erosion and sediment deposition. These processes result in high turbidity and suspended solids, negatively affecting in-stream beneficial uses, including fish and other aquatic habitat, fish spawning, and aquatic plant productivity. 6-20 R. W. Beck X0011592.112 CURRENT CONDITIONS 6.7 WETLANDS Historically, wetlands covered most of the Green River Valley floor. These wetlands were all part of the same ecosystem. In the past 80 years, however, major flood control projects (i.e., levees, Howard Hanson Dam, drying up of the Black River), and the incremental filling and development of wetlands have eliminated or reduced many wetlands and fractured the ecosystem. This section provides a description of the existing functions and values of the remaining wetlands within the Valley area and provides a brief summary of wetland category designations in accordance with the City's Wetland Management Ordinance. A majority of the wetland resources within the Renton city limits is located within the Valley area. The Valley area contains 54 inventoried wetlands totaling approximately 292 acres (see Figure 6-7 of this document and Volume 2, Appendix A-2 of the draft Plan and EIS (Renton, 1996)). 6.7.1 CITY-COO RDI NATE D WETLAND INVESTIGATIONS Wetlands within the study area were originally mapped and subsequently updated as part of separate City-coordinated inventory projects. The initial mapping was done in 1981 (Renton, 1981) and again in 1991 (Jones & Stokes, 1991) to respond to Growth Management Act mandates. The 1991 study catalogued information about each wetland such as wetland type, size, dominant species, habitat quality, whether the wetland is inundated year-round or seasonal, flow pattern, and hydrologic connection. The inventory also provided an evaluation of wetland functions and values. These functions and values are important when considering potential impacts on wetlands from proposed flood reduction alternatives and when developing appropriate mitigation strategies. Since the original wetland inventory was completed, the City has made two updates in the mapping and inventory information in 1992 (R. W. Beck, 1993) and 1996 (Jones & Stokes, 1996). The updates incorporated new or revised information, such as site-specific wetland delineations made in accordance with the City's Wetland Management Ordinance. The ESGRWP study includes the most recent 1996 wetland information. 6.7.2 WETLAND FUNCTIONAL VALUES This section contains a general description of the wetlands and wetland functional values within the Valley area. The existing Valley area wetlands are illustrated on Figure 6-7. A table in Volume 2, Appendix A-2 of the draft Plan and EIS (Renton, 1996), provides a general description of each Valley area wetland. Wetlands within the study area provide a variety of functional values, depending on a number of factors, including, but not limited to, size, location of the wetland in the watershed, the type and amount of vegetation, and the proximity of the wetland to stream corridors. If a wetland will be affected by possible flood x0011592.112 R. W. Beck 6-21 SECTION 6 control solutions, its existing functional values must be assessed in detail so that if mitigation is proposed, the field values in the replaced wetland can be duplicated. The functional values provided by Valley area wetlands are discussed in the following paragraphs and are based in part on the Federal Highway Administration Wetland Functional Assessment Method (Adamus, 1983). 6.7.2.1 GROUNDWATER DISCHARGE AND RECHARGE The groundwater discharge function of a wetland helps to maintain a high water table in wetlands and contribute water necessary to maintain streams during dry months. Groundwater recharge can replenish groundwater supplies to the underlying aquifers. It is difficult, however, to predict recharge and discharge from the physiographic setting of the wetland; more detailed hydrogeological studies are usually necessary. Certain wetlands contribute significantly to recharging regional groundwater. The majority of hydrologists believe, however, that most wetlands in areas where glaciation has occurred (such as the Northwest) do not recharge aquifers (Erwin, 1990). Wetlands may, however, recharge shallow or perched lenses of groundwater that, in turn, discharge to streams. Many of the wetlands along Springbrook Creek act both as recharge and discharge sites, depending on the season. During high water periods, wetlands store overbank flows and recharge local groundwater. During low flow periods, the wetlands act as discharge sites, helping to maintain stream flow in Springbrook and Panther creeks. 6.7.2.2 FLOOD STORAGE Wetlands can reduce peak storm runoff rates by temporarily storing and then slowly releasing stormwater. Such attenuation of flood flows results in lower peak runoff rates occurring for longer durations. The flood storage value of a wetland varies with factors such as size, topography, the hydraulic connection to the drainage system, location within the watershed, soils, surrounding land uses, and the type and amount of vegetation present. 6.7.2.3 SHORELINE ANCHORING Wetland vegetation binds shoreline and streambank sediments with root systems, thereby anchoring the substrate. Additionally, above-ground vegetation reduces velocities and turbulence during overland flows, which helps to minimize erosion. 6.7.2.4 WATER PURIFICATION Wetlands can purify water through a variety of mechanisms. The low current velocities in wetlands cause sediments, metals, and certain chemicals to be deposited. Once in the wetlands, mechanical, chemical, and biological processes can remove certain pollutants from the water column. The ability of a wetland to perform this function is based on a number of factors, such as residence time of 6-22 R. W. Beck X0011592.112 CURRENT CONDITIONS the water in the wetland and the type and density of vegetation. Wetlands that are densely vegetated with emergent plants have the ability to trap sediments and take up pollutants in the water. Biofiltration is particularly important when a wetland discharges into a watercourse. This function is also highly dependent on the relationship of the wetland to surrounding water bodies. Wetlands that receive significant quantities of pollutant-laden water, either through stormwater input or overbank flood flow, possess a high water purification potential. 6.7.2.5 FOOD CHAIN SUPPORT Wetlands can be highly productive ecosystems that are used by numerous species for nesting, spawning, rearing, and feeding. Primary productivity is usually high in wetlands, and is generally highest in emergent wetlands that contain water year-round because they support fast-growing plant species. Wetlands trap and store nutrients, thereby providing a constant source of nutrients for release over time. This prolonged release of nutrients creates conditions that support intricate food chains, high species diversity, and long, complex life cycles. These conditions are predominant in mature wetlands (Erwin, 1990). 6.7.2.6 WILDLIFE HABITAT Many bird, mammal, amphibian, and reptile species depend on wetlands for all or part of their life cycle. The wildlife habitat value of a wetland depends, in part, on the structural and species diversity of plant communities, the proximity of desirable upland habitat, and surrounding land uses. 6.7.2.7 FISH HABITAT Some wetlands are important sources of food and habitat for fish species. In many urban streams, fish use is limited due to degraded water quality, lack of suitable habitat diversity, and inconsistent flows. 6.7.2.8 ACTIVE AND PASSIVE RECREATION, HERITAGE, AND EDUCATION Wetlands can provide valuable opportunities for recreation and education, such as bird watching or natural system studies. 6.7.3 WETLAND MANAGEMENT ORDINANCE CATEGORIES This section contains a brief summary of the Valley area wetlands and their designated categories as defined by the City's Wetland Management Ordinance. Chapter 6 of the draft EIS (Renton, 1996) contains a detailed definition of wetland categories. In general, three wetland categories are defined using a wetland rating system based on plant communities, habitat diversity, degree of disturbance, and wetland size. Category 1 wetlands are the highest value wetlands. Category 2 wetlands are the second highest value wetlands. Category 3 wetlands are generally defined as wetlands that are severely X0011592.112 R. W. Beck 6-23 SECTION 6 disturbed or newly emergent, (e.g., a wetland occurring on top of previously placed fill material). 6.7.3.1 CATEGORY 1 WETLANDS Of the 19 wetlands potentially affected by the flood control measures being considered, three are Category 1 wetlands (Panther Creek Wetland, W-7N and W- 12a). Panther Creek Wetland (59 acres), also known as Wetland W-4, is the largest wetland within the project area. This wetland is located east of SR-167 and is a mix of forested, open water, scrub-shrub, and emergent wetland. The dominant vegetation in the southern portion of the southern portion of the wetland is reed canarygrass, willow, and cattails. During storm events, Panther Creek discharges a portion of its flows into the south end of the Panther Creek Wetland. Wetland W-7N is 12 acres in size and located between SW 19th Street on the north and SW 21st Street on the south and immediately west of East Valley Road. The wetland has a high diversity of vegetative types. Wetland W-12a (also known as the Renton wetland), which is approximately 22 acres, lies west of Springbrook Creek. The wetland is physically separated by a berm from W-12b, a Category 2 wetland, but they are hydraulically connected by an 18-inch culvert through the berm. Vegetation includes willow, hardhack, and cattails, with areas of open water in W-12a. 6.7.3.2 CATEGORY 2 WETLANDS Six Category 2 wetlands are potentially affected by the flood control measures (W-8N, W-10N, W-10S, W-11, W-12b, and 13Sj) and range in size from 2.9 to 24 acres. Wetlands W-10N, W-10S, and 13Sj total 22.4 acres and include dense willows, cattails, and open water (13Sj). Vegetation in wetlands W-8N, W-11, and W-12b include cattails, willow shrub, and hardhack. 6.7.3.3 CATEGORY 3 WETLANDS The remaining 11 wetlands (W-9a, W-13Na, W-13Nd, W-16a, W-16b, W-32, W-48d,e,f, W-49, and W-53) potentially affected by project alternatives are Category 3 wetlands. Wetland 32 is 6.7 acres and lies on fill west of Springbrook Creek, with vegetation including reed canarygrass, blackberry, cottonwoods, and shrubs. The site is scheduled to be used as a wetland mitigation bank site for public and private projects that will need off-site wetland mitigation. Wetland W-48 is a narrow linear wetland/roadside ditch that lies immediately west of SR-167. Vegetation includes cattails, willows (trees and shrubs), and reed canarygrass. The wetlands in the project area may be subject to regulations set forth in Section 404 of the Clean Water Act (33 CFR Parts 320 through 330). The City of Renton has adopted the 1987 U.S. Army Corps of Engineers (Corps) Wetlands Delineation Manual for use in delineating wetlands (Department of the Army Environmental Laboratory 1987). 6-24 R. W. Beck X0011592.112 CURRENT CONDITIONS 6.7.4 CITY WETLAND OWNERSHIP The City of Renton presently owns or has easements over the Black River Riparian Forest (Wetland W-5), the Renton Wetland (Wetland W-12), the majority of the Panther Creek Wetland (Wetland W-4) located east of and adjacent to SR-167, Wetland W-32 (Wetland Mitigation Bank Site), and portions or all of Wetlands W-3, W-5a, W-7N, W-8N, W-9a, W-10N, W-11, W-16a, W-16b, W-22, W-45, and W-54. The City is seeking to obtain ownership/easement of the entire Panther Creek Wetland. 6.8 FISH AND WILDLIFE 6.8.1 FISH AND WILDLIFE INVESTIGATIONS Information gathered on Valley area fish and wildlife was taken from several sources. The most in-depth study of the area fish resource was done as part of the Comprehensive Fisheries Assessment of the Mill Creek, Garrison Creek and Springbrook Creek System (Harza, 1995). Other information sources include a habitat inventory completed as part of the BRWQMP (R. W. Beck, 1993), the King County Basin Planning Program's Black River Reconnaissance Report (King County, 1987), previous Metro studies, and a study on the existing fish use in Panther Creek (R. W. Beck, 1989). 6.8.2 FISH 6.8.2.1 SPRINGBROOK CREEK The discussion of the existing fish resource in Springbrook Creek focuses on fish habitat and fish passage. Springbrook Creek within the study area does not provide suitable habitat for adult spawning because suitable spawning substrate does not exist and water quality is poor. Springbrook Creek through the Valley area (and upstream in the Kent Valley) is a low gradient stream. Residential construction on the Valley hillside in the watershed has led to increased runoff and is thought to contribute to erosion of hillside ravines draining to the Valley floor. While the remaining currently accessible fish spawning areas exist in the upper tributaries, including Mill Creek (Kent), Garrison Creek (Kent), and Springbrook Creek (Kent), sediment build-up in the lower reaches of these systems and along the Valley floor combined with poor water quality eliminates these lower reaches for spawning. Such problems are documented in the King County Basin Planning Program's Black River Reconnaissance Report (King County, 1987). The Comprehensive Fisheries Assessment of the Mill Creek, Garrison Creek, and Springbrook System (Harza, 1995) included an in-depth study of water quality impacts on the fish resource. Historical data and data collected as part of the study were reviewed and compared with acute concentrations, which are lethal X0011592.112 R. W. Beck 6-25 SECTION 6 to fish, and concentrations that would impair or stress fish. Harza also characterized habitats throughout the watershed, conducted fish and macroinvertebrate population surveys and analysis, made an assessment of factors limiting salmonid production and created detailed recommendations for preserving and restoring of the fisheries resource in the watershed. Some of the major findings include the following: ■ Water samples taken during the 1994 upstream migration fish run indicated that dissolved oxygen levels at low flows were often below the lethal limit to fish. Dissolved oxygen levels were marginally acceptable for adult salmon during the period of upstream passage and would seem to be one of the most likely reasons inhibiting fish from reaching spawning areas. ■ Water temperatures at low flows are higher than optimal conditions. ■ Levels of metals can be high and in some instances may be acutely toxic to fish. ■ Macroinvertebrate densities are low throughout the watershed and types of macroinvertebrates found in the low gradient habitats indicate poor water quality. The abundance, type, and diversity of macroinvertebrates is also limited by the streambed movement, as the low diversity and lack of long- lived macroinvertebrates seems to suggest. ■ Streams in the watershed have very little instream structure (i.e., woody debris) or pool habitat. Riparian habitat is also poor in many reaches. ■ Based on capture of a fry-sized coho in the system before WDFW stocked Mill Creek in 1994 indicates some natural reproduction, but the number of spawning fish is very low. In summary, all of these data suggest that poor water quality is likely responsible for the mortality of salmon in the lower gradient Springbrook Creek system and is likely one of the factors limiting the ESGRW fish resource (Harza, 1995). Given the extremely low levels of dissolved oxygen in the summer and fall, Harza rejects the premise that the low gradient habitat is a suitable passageway to the upland spawning habitat, unless dissolved oxygen levels are raised by passive or active mechanical reaeration. The streamside corridor of Springbrook Creek supports a mixture of shrubs and grasses. Landowners, however, have landscaped their property adjacent to the stream banks in certain sections. The overstory canopy is restricted in most reaches through the Valley area, leaving the stream surface open to solar insolation. The open nature of the lower stream section and the BRPS forebay also provides prime foraging sites for large fish-eating birds such as great blue herons. With little available cover, rearing salmonids become susceptible to heavy losses from predation by herons and other predators. However, a section of Springbrook Creek downstream from Grady Way is developing an overstory that provides thermal protection for most of the day and the section from 6-26 R. W. Beck X0011592.112 CURRENT CONDITIONS SW 16th Street to just north of SW 23rd Street has an excellent riparian area with larger trees and provides good thermal protection. Springbrook Creek within the Valley area passes through several culvert crossings and bridges before reaching the BRPS. Fish passage through these structures and along the creek within the Valley is not currently a problem during most conditions. During flood flows, upstream passage would be temporarily restricted or prevented by high water velocities in the short reach upstream of SW 16th Street and through existing culverts. Downstream and upstream salmonid fish passage was incorporated into the BRPS, operated by King County. Fish can pass upstream via a fish ladder and a supply pump and downstream via an air lift system. Detailed descriptions of the fish passage facilities at the BRPS are contained in the Comprehensive Fisheries Assessment (Harza, 1995). Upstream fish passage is normally operated from mid- September through January 31. Downstream migration is normally operated from early April to mid-June for about 8 hours a day. While the pump station does provide for upstream/downstream migration, the Comprehensive Fisheries Assessment included minor modifications to improve its effectiveness for fish passage. The BRPS is equipped with a fish counter that counts upstream migrating fish. The number of fish that passed through the BRPS facilities between 1983 and 1996 is shown in Table 6-7. Coho salmon fry (those under a year old) were stocked into Mill Creek (Kent) as early as 1976 by the Washington State Department of Fish and Wildlife (WDFW). Between 1981 and 1992, an average of 96,000 coho fingerlings was released into Mill Creek annually. In 1992, after fish production potential in Mill Creek was analyzed, the WDFW decided to limit the number of fish stocked in Mill Creek to 50,000 annually. The fish are placed in various locations along Mill Creek in Kent (Harza, 1995). Since 1995, coho have also been stocked in Springbrook, Garrison, and Panther creeks. Without suitable spawning habitat and questionable rearing capacity due to degraded water quality, especially during the warm summer months, lower Springbrook Creek offers little in the way of fish habitat within the study area. Upstream of Renton, however, Springbrook Creek and its tributaries, Mill Creek and Garrison Creek, contain habitat conditions suitable for salmonid spawning and rearing. In that respect, lower Springbrook Creek serves as an essential link between the Green River and headwater spawning grounds. The lower reaches of Springbrook Creek should be managed so that they continue to serve in that vital capacity. The Comprehensive Fisheries Assessment contains several recommendations for improving the fish resource within the watershed. The study's general recommendations that pertain to the Valley area drainage system include the following: ■ Stabilize stream channels and create instream or side channel pool habitat. X0011592.112 R. W.Beck 6-27 SECTION 6 ■ Minimize dredging in the low gradient portion of the watershed to decrease turbidity. ■ Improve water quality for the entire watershed with emphasis on dissolved oxygen, temperature, high turbidity, and heavy metal concentration. 6.8.2.2 PANTHER CREEK A specific investigation of the fish resource in Panther Creek was completed in 1989 by the Watershed Company (R. W. Beck, 1989). This evaluation was supplemented with field visits and a review of Panther Creek flow data since 1989. In general, few fish are expected to be present in Panther Creek. Reasons for this conclusion include both habitat problems (i.e., streambed movement, sedimentation) and upstream and downstream migration blockages throughout the system. Habitat would generally be reduced due to low base flows. A review of the data for the Panther Creek gage installed at the Talbot Road crossing shows an average flow of 1.9 cfs during the spawning seasons (October and November) between 1991 and 1994 (King County, 1995). The average flow during the outmigration (approximately April through June) for this same period was 1.3 cfs. Fish passage is limited due to several natural (e.g., low base flows, braided channels through an alluvial fan, and entrapment in the Panther Creek wetland) and constructed (e.g., long pipes and large vertical drops) barriers. There is a 3- to 4-foot drop at the outlet of the Talbot Road culvert crossing. From there, Panther Creek flows downstream through an alluvial fan at the base of Talbot Hills. Through the alluvial fan the channel becomes braided and likely loses water to infiltration into the alluvial streambed. During very low flows, creek flows extend west to two culverts crossing SR-167. These culverts discharge to a short drainage channel connecting to an approximately 3,000-foot-long pipe system along the East Valley Road and SW 34th Street to Springbrook Creek. Fish passage through a long section of pipe like this is possible, but not desirable. During flood flows, Panther Creek exceeds the capacity of these culverts and overflows into the Panther Creek wetland or into the ditch/wetland that runs along the west side of SR-167. In addition, at least one of the braided channels in the alluvial fan carries flow north directly into the Panther Creek wetland. The braided channel that extends into the wetland eventually loses its channel shape, and water being carried by the channel spreads into a sheet flow through dense vegetation. During a period of moderately heavy rain on February 6, 1996, one- tenth of the flow was estimated to pass directly into the wetland while one remainder likely reached the SR-167 culvert crossings. Any downstream migrating fish would not be able to migrate through the Panther Creek wetland as water flows in a sheet flow pattern through dense vegetation. Upstream of Talbot Road, the 1989 study identified the following passage barriers: ■ Some debris jams posing potential or partial barriers between Talbot Road S to SW 179th Street (Carr Road). 6-28 R. W. Beck X0011592.112 CURRENT CONDITIONS ■ A 12-foot-high series of cascades over rocks and debris just downstream of the SW 179th Street culvert. ■ A 12-foot-high waterfall about 100 feet upstream of SW 179th Street formed by an earthen berm and concreted channel section, apparently the outfall of a now silted-in pond. Even though anadromous fish do not have access to Panther Creek at this time, areas of Panther Creek are suitable for spawning. However, conditions observed during field studies indicate that spawning and rearing habitat restoration measures would be needed in addition to restoring access if the creek were to support a viable, self-perpetuating fishery. The 1989 investigation included a fish use sampling program using electrofishing methods from SR-167 to Panther Lake. The locations, dates, and catches are presented in Table 6-8. The Comprehensive Fisheries Assessment contains recommendations for improving passage and habitat in Panther Creek (Harza, 1995). As indicated in Table 6-8, the fish use of Panther Creek was fairly low —only one adult trout and three trout fry were captured in the creek. The trout fry were an indication that at least some successful trout spawning occurred near or upstream of that point during the previous spawning season. The lone, large rainbow trout captured is not typical of such small streams, and probably traveled downstream from Panther Lake or other ponds in the system. More recently (1995), while conducting some survey work in several Green River tributaries, the Muckleshoot Fisheries Department surveyed a short 25-foot reach of Panther Creek near where the creek crosses 108th Avenue (King County, 1995a). One coho fry was recovered by electroshocking; other fry were also observed. In 1995, the WDFW began planting coho fry in the upper reaches of Panther Creek. A total of 9,328 coho fry were planted into Panther Creek and 14,575 planted into Panther Lake. The WDFW also planted 6,100 rainbow trout in Panther Lake in 1995 (King County, 1995a). King County classifies Panther Creek in its jurisdiction as a Class 2 stream with salmonid use, requiring a 100-foot buffer on each side of the stream, as measured from the ordinary high water mark. 6.8.2.3 ROLLING HILLS CREEK There is no evidence of fish use in Rolling Hills Creek, except for possibly resident fish farther up in the system as reported by residents (see BRWQMP WDFW comment letter in Section 19; R.W.Beck, 1993). X0011592.112 R. W. Beck 6-29 SECTION 6 6.8.3 WILDLIFE Great blue herons have historically nested in trees adjacent to the constructed BRPS floodwater storage pond. Sediment bars in the flood storage pond are used as feeding areas by the herons. In 1990, 28 nesting herons were counted in this rookery by the Seattle Audubon Society (G. Adams, 1990; personal communication). Fewer nests have occurred in recent years. The Black River wetland (Wetland Inventory No. W-5), floodwater storage pond, and Panther Creek wetland also provide habitat for shorebirds and migratory waterfowl. Bird counts conducted by the Seattle Audubon Society indicate that more than 30 species of birds, including bald eagles and great-horned owls, have been observed in the Black River wetland area. Small mammals, including weasels, rabbits, opossums, and raccoons, have also been sighted (G. Adams, 1989; S. Krom, 1990). A detailed listing of avifauna, mammals, reptiles,amphibians and vegetation for the Black River wetland has been compiled for the Renton Parks Department with the assistance of the Seattle Audubon Society and Renton Citizens for Wildland Preservation. Work on collecting more information on habitat and wildlife use in the Black River wetland area is ongoing. A citizens group, the Friends of the Black River, is taking an active role in the stewardship of the Black River wetland and its adjacent and connecting habitats. The high levels of metal contamination found in sediments in Springbrook Creek are a concern for wildlife. The concentrations measured by Metro (1988, 1989) suggest that the potential feeding and foraging habitat present in Springbrook Creek and the ESGRW may be impaired. Some beaver activity has occurred on Springbrook Creek. King County Drainage District No. 1 periodically inspects the channel. If beaver activity threatens to reduce flow conveyance capacity of the system, the District arranges for the beavers to be live-trapped and given to the State Department of Fish and Wildlife for transplanting in remote areas of western Washington. Riparian habitat along Springbrook Creek south of SW 23rd Street is sparse, with non-native reed canarygrass and Himalayan blackberry being the dominant cover. The low diversity riparian habitat is generally poor for wildlife. More detailed wildlife and habitat information for the Boeing Longacres Office Park and surrounding valley area can be found in the Boeing Longacres Environmental Impact Statement (Jones &Stokes, 1994). Wildlife of the Panther Creek wetland were previously described in a series of wildlife monitoring reports from 1990 through 1993. In general, Panther Creek wetland supports a variety of small mammals,birds, and amphibians. Nine species of mammals, 48 species of birds, seven species of amphibians, and two species of reptiles have been recorded using the wetland (Beak Consultants, 1990, 1991; Jones & Stokes Associates, 1992; Shapiro and Associates, 1993). I 6-30 R. W. Beck X0011592.112 SECTION 6 TABLE 6-1 BLACK RIVER PUMP STATION PUMP CAPACITIES Rated Design Operation Pump Capacity(cfs) Power (On-Off) P-1 75 Electrical Automatic P-2,P-4 150 Diesel Automatic P-3, P-5, P-6, P-7,P-8 514 Diesel Manual TABLE 6-2 BLACK RIVER PUMP STATION ALLOWABLE PUMP RATES PUMP OPERATIONS AND PROCEDURES PLAN Measured Flows at BRPS (P 1) Maximum Allowable Auburn Gauge(cfs) Pumping(cfs) Less than 9,000 As required 9,000 2,942' 9,500 2,900 10,000 2,400 10,500 1,900 11,000 1,400 11,500 900 12,000 400 cfs to 0 cfs depending on levee monitoring by King County Director of Public Works or his/ her designee ' Installed capacity. Current nominal capacity of BRPS is 1,917 cfs. R. W. Beck X0011592.112 TABLE 6-3 Summary of Peak Flows and Water Surface Elevations Current Land Use Conditions FEQ Hydraulic Analysis (Elevation Datum NGVD) Road- 2-Yr Cur.Flow 10-Yr Cur.Flow 25-Yr Cur,Flow 25-Yr Cur.Flow 100-Yr Cur.Flow 100-Yr Cur.Flow way Top Conveyance(3) Storage(3) Conveyance(3) Storaae(3) Elev. Location/Discription Flow Elev Flow Elev Flow Elev Flow Elev Flow Elev Flow Elev (cfs) (feet) (cfs) (feet) (cfs) (feet) (cfs) (feet) (cfs) (feet) (cfs) (feet) Panther Creek u/s ofSR-167(1) 62 83 91 32 170 82 Rolling Hills Creek at Renton(1)(2) 68 20.4 88 20.7 94 20.8 34 19.6 167 21.8 87 20.7 Shopping Center Culv.Outlet Rolling Hills u/s 1-405 132"culvert(1)(2) 68 16.6 88 16.9 94 16.9 34 16.3 167 17.8 87 16.8 SR-167 north crossing 45 14.7 64 15.4 76 15.8 32 14.1 100 17.0 58 15.2 Springbrook Creek BRPS outflow 532 725 876 480 1044 1360 BRPS inflow 532 3.8 725 3.8 876 3.9 480 4.6 1044 4.1 1360 8.4 Floodwater Storage Pond Inflow 533 4.0 726 4.2 876 4.3 310 4.6 1044 4.5 734 8.4 Grady Way u/s 456 5.7 650 6.3 782 6.7 272 4.9 935 7.2 638 8.6 SW 16th Street 453 6.3 649 7.1 780 7.3 270 5.5 934 7.7 577 8.6 Confluence of Rolling Hills Creek 449 8.7 646 9.7 775 10.3 268 7.4 930 11.0 571 9.7 Confluence of SW 23rd St Channel 396 9.6 575 10.7 684 11.3 234 8.3 819 12.0 502 10.4 SW 27th u/s 17.9 385 10.3 571 12.0 681 13.0 227 8.8 825 14.2 492 11.4 SW 34th u/s 14.9 341 11.0 560 13.3 641 14.5 195 9.3 887 15.4 490 12.4 Oakesdale d/s 17.1 340 11.6 563 13.8 646 14.9 195 10.1 891 16.0 489 12.9 Oakesdale u/s 17.1 323 11.9 526 14.6 602 16.0 183 10.2 833 17.4 463 13.6 SW 43rd d/s 22.9 320 12.5 525 15.0 601 16.3 181 10.9 830 17.7 459 14.0 SW 43rd u/s 22.9 320 12.6 525 15.1 601 16.5 181 11.0 830 18.2 459 14.2 Notes (1)FEQ simulated flows at these locations are based upon frequency analysis of Springbrook Creek inflows to the BRPS forebay. Refer to ESGRWP Hydrologic Analysis Report(NHC, 1996) for flows based upon frequency analysis of Panther Creek and Rolling Hills Creek. (2)Flows are based upon assumption that capacity restriction through Renton Shopping Center is improved such that no attenuation from surface ponding occurs. (3)Conveyance event reflects a severe local rainstorm without pumping restrictions at the BRPS due to high Green River flows. Storage event reflects a high Green River flow event in which the BRPS must restrict pumping rates in accordance with GRIA. (4)u/s=upstream,d/s=downstream (5)Note that summary tables do not reflect wider SW 16th Street bridge opening and minor elevation adjustments at Oakesdale Avenue. See discussion of modeling in Section 8.3 of Plan. TABLE 6-4 Summary of Maximum Elevation and Durations Major Wetlands -- 2-Year Event Current Land Use Conditions (Elevation Datum NGVD) Wetland Inventory FEQ Wetland Hydraulic Current Flows Location Description Description Connection Maximum Elevation Duration (See Fig. 6-7) (See Fig. 6-4) Elevation(3) 1a(not used) 7N 1b 9.0(culvert to Rolling Hills Cr. does not Rollings Hills Cr.) (5) inundate wetland (6) 2 (not used) 8N 3 10.0(weir connected 11.8+/-(1) 3 hrs (1) 23rd Str. Channel) (10) 10 4 10.0(weir connected Springbook Cr. does not to Springbrook Cr.) inundate wetland 16 5 11.5 (weir connected Springbook Cr. does not to Springbrook Cr.) (10) inundate wetland 11 6 10.5(weir connected Springbook Cr. does not to Springbrook Cr.) (10) inundate wetland 12b 7A 10.0(weir connected 10.31 4 hrs (4) to Springbrook Cr.) (10) 12a 76 13.5(weir to 7A) (7) 13.60 (8) (2) 9.0(culvert to 7A) 10.5(9) (2) 13Sj 7C 10.1 (culvert to 7B) 13.61 (8) (2) 11.3(9) (2) 51 8 16.0(weir connected Springbook Cr. does not to Springbrook Cr.) inundate wetland 14 9 16.0(weir connected Springbook Cr.does not to Springbrook Cr.) inundate wetland 32 10 16.0(weir connected Springbook Cr.does not to Springbrook Cr.) inundate wetland 4 11 a 14.0 (weir connected 14.62 (2) to Rolling Hills Cr.) 4 1 1 b 13.5(culvert to 11 a) 14.55 (2) 4 11 20.3(weir to Panther Cr.) 14.55 (2) 13.5 (weir to 11 b) (10) 13Nb-Nd 12 (11) (11) (11) For notes see the following page. Notes For Table 6-4 (1) The maximum elevation for Wetland 8N is based on review of wetland crest gage data rather than FEQ model. The crest stage data is considered more reliable for this wetland because of a simplifying assumption used for the hydraulic analysis of the Panther Creek Wetland (PCW) and SW 23rd Street drainage channel. The FEQ representation included the assumption that there were only two functioning outlets for the PCW (crossing SR-167), the Rolling Hills Creek 36"x48" box culvert and the Panther Creek (24" and 30") culverts. The simulation does not include outflows from the series of poorly functioning SR-167 culverts between SW 23rd Street and SW 34th Street (that ultimately drain to the SW23rd Street drainage channel). Rather, the Rolling Hills Creek drainage system is modeled with a larger pipe size to account for the PCW outflows through this series of culverts. As a result, the simulated flows through the SW 23rd Street drainage channel and the maximum water surface elevation of Wetland 8N are likely undersimulated. The 11.8 elevation corresponds to a measured elevation during an approximate 2-year flood flow in Springbrook Creek (Dec. 1995). The FEQ simulation results give a maximum elevation of 10.08 and a duration of 3 hours. The FEQ simulation result for duration (3 hrs) is likely undersimulated as well but a short duration would be expected. The simulation of the PCW appears reasonable and is consistent with crest gage data records. (2) Inundation reflects local subbasin inflows rather than overflows from Springbrook Creek. Therefore, simulation reflects constant inundation from local inflows. (3) See R. W. Beck 1996a, Table 6, for more detailed information on hydraulic connections. (4) Based upon duration of Springbrook Creek flows above elevation 10.0. (5) An existing 12" culvert connects this wetland to the 60" storm drain conveying Rolling Hills Creek. This connection was not modeled in FEQ because of its negligible size. (6) Simulated elevation in 60" storm drain conveying Rolling Hills Creek is 9.2. This is near the elevation of the hydraulic connection to the wetland. However, the simulated elevation may be artificially high due to modeling approach (see note 1). Therefore, the creek would likely not inundate the wetland. (7) The berm between FEQ wetlands 7A and 7B is modeled as a weir. An existing 18" culvert passing through the berm at elevation 9.0 (City field book 641-60) was assumed not to be functioning because of its small size. Also, an initial water level of 13.5 feet was assumed for the existing system simulation in FEQ wetlands 7B and 7C. This was because the 18" culvert X011592.112 AUGUST 1997 R. W. Beck was severely choked by vegetation, sediment, and debris at the time the existing drainage system was being simulated. This is documented in the Hydraulic Analysis Report (R. W. Beck, 1996a). Since that time the culvert has been replaced (City File No. LUA-96-142,SME) with a new 18" culvert which is functioning at full capacity. (8) Simulated elevation assuming the 18" culvert between FEQ 7A and 713 is not functioning and assuming an initial water level of 13.5 in FEQ 7B and 7C (see note 7). (9) Elevation modeled using the King County backwater model program and flow information from the FEQ simulation, assuming the 18" culvert between FEQ 7A and 7B is functioning at full capacity. This elevation is used in the EIS impact analysis because it reflects current conditions more accurately as evidenced by recent crest stage gage data collected since the culvert was replaced (see note 7). (10) Wetland has known low flow outlet culvert(s) or shallow ditch below the modeled weir elevation. However, the low flow outlet was not modeled because of its small size and therefore insignificant capacity. (11) Simulation results for FEQ wetland 12 cannot be used in determining maximum 2-year elevation and duration data for wetland impact analysis of inventory wetlands W13Nb-Nd (the Boeing CSTC facility mitigation wetlands). This is because the FEQ model combines the CSTC wetlands with the northern portion of the Boeing Longacres Office Park, but assumes a single outfall located at about SW 21st Street on Springbrook Creek, a distance of about 2,000 feet upstream of the CSTC outfall. Also the CSTC wetlands were modeled assuming a 36" outlet based on preliminary plans available at the time the model representation of the wetlands was configured,but flows from the site are in fact controlled by an outlet control structure with an 18" outlet pipe installed when the CSTC facility was constructed. The outfall from the CSTC wetlands is only about 500 feet upstream of SW 16th Street. Given the promixity of the outfall to the previously widened channel reaches downstream of SW 16th Street and the controlling influence of the 18" outlet pipe, the maximum elevations and durations of flows in the wetlands W13Nb-Nd would be relatively unaffected by the channel widening of Springbrook Creek in the reach adjacent to the CSTC site or by other ESGRWP elements proposed farther upstream. R. W. Beck 10/30/% X1159121.801 CURRENT CONDITIONS TABLE 6-5 SUMMARY OF WATER QUALITY PROBLEMS SPRINGBROOK CREEK, PANTHER CREEK,AND ROLLING HILLS CREEK Problem Sediment Water Quality-Metals Water Quality-Fecals Water Quality- Water Quality-Other Habitat and Other Definition Quality Nutrients Physical Problems Panther Creek No problems High in storm flow;major High in base and storm High total phosphorus in High temperature in base Streambank erosion source is runoff from flow;high base flow levels storm flow likely caused flow potentially from solar problems reported in paved surfaces possibly due to in part by heavy sediment insolation at Panther upper 1.4 to 2.6 miles; malfunctioning on-site load(from construction Lake;high turbidity and culverts create barriers to wastewater systems,illicit sites),residential fertilizer suspended solids in storm fish at RM 1.95 and Talbot connections,and/or use,animal waste,and flows likely caused by in- Road;large organic debris leaking sewer lines; on-site wastewater stream erosion between dams create barriers to higher storm flow levels disposal RM 1.4 and 2.6 and fish between RM 1.8 and also may be influenced by erosion from land-clearing 2.55;erosion has other human activities activities eliminated most pools and such as agriculture and benthic organisms hobby farming between RM 1.8 and 2.55 Rolling Hills No problems High in storm flow; High in base and storm None observed High turbidity and Sedimentation at 22nd Creek observed major source is runoff flow,high base flow levels suspended solids in storm Court caused by upstream from paved surfaces possibly due to leaking flow probably caused by erosion due to drainage sewer lines;higher storm in-stream erosion and from Fred Nelson JHS has flow levels may also be erosion at construction damaged fish habitat in influenced by other sites;oil sheen frequently area;outfall at Benson human activities such as observed in upper section Road eroding stream bank agriculture and hobby of creek caused by farming unknown source(s) Source: Black River Water Quality Management Plan(R.W.Beck,1993) X0011592.112 R. W. Beck SECTION 6 TABLE 6-5 SUMMARY OF WATER QUALITY PROBLEMS SPRINGBROOK CREEK, PANTHER CREEK, AND ROLLING HILLS CREEK (CONTINUED) Problem Definition Sediment Quality Water Quality- Water Quality- Water Quality- Water Quality- Habitat and Other Metals Fecals Nutrients Other Physical Problems Springbrook Creek High total organic High zinc in base flow High in base flow;high High total phosphorus Elevated temperature Little vegetative cover; (in Valley area) carbon,metals,and caused by unknown base flow levels in base and storm and low dissolved deposition of sediments total petroleum source(s)upstream of probably due to flows;source of oxygen during base transported from hydrocarbons; study area;all metals malfunctioning on-site elevated concentrations flows worsened by lack streams draining the numerous industrial/ elevated in storm flow; wastewater systems in base flows may be of vegetative cover;low plateau has damaged commercial facilities, source includes runoff upstream of subbasin, both natural and result flows result from long- fish habitat and benthic two known from paved surfaces or leaking sewer lines of malfunctioning on- term increase of organisms contaminated sites,and with significant loading or illicit connections; site wastewater systems impervious surface 11 spills involving from upstream of study higher storm flow upstream of subbasin coverage and loss of oil/petroleum and area levels may be or leaking sewer lines; wetlands in basin;high hazardous materials influenced by other source of high levels in turbidity and reported in 1990-91 in human activities such storm flows probably suspended solids in basin could contribute as agriculture and also includes fertilizer storm flow probably to sediment hobby farming application and erosion caused by upstream in- contamination from land-clearing stream bank erosion activities and erosion from construction sites Source: Black River Water Quality Management Plan (R.W.Beck,1993) R. W. Beck x0011592.112 CURRENT CONDITIONS TABLE 6-6 MAINSTREAM SPRINGBROOK CREEK— UPSTREAM/DOWNSTREAM WATER QUALITY Kent Station Near Metro Station at Ecology Parameter Renton City Limits 16th Street Bridge Standard Temperature (°C) 11.5 10.9 <18 Dissolved oxygen (mg/1) 6.8 6.4 >8 Fecal coliform(mg/1) 254' 534' <1002 Suspended solids (mg/1) 30 34 NA Turbidity (NTU) 37 26 <53 Ammonia(mg/1) 0.50 0.34 1.5-2.44 Total phosphorus(mg/1) 0.24 0.21 <0.055 Total zinc(mg/1) 0.140 0.100 <0.052-0.0946 Total copper(mg/1) 0.014 0.010 <0.006-0.0106 Total lead(mg/1) 0.016 0.020 <0.0009-0.0026 Source: Draft SWU Comprehensive Plan (HDR Engineering, 1995) 1. Geometric mean,arithmetric means for other parameters. 2. With 10% of the samples not exceeding 200 organisms/100 mis. 3. Turbidity cannot increase more than 5 units above background when background is 50 NTU or less. 4. Chronic criterion varies with temperature and pH. 5. Not a standard but a guideline. 6. Chronic criteria for the dissolved metal at a hardness of 50 to 100 mg/l(as CaCO3). See Volume 2-Appendix A-3 for a more complete description of Ecology standards. See Draft SWU Comprehensive Plan (HDR Engineering, 1995) for additional information about the sampling program. x0011592.112 R. W. Beck SECTION 6 TABLE 6-7 NUMBER OF SALMONIDS PASSING BLACK RIVER PUMP STATION 1983-1996 Period Number of Salmonids 1983- 1984 155 1984- 1985 119 1985- 1986 47 1986- 1987 82 1987- 1988 166 1988- 1989 95 1989- 1990 77 1990- 1991 70 1991 - 1992 291 1992- 1993 107 1993- 1994 120 1994- 1995 268 1995 - 1996 355 1996- 1997 206 Average 154 R. W. Beck x0011592.112 CURRENT CONDITIONS TABLE 6-8 PANTHER CREEK(WRIA 09-0006) ELECTROFISHING SUMMARY Date Reach Location No. Species Length Range 5/V89 Panther Creek between the 1 Rainbow Trout 15 inches wetlands upstream of SR-167 and (Oncorhynchus mykiss) Talbot Road 3 Trout Fry 1 inch (O. mykiss or O. clarkt) 3 Sculpins 2.5 to 3.75 (Cottus spP.) inches 1 Black Crappie 1.75 inches (Pomoxis nigromaculatus) 5/2/89 Panther Creek between its mouth 11 Threespine sticklebacks 0.5 to 2.25 at Springbrook Creek to the East (Gasterosteus aculeatus) inches Valley Road 5/2/89 Panther Creek along 106th Ave No fish captured or SE, north of SE 192nd Street observed Source: R.W. Beck, 1989 X0011592.112 R. W. Beck East Side Green River Black River King County I Watershed Boundary Water Quality �• Management Plan '•••0060.�' �•� .......... Study Area ,l ,,�' `� �•. �� ♦ 1 .010 ♦ L ••� • ♦♦♦ •�� ' ��.�'� Glee `-----•''� —•—."7 j �"'. `..•.: ♦♦j i Panther Lake I I • ��,• j Q I I I _ �,� •' �'—"I King Count Garrison i i .• 405 I — �� Renton, Creek Renton i j Ln ��► I - -t King County r-j I �.• r' ••.� . Springbrook •fir. C.—._._ L._._,_.J ,� ,..... r Valley Area 167 Kent •� L • �iiiiiiiiii�i �• 7 Springbrook Creek East Valley Road i ✓��1 1 Springbrook r co Creek 167 I Renton Mill O • —.—._ �-- - - - �•� Tukwila 17 cree/r ; I `. , .• i een Kent Black River TUk 161 181 I — i� Pump Station ; u wjlo j 7 j N L._...1 N Kent , Tukwila l� Kent r- - � ` Lagoons �•�� 1 /1 f.� f..,. r� 1 ` lid- ■ �� r`♦ o I EAST SIDE GREEN RIVER `� er WATERSHED PROJECT UI-5 o 3000 s000 FIGURE 6-1 APPROXIMATE SCALE IN FEET PROJECT AREA Black River �- N Pump Station Renton ^ SO1 b Hitla-- 'hzl5utary l`-r 0 ; Tukwila 4 ." r' I 10 S 1 soth t I Unincorporated King County 167 Panther Lake - r > L r lr, 7% r � i Kent /Z La oones oN - l , Kent "1 r- LEGEND Commerciall' _I S Multi—family "^ High Density Residential �� I Medium Density Residential Low Density Residential Upper Land Cleared Upper Land Forested Lowland Undeveloped Approximate Jurisdictional Boundaries East Side Green River Watershed SCALE Current Land Use miles n 1 1/2 o 2 northwest hydraulic consultants NOTE: This Figure is based on 1989 Aerial Photographs. Figure 6-3 .............. ................. ................... ... ...................... .................. .............. .4 J:k.. ... ..............I..T......... ........................ ... ....... .. HA5............. I M. ........... . ........... .......... ;q i i .......... ..... p AV. . ...... Rl, AV S 04 P4 Z5 ............. •......................... ........................... ... ............... .................. .............. L.......... ........ . ........................ r(l ............................"I...,....... ........... .............. ...... .................✓ ............... SHATTUCK .............. OR AND o, 'WETLP""' Ilb ZR CREEK ps ........ PANV ............. ........ \Ix sire ............ .... .......... ............... ... ...................... ...... .......................... 3r...... ............. ................................... ...............---.... ............... A. .................... .......... ..................... 3r ...................... ........... ........... ............. T r 16 slo 1A Wil V .......... 3 S.. sa .......... j! ........ ..................... ........ L ............................. .. ......... ......... ............... ...................... ....... ................................. ............... L................... .................... 4ir ..................... ear ...........I .......... ....................... .................. ................... .....................I ND ........ ..... sl "A..............-, 8 V)I 513 ...........j L ................ ............... .............. ................._..SCALE SCALE 1"=1000' 12 ,o S 14 ........ ........................................... ................................ AL V ,3 10 ............ . ... ...............--.---..-- ,;...... ............. 0AI KESIDM A V, W, 7c 12 s9c. co 57ck NJ E 'T RAI' ss P5F8Y 617 jA CK-ON ......................................... ..................................................... .............. MILL .......... ........ CREEK ........... \ I , I" ,�=v .......... ......... ......... -nON PQ I. ..................... STATION K W:LA CA LRill FQ.REBAY ............. ...... ..... ............................... RENIMN t ITS ................... ......... ............. ........... ............. .... EAST SIDE GREEN RIVER ............ ................ .......... ............................................. ................ .............. WATERSHED PROJECT --l-T..........-:,.BLACK, RIVER LEGEND FIGURE 6-4 PUMP ;ter CONVEYANCE SYSTEM MODELED MAJOR DRAINAGE SYSTEM MODELED BY FEQ �_�� k=`' !'.`�,' ��' �� `�,......... Q WETLAND NUMBER 4- TO GREEN-DUWAMISH ink APPROXIMATE SUBBASIN BOUNDARY RIVER s PANTHER CREEK 5- ................... .................... j............. .................... V) SMITHERS ----------------------- V) .................. . ....... f-, s .................... ............. RENTON I ......................... .. ..... ................ .............. tca�jlaI ::AV 4126 �)HOPPING .................... ....... -------- c-li ..............- '!............. MORRIS AV S .. .................... ENTER "44 RD S WHIT— ROLU0 HILLS CREEK V) LE cn ................... ............. (D ---ll. ........... ...... .................................... ..................I-- ...... ...................................... ..... ..................................VA. ............. ......... ... ...... .......... ............. ........... ............ C/) ........... ..........I............. ...... SHATTUCK A ............. ........... EY .........�ks VALL ..................... ....... ul TALBOT C a- U) GENERAL CREEK wl-1111111 .......... .000 ..................... .......... .......................... HOSPITAL ............. .MCC ir Lr): RP\Nk5( ........ ....... ............ .............(-�.). ..... ............ .......... 48� .................... yo�............. .............. J ...... ... ........ .......... ....... ......... ........ ............ . ..... "N ................................... ........... 36" 36"X48" 0) SR-167 ....................... B ...... N". ". . : I................... ............. ............... ..................... 18, E Ul) E VALLEY RD VALLEY 36 RD W PIC loy- V)l CN CIO . ......... !......- .......... ....... P) V) v V) F— V) C14: k U, .......... .............. ...........................; , 1 1 : a i i .......... ....................... ............ .......... ....... ...... ------------ .................. .......... ........ ............. ........................7.......... ....................... ............ .... 60" -c- -1405 LIND LIND AV S AV SW' P0 5 101- cn; ....................... c) C14 ;to Lr) i LA C4 c') 21" ....................... ........... C/I Lj- ................... 0 ................................. 09 USCALE 1"=1000' THOMAS AV SW C/) Ln cn ev, C14.................. .......... ..................." .............................................................. ........... POWELL AV SW 1 .............. �164 CONNECTING X CHANNEL PROJECT�p ........ LEGEND .... ...... ................... 54' (COMPLETED ............... ................................ L Y OR 60" .............................................--............ 1995 3 6" OAKESDALE AV SW 0 36" DIAMETER STORM DRAIN "j Ln 36 x STREAM/DRAINAGE CHANNEL VALLEY AREA -00 OBSERVED FLOODED AREAS (ONLY AREAS CULVERT(S)(STUDY AREA) cr- Q- -3 WITHIN STUDY AREA ARE SHOWN) PIC-1 1101� LOCATION/DIRECTION OF PICTURE Of V"f NO. 1 , REFER TO FIGURE 6-6 JACKSON SW ................... ...........1-1.............. : ry ..................................-.................. j ............ PUMP STATION . ..... .......... ......... ... CREEK FLOOD WATER ......... K, N--\ ............. �:��.:: —. , ..........:.4 —:�, f STORAGE POND .......... TU K W I L"A' ........... ----------...........RENTON CITY LIMITS ........... ... .......... ........... ........... ........................ ................................................ ......... ................... ........ ....................... ............... ................. ................. ........... EAST SIDE GREEN RIVER --nd.2 ..AV ................ .......... .................. .......... ........... .............. WATERSHED PROJECT ..............-- ................................................................ RR ........... ...... ........... . ...... -�*W—y............. B L-AC ....... ......... �'l WEST ,,'V ............. FIGURE 6-5 RIVER . .................. ............. PUMP y x, FLOOD AREAS STATION CURRENT CONDITIONS 48n TO GREEN—DUWAMISH RIVER _ LL Picture Number 1 - Picture taken looking upstream toward Lind Avenue SW on the SW 23rd Street Drainage Channel from near its confluence with Springbrook Creek 771 y i Picture Number 2-Picture taken looking downstream East Side Green River Watershed Project on Springbrook Creek from its confluence with the SW 23rd Street Drainage Channel FIGURE 6-6A Photographs of Selected Reaches r Y? �I �l c' g Picture Number 3 - Picture taken looking downstream on Springbrook Creek h: from the SW 34th Street road crossing t, = i _- Picture Number 4- Picture taken looking upstream on Springbrook Creek from the Oakesdale Avenue SW road crossing East Side Green River Watershed Project s FIGURE 6-6A(Continued) Photographs of Selected Reaches ail Picture Number 1 - Flooding of the intersection of Lind Avenue SW and SW 41st Street during February 8-9 1996 flood Picture taken near the northeast corner of the intersection looking west - Picture Number 2 - Flooding of SW 43rd Street East Side Green River Watershed Project near Lind Avenue SW during February 8-9 1996 flood FIGURE 6-613 Picture taken from south side of SW 43rd Street near intersection with Lind Avenue SW looking west Photographs of Problem Areas Picture Number 3 - Flooding of East Valley Road between SW 27th Street and SW 34th Street during 1/9/90 flood Picture taken near the soutwest corner of SW 27th Street and East Valley Road looking south Picture Number 4- Flooding of SW 43rd Street and East Side Green River Watershed Project adjacent parking lots between East Valley Road and Lind Avenue SW during 1/9/90 flood FIGURE 6-613(Continued) Picture taken near the northwest corner of East Valley Road and SW 43rd Street looking west Photographs of Problem Areas LPN I w5 Black Rive Pump St \ �® Sb ®g` a v - S ra e o D 500' 0 500' 1000, W-21 1N=trll s Rmt.■YRaq.p SCALE • �® UU••' w-13M -Ift 13N W-13114e - W 13Sf 3se W-13Si W-13Sg z Lid] W-13Sh W-16d los W- w W to w _W_14 LEGEND _mow Q -1a �••�� aroject Bourdarr 32 EB - r - 33b W Cn) Ln N W-34 S IBMst fill W-1 N w 9 15 97 ' •low St Figure 6-7 Wetlands Map City of Renton East Side Green River Watershed Project SeclioN l FUTURE CONDITIONS 1 1 1 1 SECTION 7 FUTURE CONDITIONS 7.1 GENERAL This section describes the anticipated future conditions of the Valley area drainage system assuming that the ESGRW will continue to develop to the maximum densities allowed under adopted City of Renton, Kent, Tukwila, and King County land use plans. This section focuses on flooding that could occur in the future if no new measures are taken to correct existing flooding problems or to mitigate the impacts of future development beyond the mitigating measures already required for development, such as on-site detention. Anticipated impacts to environmental resources such as water quality, fish, and wetlands are discussed briefly in this section. Specific impacts to these environmental resources as well as others under future conditions are described in detail in the accompanying EIS under the "No Action" alternative. The current conditions of the drainage system described in Section 6 of the Plan include several flooding and environmental resource problems. In general, these problems will worsen in the future if no corrective or preventive actions are taken. 7.2 FUTURE LAND USE The future land use of the ESGRW is illustrated in Figure 7-1 and is based on the comprehensive land use plans of King County and the cities of Kent, Renton, and Tukwila (NHC, 1996). Future land use in the Renton Valley area will primarily consist of commercial/industrial areas and remaining large wetland areas, some of which are already owned by the City and others that are assumed to remain undeveloped. These areas are shown in Figure 5 contained in the ESGRWP Hydrologic Analysis (NHC, 1996). Based on land use as it existed in 1989, future development in the Renton Valley is estimated to result in the conversion of approximately 590 acres of undeveloped lowland area to commercial/industrial uses. The increase in impervious surface area (roads, roofs, and parking lots) will be one of the primary impacts of future development on the drainage system. The resulting impacts to the drainage system include significantly higher runoff volumes, higher peak runoff rates, and a reduction in base flows. The total amount of impervious surface for the ESGRW is projected to increase by approximately 45 percent, from approximately 5,300 acres to 7,740 acres. An approximate breakdown of the current and future impervious area for each jurisdiction in the watershed is included in Table 7-1. The estimated breakdown by jurisdiction based upon a summary of acreages for the different subbasins X0011592.112 SECTION 7 within the ESGRW (NHC, 1996). The breakdown between jurisdiction is considered approximate because some of the subbasins included areas within more than one jurisdiction and the estimate assumed that the percentage impervious surface is uniform throughout the subbasins. Therefore, a small amount of error could be introduced for a subbasin if it is common to more than one jurisdiction and a portion of the subbasin in one jurisdiction is more intensely developed than the portion in another jurisdiction. 7.3 FLOODING 7.3.1 ANALYSIS The effects of future land use on the existing drainage system were analyzed using the HSPF hydrologic computer model and the FEQ hydraulic computer model. The application of these computer models to evaluate the drainage system's response to flood events was previously discussed in Section 6.5. The detailed hydrologic and hydraulic analyses are documented in the ESGRWP Hydrologic Analysis (NHC, 1996) and the ESGRWP Hydraulic Analysis (R. W. Beck, 1996a), respectively. The analysis assumed future land use at buildout conditions (see Section 7.2). The future land use condition analysis included the assumption, with a few exceptions, that there would be no constructed improvements to the existing system. These exceptions relate to stormwater detention projects or conveyance improvements either being constructed or planned by the cities of Renton and Kent as well as the Washington State Department of Transportation (WSDOT) that would have an effect on the projected flows along Springbrook Creek. These projects include: ■ Planned City of Renton conveyance improvements on SW 43rd Street system from approximately Lind Avenue S to Springbrook Creek. ■ Planned City of Renton conveyance improvements along SW 7th Street system between Shattuck Avenue and Springbrook Creek (Note: these improvements are being considered as part of a separate City project). ■ Planned City of Renton conveyance improvements along the SW 34th Street drainage system between approximately EVR and Springbrook Creek. ■ City of Kent Lagoons Project, which was substantially completed in the summer of 1996. ■ Planned City of Kent 98th Avenue detention pond. ■ Planned City of Kent conveyance improvements on Mill Creek upstream of SR-167. ■ WSDOT Upper Springbrook Creek SR-167 culvert replacement planned for construction in 1996 or 1997. 7-2 R. W. Beck X0011592.112 FUTURE CONDITIONS These improvements are included in the model simulations because they would affect the flows in Springbrook Creek. The conveyance improvements listed above would tend to reduce current flooding thereby reducing flood storage provided by the system and increasing downstream flow rates. The large detention pond projects would add flood storage to the system and attenuate downstream flow rates. One change in the hydrologic/hydraulic computer models under future land use conditions was the watershed boundary. Runoff from a small subbasin (S15; see Figure 6-4) was considered noncontributing during the current land use condition simulations. Subbasin S15 includes an area in the City of Tukwila, which prior to this study did not contribute significantly to the Valley area drainage system. Drainage improvements have been completed or are pending that significantly increase the capacity of the system connecting this area to Springbrook Creek. These improvements are included in the future conditions simulations. 7.3.2 HYDROLOGIC/HYDRAULIC ANALYSIS RESULTS Results of the computer simulations, including the peak flows and corresponding maximum water surface elevations, are summarized for future land use conditions in Table 7-2. Profiles of the 100-year "conveyance' and "storage" floods are also shown on Figure 7-2. As discussed in Section 6.5.1, the conveyance event reflects a severe local event without BRPS pumping restrictions while the storage event reflects a severe Green River flood that causes the BRPS to restrict its pumping rates in accordance with the Green River Interlocal Agreement (GRBP, 1992). This figure also shows the current condition 100-year event simulations. The following sections provide an analysis of the computer simulation results. The analysis is divided into four groups: ■ Springbrook Creek water surface elevations and stream channel velocities. ■ Simulated flooding problems of drainage systems tributary to Springbrook Creek. ■ Valley area wetlands. ■ BRPS. 7.3.2.1 SPRINGBROOK CREEK WATER SURFACE ELEVATIONS AND STREAM CHANNEL VELOCITIES The 100-year future land use condition "storage" simulation event results in the highest simulated Springbrook Creek water surface elevations between the BRPS and immediately upstream of SW 27th Street. Upstream of SW 27th Street, the 100-year future land use "conveyance" simulation flood results in the highest simulated water surface elevations. X0011592.112 R. W. Beck 7-3 SECTION 7 Under the future conditions simulation, the SW 34th Street crossing and the Oakesdale Avenue crossing are overtopped. Overtopping at both culvert crossings begins with approximately a 10-year "conveyance" flood on Springbrook Creek and also with about a 100-year"storage" flood. Maximum simulated stream channel velocities are higher (5 to 15 percent) than the current condition simulations because of the higher flow rates. As in the current condition simulations, the reach upstream of SW 16th Street is the major concern, having 2-year and 100-year maximum simulated velocities of 8.3 and 10.1 fps, respectively. The significant increase in the predicted maximum water surface elevations for Springbrook Creek between current and future conditions is illustrated in Figure 7-2. An increase of 4.4 feet in water surface elevation at the BRPS forebay is predicted between the 100-year current and future land use "storage" floods. This illustrates the significant increase in stormwater volume that will result from continued development within the watershed. Collecting stormwater from Subbasin S15 (Tukwila, see Figure 6-4) to the ESGRW system also adds to the stored stormwater volume. This subbasin was assumed not to drain to the ESGRW system for current conditions simulations. The water surface elevation at SW 43rd Street during the 100-year "conveyance" flood is predicted to increase by approximately 1.3 feet between current and future land use conditions. The increase in Springbrook Creek water surface elevations will exacerbate the current flooding problems. For example, the predicted volume of surface ponding for the East Valley Road system for the current and future conditions 100-year "conveyance" flood is 12 and 49 acre-feet, respectively. The East Valley Road flooding problem will become much more serious than it is currently if no corrective action is taken. The increase in simulated water levels is more pronounced for the more frequent events. For example, at SW 43rd Street, the increase in water levels between current and future conditions is 3 feet for the 10-year event. Therefore, flooding on those tributary systems that currently flood during the 10-year event would be expected to become dramatically worse. A summary of the 100-year flood simulation flows and elevations using FEQ is provided in Table 7-3. This table compares these results to Springbrook Creek FEMA peak flows and base flood (100-year) elevations. FEMA elevations are also illustrated on Figure 7-2. The FEMA information was taken from the Flood Insurance Study, King County, Washington (FEMA, 1996). This 1996 FEMA study was actually an update of a prior study and the flood elevations were taken directly. It should be noted that the FEMA study does not consider future land use conditions. The comparison indicates that all FEQ simulated elevations for Springbrook Creek are lower than FEMA elevations with the exception of the future land use condition 100-year "conveyance" flood between Oakesdale Avenue and SW 43rd Street. Therefore, the predicted water surface elevations of Springbrook Creek downstream of Oakesdale Avenue should not exceed the FEMA base flood elevations as development continues in the watershed. 7-4 R. W. Beck X0011592.112 FUTURE CONDITIONS Conversely, the FEMA mapping does not map those frequently flooded areas in the Valley area that are situated away from Springbrook Creek, such as SW 43rd Street and East Valley Road. Simulated water levels in these systems are above the FEMA flood elevations of Springbrook Creek and should be considered part of the floodplain. The City of Renton anticipates requesting a comprehensive map revision from FEMA after some of the improvements proposed in this plan have been implemented. As noted previously, there is an increase in maximum simulated velocities of 5 to 15 percent between current and future land use condition flows. The major area of concern along Springbrook Creek is upstream of SW 16th Street. High velocities in this reach could cause significant erosion problems. One other stream channel that was simulated to have relatively high velocities was Rolling Hills Creek upstream of the I-405 crossing. This reach was simulated to have velocities of 5 and 7 fps for the 2-year and 100-year future land use condition events, respectively. This section of Rolling Hills Creek is outside the study area. 7.3.2.2 SIMULATED FLOODING PROBLEMS OF DRAINAGE SYSTEMS TRIBUTARY TO SPRINGBROOK CREEK Under future land use conditions, higher Springbrook Creek water levels and higher local runoff rates would result in a significant increase in the frequency and depths of flooding for systems that are tributary to Springbrook Creek. The flooding problems identified under current land use conditions in Section 6.5.2.2 would become worse. Based upon the FEQ and BWPIPE backwater model (King County, 1990) analyses, several of the problem tributary systems would tend to flood during approximately the 2-year event. In addition to the flooding problems identified previously, a new flooding problem is simulated by the FEQ hydraulic model to occur under future land use: ■ The SW 16th Street System west of Springbrook Creek begins to flood with a 100-year "storage" flood. This system consists of the storm drain conveying Subbasin S15 (Tukwila) flows to Springbrook Creek. The model predicts the worst flooding of systems in this category will occur in the SW 7th Street and East Valley Road systems. The FEQ simulation predicted surface ponding at those locations of 47 and 49 acre-feet, respectively, for the 100-year"conveyance" flood. The FEQ model also predicted that the SW 16th Street system east of Springbrook Creek would begin to flood with a 100-year "conveyance" flood. However, in 1997 a new 24-inch diameter storm drainage trunk line will be installed in SW 16th Street beginning from Raymond Avenue SW and extending west to connect to an existing 24-inch pipe at the intersection of Oakesdale Avenue SW and SW 16th Street. The existing 24-inch pipe outfalls into Springbrook Creek through the east abutment of the SW 16th Street bridge. The new storm drain is predicted to provide 100-year level of protection, even under future land use conditions. X0011592.112 R. W. Beck 7-5 SECTION 7 It is important to note that the hydraulic analyses consisted of modeling only the major tributary systems. Therefore, additional flooding problems of smaller drainage collection systems not investigated in this study should be anticipated. 7.3.2.3 VALLEY AREA WETLANDS As under current land use conditions, the Valley area wetlands provide significant flood storage volume. The Valley area wetlands are simulated to provide 772 acre-feet of storage collectively during the future condition 100-year "conveyance" flood. Water surface elevations and periods of inundation for the wetlands for the more frequent 2-year flood simulation for both current and future land use conditions are shown in Table 7-4. This table illustrates the predicted increase in water elevations and periods of inundation between current and future land use conditions. For future land use conditions, Springbrook Creek 2-year flows do not inundate FEQ wetland numbers 5, 8, 9, and 10 (City wetland inventory designations Nos. 16, 51, 14, and 32). 7.3.2.4 BLACK RIVER PUMP STATION As shown in Table 7-2, the maximum pumping rates of the BRPS for future conditions vary from 726 cfs to 1,700 cfs for the different flood frequencies. As would be expected, the maximum pumped flow rates and elevations in the forebay will increase as the watershed continues to develop. Similar to current conditions, the maximum of 1,700 cfs is simulated for the 100-year "storage" flood. The 1,700 cfs reflects the use of all the flood control pumps currently operable at the pump station. This occurs after Green River flows drop to a level where increased pumping is allowed and all the pumps are turned on to evacuate the stored water. For the 100-year "storage" flood, the maximum simulated elevation at the BRPS forebay is 13.0 feet. It is also important to note that this simulation results in a peak pumping rate of 1,700 cfs, reflecting the use of all flood control pumps currently operable at the BRPS. As discussed in the ESGRWP Hydrologic Analysis report, the required storage in the ESGRW system is sensitive to the pumping rates at the BRPS. Simulations showing that the maximum capacity of the pump station can be reached stress the importance of maintaining the pumps at maximum efficiency. 7.3.3 FLOODING PROBLEMS The hydrologic/hydraulic analyses (NHC, 1996; R. W. Beck, 1996) show that the existing flooding problems will worsen under future conditions. In addition, new flooding problems will occur. Anticipated water quantity problems are summarized below. The summary also indicates whether the problem exists under current conditions or is predicted for future conditions. Current and Future Condition Flooding Problems ■ Springbrook Creek overtopping of SW 34th Street. 7-6 R. W. Beck X0011592.112 FUTURE CONDITIONS ■ Springbrook Creek overtopping of Oakesdale Avenue. ■ The East Valley Road system in the vicinity of SW 34th Street and where Panther Creek enters the system. ■ The East Valley Road system south of SW 23rd Street. ■ The SW 43rd Street system, particularly in the vicinity of Lind Avenue SW. ■ The SW 7th Street system (this problem is listed here; however, the problem is being addressed under a separate City study and not the ESGRWP). ■ Flooding of smaller systems that discharge to the SW 43rd street and EVR/34th Street drainage systems such as the SW 41st Street and Lind Avenue drainage systems. ■ Flooding of the Renton Shopping Center (this problem is listed here; however, the problem is outside the ESGRWP study area). Future Conditions Flooding Problems ■ Flooding of the 48-inch-diameter system draining an area within the City of Tukwila (subbasin S15; see Figure 6-4). As with current conditions, the frequency of the flooding problems would far exceed the City's objective for providing a 100-year level of protection (Policy EN-G) (Renton, 1995a). 7.4 ENVIRONMENTAL RESOURCES The current conditions of the environmental resources in the study area, including water quality, fish and wildlife, and wetlands, were described in Sections 6.6 through 6.8. The condition of the environmental resources under future land use conditions are briefly discussed in this section; more detailed future environmental conditions are discussed in the project's draft and final Environmental Impact Statements. 7.4.1 WATER QUALITY If no corrective actions are taken, water quality would likely remain degraded and probably worsen, especially flood-related impacts to water quality. Flood- related impacts to water quality include those that are associated with stream channel vertical erosion (incision) and aggradation (i.e., scour and fill) combined with lateral erosion and sediment deposition. High turbidity and suspended solids occur as a result of these processes and have a negative impact on beneficial stream uses including fish and invertebrate habitat, fish spawning, and aquatic plant productivity. Flooding can also affect water quality by introducing chemicals or other hazardous materials, including petroleum products stored at commercial and industrial sites in the Valley. Flood waters may also cause sanitary sewer systems X0011592.112 R. W. Beck 7-7 SECTION 7 to back up or overflow, resulting in discharges of untreated wastewater. Flooding may also result in the washoff of contaminated surface soils that have been previously affected by activities such as wrecking yards, automotive repair, and illegal waste disposal. Future water quality will also be affected by the significant amount of development that will occur in the watershed. Anticipated impacts include increase in runoff rates and volumes, increases in pollutant loading from impervious surfaces, and erosion and sedimentation from land construction and clearing activities. On-site detention and treatment of stormwater as well as erosion control measures are required by all jurisdictions in the watershed to help reduce such impacts from future development. While these requirements will reduce the impacts of new development, water quality would continue to be degraded from existing development. Improvement in water quality will depend on corrective actions taken to correct existing problems. Several actions within the Renton and northern King County portion of the watershed are identified in the BRWQMP (R. W. Beck, 1993). These actions will be carried out through the SWU Comprehensive Plan (HDR, 1996). Proposed water quality improvements in the Kent portion of the basin are identified in the City of Kent Five Year Water Quality Program, 1992-1996 (Resource Planning Associates, 1991). The S WU Comprehensive Plan recommends coordinating with the City of Kent on improving water quality within the basin. 7.4.2 FISH AND WILDLIFE Springbrook Creek within the study area presently does not provide suitable habitat for adult spawning because of a lack of suitable spawning substrate and poor water quality. It does, however, provide rearing habitat and serves as a corridor for fish migrating up and downstream, except possibly sometimes during summer and fall when dissolved oxygen levels can be extremely low. Low dissolved oxygen levels, elevated summer water temperatures, high levels of metals, and other water quality problems affect the ability of the stream to support fish. Water quality in the low gradient Springbrook Creek (in Renton and in upstream Kent) is likely one of the factors limiting the ESGRW fish resource (Harza, 1995). Under future conditions, the effects of water quality conditions for fish would remain unchanged and would likely worsen due to higher peak flow rates and runoff volumes that would tend to increase the incidence of flooding, stream bank erosion, and sedimentation. The increase in runoff volume would result in a corresponding increase in the average annual flows. Base flows would alternatively be reduced as a result of the loss of groundwater recharge. Although passage in Springbrook Creek is not currently a problem under most conditions, upstream passage would be restricted or prevented by high water velocities in the short reach upstream of SW 16th Street and through existing culverts, if high flows occur at times when adult salmon are returning to spawn. However, it is not unusual for fish to be delayed during high flow events. One 7-8 R. W. Beck X0011592.112 FUTURE CONDITIONS additional concern is that juvenile salmonids may be subjected to stranding as flood waters recede from areas where high flows overtop stream banks and flood adjacent bottomland. Erosion occurring upstream of and within the study area and the resulting sediment deposition in the study area would continue to reduce Springbrook Creek's ability to support aquatic organisms serving as an important source of food for juvenile fish by limiting the ability of invertebrates to develop and diversify and reducing the diversity of the substrate habitat. As discussed under the current conditions section, lower Springbrook Creek should be managed to serve as an essential link between the Green River and headwater spawning grounds. The Comprehensive Fisheries Assessment of the Mill Creek, Garrison Creek and Springbrook System (Harza, 1995) identified a program of improvements for the lower Springbrook Creek system (see Section 6.8.2.1). These improvements would improve the fish resource. Riparian habitat along the majority of Springbrook Creek is dominated by non- native vegetation. Under future conditions, this condition is likely to remain. Some degradation of riparian habitat and wildlife use would be expected under future conditions if no corrective measures are taken. This degradation would be caused by the physical damage from increased flood flows and resulting erosion. In addition, the conversion of connecting vegetated uplands to development would reduce available wildlife habitat. 7.4.3 WETLANDS Section 6.7.2 provided a description of the existing functions and values of the wetlands within the Valley area. In general, only minor changes to wetland functions and values are predicted. Under future conditions, as mentioned above, the Valley area wetlands would be subject to greater flood flow rates and volumes and would provide greater flood flow attenuation. By providing more flood flow storage, the wetlands would help to reduce downstream flow increases that result from future development. The hydraulic computer simulation shows that the increase in flood storage provided by the wetlands for the 100-year event is 133 acre-feet for about a 20 percent increase. A comparison between current and future water levels and periods of inundation for the 2-year event is shown in Table 7-4. X0011592.112 R. W. Beck 7-9 SECTION 7 TABLE 7-1 APPROXIMATE CONTRIBUTING IMPERVIOUS SURFACE AREA BY)URISDICTION EAST SIDE GREEN RIVER WATERSHED Current Land Use Future Land Use Increase Jurisdiction Impervious Percent of Impervious Percent of Impervious Percent Area (ac) Total Area(ac) Total Area (ac) of Total Renton 1,430 27% 2,105 2717o 675 28% Kent 3,119 59% 4,466 587o 1,347 55% King County 561 11% 877 11% 316 13% Tukwila 185 3% 294 4% 109 4% Total 5,295 10070 7,742 100% 2,447 100% Notes (1) Impervious area estimates are based on land use summary tables from ESGRWP Hydrologic Analysis (NHC, 1996). Impervious area estimates are considered approximate (See Section 7-2). (2) Based upon the following percent impervious for various land uses: Land Use Impervious Percentage Commercial/Industrial 857o Multifamily 46% High-Density Residential 34% Medium-Density Residential 207o Low-Density Residential 10% R. W. Beck X0011592.112 TABLE 7-2 Summary of Peak Flows and Water Surface Elevations Future Land Use Conditions FEQ Hydraulic Analysis (Elevation Datum NGVD) Road- 2-Yr Fut.Flow 10-Yr Fut,Flow 25-Yr Fut.Flow 25-Yr Fut.Flow 100-Yr Fut.Flow 100-Yr Fut.Flow way Top Conveyance(3) Storage(3) Conveyance(3) Storage(3) Elev. Location/Discription Flow Elev Flow Elev Flow Elev Flow Elev Flow Elev Flow Elev (cfs) (feet) (cfs) (feet) (cfs) (feet) (cfs) (feet) (cfs) feet (cfs) (feet) Panther Creek u/s of SR-167(1) 62 86 96 32 170 92 Rolling Hills Creek at Renton(1)(2) 70 20.4 89 20.7 102 20.9 35 19.6 174 21.8 99 20.9 Shopping Center Culv.Outlet Rolling Hills u/s I-405 132"culvert(1)(2) 70 16.6 89 16.9 102 17.0 35 16.3 174 17.8 99 16.9 SR-167 North Crossing 45 14.7 71 15.6 82 16.0 32 14.1 98 17.0 69 15.6 Springbrook Creek BRPS outflow 726 1021 1095 960 1223 1700 BRPS inflow 726 3.8 1021 4.0 1095 4.1 960 5.5 1223 4.1 1700 13.0 Floodwater Storage Pond Inflow 728 4.2 1023 4.5 1095 4.6 464 5.5 1223 4.7 1153 13.0 Grady Way u/s 593 6.2 904 7.1 959 7.2 413 5.6 1 110 7.6 1045 13.0 SW 16th Street 584 6.7 897 7.6 951 7.8 408 6.1 1106 8.2 960 13.0 Confluence of Rolling Hills Creek 561 9.4 882 10.8 933 11.1 395 8.4 1088 11.6 898 13.1 Confluence ofSW 23rd St Channel 526 10.4 807 11.9 843 12.1 360 9.4 989 12.6 807 13.3 SW 27th u/s 17.9 518 11.5 808 14.0 831 14.3 350 10.0 989 15.6 775 143 SW 34th u/s 14.9 564 12.9 840 15.3 847 15.4 309 10.6 1219 16.1 845 15.2 Cakesdale d/s 17.1 567 13.5 843 15.9 849 15.9 311 11.3 1227 16.9 846 15.8 Cakesdale u/s 17.1 527 14.3 787 17.3 800 17.4 292 11.5 1167 17.9 792 173 SW 43rdd/s 22.9 525 14.7 781 17.6 795 17.6 291 12.1 1158 18.3 783 17.6 SW 43rdu/s 22.9 525 14.9 781 18.1 795 18.1 291 12.3 1158 19.5 783 18.0 Notes (1)FEQ simulated flows at these locations are based upon frequency analysis of Springbrook Creek inflows to the BRPS forebay. Refer to ESGRWP Hydrologic Analysis Report(NHC, 1996) for flows based upon frequency analysis of Panther Creek and Rolling Hills Creek. (2)Flows are based upon assumption that capacity restriction through Renton Shopping Center is improved such that no attenuation from surface ponding occurs. (3)Conveyance event reflects a severe local rainstorm without pumping restrictions at the BRPS due to high Green River flows. Storage event reflects a high Green River flow event in which the BRPS must restrict pumping rates in accordance with GRIA. (4)u/s=upstream,d/s=downstream (5)Note that summary tables do not reflect wider SW 16th Street bridge opening and minor elevation adjustments at Oakesdale Avenue. See discussion of modeling in Section 8.3 of Plan. TABLE 7-3 Comparison of Peak Flows and Water Surface Elevation FEQ Computer Model and FEMA (1) (Elevation Datum NGVD) Road- 100-Yr Cur.Flow 100-Yr Fut.Flow 100-Yr Cur.Flow 100-Yr Fut.Flow FEMA 5 way Top Conveyance(6) Conveyance(6) Storage 6 Storage 6 _ Elev. Location/Discription Flow Elev Flow Elev Flow Elev Flow Elev Flow Elev. (cfs) (feet) (cfs) (feet) (cfs) (feet) (cfs) ((feet) (cfs) Panther Creek u/s of SR-167(2) 170 170 82 92 16.0 Rolling Hills Creek at Renton(2)(3) 167 21.8 174 21.8 87 20.7 99 20.9 130 24.0 Shopping Center Culy.Outlet Rolling Hills u/s 1-405 132"culvert(2)(3) 167 17.8 174 17.8 87 16.8 99 16.9 91 24.0 SR-167 North Crossing 100 17.0 98 17.0 58 15.2 69 15.6 16.0 Springbrook Creek BRPS outflow 1044 1223 1360 1700 BRPS inflow 1044 4.1 1223 4.1 734 8.4 1153 13.0 1230 15.0 Floodwater Storage Pond inflow 1044 4.5 1223 4.7 734 8.4 1153 13.0 15.0 Grady Way u/s 935 7.2 1110 7.6 638 8.6 1045 13.0 1100 16.0 SW 16th Street 934 7.7 1106 8.2 577 8.6 960 13.0 16.4 Confluence of Rolling Hills Creek 930 11.0 1088 11.6 571 9.7 898 13.1 15.8 Confluence of SW 23rd St Channel 819 12.0 989 12.6 502 10.4 807 13.3 16.0 SW 27th u/s 17.9 825 14.2 989 15.6 492 11.4 775 14.3 16.3 SW 34th u/s 14.9 887 15.4 1219 16.1 490 12.4 845 15.2 16.8 Oakesdale d/s 17.1 891 16.0 1227 16.9 489 12.9 846 15.8 17.3 Oakesdale u/s 17.1 833 17.4 1167 17.9 463 13.6 792 17.3 17.4 SW 43rd d/s 22.9 830 17.7 1158 18.3 459 14.0 783 17.6 17.8 SW 43rd u/s 22.9 830 18.2 1158 19.5 459 14.2 783 18.0 1055 17.8 Notes (1)FEMA uses current land use conditions and does not consider future land use conditions. Elevations are from FEMA floodway data tables. (2)FEQ simulated flows at these locations are based upon frequency analysis of Springbrook Creek inflows to the BRPS forebay. Refer to ESGRWP Hydrologic Analysis Report(NEC,1996) for flows based upon frequency analysis of Panther Creek and Rolling Hills Creek. (3)Flows are based upon assumption that capacity restriction through Renton Shopping Center is improved such that no attenuation from surface ponding occurs. (4)u/s=upstream,d/s=downstream (5)Rise in FEMA water surface elevation at SW 16th Street from the confluence of Rolling Hills Creek is due to unresolved discrepancy at the upstream boundary of 1989 FEMA restudy(FEMA, 1989). (6)Conveyance event reflects a severe local rainstorm without pumping restrictions at the BRPS due to high Green River flows. Storage event reflects a high Green River flow event in which the BRPS must restrict pumping rates in accordance with GRIA. (7)Note that summary tables do not reflect wider SW 16th Street bridge opening and minor elevation adjustments at Oakesdale Avenue. See discussion of modeling in Section 8.3 of Plan. TABLE 7-4 Summary of Maximum Elevation and Durations Major Wetlands -- 2-Year Event Current and Future Land Use Conditions (Elevation Datum NGVD) Wetland Inventory FEQ Wetland Hydraulic Current Flows Future Flows Location Description Description Connection Maximum Elev. Duration Maximum Elev. Duration (See Fig.6-7) (See Fig.6-4) Elevation(6) 1a(not used) 7N lb 9.0(culvert to Rolling Hills Cr.does nol 10.1 (7) (7) Rollings Hills Cr.)(1) inundate wetland(1) 2(not used) 8N 3 10.0(weir connected 11.8+/-(1) 3 hrs(1) 12.0+/-(2) 29 hrs(2) 23rd Str.Channel)(1) 10 4 10.0(weir connected Springbook Cr.does not 10.59 18 hrs to Springbrook Cr.) inundate wetland 16 5 11.5(weir connected Springbook Cr.does not Springbook Cr.does no to Springbrook Cr.)(1) inundate wetland inundate wetland 11 6 10.5(weir connected Springbook Cr.does not 11.54 14 hrs(4) to Springbrook Cr.)(1) inundate wetland 12b 7A 10.0(weir connected 10.31 4 hrs(5) 11.54 23 hrs(5) to Springbrook Cr.)(1) 12a 78 13.5(weir to 7A)(1) 13.60(8) (3) 13.67(8) (3) 9.0(culvert to 7A) 10.5(9) (3) 11.7(9) (3) 13Sj 7C 10.1 (culvert to 76) 13.61 (8) (3) 13.83(8) (3) 11.3(9) (3) 12.1 (9) (3) 51 8 16.0(weir connected Springbook Cr.does not Springbook Cr.does no to Springbrook Cr.) inundate wetland inundate wetland 14 9 16.0(weir connected Springbook Cr.does not Springbook Cr.does no to Springbrook Cr.) inundate wetland inundate wetland 32 10 16.0(weir connected Springbook Cr.does not Springbook Cr.does no to Springbrook Cr.) inundate wetland inundate wetland 4 11a 14.0(weir connected 14.62 (3) 14.63 (3) to Rolling Hills Cr.) 4 11 b 13.5(culvert to 11 a) 14.55 (3) 14.57 (3) 4 11 20.3(weir to Panther Cr. 14.55 (3) 14.57 (3) 13.5(weir to 11b)(1) 13Nb-Nd 12 (1) (1) (1) (1) (1) For notes see the following page. Notes For Table 7-4 (1) See applicable notes on Table 6-4. (2) Based on review of hydraulic modeling of SW 23rd Street drainage channel (NRCS, 1995), future increases in water levels should not be significantly over current conditions. The study indicates that water surface elevations in the vicinity of Wetland 8N increase little for relatively large flow increase, in particular when water levels are above the ground level of the downstream Olympic Petroleum line crossing (that acts as a weir) and when Springbrook Creek is at or below 2-year water levels. See hydraulic profiles in NRCS, 1995. The FEQ simulation results give a maximum elevation of 10.67 and a duration of 29 hours. The elevation simulated by FEQ is lower than the elevation based on NRCS hydraulic modeling because of the modeling assumptions used in FEQ regarding flows from the Panther Creek Wetland (see note 1 of Table 6-4). The FEQ simulation result for duration (29 hrs) is likely undersimulated as well, but a short duration would be expected. (3) Inundation reflects local subbasin inflows rather than overflows from Springbrook Creek. Therefore, simulation reflects constant inundation from local inflows. (4) Based upon duration of Springbrook Creek flows above elevation 10.5. (5) Based upon duration of Springbrook Creek flows above elevation 10.0. (6) See R. W. Beck 1996a, Table 6, for more detailed information on hydraulic connections. (7) Simulated elevation in 60" storm drain conveying Rolling Hills Creek is 10.1. However, the elevation in the wetland would be less than 10.1 because: a) the simulated elevation in the 60" storm drain may be artificially high due to modeling approach (see note 1 of Table 6-4); b) flows into the wetland from the creek would be severely limited by the small size of the 12" culvert and the small head pressure; and c) the duration that flows are above the invert of the 12" would be relatively short lived. (8) Simulated elevation assuming the 18" culvert between FEQ 7A and 7B is not functioning and assuming an initial water level of 13.5 in FEQ 7B and 7C (see note 7 in Table 6-4). (9) Elevation modeled using the King County backwater model program and flow information from the FEQ simulation, assuming the 18" culvert between FEQ 7A and 7B is functioning at full capacity. This elevation is used in the EIS impact analysis because it reflects current condition more accurately as evidenced by recent crest stage gage data collected since the culvert was replaced (see note 7 in Table 6-4). X011592.112 AUGUST 1997 R. W. Beck Y Black River Pump Station / % Renton Mae %r 07 n r�/ ,j ( Tukwila l Pan Ck Note: This figure depicts the zoned full build—out land—use. The modeled land—use was obtained by overlaying the future zoned land—use with areas assumed to �� + remain undeveloped (large wetlands, steep slopes, etc). The areas assumed SW 43rd St to remain undeveloped are shown in s tenth s Figure 5 of NHC, isss. — Unincorporated r;z King County tat Panther „ r hake 1/2 r i r:'a - rC.J 616 l i LEGEND Kent Commercial ri Multi—family High Density Residential Medium Density Residential Low Density Residential Upper Land Cleared Upper Land Forested Lowland Undeveloped Parks ® Approximate Jurisdictional Boundaries East Side Green River Watershed SCALE Zoned Future Land Use miles 2W77 1 1/2 0 1 z northwest hydraulic consultants Figure 7-1 SPRINGBROOK CREEK WATER SURFACE ELEVATION PROFILE EXISTING CHANNEL SYSTEM CURRENT AND FUTURE LAND USE CONDITIONS 100-YEAR EVENT 22 ROADWAY SURFACE 20 18 TOP OF CULVERTS 16 14 ---------------------------- --------------------- --- ----- -� -------- ------ CD 12 i Z ---------------- v 10 - .� O O ---------------------------------------------------------- ------ s t _> i N a v W W i � i 6 BOTTOM OF CULVERTS i ! o 0 4 Cl) rn 0 rn 2 Bottom Profile 0 s 0 0 a i 0 0 a -2 Y a 0 5000 10000 15000 20000 Distance (ft) EAST SIDE GREEN RIVER LEGEND WATERSHED PROJECT High Springbrook Creek Flows (Conveyance) --------------- High BRPS Storage (High Green River Flows) FIGURE 7-2 Current Land Use Conditions Current Land Use Conditions SPRINGBROOK CREEK High Springbrook Creek Flows (Conveyance) -___—_-- High BRPS Storage (High Green River Flows) WATER SURFACE PROFILE Future Land Use Conditions Future Land Use Conditions FEMA Base Flood ' SECTION 8 ALTERNATIVE SOLUTIONS AND EVALUATION 1 1 1 1 1 1 1 1 1 1 1 1 SECTION 8 ALTERNATIVE SOLUTIONS AND EVALUATION 8.1 GENERAL This section describes the flood control alternatives evaluated to reduce flooding and improve environmental conditions in the Valley area. There are many approaches to providing flood control and this section also describes the process used by the City, NRCS, and consultant team to define alternative flood control measures. This process is summarized in Section 8.2. The alternative identifica- tion process described below led to the alternative descriptions, presented in Section 8.3. The alternative flood control measures were then evaluated using several evaluation criteria. These criteria are discussed in Section 8.4 and generally follow similar criteria used under the impact evaluation included as a part of the project EIS. The alternative evaluation is summarized for each criterion in a tabular format. The tables reflect summaries of detailed evaluations presented in the form of technical memoranda in Appendix A of the draft Plan and EIS (Renton, 1996). 8.2 ALTERNATIVES DEFINITION PROCESS Early in the planning effort, the City and consulting team conducted an internal workshop to identify potential measures to reduce flooding along Springbrook Creek. As discussed under the project history, the past ESGRW Plan efforts with NRCS had defined improvements for the P-1 Channel through the Valley area. However, deficiencies in the previous planning work with respect to cost and impacts of the large P-1 Channel on environmental resources south of SW 16th Street led to the current planning effort. Therefore, the workshop was conducted to "brainstorm' other potential solutions. The focus of the brainstorming session was on Springbrook Creek and how to reduce flood levels. Twelve preliminary alternatives were identified. The alternatives were evaluated on a preliminary basis considering impacts to wetlands, water quality, and fish. The alternatives were screened down to a list of four preliminary flood control solutions. Some of the alternatives that were not considered feasible and eliminated from further consideration are listed on Table 8.1. The preliminary alternative screening process is described in Volume 3, Appendix C of the BRWQMP (R. W. Beck, 1993). Following the initial screening process, the City and consulting team performed a detailed analysis of the four preliminary flood control alternatives. The evaluation of alternatives incorporated a significant amount of information that had been developed throughout the planning effort including water quality and X0011592.112 SECTION 8 sediment characterizations, wetland and stream inventories, fish resource inventories, preliminary cost estimates, hydraulic evaluations, and other information. The flood control alternatives focused not only on Springbrook Creek but also included several other flood control measures in the Valley area such as pipe system improvements and channel improvements of tributary systems. Detailed information on this preliminary evaluation is included in Volume 3, Appendix K of the BRWQMP (R. W. Beck, 1993). The environmental information used in the analysis is also included in the BRWQMP, such as the wetland inventory in Volume 3, Appendix F, and the water quality assessment in Volume 2. Summary descriptions of the four alternatives considered in the preliminary evaluation is included in Volume 1, Section 3, of the BRWQMP. Subsequent to this preliminary evaluation process, it became necessary to reconsider the adequacy of these four preliminary alternatives, primarily because of changes in flow rates predicted by the project hydrologic and hydraulic models. Changes in flow rates were the result of many modifications to these models,including: ■ Revising the hydrologic model to incorporate the more recent land use information prepared under the Growth Management Act. ■ Refining the hydrologic model simulation to include the significant flood events of 1990 and 1991 in the flood flow frequency analysis. ■ Adding the Springbrook Creek channel improvements from SW Grady Way to SW 16th Street completed in the summer of 1995 into the hydrologic and hydraulic models. ■ Incorporating changes in flow from the City of Kent portion of the watershed that reflect the latest information of future conditions in Kent, including regional stormwater facilities such as the Lagoons project. Also, one of the four initial alternatives, a proposed pump station at the Kent Lagoons project (see Table 8-1), was eliminated from further consideration. This was largely because it was determined that a new 30 cfs pump station to the Green River, the maximum capacity allowed by the GRIA (GRBP, 1986), would have little effect in reducing downstream flows in Renton. Following the update of the hydrologic and hydraulic models of the existing drainage system, including the modifications noted above, the City, NRCS, and the consultant team conducted an internal workshop in April 1995 to redefine the preliminary alternatives. Again, a total of four preliminary alternatives were selected, including the no action alternative required for environmental review under SEPA (see Section 4.2.3). Each of the action alternatives consisted of a comprehensive set of improvements to several major valley area drainage systems, such as Springbrook Creek, Panther Creek, and other tributary channel/pipe systems. 8-2 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION These alternatives were defined in a preliminary nature, e.g., specifying a reach of Springbrook Creek to be widened but not specifying the extent of widening in terms of widths and depths. Descriptions and graphics of the four preliminary alternatives were prepared and presented at a May 16, 1995 public workshop and May 18, 1995 agency workshop. A major purpose of the workshops (described in Section 5) was to inform the Valley area land owners, public, and interested agencies of the preliminary alternatives and to solicit their input. A copy of the meeting agenda, minutes, and graphics of the four preliminary alternatives presented at these meetings is included in Appendix B of the draft Plan and EIS (Renton, 1996). Information collected during the public and agency workshops was used to further redefine the flood control alternatives. One of the major conclusions was that one of the flood control alternatives, i.e., the alternative that generally followed the original P-1 Channel alignment, was considered not feasible and eliminated from further evaluation. This alternative (defined as Alternative 4 in Volume 2, Appendix B, Agency Workshop of the draft Plan and EIS (Renton, 1996)) included a flood flow diversion channel that would carry high Springbrook Creek flows between approximately SW 43rd Street and SW 23rd Street. Under the alternative, the flood flow diversion channel would generally follow and be similar in cross-section to the original P-1 Channel alignment (as defined by prior NRCS work plans). This alternative was eliminated from further consideration due to several factors including: ■ Substantially higher costs due to greater land acquisition and the much more significant extent of improvements compared with other alternatives, e.g., channel excavation quantities, revegetation, dewatering and controlling of water, and the cost associated with the likely requirement to relocate major utilities such as the City of Seattle Cedar River pipeline and Olympic petroleum pipelines. ■ Greater impacts to wetlands and corresponding wetland mitigation by constructing the channel through some wetlands and by potentially dewatering adjacent wetlands due to the low channel bottom elevation. ■ Difficult construction because much of the channel bottom would be near or below the groundwater elevation. ■ Greater potential for water quality problems due to the more significant construction and dewatering. ■ Increased maintenance needs because both the high-flow channel (P 1 Channel alignment) and low flow channel (Springbrook Creek) would need to be maintained. ■ The high flow channel would pass adjacent to a State Priority Listed contaminated site (Sternco Property), increasing the concern for water quality and sediment quality problems. ■ Lack of general public and agency support compared with other alternatives. X0011592.112 R. W. Beck 8-3 SECTION 8 The alternatives at this point in the planning process were still preliminary in nature. The FEQ hydraulic computer model was then used to simulate the two remaining action alternatives to define the extent of improvements (i.e., width of channel widening, size of culvert crossings, etc.) necessary to achieve the desired level of flood protection. The desired level of flood protection was based primarily upon achieving target water levels for the future condition 25-year and 100-year floods. The target water levels as well as other alternative criteria were defined by the City with assistance from NRCS and the consultant team (Renton, 1995; see also Volume 2, Appendix D of the draft Plan and EIS (Renton, 1996)). The results of the FEQ modeling are presented in the ESGRWP Technical Memorandum - Hydraulic Modeling of Flood Control Alternatives (R. W. Beck, 1995a). After the FEQ hydraulic modeling of alternatives was completed, the format of the flood control alternatives was modified into the current format presented in this plan and the EIS. The alternative descriptions went from a no action alternative and two overall Valley area action alternatives, inclusive of all proposed project elements on all affected drainage systems, to a set of five alternative categories that deal with specific systems. The revised format included alternative flood control measures for the following systems. ■ Springbrook Creek Alternatives (SC) ■ Panther Creek Alternatives (PC) ■ SW 23rd Street Drainage Channel Alternatives (23ST) ■ Wetland Mitigation Bank and Wetland Hydraulic Modifications (W) ■ Pipe System Improvements (PS) This approach allowed a more detailed impact evaluation of specific systems. It also provided greater flexibility in selecting the best alternative for each drainage system component and the system as a whole. 8.3 DESCRIPTION OF FLOOD CONTROL SOLUTIONS This section presents the detailed descriptions of flood control alternatives for solving current and future flooding problems and improving environmental conditions in the Valley area. The process by which the alternatives were developed was described in the previous section. The alternatives are presented for the five major categories listed above. These alternatives were, in general, developed to work together to meet the City's project goals and objectives. For example, to reduce flooding, both improvements to Springbrook Creek as well as improvements to tributary pipe systems are necessary. The alternatives were developed to work together to correct the major flooding problems for the future condition 100-year event. Several alternatives categories include more than one improvement (individually defined as an element) along the particular system. Some of these elements are included in more than one alternative. For example, replacing the existing 8-4 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION Springbrook Creek culvert crossings for SW 27th Street and SW 34th Street are elements of both Springbrook Creek Alternatives 2 and 3. A summary of all alternative elements is illustrated in Figure 8-1. Conceptual cross section, profile, and/or plan view figures depicting specific alternative elements are included at the end of this section. As noted above, the FEQ hydraulic model was used to simulate the hydraulic response to the flood control alternatives. A summary of the simulated peak flows and water levels for the current and future land use condition 2-year event and the future land use condition 25-year and 100-year events (both storage and conveyance) is provided in Table 8-2. The 2-year event was simulated for both current and future land use to provide information on impact to wetlands from the more frequent storm events. The 25-year and 100-year events were simulated for future land use conditions only because future flows were used to size alternative flood control measures. Table 8-2 summarizes the results for the No Action alternative, which assumes no flood control measures are implemented, as well as for various combinations of the flood control alternatives. The alternative combinations are described in the table. Table 8-3 provides a summary of the hydraulic simulation results for Valley area wetlands for the 2-year event under both current and future land use conditions. It should be noted that after the completion of the FEQ modeling of alternatives, two minor inaccuracies were identified in the FEQ model. The first was the width of the SW 16th Street bridge, the opening width had not been updated to account for the improvements made as a part of the connecting channel project between Grady Way and SW 16th Street. The second was the average invert elevations of the Oakesdale Avenue culverts, which had been input to the model slightly lower than their actual invert elevations. The two inaccuracies are considered minor and are not considered to affect the results. To confirm this, these two changes were made in the FEQ model and a comparison was made to evaluate the effects that these inaccuracies had on the simulation results. The comparison was made on Alternative SCZTCZ/23STZTIPE2 for the 100-year future land use condition simulation. The largest difference in the maximum simulated water levels occurred at the upstream side of the SW 16th Street bridge and was 0.36 feet. The difference in maximum simulated water levels quickly dissipated upstream of the SW 16th Street bridge. At the upstream sides of SW 27th Street and Oakesdale Avenue, the difference in simulated maximum water levels were 0.12 and 0.02 feet, respectively. The comparison confirms that the inaccuracies are minor and do not warrant updating the model results, particularly because the critical elevations for designing flood control improvement are at the upper end of the system, in the vicinity of Oakesdale Avenue, where the simulated difference is insignificant. It should also be noted that these inaccuracies occurred to the existing system models. These inadequacies would have less of an impact in the existing system simulation results because the water levels are dominated by the culvert capacity restrictions at SW 27th Street, SW 34th Street, and at the Oakesdale crossing. X0011592.112 R. W. Beck 8-5 SECTION 8 8.3.1 SPRINGBROOK CREEK ALTERNATIVES The Springbrook Creek Alternatives and alternative elements are illustrated on Figure 8-2. SPRINGBROOK CREEK ALTERNATIVE 1 (SC1) — NO ACTION The No Action alternative is an analysis of what happens to Springbrook Creek without any improvements under current and future land use conditions. Under current conditions, Springbrook Creek water levels rise during large flood events such that the Valley area is subject to significant, recurring flooding. Flooding results in damage to public and private property, habitat and water quality degradation, channel erosion and sedimentation problems, traffic and business disruption, health and safety concerns, and impairment of access for emergency vehicles. The low gradient and narrow width of the valley drainage systems necessitate intermittent sediment, vegetation, and debris removal to maintain conveyance capacity. The City, Drainage District No. 1, Washington State Department of Transportation, and others currently have regular program for the maintenance of drainage systems within the project area. Under SCl, these maintenance activities would need to continue. Major current flooding problems simulated through hydrologic and hydraulic studies and corroborated by observations during recent floods occur at the locations listed below: FLOODING PROBLEMS ALONG THE MAIN STEM OF SPRINGBROOK CREEK ■ Springbrook Creek overtopping SW 34th Street and localized flooding. ■ Springbrook Creek overtopping Oakesdale Avenue and localized flooding. ■ Flooding problems along systems tributary to Springbrook Creek. High water levels in Springbrook Creek reduce the capacity of several tributary systems by creating backwater conditions that are a contributing factor in the following flooding problems: ■ Flooding along East Valley Road from approximately SW 23rd Street to SW 43rd Street. ■ Flooding along SW 43rd Street from approximately Oakesdale Avenue to east of Lind Avenue. ■ Flooding along Lind Avenue from SW 43rd Street to north of SW 41st Street. If no improvements are implemented along the main stem of Springbrook Creek, the existing flooding problems will continue to negatively impact the Valley area and will worsen in the future as development in the watershed continues. In addition to the problems caused by flooding, the current environmental conditions of Springbrook Creek are a concern to the City. Water quality is 8-6 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION degraded and fish rearing and riparian habitat is limited. These problems may because worse unless measures are implemented to correct the problems and to increase the function and value of Springbrook Creek, its associated wetlands, and tributary streams. Under both current and future conditions, there is potential for significant erosion along a reach of Springbrook Creek upstream of SW 16th Street. Stream velocities in this reach are predicted to exceed 8 feet per second (fps) for the relatively frequent events (2-year future condition flood). SPRINGBROOK CREEK ALTERNATIVE 2 (SC2) - LOCALIZED IMPROVEMENTS TO SPRINGBROOK CREEK This alternative would include localized improvements to Springbrook Creek that, when combined with other Valley drainage system improvements, reduce flooding problems. It would also include elements to improve riparian habitat. This alternative focuses on limiting the extent of improvements/modifications to the Springbrook Creek stream channel by keeping the overall length and width of channel improvement to a minimum. Alternative 2 includes a number of discrete elements (projects) that are described in the following paragraphs. SC2- Element 1: Improvements at Roadway Crossings. This element includes improvements at four Springbrook Creek roadway crossings that are conveyance restrictions. These crossings include a private bridge north of SW 27th Street, SW 27th Street, SW 34th Street, and Oakesdale Avenue. These improvements are described as follows: ■ Bridge North of SW 27th Street — This is a private bridge that will be removed. It is the City's understanding that the bridge is no longer in use and that, prior to the extension of SW 27th Street, it was used for access to a property on the west side of Springbrook Creek. ■ SW 27th Street and SW 34th Street — These two existing crossings each consist of multiple culverts. The crossing at SW 27th Street includes two 128-inch wide by 83-inch high corrugated metal pipe (CMP) arches. The crossing at SW 34th Street includes four 6-foot diameter CMP culverts. Although the specific type of improvement will be determined during final design, the proposed improvement is to replace the culverts with multiple- span, three-sided, precast concrete box culverts. Replacement with conventional bridges was considered; however, bridges are not preferred because they require certain maintenance and inspection not required for culverts, they are likely to cost as much or probably more than three-side box culverts, and the expected problems with achieving the minimum 2-foot clearance between the 100-year water surface and bottom (low chord) of the bridge as required by the King County Surface Water Design Manual (KCSWDM). Very large single open-bottom arch culverts were also considered, such as the 21-foot-wide by 10.5-foot-deep culvert at X0011592.112 R. W. Beck 8-7 SECTION 8 SW 43rd Street; however, the hydraulic analysis indicated that a large arch culvert would be of insufficient size to achieve the desired headloss. For planning purposes, the three-sided box culverts were sized to lower upstream water levels as well as minimize headloss through the crossings. The City and NRCS defined a target headloss of no more than 0.1 and up to a maximum of 0.2 foot. Using this criterion as a guide, the box culverts were sized as two side-by-side, 30-foot-wide, three-sided box culverts. The SW 27th Street culvert was sized with one box with a 10-foot height spanning the low flow channel and the other box with a 5-foot height spanning a high flow bench. This type of configuration was chosen because it is desirable to maintain a low flow channel width that is approximately the same as the existing channel. The SW 34th Street culvert was sized as two side-by-side, 8-foot-high, 30-foot-wide, three-side box culverts. Having one box higher for the SW 34th culvert was not simulated because there is probably insufficient height between the existing stream grade (about elevation 5 NGVD) and the top of roadway elevation (14.9 NGVD) to have a high flow box. The box culverts for both streets would need a low flow channel for fish. These configurations resulted in simulated headlosses for the 100-year future event of 0.03 foot and 0.09 foot, for SW 27th Street and SW 34th Street, respectively. Detailed analysis at SW 27th Street and SW 34th Street will be conducted during the predesign phase to determine the optimal type and size of structure that yields the desired performance at the least cost. Consideration will be given when sizing the structure to accommodate below-grade trail crossings at these two locations. The three-sided box configuration would improve fish passage through these crossings because of lower stream velocities and because the bottom of the culverts would be a natural stream channel. Coordination between the planned SW 27th Street HOV project(see Section 4.1.6) and the SW 27th Street culvert replacement is necessary to ensure that the two projects are compatible. ■ Oakesdale Avenue—The hydraulic analysis shows that the Oakesdale Avenue crossing can be overtopped during flood events. The Alternative 2 design goal for improving the Oakesdale crossing is to eliminate roadway overtopping for the future condition 100-year event. Assuming the other downstream improvements of this alternative are implemented to lower Springbrook Creek water levels, the Oakesdale Avenue roadway overtopping can be eliminated by slip-lining (e.g., using a reinforced fiberglass liner) the existing 6-foot-diameter CMP culverts to reduce roughness and increase capacity, plus adding two new 6-foot-diameter concrete culverts. It should be noted that a Metro sewer interceptor is installed directly below the existing culverts and, thus, any new culverts would have to be installed above the sewer. Ideally, one of the new culverts should be a larger 7-foot-diameter concrete culvert set below grade to have a gravel bottom to meet the City's fish criteria for new culverts. This may not be possible, given the conflict with the Metro sewer. Detailed analysis of the crossing would be conducted during the predesign phase to determine how best to use the existing culverts 8-8 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION and improve passage for fish. For example, consideration could be given to putting a drop within one of the new culverts after it has passed over the Metro sewer. In addition, small weirs (e.g., 0.5-foot) could be placed in front of the other culverts so that low flows would pass through the new culvert having the drop. SC2 - Element 2: Channel Improvements from SW 16th Street to SW 23rd Street. This element would include widening and restoring approximately 3,400 linear feet of channel between SW 16th Street and SW 23rd Street. Based upon the hydraulic modeling, this channel reach was found to be a capacity restriction. In addition, the lower section of this reach was identified as having an erosion problem. Stream velocities in this reach are predicted to exceed 8 feet per second (fps) for relatively frequent events (2-year future condition flood). A preliminary cross-section of the channel improvement is given in Figure 8-3. The proposed channel improvement would include excavating 10-foot-wide high flow benches above a 27-foot-wide, 2.5-foot-deep low-flow channel. Along portions of the channel reach it may be possible to excavate the high flow benches without disturbing the low flow channel, while along other portions of the channel it may be necessary to reshape the entire channel section. The extent of channel that can be improved without disturbing the low flow channel will be determined during design. With the improved cross-section, the channel velocities in the area upstream of SW 16th Street would be reduced from the predicted 8 fps,2-year flood to 3.5 and 4.5 fps for the 2-year and 100-year future events, respectively. Channel armoring using bioengineering techniques would be considered for the improved channel section. These improvements would avoid deepening or relocating Springbrook Creek where it crosses the City of Seattle 60-inch-diameter water pipeline at SW 23rd Street. The channel improvement would incorporate an asphalt surfaced recreational trail approximately 2,100 feet in length to connect existing sections of the Springbrook Creek trail presently terminating at SW 19th Street and about 200 feet south of SW 23rd Street. The trail would be located either on the westerly high flow bench or along top of the west bank. The portion of trail from SW 19th Street to SW 23rd Street is the responsibility of the Hunter Douglas development project (LUA-96-104, SM; formerly Raymond Avenue Center West). The trail will be constructed by either the Hunter Douglas project or by the City as part of the channel widening project with funding provided by Hunter Douglas. Portions of the existing trail from SW 16th Street to SW 19th Street may need to be relocated to the top of the widened channel or onto the high flow bench. Also, coordination between the planned crossing of Springbrook Creek by Oakesdale Avenue (see Section 4.1.6) and the channel widening is necessary to ensure that the two projects are compatible. X0011592.112 R. W. Beck 8-9 SECTION 8 SC2- Element 3: Channel Maintenance Program. As with the no action alternative, a maintenance program for vegetation and sediment removal would be needed to maintain the conveyance capacity provided by the channel system. The City is obligated under operation and maintenance agreements with NRCS to remove sediment and perform other maintenance activities along the previously constructed floodwater storage pond (P-1 Pond) and channel upstream to SW 16th Street. However, because of the complex issues that would need to be addressed pertaining to the floodwater storage pond and its surrounding riparian area, a maintenance plan for the floodwater storage pond is beyond the scope of this EIS, but is instead planned as a separate future proposal. Separate from development of a comprehensive plan for the pond, a specific maintenance action is proposed for the removal of sediments that have accumulated in the construction channel a limited distance downstream of SW Grady Way. This action would be in partial fulfillment of the City's obligation under agreement with NRCS for operation and maintenance of the previously constructed channels. Sediments have accumulated in the constructed channel downstream of the SW Grady Way five-cell box culvert since the downstream channel and box culvert were constructed in 1987. This accumulation is due, in part, to the fact that prior to improving the channel upstream of SW Grady Way (to SW 16th Street), three of the five cells of the box had been partially blocked, thereby creating dead zones with little or no velocity, which then accumulated sediment. In addition, the substantial increase in channel size downstream of the box culvert tended to reduce flow velocities which also encouraged sediment deposition. The proposed location of sediment removal is shown in Figure 8-2. A schematic of a typical cross section for sediment removal is shown in Figure 8-4. Sediment would be removed from approximately 800 feet of channel at the downstream end of the SW Grady Way box culvert. Most of these sediments are likely large grained material, such as sand, that tends to settle quickly out of the water column. Removal would be accomplished by either dragline, clam shell, or other excavation method from the maintenance berm on the west side of the channel, with removed sediments disposed of off site. Sediment would be removed from within the channel to restore the channel to its originally constructed grade. Vegetation on the banks would be left undisturbed as much as possible. Vegetation along the banks that is disturbed would be revegetated. Removal of the sediments would be accomplished during the summer months within a specific construction window established by the Department of Fish and Wildlife when instream flows are lower. Also, the level of the water in the downstream floodwater storage pond,which is controlled by the operation of the BRPS,would be lowered to a nominal elevation of 0.0 feet (NGVD 1929 datum) in accordance with the operation manual for the pump plant (SCS, 1972). The operation manual proscribes two seasonal base water levels in the pond upstream of the pump station. From June 15 to November 1 the water elevation 8-10 R. W. Beck x0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION in the pond is to be nominally 0.0 feet. From November 1 to June 15 the pool elevation is to be nominally 2.0 feet. However, King County, which operates the pump plant, has been typically holding the pond water elevation between 2 and 3 feet year-round. Doing so encourages the accumulation of sediments in the previously constructed channel by reducing flow velocities. SC2-Element 4: Improve Riparian Habitat/Selective Plantings. This alternative would include planting the top of the existing channel with trees that will ultimately fill out, providing a canopy and shade over the channel. The shade would help lower water temperatures leading to an increase in dissolved oxygen. The tree plantings would be placed outside of the flood flow channel so as not to cause a conveyance restriction. Some plant species capable of providing such cover include black cottonwood, balsam poplar, quaking aspen, and red alder. This element would also include periodic landscape maintenance to encourage trees to fill out and increase shade. The landscape maintenance could be incorporated into a public involvement program. This element would also include selective placement of instream structures for the portion of channel being widened under SC2 - Element 4 (SW 16th Street to SW 23rd Street). Instream structures such as root wads would be sporadically placed in the channel to provide cover for fish. SPRINGBROOK CREEK ALTERNATIVE 3 (SC3) — SPRINGBROOK CREEK GREENWAY IMPROVEMENTS This alternative includes many of the same improvements as SC2. It differs from SC2 in that improvements to Springbrook Creek would be more extensive and would include additional reaches of improvement between SW 30th Street and the existing railroad bridge just north of SW 41st Street. The improvements would also be of a different nature and include greater widening and more streamside planting, reflecting a greenway concept. The greater cross-section area of the improvement would decrease the need for channel maintenance. A disadvantage of the wider cross-section is the increased right-of-way necessary for channel improvements. The SC3 project elements include the following: SC3 -Element 1: Improvements at Roadway Crossings. This element would include improvements at four Springbrook Creek roadway crossings that are conveyance restrictions. Three of these improvements would be the same as described under Alternative 2, including the private bridge north of SW 27th Street (not in use), SW 27th Street, and SW 34th Street. Oakesdale Avenue would also be improved, except the improvements would be more extensive than as described under Alternative 2. The Oakesdale Avenue crossings would be improved with three-sided, precast concrete box culverts similar to SW 27th Street and SW 34th Street. This improvement includes replacing the existing culvert crossings with side-by-side, 30-foot-wide, three-sided box culverts, with one box spanning the low flow x0011592.112 R. W. Beck 8-11 SECTION 8 channel and the other box spanning a high flow bench. The three-sided box configuration should also improve fish passage through these crossings because they will have a natural bottom and because they have lower stream velocities, due to their large cross sectional area. Replacing the Oakesdale Avenue crossing three-sided precast concrete box culvert would help lower upstream water levels beyond that of SC2 up through SW 43rd Street. In doing so, the water levels for the future condition 100-year event could be brought down to the current FEMA flood elevation at SW 43rd Street. It should be noted that the current FEMA flood elevations are actually based upon pre-1979 land use conditions and not future build-out land use conditions. SC3 - Element 2: Channel Improvements. This element would include channel widening and restoration between SW 16th Street and SW 23rd Street, and between SW 30th Street and the existing railroad bridge just north of SW 41st Street. The improvements would focus on a greenway concept that would incorporate high flow benches and more intensive plantings near the low flow channel to create wildlife habitat and to improve fish habitat by providing overhanging vegetation and lower water temperatures. The high flow benches would be designed to carry flood flows above the 2-year event. A public access trail would also be integrated into certain reaches. Preliminary cross-sections of the channel improvements for the different reaches are shown in Figure 8-5 and described as follows: ■ SW 16th Street to SW 23rd Street — This improvement includes a high flow bench on both sides of the creek. The channel improvement would be made by maintaining the existing channel bottom and excavating out at a 3:1 side slope up to a high flow bench. Some reshaping of the low-flow channel may be necessary, the extent of which will be determined during design. The high flow bench would be between 10 feet and 17 feet wide and the side slopes would continue up at 3:1. Again, the reach was identified as a current erosion problem. With the improved cross section, the channel velocities in the area upstream of SW 16th Street would be reduced to 4 to 4.5 fps for the 2-year and 100-year future events, respectively. Channel armoring using bioengineering techniques would need to be considered for the improved channel section. An asphalt surfaced recreational trail would be incorporated into the channel improvement similar to Alternative 2. For hydraulic modeling purposes the high flow bench was given a lower Manning's roughness (0.05) to reflect some maintained vegetation along the trail. This alternative approach would differ from SC2 Element 2 in that the elevation of the high flow bench would be higher, by approximately 5 feet, and the width of the high flow benches as well as the channel top width would be wider. Although the specific dimensions would be determined 8-12 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION during final design, the width of the high flow benches could be as much as 7 feet wider and the overall top width could be as much as 20 feet wider. As with SC2, coordination between the channel widening and the planned crossing of Springbrook Creek by Oakesdale Avenue SW (see Section 4.1.6) would be necessary to ensure that the two projects are compatible. ■ SW 30th Street (south of Renton Wetland) to SW 40th Street (railroad bridge) — This improvement would include high flow benches on only the west side of the creek upstream of SW 34th Street. The existing channel up to about the 2-year flow elevation would remain in place and would not be disturbed with the exception that additional plantings would be introduced among the existing vegetation to improve riparian habitat. A high flow bench would be excavated above the 2-year flood level. The bench would be approximately 30 feet wide with side slopes of 3:1. SC3-Element 3: - Channel Maintenance Program. The channel maintenance program under this alternative would include sediment removal downstream of the SW Grady Way box culvert as under SC2. The main difference from SC2 is that the vegetative management program would be reduced. Under this alternative, the channel improvements described under Elements 1 and 2 above allow for more intense vegetation along the channel banks for the entire length of Springbrook Creek, not just in areas where the channel would be widened. As a result, the City would, over the long-term, need to perform maintenance less frequently. SC3-Element 4: Improve Riparian Habitat/Extensive Plantings. This alternative would include planting the sides of both the existing and widened channels with shrubs and trees to increase shade and cover for fish. The increased shade would help lower water temperatures and increase dissolved oxygen. The increased plantings would provide protection for fish as well as increase biotic activity providing food for fish. The plantings would be concentrated along the banks, approximately between the average flow depth and the 2-year flood flow depth. For hydraulic modeling purposes, a Manning's roughness value of 0.09 was assumed for the planting densities. This element would also include periodic landscape maintenance to encourage trees to fill out and increase shade. The landscape maintenance could be incorporated into a public involvement program. This element would also include selective placement of instream structures along both the existing and widened portions of channel. Instream structures such as root wads would be sporadically placed in the channel to provide cover for fish. 8.3.2 PANTHER CREEK ALTERNATIVES Currently, Panther Creek enters the valley from Talbot Hills and flows through the two southernmost culverts crossing under SR-167 in the Valley area (between SW 34th Street and SW 39th Street). As the creek enters the Valley area, it flows through an alluvial fan at the base of Talbot Hills. Through the alluvial fan the x0011592.112 R. W. Beck 8-13 SECTION 8 channel becomes braided. Panther Creek low flow extends to the two southernmost culverts crossing SR-167. During moderate and high flows, Panther Creek exceeds the banks of the low flow channel through the alluvial fan and begins to flow in other braided channels, some of which carry flow north directly into the Panther Creek Wetland. Flows through the alluvial fan that are not diverted to the wetland follow the low flow channel to reach the two southernmost SR-167 culvert crossings. These culverts discharge to a short drainage channel connecting to an approximately 3,000-foot-long pipe system along the East Valley Road and SW 34th Street to discharge to Springbrook Creek. During high and moderate flows, the portion of Panther Creek flow to reach the SR-167 culverts exceeds the capacity of these culverts, causing the creek to back up and direct more flow north to the Panther Creek Wetland. The portion of flow that does pass the SR-167 culverts to enter the EVR system is joined with local runoff and exceeds the capacity of this system, causing flooding. The system in EVR was not sized to handle any Panther Creek flow and, consequently, the Panther Creek connection to this system contributes to the EVR flooding problem. In addition, the system also overflows to the north to enter the ditch/wetland that runs along the west side of SR-167. The flood flows that enter the wetland back up against the SR-167 highway embankment and are slowly released under the highway through a series of partially functioning culverts. Many of these culverts are partly or fully silted in and some had completely submerged outlets. The poorly functioning culverts are a maintenance concern for the City and the Washington State Department of Transportation. Two Panther Creek alternatives, in addition to the No Action alternative, have been identified for improving the existing Panther Creek connection to Springbrook Creek. Panther Creek alternatives and alternative elements are illustrated on Figure 8-6. PANTHER CREEK ALTERNATIVE 1 (PC1) — NO ACTION Under the No Action alternative, Panther Creek low and moderate flows would continue to flow through the two southernmost SR-167 culvert crossings to enter the EVR and SW 34th Street drainage systems. The EVR system is subject to recurrent flooding, in part because it was never designed to handle Panther Creek flows in addition to the local runoff. Hydraulic analyses (R. W. Beck, 1996) indicate that the combined capacity of the two SR-167 culverts is approximately 30 to 37 cfs for the 2- and 100-year current condition events respectively. During floods, any flows reaching the SR-167 culverts in excess of the 30 to 37 cfs would be diverted towards the Panther Creek Wetland. Because of the braided nature of the alluvial fan, determining an exact split of Panther Creek flows directed toward the wetland versus the SR-167 is difficult and would vary with physical changes in the braided stream. 8-14 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION It should be noted that the alluvial fan will continue to build up over time, and this build up could affect the location and direction of Panther Creek flows. Consequently, while under current conditions the Panther Creek low flows enter the SR-167 culverts, the shifting of the creek caused by the build up of the alluvial fan could naturally redirect the flow to the Panther Creek Wetland. PANTHER CREEK ALTERNATIVE 2 (PC2) — HIGH FLOW BYPASS TO PANTHER CREEK WETLAND This alternative includes maintaining Panther Creek low flows through the EVR and SW 34th Street systems and diverting moderate and high flows to the Panther Creek Wetland. Maintaining low flows, (approximately 5 cfs) would allow for continued downstream migration of fish through the EVR system. Based upon preliminary HSPF hydrologic modeling, Panther Creek flows would be at or below 5 cfs approximately 70 to 80 percent of the time. These improvements would reduce flows entering the EVR and SW 34th Street system; however, even with the reduction in flows, additional pipe system improvements along SW 34th Street would be necessary to reduce flooding along EVR. The detailed improvements would include the following: PC2- Element 1: Modify Existing Flow Split at SR-167. This element would include installing a structure at the north culvert of the southerly SR-167 culverts that is designed to pass low flows of approximately 5 cfs to the existing EVR system and divert excess flows into the Panther Creek Wetland. The other southernmost culvert would be plugged. The structure would be designed to allow downstream migration of fish. The structure would likely include an overflow weir that would begin to divert flow into the PCW when flows exceed 5 cfs. It is important to note that this diversion happens in the present condition (i.e., high flows overflow the low flow channel through the alluvial fan as well as exceed the capacity of the two southernmost culverts and consequently flow into the PCW). The difference between current conditions and this alternative is that with the new structure, flow passing to the EVR and SW 34th Street systems would be limited to approximately 5 cfs for all storm events. Approximately 30 and 37 cfs pass through the SR-167 culverts under current conditions for the 2-year and 100-year floods, respectively. PC2- Element 2: SW 34th Street System Improvements. This element would include replacing an existing 36-inch-diameter concrete pipe system with a 48-inch-diameter system or larger from approximately East Valley Road to Lind Avenue. PANTHER CREEK ALTERNATIVE 3 (PC3) — MAINTAIN EXISTING FLOW INTO SW 34TH STREET SYSTEM This alternative includes maintaining Panther Creek low and moderate flows (up to 37 cfs) through the two southerly SR-167 culvert crossings. For this alternative, the entire downstream system along EVR and SW 34th Street would need to be improved. The detailed improvement is described as follows. X0011592.112 R. W. Beck 8-15 SECTION 8 PC3- Element 1: This element would include replacing the existing 24-inch to 60-inch pipe system along EVR and SW 34th Street with a larger diameter system. Specific sizing will be done during predesign. On a preliminary basis, it is assumed that the 60-inch pipe would be replaced with a 72-inch, and the 24-inch pipe would be replaced with a 54-inch. The system would be sized to convey Panther Creek flows of up to 37 cfs for the 100-year event plus local runoff. This improvement would also include any required channel improvements between the outlet of the two southerly SR-167 culverts and EVR such as berming along the north bank to prevent overflows into the west SR-167 ditch, or including a side weir to allow some flows to continue to overflow as occurs in existing conditions. PANTHER CREEK ALTERNATIVE DISCUSSION The above described Panther Creek alternatives affect the SW 23rd Street Drainage Channel Alternatives. The SW 23rd Street Drainage Channel Alternatives, described later in this section, generally include replacing a series of SR-167 culverts with a new culvert at SW 23rd Street as well as conveyance improvements along the SW 23rd Street drainage channel. There are several environmental and design issues that have been identified affecting the Panther Creek alternatives as well as the SW 23rd Street Drainage Channel Alternatives. These issues include: ■ In 1995, the Washington State Department of Fish and Wildlife began planting coho fry in the upper reaches of Panther Creek. As a result, there is potential for downstream migration of fish through the system, although several factors exist which likely reduce the survivability of the fish plants. These factors include low base flows, braided channels through the alluvial fan between Talbot Road and SR-167, overflows into and subsequent entrapment in the Panther Creek Wetland, long pipes, and upstream migration barriers (road culverts, etc.). Also, the habitat in Springbrook Creek is highly degraded. See Section 6.8.2 for a more detailed discussion of natural and constructed fish passage barriers and other habitat problems. ■ Impacts to Wetlands — Several wetlands could possibly be affected by these alternatives: Panther Creek Wetland (W-4), SR-167 west side ditch/wetland (W-48d and e), Wetlands No. 8N and 10N (along the south side of SW 23rd Street between Springbrook Creek and EVR) and Wetlands W-48f/W-53 (Panther Creek between SR-167 and EVR). The improvements are intended to minimize impact to these wetlands and, in some instances, enhance them by increasing wetland hydrology. ■ Impact to groundwater (lowering) and resulting potential for settlement of area peat soils. ■ Portions of the existing channel system along SW 23rd Street were designed and built very low assuming that the original P-1/P-9 channels would be built (see Section 6.4.6). These include the Lind Avenue culvert crossing, the EVR culvert crossing, as well as local pipe systems draining to this channel. As a 8-16 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION result, the existing low systems accumulate sediment and are a maintenance problem for the City. ■ There is a mosquito problem in the Talbot Hill area, east of the Panther Creek Wetland. Currently, the City is applying an ultra low volume insecticide in the spring and summer along the hillside above this wetland to reduce adult mosquito populations. System improvements that offer opportunities for reducing mosquitoes are considered desirable (see also Section 4.1.4). ■ Initial consideration was given to plugging all of the SR-167 undercrossings south of SW 23rd Street and completely diverting Panther Creek into either (1) the Panther Creek Wetland and then a new SR-167 crossing at SW 23rd Street, or(2) along the SR-167 westside ditch/wetland and then west along the SW 23rd Street drainage channel to completely eliminate Panther Creek flow tributary to the EVR flooding problem. However, this type of approach would result in significant impacts to fish and wetlands. In order to maintain downstream fish passage through either the PCW or the SR-167 westside ditch/wetland, channel improvements through the wetland would likely be necessary. These channel improvements would be costly and significantly alter the character of the affected wetland. In addition, maintaining any kind of a channel through the wetland would be difficult due to vegetation growth, bank sloughing, and sediment build-up. In addition, even with diversion of the creek, water levels in the Panther Creek Wetland would likely drop below the outlet of the wetland as it does under present conditions, which could cause fish stranding. Another difficulty is that the SR-167 westside ditch/wetland is located primarily within WSDOT right-of-way. WSDOT may be reluctant to allow a new fish stream to be located in their right-of-way because its presence could hinder future widening of the highway, if found necessary. Also, maintaining an open waterway along the west side of SR-167 would be very difficult, if not impossible, given the poor access. 8.3.3 SW 23RD STREET DRAINAGE CHANNEL ALTERNATIVES The SW 23rd Street alternatives and alternative elements are illustrated on Figure 8-6. SW 23RD STREET ALTERNATIVE 1 (23ST1) — NO ACTION The two existing 18-inch culverts conveying the SW 23rd Street channel drainage under the Olympic Gas line crossing west of Line Avenue SW are undersized and cause high upstream water surface elevations at EVR. Such high water surface elevations reduce the capacity of the tributary system along EVR from the south and cause flooding between approximately SW 23rd Street to SW 30th Street. This EVR pipe system receives runoff from local areas plus outflows from the Panther Creek Wetland that discharge through a series of poorly functioning culverts between SW 23rd Street and SW 34th Street (see Section 6.4). It is unlikely that the EVR system was sized to handle the outflows from the wetland. x0011592.112 R. W Beck 8-17 SECTION 8 Flooding will continue to worsen if no actions are taken. Also, as mentioned above in Section 8.3.2, portions of the existing channel system along SW 23rd Street were designed and built very low assuming that the P-1/P-9 channels would be built. As a result, the existing low areas accumulate sediment and are a maintenance problem for the City. The adequacy of the SR-167 culvert crossings between SW 23rd Street and SW 34th Street and the outlet channel to the EVR system is also a long-term drainage concern for the City. Many of these culverts are filled in and/or only partially functioning. The ones that are functioning are submerged most of the year. Access for maintaining these culverts is difficult because the culverts are 15 to 20 feet below the elevation of SR-167 and are separated from the road by a guard rail. Maintenance of the SR-167 culverts is the responsibility of the Washington State Department of Transportation (WSDOT). If neither of the following action alternatives are implemented, then it is assumed that WSDOT would perform maintenance of the culverts so as to restore them to function at full capacity. SW 23RD STREET ALTERNATIVE 2 (23ST2) — MINOR CONVEYANCE IMPROVEMENTS This alternative includes making minor improvements along the SW 23rd Street drainage channel and replacing the series of poorly functioning SR-167 culvert crossings with a new crossing at SW 23rd Street. 23ST2- Element 1: Replace SR-167 Culvert Crossings with New Crossing at SW 23rd Street. This element includes plugging the poorly functioning SR-167 culverts between the southernmost culverts (carrying Panther Creek) and SW 23rd Street and replacing these culverts with a new SR-167 crossing at SW 23rd Street (described below). This replacement would result in a total of three outlets across SR-167: the new SR-167 culvert crossing at SW 23rd Street, the southerly culvert(s) carrying Panther Creek low or low-to-moderate flows as described under the Panther Creek Alternatives, and the existing 3-foot by 4-foot box culvert outlet located near I-405 that conveys runoff from the Rolling Hills basin. A schematic plan and profile of the SW 23rd Street drainage channel under this alternative is illustrated on Figure 8-7. The proposed approach is to close the culverts because access to the culverts is difficult and creates a safety hazard for workers because the only access is from SR-167. If the culverts were to remain operational, then a safer access would be needed whereas access at SW 23rd Street already exists. Creating safe access to the other culverts would require fill into the Panther Creek wetland and Wetland W-48e. As is, the culverts are difficult to visually inspect and the flow through the culverts is a contributor to the flooding problems in EVR. An undesirable but optional approach is for one of the SR-167 cross culverts (located at about SW 29th Street) to remain operational. All other cross culverts would be closed and this culvert fitted with an intake restrictor that limits flow during flood events, but would permit flow to pass freely through the culvert during the dry summer 8-18 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION months. This restrictor would prevent high flows from draining across SR-167, through the existing ditch at about SW 29th Street, and into the East Valley Road system. Instead, the high flows would pass through the proposed culvert at SW 23rd Street and into the SW 23rd Street channel system. Access for installation and maintenance of the restrictor would be needed. Providing access would be very costly, create hazardous traffic conditions on SR-167, and require fill into the Panther Creek wetland and W-48e. By using this approach, the movement of low flows from east of SR-167 to the west ditch wetlands could be maintained. However, the proposed action is to close all culverts but the culvert carrying Rolling Hills Creek, the southernmost culvert(s) carrying Panther Creek, and the new culvert at SW 23rd Street. The new culvert crossing under SR-167 at SW 23rd Street would provide a new outlet from the Panther Creek Wetland to act as a replacement for the series of poorly or non-functioning crossings to be plugged. In terms of capacity, the culvert should be 72 inches in diameter. However, if this culvert needs to be designed for fish passage, it would need to be larger to allow partial burial of the culvert bottom. Use of a constant weir elevation is proposed for this project (i.e., the weir set at a constant elevation throughout the year). However, the culvert inlet structure should be constructed so that the weir elevation could be adjusted so as to not preclude the ability to adjust wetland water levels if the necessary permits and approvals for doing so are obtained through a future, separate project proposal. For example, the weir could be adjusted at its inlet to allow seasonal or intermittent adjustment of the PCW water levels for purposes such as control of mosquito larvae or invasive vegetation. For hydraulic modeling of flood simulations, the flood control weir elevation was set at 12.5 feet NGVD to simulate an initial water level in the wetland consistent with wet season water levels measured at City wetland crest stage gages #2 and #3. This elevation was selected to somewhat conservatively model the wetland with some of its storage already filled and unavailable to attenuate flows. However, the modeled weir elevation is about 2.5 feet above the elevation of the existing outlet ditch for the PCW that is located on the west side of SR-167 at about SW 29th Street. Therefore, a V-notch or small diameter orifice will be used below the flood control weir to replace the function of the existing outlet ditch in passing low flows to the downstream system. The size and configuration of the V-notch or orifice will be determined in final design. Setting the flood control weir or low flow outlet below the existing outlet is not considered an option because of potential environmental impacts associated with significant reductions in wetland hydrology, i.e., loss of wetland area, changes in habitat, and others. Additionally, the width of the weir was sized so that 100-year future condition flood storage is similar to the storage currently being provided in the wetland, thereby maintaining the function of the wetland in attenuating downstream flows. X0011592.112 R. W. Beck 8-19 SECTION 8 In the agency meeting of May 18, the agencies stated they would like the project to achieve both fish passage and rearing habitat improvements where possible. In a separate meeting with the Corps on May 25, 1995, the Corps suggested that the proposed culvert at SW 23rd Street provide for fish passage, even if fish are not allowed into the wetland until some time in the future. In this way, if the culvert were designed for fish passage, it would be low enough so as not to preclude construction of a fish passage channel through the wetland at some future time. Installing the culvert at a lower elevation will add to the cost because of the increased length required to daylight the culvert beyond the fill slope of SR-167. This alternative also includes removal of existing risers on EVR culvert inlets and constructing a new channel from EVR to SR-167. There are problems associated with providing fish passage through this structure in the future because passage further upstream would not be possible through the Panther Creek Wetland unless an excavated channel was constructed and maintained. Under current environmental regulations, an excavated channel through the wetland would likely not be permitted due to potential wetland impacts. Also, the channel would likely fill in with vegetation and become a significant maintenance problem. In addition, numerous other fish passage and habitat problems (e.g., alluvial fan, and low base flows) severely limit the potential for Panther Creek to provide passage to upstream migrating salmonids. 23ST2- Element 2: Olympic Gas Line Relocation or Culvert Replacement. This element includes replacing the two existing 18-inch culverts that carry the SW 23rd Street drainage channel flows underneath the existing Olympic Pipeline Company petroleum product lines (20-inch, 16-inch, and 10-inch) located west of Lind Avenue with a new, larger box culvert. The dimensions of the box culvert have to be short in depth and wide to fit under the existing gas lines. For preliminary sizing, a 10-foot-wide by 2-foot-deep open area was assumed. A disadvantage of the new culvert is that, because of the existing pilelines, it would have to be installed very low. As a result, the bottom elevation could be approximately 2 feet below the downstream channel invert. This configuration would result in sediment accumulation over time and require periodic maintenance. Another option that could be considered includes the relocation of the pipelines below the grade of the channel. The hydraulic model simulations and cost estimates assume that the improvement would be made with a new box culvert. An existing abandoned beaver dam at the mouth of the SW 23rd Street channel would be removed to allow fish to use the channel. SW 23RD STREET ALTERNATIVE 3 (23ST3) —MAJOR CONVEYANCE IMPROVEMENTS This alternative would be similar to SW 23rd Street Alternative 2 except that the existing drainage channel between Springbrook Creek and SR-167 would be widened and deepened to provide a positive grade through the system and reduce maintenance needs. A schematic plan and profile of the SW 23rd Street drainage channel under this alternative is illustrated on Figure 8-8. 8-20 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION 23ST3 - Element 1: Replace SR-167 Culvert Crossings with New Crossing at SW 23rd Street. This element would be the same as SW 23rd Street Alternative 2- Element 1. 23ST3 - Element 2: Olympic Gas Line Relocation or Culvert Replacement. This element would be the same as SW 23rd Street Alternative 2-Element 2. 23ST3 - Element 3: Channel Widening and Deepening. This element would include widening and deepening the existing channel along SW 23rd Street between SR-167 and Springbrook Creek to provide positive drainage. A preliminary channel cross section has a 5- to 10-foot-wide bottom width with 3:1 side slopes. A sketch of the improved cross section is shown on Figure 8-9. Note that extensive plantings and instream habitat structures would be used similar to the Springbrook greenway concept (SC3). One item to note is that deepening the channel and using side slopes of 3:1 would create a very large channel section and affect adjacent wetlands (Wetland W-8N and W-10N). The 3:1 side slopes were selected to be consistent with NRCS criteria for channel design. It would be possible to reduce the channel side slopes as well as the channel bottom width and still achieve the flood protection objectives. However, this would probably require an exception from NRCS channel design criteria. 8.3.4 WETLAND MITIGATION BANK AND WETLAND HYDRAULIC MODIFICATIONS The City is proposing hydraulic modifications to two wetlands as well as a wetland mitigation bank. For each wetland project and the mitigation bank, the following paragraphs describe of the existing wetland, and an evaluation of the No Action alternative and the proposed action. The locations of the wetland alternatives are shown in Figure 8-10. WETLAND 12 — EXISTING CONDITIONS Wetland 12 is noted in the City's wetland inventory as being approximately 35 acres and being partially a Category 1 wetland (W-12a) and partially a Category 2 wetland (W-12b) under the City of Renton Wetlands Management Ordinance. The wetland is several feet lower in elevation than the surrounding grade of SW 27th Street and the vacant fill bordering the wetland to the south. It is bisected into two cells (W-12a/W-12b) by a north-south berm which appears to have been constructed in the mid-1970s. The berm was used as an access road to a fill site adjacent to and north of what is now SW 27th Street. The wetland is at the lower end of an approximately 300-acre subbasin extending from SW 27th Street on the north to SW 43rd Street on the south, and from Oakesdale Avenue on the east to West Valley Highway on the west. The subbasin is predominately open space/vacant land, with the exception of the X0011592.112 R. W. Beck 8-21 SECTION 8 Burlington Northern auto-transfer facility along Oakesdale Avenue SW near SW 34th Street and the developed areas in the City of Tukwila. Most of the area tributary to the wetland drains into the western cell through a 48-inch CMP culvert from the South Marsh wetland (W-13Sj) on the Boeing Longacres Office Park property to the west. The balance of the tributary area includes the slopes immediately surrounding the wetland and a small area drained by a storm piping system in Oakesdale Avenue SW. The large storage volume available in the western cell and the connecting South Marsh, attenuates inflows which exit the west cell into the east cell through an 18-inch culvert in the berm. Flows entering the east cell discharge into the adjacent Springbrook Creek. In addition to receiving runoff from local tributary areas, the wetland also serves infrequently as an off-channel floodwater storage reservoir during peak events on Springbrook Creek. The depth of flooding just upstream of SW 27th Street and in the wetland is summarized in the ESGRWP Hydraulic Analysis Report (R. W. Beck, 1996a). Because of the small size of the culvert connecting the east and west cells of the wetland, the hydraulic modeling of the existing system assumed that there is no connection and water from Springbrook Creek must first overtop the berm to spill into the western cell of the wetland. WETLAND 12 —ALTERNATIVE 1, NO ACTION Assuming no action, Wetland 12 and the South Marsh will continue to function as off-channel storage for Springbrook Creek and will also attenuate local inflows. Wetland 12 is owned by the City and will remain open space, with a recreational trail along Springbrook Creek planned for construction at some future time under a separate Parks Department project. Based on projected future land use conditions in the watershed, overbank flooding of Springbrook Creek will occur more frequently and to somewhat greater depths. Periodic maintenance of the culvert in the berm would be necessary to prevent plugging. This maintenance would include removal of sediment and vegetation in and around the culvert entrances and infrequent replacement. WETLAND 12—ALTERNATIVE 2, CULVERT REPLACEMENT The proposed action under this alternative is to replace the existing 18-inch culvert connecting the east and west cells of the wetland with two or three 36-inch culverts. The new culverts would be installed at the same elevation as the existing culvert, thereby maintaining the existing storage and open water components in the west cell of the wetland and in the South Marsh. A second option would be to remove the existing culvert and replace it with an open channel or weir. The bottom of the channel or weir could be set to maintain the existing open water features of the wetland. The purpose of replacing the existing culvert is to restore the hydraulic connection between Springbrook Creek and the area west of the berm. As described above, the existing 18-inch culvert was assumed to not be functioning 8-22 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION because of its small size. Presently, the berm must overtop before the wetland areas west of the berm can provide significant function as off-channel storage for Springbrook Creek. With the planned improvements to Springbrook Creek, especially the replacement of the SW 27th Street culvert crossing, the flood elevations just upstream of SW 27th Street (adjacent to the wetland) would be reduced so that even the 100-year flood levels will not exceed the elevation of the berm. Replacing the existing 18-inch culvert in the berm would allow overflows from Springbrook Creek to move freely through the berm and be stored in the wetland areas west of the berm. This storage, in turn, would help attenuate flows in Springbrook Creek and thereby reduce the extent of improvements needed on the main stem of Springbrook Creek. WETLAND 32 (WETLAND MITIGATION BANK SITE) - EXISTING CONDITIONS Wetland 32, as noted in the City's wetland inventory, is located south of SW 34th Street, west of Springbrook Creek, north of SW 40th Street, and east of Oakesdale Avenue SW(Sec 25,T23N, R4E) on land owned by the City. The site is 13.93 acres and consists of 7.24 acres of upland meadow and 6.69 acres of emergent, young shrub and forested wetland. The wetlands are classified as Category 3 under the City of Renton Wetlands Management Ordinance. The site was filled during the Orillia Fill Project in about 1978, and the topography is relatively flat with small depressions that developed into wetlands. A berm along the creek that rises to approximately 3 feet above the site is likely the result of dredging in the creek and side-casting of the spoils. The source of water for Wetland 32 is precipitation. The wetland does not have any inlet or outlet, and the elevation of the wetland is 7 to 8 feet higher than the normal flow levels of Springbrook Creek. The site is not within the 100-year FEMA floodplain. WETLAND 32 —ALTERNATIVE 1, NO ACTION Assuming no action, the site will continue to be preserved as open space in accordance with restrictions placed on the property when it was acquired by the City. However, the site will also remain isolated from Springbrook Creek and provide no off-channel flood storage. WETLAND 32 —ALTERNATIVE 2, MITIGATION BANK/EXCAVATE LARGE OFF-CHANNEL STORAGE The proposed 14-acre Wetland Mitigation Bank (City Wetland No. 32) site is located along Springbrook Creek on the east side of Oakesdale Avenue between approximately SW 34th Street and SW 40th Street. This element includes enhancing and expanding Wetland No. 32 to create mitigation credits for use in compensating off-site wetland impacts from other projects occurring in the same drainage basin. Expansion of the wetland would also provide additional flood x0011592.112 R. W. Beck 8-23 SECTION 8 storage volume, create off-channel habitat, and enhance the downstream system by attenuating flows and improving water quality. The preferred approach to create and enhance wetlands on the banking site is to excavate past fill material to lower site grades and restore a hydraulic connection with Springbrook Creek. The connection of the site to the creek will allow free movement of water between the wetland and the creek and prevent fish entrapment in the wetland. Flows from the creek would backup and/or overflow onto the site, be temporarily stored, and return to the creek as flows in the creek recede. Providing the additional storage is important because it would help offset the reduction in off-channel storage provided by other areas of the system that would result from the lowering of Springbrook Creek water levels as proposed under the Springbrook Creek alternatives. WETLAND 7-N— EXISTING CONDITIONS Wetland 7-N is noted in the City's wetland inventory report as approximately 12 acres and as a Category 1 wetland under the City of Renton Wetlands Management Ordinance. The wetland, which is within the 100-year FEMA floodplain, is several feet lower in elevation than the surrounding grade of SW 19th Street on the north, East Valley Road on the east, and the vacant properties to the west and south. The property to the west is the site of the City's Fire Station 14 development. The wetland is located on land now under City ownership. The City recently accepted dedication of an approximately 11-acre tract from the Austin Company that included most of Wetland 7-N. The remainder of the wetland lies on SW 21st Street right-of-way and the Fire Station 14 property. The source of water for the wetland is primarily direct precipitation and groundwater. Runoff from Fire Station 14 discharges to the wetland only after water quality treatment. A small 12-inch CMP storm drain connects the wetland to the 60-inch storm drain in SW 19th Street which conveys Rolling Hills Creek. The invert elevation of the 12-inch pipe is about 9.0 feet (NGVD) just below the simulated elevation of the 2-year current conditions flow in the 60-inch storm drain, of 9.2 feet (see Note 6 of Table 6-4) and several feet below the simulated 100-year future conditions flow elevation of 14.0 feet. WETLAND 7-N— ALTERNATIVE 1, NO ACTION Assuming no action, the wetland is likely to remain unaffected by development on the surrounding properties, remain isolated from Rolling Hills Creek in the 60-inch storm drain, and provide little off-channel storage. 8-24 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION WETLAND 7-N — ALTERNATIVE 2, CULVERT REPLACEMENT The proposed action is to replace the existing 12-inch culvert with at least a 36-inch culvert as the same elevation at the existing culvert, thereby maintaining the existing dead storage and open water components in the wetland. Because the elevation of the 12-inch pipe is just below the simulated water elevation in the 60-inch storm drain for the 2-year storm, providing a larger connection to the wetland should not affect the normal hydroperiod of the wetland. The larger pipe would restore the hydraulic connection of the wetland to the adjacent drainage systems. For events greater than a 2-year event, water would be able to move more freely between the wetland and Rolling Hills Creek, thereby adding more floodwater storage to the drainage system and attenuating flows. 8.3.5 PIPE SYSTEM IMPROVEMENTS There are several pipe improvements that are needed to help reduce flooding. These improvements are grouped together as Alternative 2, with the No Action alternative being Alternative 1. The locations of the proposed pipe improvements are shown on Figure 8-11. PIPE SYSTEM IMPROVEMENTS ALTERNATIVE 1 (PS1) — NO ACTION Under this alternative, flooding would continue at the locations noted below. The flooding problems would worsen as development continues in the watershed. Even if the Springbrook Creek alternatives are implemented, flooding of these systems would continue: ■ Flooding along East Valley Road from approximately SW 23rd Street to SW 30th Street. This flooding is associated with the lack of capacity in the EVR system. ■ Flooding along SW 43rd Street from approximately Oakesdale Avenue to east of Lind Avenue. This flooding is associated with the lack of capacity in the SW 43rd Street system. ■ Flooding along Lind Avenue from SW 43rd Street to north of SW 41st Street. This flooding is associated with the lack of capacity in the SW 43rd Street system. In addition to these flooding problems, pipe system improvements to solve two other flooding problems are noted here, but are considered separate City projects and not covered further. These problems include the Renton Village and SW 7th Street flooding problems. PIPE SYSTEM IMPROVEMENTS ALTERNATIVE 2 (PS2) — PIPE SYSTEM IMPROVEMENTS This alternative includes several pipe system improvements to reduce flooding in the Valley area. The replacement sizes are based upon preliminary hydraulic analysis and may be subject to change during final design. X0011592.112 R. W. Beck 8-25 SECTION 8 SW 43rd Street System Improvement. System improvements are necessary from approximately Lind Avenue to Springbrook Creek. Although several alignments for a new system are possible, the preferred alignment begins near the intersection of SW 43rd and Lind Avenue and extends north along Lind Avenue and then west along SW 39th Street. Preliminary sizing of this system indicates that an 84-inch-diameter concrete pipe system is necessary to solve flooding for the future 100-year event. Alternatively, a 72-inch-diameter pipe system would solve flooding for the future 25-year event. Large diameter pipe is necessary because the area is very flat and the pipe system must convey runoff over a long distance. The new SW 43rd Street system would be approximately 3,500 feet in length and there is only about 2 feet of drop between the road elevations at Lind Avenue SW and the 100-year flood elevation on Springbrook Creek at SW 39th Street, assuming either the SC2 or SO alternative is implemented. The sizing assumes that the existing pipe system that extends west along SW 43rd Street and then north along Oakesdale Avenue will remain in place to convey flow and that a short section of the Oakesdale Avenue system, approximately 55 feet of 36-inch-diameter pipe, will be replaced with 54-inch-diameter pipe. East Valley Road System Improvements. System improvements are necessary from approximately SW 29th Street to the discharge at the existing channel along SW 23rd Street. Improvements will include replacing an existing 30/36-inch system with a 48-inch-diameter system. Rolling Hills Culvert. This improvement includes removing an existing culvert that carries Rolling Hills Creek between Springbrook Creek and Raymond Avenue (along SW 19th Street) and restoring this section as an open channel. This element is not required for solving a flooding problem. The culvert serves no real purpose and removing it will result in an environmental benefit. 8.4 ALTERNATIVE EVALUATION 8.4.1 ALTERNATIVE EVALUATION PROCESS Using the description of alternative flood control solutions in Section 8.3, the City and its consulting team conducted a detailed evaluation. Each alternative was evaluated using the 14 different evaluation factors listed below. An explanation of how the factors were considered when evaluating the alternatives is provided in the following subsection. A technical memorandum was prepared for each evaluation factor. The technical memoranda were generally developed to identify impacts resulting from the alternative improve- ments (associated with the particular criteria) as well as other considerations. The technical memoranda are included in Volume 2 - Appendix A of the draft Plan and EIS (Renton, 1996). A summary of the evaluation results for each evaluation criterion is presented in Tables 8-4 through 8-17. 8-26 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION 8.4.2 EVALUATION FACTORS The following factors were considered: ■ Hydraulic Considerations ■ Wetlands ■ Water Quality/Sediment Quality ■ Fish Resources ■ Wildlife Habitat/Vegetation ■ Cost ■ Aesthetics ■ Land Use ■ Operations and Maintenance (City Lead) ■ Implementation and Financing ■ Utilities (City Lead) ■ Transportation (City Lead) ■ Groundwater ■ Recreation (City Lead) Each is discussed briefly below. 8.4.2.1 HYDRAULIC CONSIDERATIONS Under this criterion, alternatives are evaluated in terms of their hydraulic impacts such as their impacts on peak flows in the system, maximum water levels, or flood storage. The basis for this evaluation is prior hydrologic and hydraulic studies performed by the consulting team and the City of Renton, in particular the ESGRWP Hydraulic Analysis, Technical Memorandum of Flood Control Alternatives (R. W. Beck, 1995a). The simulation results of the analysis are presented in Tables 8-2 and 8-3. The summary of the impact evaluation is presented in Table 8-4. 8.4.2.2 WETLANDS Under this criterion, alternatives are evaluated in terms of their impacts to wetlands within the Valley area and their consistency with wetland regulations (Title IV, City of Renton Building Regulations, Chapter 32). This evaluation is based upon the alternative descriptions; results of the hydrologic modeling conducted for wetlands located in the Valley area; a September 1995 true-color aerial photograph (1"=500') of the project area; prior wetland analyses of the project area; field reconnaissance on February 6, 1996; and the 1996 update to the City's wetland inventory (including field reconnaissance) for the project area. X0011592.112 R. W. Beck 8-27 SECTION 8 Functions and values of wetlands in the Valley area are defined in Appendix F of the BRWQMP (R. W. Beck, 1993) and associated wetland inventory. The type and magnitude of impact for this project have been determined through information gathered during the wetland inventory, hydrologic analysis, and a review of wetlands literature. The summary of the wetland impact evaluation is presented in Table 8-5. 8.4.2.3 WATER QUALITY/SEDIMENT QUALITY Alternatives are evaluated under this criterion in terms of potential impacts to water and sediment quality. Water quality parameters such as dissolved oxygen, temperature, pH, conductivity, turbidity, fecal coliform bacteria, and toxicants are considered. The basis of this evaluation relies on water quality standards that have been established by the State of Washington (WAC 173-201A). These standards are designed to protect and promote the survival and longevity of aquatic organisms. The applicable standards are based on the class of water under consideration. Springbrook Creek has been identified as a Class A water and therefore is expected to meet those Class A standards identified in Table WT1 of the Surface Water and Sediment Quality Considerations Technical Memorandum (see Volume 2, Appendix A-3 of the draft Plan and EIS (Renton, 1996)). This analysis also identifies potential enhancement measures that will help to improve water quality for each of the proposed alternatives. Generally, flood control measures can be expected to enhance and improve water quality simply because a reduction in flooding or excessive flow events result in reduced erosion and sedimentation which, in turn, reduces the in-stream levels of turbidity and suspended solids. However, construction activities that alter existing stream channel(s) and stream channel hydrology may also potentially result in adverse impacts to water quality. These potential impacts, if they exist, are noted for each of the alternatives. Because sediments act as a final sink or resting place for contaminants, the disturbance of stream sediments can be a concern if contaminant levels are high. Therefore, this analysis also addresses issues related to the removal and handling of stream sediments for the proposed alternatives. The summary of impacts to surface water and sediment quality by alternative is presented in Table 8-6. 8.4.2.4 FISH RESOURCES The alternatives were evaluated for their impact to fish populations and aquatic habitat using the following three primary criteria: ■ Ability of an alternative to provide instream habitat for salmonids, such as cover from predators and protection from unacceptable water velocities. ■ Ability of an alternative to provide/improve fish passage. 8-28 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION ■ Ability of an alternative to improve water quality specifically for fish. Each alternative was measured against the criteria listed above and impacts were judged on the basis of the consultant's field studies and hydraulic models as well as professional judgment. A summary of impacts to fish populations and aquatic habitat by alternative is presented in Table 8-7. 8.4.2.5 WILDLIFE HABITATNEGETATION Under this criterion, alternatives are evaluated in terms of their impacts to: ■ Species listed under the federal Endangered Species Act. ■ Washington Department of Fish and Wildlife (WDFW) defined Priority Habitats and Species (WDFW, 1996). ■ Washington Department of Natural Resources (WDNR) defined high quality native habitats (WDNR, 1995) or other areas where diverse native vegetation or wildlife communities are present. This evaluation is based on (1) the alternative descriptions; (2) habitat types identified on a September 1995 true-color aerial photograph (1" = 500'); (3) prior field studies performed by the consulting team, in particular the Critical Areas Inventory and 1996 update (Jones & Stokes, 1991, 1992, 1996); (4) WDFW Priority Habitats and Species data; and (5) Washington Natural Heritage Program rare plant database. A summary of impacts to vegetation and wildlife by alternative is presented in Table 8-8. 8.4.2.6 COST Conceptual level cost estimates were developed for each element of the flood control alternatives and are summarized in Table 8-9. The detailed estimates are contained in Volume 2, Appendix C of the draft Plan and EIS (Renton, 1996). Costs are broken down into three categories: construction, administrative, and land acquisition. Construction costs included a construction contingency of 30 percent. Administrative costs were assumed to include state sales tax, design, permitting, project administration/management, and construction management. Administrative costs were estimated at either 30 or 40 percent of the construction cost depending on the complexity of design and permitting issues, with 40 percent for alternative elements having more complex design and permitting issues. Land acquisition is primarily required for the improvements to Springbrook Creek between SW 16th Street and SW 23rd Street (SC2 Element 2 and SC3 Element 2A). The cost for land acquisition was estimated based upon recent City acquisitions of property related to the project. The cost of future acquisitions may be more or less than the cost assumed for preliminary estimates, and will be determined on a case-by-case basis in negotiations with the affected property owners. X0011592.112 R. W. Beck 8-29 SECTION 8 8.4.2.7 AESTHETICS Under this criterion, alternatives are evaluated in terms of their impacts to aesthetics. The degree of impact is evaluated through professional judgment based on the Federal Highway Administration methodology. This methodology is a frequently used visual assessment and resource management system that is applied in urban settings (Federal Highway Administration, 1983). An impact is considered significant if an alternative would: ■ Reduce or eliminate views of distinctive natural features. ■ Reduce the quality of a view. ■ Significantly increase light and glare in the project vicinity. ■ Conflict with City of Renton land use policies regarding visual resources. A summary of impacts to aesthetics by alternative is presented in Table 8-10. 8.4.2.8 LAND USE Under this criterion, alternatives are evaluated in terms of their impacts to existing and future land use considerations. The basis of this evaluation are the alternative descriptions, a September 1995 true color aerial photograph (1" = 500') of the study area, and the City of Renton Comprehensive Plan (February 1995) and City of Renton Zoning Code Qune 1993). A summary of the impacts to land use by alternative is presented in Table 8-11. 8.4.2.9 OPERATIONS AND MAINTENANCE Alternatives are evaluated under this criterion for their potential impacts to existing and future operations and maintenance activities and their frequency. Current and planned operations and maintenance activities of the City, and others currently having responsibility for such activities, form the basis of the evaluation. A summary of the impacts to operations and maintenance by alternative is presented in Table 8-12. 8.4.2.10 IMPLEMENTATION AND FINANCING Under this criterion, alternatives are evaluated in terms of right-of-way needs that may affect implementation of the alternative. In addition, potential funding sources for implementing an alternative or alternative element are identified and required regulatory permits are listed. A summary of implementation and financing impacts by alternative is presented in Table 8-13. 8.4.2.11 UTILITIES Under this criterion, alternatives were evaluated for their potential impacts to utility facilities located within the project area. Inventory maps and other record drawings of existing facilities were used as the basis for the evaluation. Evaluation factors for utilities included the potential for disruption and damage due to flooding and related negative impacts and the potential for temporary 8-30 R. W. Beck X0011592.112 ALTERNATIVE SOLUTIONS AND EVALUATION disruptions during construction. The alternatives were also reviewed for possible conflicts with other utilities and whether other utilities may need to be relocated. Much of the utility information used in the evaluation is considered approximate only. More detailed information on the location and type of existing facilities and their position relative to the planned improvements would be verified during design. A summary of impacts to utilities by alternative is presented in Table 8-14. 8.4.2.12 TRANSPORTATION Under this criterion, alternatives were evaluated for their potential impacts to existing and planned transportation facilities and vehicular and pedestrian traffic. The basis for the evaluation of planned facilities is the City's Six Year Transportation Improvement Program. Evaluation factors included the potential for disruption and damage due to flooding and related negative impacts and the potential for temporary disruptions during construction. A summary of impacts to transportation by alternative is presented in Table 8-15. 8.4.2.13 GROUNDWATER The flood control project alternatives were evaluated under this criterion according to their potential to alter groundwater flow conditions (e.g., shallow subsurface hydraulic connections between drainage channels and nearby wetlands). Effects on deeper groundwater resources are not expected because a seasonally high water table occurs throughout the study area, limiting the vertical migration of near-surface groundwater flows. When the shallow groundwater table subsides in the dry season there is typically minimal concern for the types of flooding conditions and associated impacts that are under scrutiny in this study. Potential impacts on groundwater quality were not evaluated because contaminants that infiltrate into the subsurface with runoff would likely be intercepted by shallow groundwater and discharged to surface waters a short time later, rather than migrating to deeper groundwater. Groundwater studies for the EIS on the Longacres Office Park immediately west of the project area indicated that there are no well users in the vicinity (Jones & Stokes, 1995), so groundwater quality impacts were deemed to be a relatively insignificant concern in the present study. A summary of impacts to groundwater by alternative is presented in Table 8-16. 8.4.2.14 RECREATION The alternatives were evaluated in terms of their potential impacts to existing and planned recreational facilities within the project area. The basis for the evaluation of impacts to planned facilities is the City's Comprehensive Park, Recreation, and Open Space Plan (Renton, 1992) and the Trails Master Plan (Renton, 1990). Evaluation factors included the potential for disruption and X0011592.112 R. W. Beck 8-31 SECTION 8 damage due to flooding, design and maintenance considerations, visual impacts, and possible effects on the ability to implement other future planned facilities. A summary of impacts to recreation by alternative is presented in Table 8-17. 8.4.3 SUMMARY MATRIX EVALUATION This section presents a summary of the detailed evaluation of flood control alternatives in a matrix evaluation form. The matrix, Table 8-18, provides an overall summary of the flood control alternatives. The matrix lists the alternatives under each alternative category and provides an evaluation for all of the criteria listed above. For each criteria, with the exception of cost and implementation and financing, the long-term impacts are defined as having significant negative impact, minor negative impact, no impact, minor beneficial impact, beneficial impact, or greatest beneficial impact. The total estimated cost in thousands was provided for each alternative. For implementation and financing, the evaluation is summarized by how difficult it will be to implement the alternative in comparison with other alternatives, considering the extent of land acquisition, easement/agreements, funding potential, and permit considerations. It is important to note that the summary evaluation focuses on long-term negative or beneficial impacts. The table does not include the temporary short- term negative impacts typically associated with construction projects such as impaired water quality due to erosion or temporary traffic disruption. These short-term impacts generally need to be mitigated for as a part of permit conditions, e.g., providing erosion control measures and temporary traffic control. 8-32 R. W. Beck x0011592.112 SECTION 8 TABLE 8-1 PRELIMINARY FLOOD CONTROL SOLUTIONS ELIMINATED FROM FURTHER CONSIDERATION Alternative Description Discussion Original P-1 Channel Alignment. This The major drawbacks to this alternative alternative generally followed the prior included workplans developed by NRCS(formerly ■ major environmental impacts to SCS) and consisted of a wide channel from wetlands SW 43rd Street to SW 16th Street along an 0 high cost for both land and construction alignment west of the existing Springbrook Creek alignment. Establish Critical Watershed Designation. Because the watershed is already highly This alternative included requiring greater developed,this alternative would not solve on-site detention requirements to attenuate current flooding problems. In addition,the downstream flows. degree to which greater on-site detention standards would reduce the increase in lower Springbrook Creek flows resulting from future development is considered low, primarily because detention does nothing for volume of runoff. Other disadvantages of this alternative is that it would be non- effective without concurrent regulation by Kent and King County,and that it would be costly for new development. High Flow Diversion to Green River at SW The high flow diversion would likely only 43rd Street. This alternative would include operate during high local flows and would a high flow diversion from Springbrook not be operated during high Green River Creek near SW 43rd Street to the Green flows(unless there was a large pump River. station). This alternative could be considered to have negative impact on Green River water quality. Incorporate A Pump Station in Kent This alternative passed the initial screening Lagoons Project. This alternative included a of the original twelve alternatives. pump to divert flood flows to the Green However,based upon more detailed review River from the Kent Lagoons(large regional during the design of the Kent Lagoons detention facility project). This would project,it was determined that a pump reduce downstream flow rates through both station would have little affect in reducing Mill Creek in Kent and Springbrook Creek downstream flows in Renton. This was in Renton. because a large contribution of the peak flow in Mill Creek at the confluence with Springbrook Creek is from a large commercial/industrial area downstream of the Kent Lagoons facility and because of limits on the pump size per the GRIA (GRBP, 1992). X0011592.112 R. W. Beck TABLE 8-2 Summate of Hydraulic Results - Flood Control Alternatives 2-Year Current Conveyance Event (Elevation Datum NGVD) Alternative I-No Action SC:Altemalive 2 SC:Alternative 2 SC:Altemative 3 SC:Alternative 3 PC:Altemative 2 PC:Alternative 3 PC:Altemative 2 PC:Altemative 3 23ST:Altemative 2 23ST:AIternative 3 23ST:Altemative 3 23ST:Altemative 3 PIPE: Alternative 2 PIPE: Alternative 2 PIPE: Alternative 2 PIPE: Alternative 2 WETLAND: See Note I WETLAND: See Note I WETLAND: See Note 2 WETLAND: See Note 2 2-Year Current Flow 2-Year Current Flow 2-Year Current Flow 2-Year Current Flow 2-Year Current Flow Roadway Top Elev Location/Descnptto❑ Flow Elev Flow Elev Flow Elev Flow Elev Flow Elev (cfs) (feet) (cfs) feet (cfs) (feet) (cfs) feet (cfs) (feet) Panther Creek u/s of SR-167(3) 62 61 60 61 61 Panther Creek South SR-167 Xing(3) 0 30 0 31 Proposed Culvert Crossing of 33 14.1 9 13.7 34 14.1 9 13.7 SR-167 at SW 23rd Street(3) SW 23rd Street Channel d/s 41 10.9 24 8.2 42 8.7 25 8.5 of East Valley Road(3) o Rolling Hills Creek at Renton 68 20.4 66 20.3 66 20.3 68 0.4 67 0 3 Shopping Center Culv.Outlet(3)(4) Rolling Hills u/s 132"culvert(3)(4) 68 16.6 66 16.6 66 16.6 68 16.6 67 16.6 SR-167 north crossing 45 14.66 39 14.1 39 13.7 39 14.1 39 13.8 Springbrook Creek BRPS outflow 532 525 540 499 507 BRPS inflow 532 3.8 525 3.8 540 3.8 499 3.8 507 3.8 Floodwater Storage Pond Inflow 533 4 530 4.1 545 4.1 499 4 509 4 Grady Way u/s 456 5.7 451 5.9 465 6 426 5.8 430 5.8 SW 16th Street 453 6.3 449 6.3 464 6.4 425 6.2 428 6.2 Confluence of Rolling Hills Creek 449 8.7 438 7.5 452 7.6 417 7.5 420 7.5 Confluence of SW 23rd St Channel 396 9.6 396 8 409 8.1 382 8.5 386 8.5 SW 27th u/s 17.9 385 10.26 356 8.4 391 8.5 347 8.8 371 8.9 SW 34th u/s 14.9 341 10.95 336 9.5 344 9.7 335 9.8 335 10 Oakesdale d/s 17.1 340 11.61 335 10.7 343 10.8 341 10.9 340 11 Oakesdale u/s 17.1 323 11.87 315 10.8 323 10.9 321 10.9 321 11 SW 43rd d/s 22.9 320 12.48 313 11.9 320 12 319 11.7 320 11.8 SW 43rd u/s 22.9 320 12.59 313 111 320 12.2 319 12 320 12 Notes (1) This alternative includes Wetland 12.Altemative 2,Welland 7N:Alternative 1:Wetland 32 Alternative 1. (2) This alternative includes Wetland 12:Altemative 2,Wetland 7N:Alternative I:Wetland 32 Alternative 2. (3) FEQ simulated flows at these locations are based upon frequency analysis of Springbrook Creek inflows to the BRPS forebay. Refer to ESGRWP Hydrologic Analysis Report(NHC,1996) for flows based upon frequency analysis of Panther Creek and Rolling Hills Creek. (4) Flows are based upon assumption that capacity restriction through Renton Shopping Center is improved such that no attenuation from surface ponding occurs. (5) u/s=upstream,d/s=downstream TABLE 8-2 (Continued) Summary of Hydraulic Results - Flood Control Alternatives 2-Year Future Conveyance Event (Elevation Datum NGVD) Alternative I-No Action SC:Alternative 2 SC:Alternative 2 SC:Alternative 3 SC:Alternative 3 PC:Altemative 2 PC:Alternative 3 PC:Alternative 2 PC:Alternative 3 23ST:Altemative 2 23ST:Alternative 3 23ST:Altemative 3 23ST:Alternative 3 PIPE: Altemative 2 PIPE: Alternative 2 PIPE: Alternative 2 PIPE Alternative 2 WETLAND: See Note I WETLAND: See Note 1 WETLAND: See Note 2 WETLAND: See Note 2 2-Year Future Flow 2-Year Future Flow 2-Year Future Flow 2-Year Future Flow 2-Year Future Flow Roadway Top Elev. Location/Description Flow Elev Flow Elev Flow Elev Flow Elev Flow Elev cfs feet cfs feet (cfs) (feet (c£s) feet (cfs) (feet Panther Creek u/s of SR-167(3) 62 62 62 62 62 Panther Creek South SR-167 Xing(3) 0 31 0 31 Proposed Culvert Crossing of 35 14.1 10 13.8 35 14.1 10 13.8 SR-167 at SW 23rd Street(3) SW 23rd Street Channel d/s 56 ILA 37 9.5 55 9.9 37 9.8 of East Valley Road(3) Rolling Hills Creek at Renton 70 20A 70 20.4 70 20.4 70 20.4 70 20.4 Shopping Center Culy.Outlet(3x4) Rolling Hills u/s 132"culvert(3)(4) 70 16.59 69 16.6 69 16.6 69 16.6 69 16.6 SR-167 north crossing 45 14.67 40 14.1 40 13.8 40 14.1 40 13.8 Springbrook Creek BRPS outflow 726 853 835 754 763 BRPS inflow 726 3.8 853 3.9 835 3.9 754 3.8 763 3.8 Floodwater Storage Pond Inflow 728 4.2 854 4.4 843 4.4 764 4.3 773 4.3 Grady Way u/s 593 6.2 741 6.9 742 6.9 662 6.6 668 6.7 SW 16th Street 584 6.7 733 7.2 733 7.2 654 7 660 7 Confluence of Rolling Hills Creek 561 9A 708 8.7 709 8.7 638 8.6 640 8.6 Confluence of SW 23rd St Channel 526 10.4 657 9.4 660 9.4 597 9.7 598 9.7 SW 27th u/s 17.9 518 11.5 608 9.9 631 9.9 555 10.2 577 10.2 SW 34th u/s 14.9 564 12.9 575 HA 561 1 I.I 534 11.2 534 11.4 Oakesdale d/s IT 1 567 13.5 575 12.3 575 12.3 576 12.4 576 12.5 Oakesdale u/s 17.1 527 14.3 535 12.6 525 12.6 524 12.4 524 12.5 SW 43rd d/s 22.9 525 14.65 530 13.6 530 13.5 530 13.3 530 13.4 SW 43rd u/s 22.9 525 14.9 530 13.8 530 13.8 530 13 7 530 13.7 Notes (1) This alternative includes Wetland 12:Altemative 2,Wetland 7N:Allernative 1:Wetland 32 Altemative 1. (2) This alternative includes Wetland 12:Altemative 2,Wetland 7N:Alternative I:Wetland 32 Alternative 2. (3) FEQ simulated flows at these locations are based upon frequency analysis of Springbrook Creek inflows to the BRPS forebay. Refer to ESGRWP Hydrologic Analysis Report(NHC,1996)for flows based upon frequency analysis of Panther Creek and Rolling Hills Creek. (4) Flows are based upon assumption that capacity restriction through Renton Shopping Center is improved such that no attenuation from surface ponding occurs. (5) u/s=upstream,d/s=downstream TABLE 8-2 (Continued) Summary of Hydraulic Results - Flood Control Alternatives 25-Year Future Conveyance Event (Elevation Datum NGVD) Altemative I-No Action SC:Altemative 2 SC:Altcmative 2 SC:Alternative 3 SC:Alternative 3 PC:Alternative 2 PC Alternative 3 PC:Alternative 2 PC:Alternative 3 23ST:Alternative 2 23ST:Altemative 3 23ST:Alternative 3 23ST:Altcmative 3 PIPE. Alternative 2 PIPE: Alternative 2 PIPE: Alternative 2 PIPE: Alternative 2 WETLAND: See Note l WETLAND: See Note l WETLAND: See Note 2 WETLAND. See Note 2 25-Year Fut.Flow 25-Year Fur.Flow 25-Year Fut.Flow 25-Year Fut.Flow 25-Year Fut.Flow Roadway Conveyance Conveyance Convevance Conveyance Conveyance Top Elev. Location/Description Flow Elev Flow Elev Flow Elev Flow Elev Flow Elev cfs (feet) (crs) (feet) (cfs) (feet) (cfs) (feet) (cfs) (feet) Panther Creek u/s of SR-167(3) 96 95 95 96 95 Panther Creek South SR-167 Xing(3) 0 38 0 38 Proposed Culvert Crossing of 86 15.5 38 15.6 86 15.5 38 15 6 SR-167 at SW 23rd Street(3) SW 23rd Street Channel d/s 113 12 66 10.9 114 12 66 11.5 of East Valley Road(3) Rolling Hills Creek at Renton 102 20.94 100 20.9 101 20.9 103 20.9 101 20.9 Shopping Center Culy.Outlet(3x4) Rolling Hills u/s 132"culvert(3)(4) 102 17.02 too 17 101 17 103 17 101 17 SR-167 north crossing 82 16 66 15.5 68 15.6 66 15.5 69 15.6 Springbrook Creek BRPS outflow 1095 1219 1231 1189 1181 BRPS inflow 1095 4.1 1219 4.1 1231 4.1 1189 4.1 1181 4.1 Floodwater Storage Pond Inflow 1095 4.6 1228 4.8 1230 4.8 1197 4.8 1188 4.8 Grady Way u/s 959 7.2 1098 7.9 1083 7.8 1063 Z8 1052 7 8 SW 16th Street 951 7.8 1088 8.1 1074 8.1 1053 8 1043 8 Confluence of Rolling Hills Creek 933 11.1 1060 9.9 1047 9.9 1033 10 1021 10 Confluence of SW 23rd St Channel 843 12.1 980 10.7 966 10.6 957 11.2 943 11.2 SW 27th u/s 17 9 831 14.26 883 11.2 918 11.2 858 11.7 893 11 7 SW 34th u/s 14.9 847 15.4 836 12.3 842 12.4 827 12 6 827 12.7 Oakesdale d/s 17.I 849 15.94 841 13.4 842 13.6 846 13.9 846 14 Oakesdale u/s I T I 800 17.36 796 14.2 799 14.3 794 14 794 14 SW 43rd d/s 22.9 795 17.6 791 15.1 792 15.2 793 15 793 15 SW 43rd u/s 22.9 795 18.12 791 15.6 792 15.7 793 15.5 793 15.5 Notes (1) This alternative includes Wetland 12:Alternative 2,Wetland 7N:Alternative].Wetland 32 Alternative L (2) This alternative includes Wetland 12 Alternative 2,Wetland 7N:Alternative I:Wetland 32 Alternative 2. (3) FEQ simulated flows at these locations are based upon frequency analysis of Springbrook Creek inflows to the BRPS forebay. Refer to ESGRWP Hydrologic Analysis Report(NBC,1996) for flows based upon frequency analysis of Panther Creek and Rolling Hills Creek. (4) Flows are based upon assumption that capacity restriction through Renton Shopping Center is improved such that no attenuation from surface ponding occurs. (5) u/s=upstream,d/s=downstream TABLE 8-2 (Continued) Summary of Hydraulic Results - Flood Control Alternatives 100-Year Future Conveyance Event (Elevation Datum NGVD) Alternative I-No Action SC:Altemative 2 SC:Alternative 2 SC:Allernative 3 SC:Altemative 3 PC:Alternative 2 PC:Alternative 3 PC:Altemative 2 PC:Altemative 3 23ST:Altemative 2 23ST:Altemative 3 23ST:Altemative 3 23ST:Altemative 3 PIPE: Alternative 2 PIPE: Alternative 2 PIPE: Alternative 2 PIPE: Alternative 2 WETLAND: See Note I WETLAND: See Note I WETLAND: See Note 2 WETLAND: Sce Note 2 100-Yr Fut.Flow 100-Yr Fut.Flow 100-Yr Full.Flow 100-Yr Fut.Flow 100-Yr Fut.Flow Roadway Conveyance Conveyance Conveyance Conveyance Conveyance Top Elev. Location/Description Flow El- Flow Elev Flow Elev Flow Elev Flow Elev (Cfs) (feet) efs (feet) (Cfs) (feet) (Cfs) (feet) (Cfs) (feet) Panther Creek u/s of SR-167(3) 170 165 165 167 167 Panther Creek South SR-167 Xing(3) 0 38 0 38 Proposed Culvert Crossing of 107 16.1 48 162 107 16.1 48 16.2 SR-167 at SW 23rd Street(3) SW 23rd Street Channel d/s 159 12.7 103 12.0 163 12.6 104 12.3 of East Valley Road(3) Rolling Hills Creek at Renton Shopping Center Culv.Outlet(3x4) 174 21.8 173 21 8 173 21.8 174 21.8 174 21.8 Rolling Hills u/s 132"culvert(3x4) 174 17.8 173 17.7 173 17.7 173 17.7 173 17.7 SR-167 north crossing 98 17.0 87 16.1 86 16.1 88 16.1 87 16.1 Springbrook Creek BRPS outflow 1223 1700 1700 1593 I589 BRPS inflow, 1223 4.1 1700 4.72 1700 4.5 1593 4.35 1589 5.2 Floodwater Storage Pond Inflow 1223 4.7 1747 5.4 1720 5.3 1595 5.2 1587 4.3 Grady Way u/s 1110 7.6 1498 8.8 1461 8.7 1389 8.5 1370 8.5 SW 16th Street 1106 8.2 1488 9.1 1452 9 0 1383 8.9 1363 8.8 Confluence of Rolling Hills Creek 1088 11.6 1441 11 1405 11.0 1347 10.9 1324 10.9 Confluence of SW 23rd St Channel 989 12.6 1344 11.9 1309 11.8 1254 12.2 1232 12.2 SW 27th u/s 17.9 989 15.6 1251 12.4 1303 12.4 1147 12.7 1190 12.7 SW 34th u/s 14.9 1219 16.1 1239 13.6 1239 13.6 1217 13.7 1219 13.8 Oakesdale d/s I T I 1227 16.9 1239 15.1 1239 15.0 1256 15.6 1256 15.6 Oakesdale u/s 17.1 1167 17.9 1160 16.7 1160 16.7 1164 15.7 1165 15.7 SW 43rd d/s 22.9 1158 18.3 1148 17.4 1148 17.4 1155 16.8 1155 16.8 SW 43rd u/s 22.9 1158 19.5 1148 18.6 1148 18.6 1155 17.92 1155 18.0 Notes (1) This alternative includes Wetland 12:Altemative 2,Wetland 7N:Alternative 1:Wetland 32 Alternative 1. (2) This alternative includes Wetland 12:Altemative 2,Wetland 7N:Altemative 1:Welland 32 Alternative 2. (3) FEQ simulated flows at these locations are based upon frequency analysis of Springbrook Creek inflows to the BRPS forebay. Refer to ESGRWP Hydrologic Analysis Report(NHC,1996)for flows based upon frequency analysis of Panther Creek and Rolling Hills Creek. (4) Flows are based upon assumption that capacity restriction through Renton Shopping Center is improved such that no attenuation from surface ponding occurs. (5) u/s=upstream,d/s=downstream TABLE 8-2 (Continued) Summary of Hydraulic Results - Flood Control Alternatives 100-Year Future Storage Event (Elevation Datum NGVD) Alternative I-No Action SC:Altemative 2 SC:Alternative 2 SC:Altemative 3 SC:Altemative 3 PC:Altemative 2 PC.Alternative 3 PC:Alternative 2 PC:Allernative 3 23ST:Alternative 2 23ST:Alternadve 3 23ST:Altemative 3 23ST:Alternative 3 PIPE: Alternative 2 PIPE: Alternative 2 PIPE: Altemative 2 PIPE: Alternative 2 WETLAND. See Note 1 WETLAND: See Note I WETLAND: See Note 2 WETLAND. See Note 2 100-Yr Fut Flow 100-Yr Fut.Flow 100-Yr Fut.Flow 100-Yr Fut.Flow 100-Yr Fut.Flmv Roadway Stora a Storaee Stora Storast Storage Tup F.Icv Location/Description Flow Elev Flow Elev Flow Elev Flow Elev Flow Elev (cfs) (feet) (cfs) (feet) (cfs) (feet) cfs) (feet) (cfs) (feet) Panther Creek u/s of SR-167(3) 92 92 92 93 87 Panther Creek South SR-167 Xing(3) 0 34 0 33 Proposed Culvert Crossing of 64 15 28 15 64 15 27 15 SR-167 at SW 23rd Street(3) SW 23rd Street Channel d/s 94 13.4 59 13.1 95 13 59 12.9 of East Valley Road(3) 30.9 100 20.9 94 20.8 Rolling Hills Creek at Renton 99 0.89 98 20.9 99 Shopping Center Culy.Outlet(3 x4) Rolling Hills u/s 132"culvert(3X4) 99 16.94 98 16.9 98 16.9 99 16.9 94 16.9 SR-167 north crossing 69 15.6 54 IS 54 15 53 15 53 15 Springbrook Creek BRPS outflow 1700 1700 1700 1700 1700 BRPS inflow 1700 13 1700 13.1 1700 12.9 1700 12.7 1700 12.6 Floodwater Storage Pond Inflow 1153 13 1216 13.1 1223 12.9 1207 12.7 1176 12.6 Grady Way u/s 1045 13 1097 13.2 1105 12.9 1079 12.7 1026 12.7 SW 16th Street 960 13 1085 13.2 1090 12.9 1057 12.7 1011 12.7 Confluence of Rolling Hills Creek 898 13.14 1025 13.2 1024 13 986 12.8 941 12.7 Confluence of SW 23rd St Channel $07 13.3 948 13.3 948 13.1 907 12.9 870 12.8 SW 27th Ws 17.9 775 14.3 866 13.4 900 13.1 810 13 851 12.9 SW 34th u/s 14.9 845 15.2 953 13.6 854 13.4 801 13 2 814 13.2 Oakesdale d/s 17.1 846 15.8 855 14 856 13.8 854 13.8 851 13.9 Oakesdale u/s 17.1 792 17.3 802 14.4 802 14.3 801 13.9 799 13.9 SW 43rd d/s 22.9 783 17.6 798 15.2 798 15.2 798 15 796 15 SW 43rd u/s 22.9 783 18 798 15.7 798 15.7 798 15.4 796 15.5 Notes (1) This alternative includes Weiland 12:Altemative 2,Wetland 7N:Altemative 1:Wetland 32 Altemative 1, (2) This alternative includes Wetland 12:Altemative 2,Weiland 7N:Altemative 1:Weiland 32 Alternative 2. (3) FEQ simulated flows at these locations are based upon frequency analysis of Springbrook Creek inflows to the BRPS forebay. Refer to ESGRWP Hydrologic Analysis Report(NHC,19%)for flows based upon frequency analysis of Panther Creek and Rolling Hills Creek. (4) Flows are based upon assumption that capacity restriction through Renton Shopping Center is improved such that no attenuation from surface ponding occurs. (5) u/s=upstream,d/s=downstream TABLE 8-3 Summary of Maximum Elevations and Durations - Flood Control Alternatives Major Wetlands --2 -Year Event (Elevation Datum NGVD) Current Land Use Conditions Future Conditions Maximum Elevation(ft)/Duration(hrs),if available Maximum Elevation(ft)/Duration(hrs),if available SC:Alt.I SC:Alt.2 SC:Alt.2 SC:Alt.3 SC:Alt,3 SC:Alt.I SCAlt,2 SC:Alt.2 SC:Alt,3 SC:Alt.3 PC:Alt.I PC:Alt.2 PC-Alt.3 PC:Alt.2 PC:Alt.3 PC:Alt.I PC:Alt.2 PCAlt.3 PC:Alt.2 PC Alt, Wetland Inventory FEQ Wetland Hydraulic 23ST:Alt,I 23ST:Alt.2 23ST:Alt.3 23ST:Alt.3 23ST:Alt.3 23ST:Alt.I 23ST.Alt 2 23ST Alt.3 23ST:Alt 3 23ST All 3 Location Description Description Connection PIPE.Alt.I PIPE: Alt.2 PIPE: Alt 2 PIPE: Alt.2 PIPE: Alt.2 PIPE: Alt.1 PIPE: Alt.2 PIPE. Alt.2 PIPE: Alt 2 PIPE: Alt.2 (See Fig.6-7) (See Fig.6-4) Elevation(9) WET:Alt I WET:Scc Notc 7 WET:Sce Note 7 WET Scc Note 8 WET:Scc Notc 8 WET:Alt I WET:Scc Notc 7 WET:Scc Notc 7 WET:Sce Note 8 WET Sec Note ll Flood Water Storage Modeled as NA 4.0/(3) 4.1/(3) 4.1/(3) 4.0/(3) 4.0/(3) 4.2/(3) 4.4/(3) 4.4/(3) 4.3/(3) 4.3/(3) Pond Channel Reach I(not used) 7N 1b 9.0(culvert to (1)(2) (2)(10) (2)(10) (2)(10) (2)(10) 10.1(1) 9.2(5) 9.2(5) 9.2(5) 9,2(5) Rollings Hills Cr.) 2(not used) SN 3 10.0(weir connected -11.813 hr(1) (2) (2) (2) (2) -12.0/29 hr(1) 10.03/(4) (2) (2) (2) 23rd Str.Channel)(13) 10 4 10.0(weir connected (2) (2) (2) (2) (2) 10.59/18 hr (2) (2) (2) (2) to Springbrook Cr.)(13) 16 5 11.5(weir connected (2) (2) (2) (2) (2) (2) (2) (2) (2) (2) to Springbrook Cr.) 11 6 10.5(weir connected (2) (2) (2) (2) (2) 11.54/14 hrs(1) (2) (2) (2) (2) to Springbrook Cr.)(13) 12b 7A 10.0(weir connected 10.31/4 hr(1) 10.3/(14) 10.3/(14) 10.3/(14) 10.3/(14) 11.54/23 hrs(1) 10.5/(14) 10.5/(14) 10.5/(15) 10.5/(15) to Springbrook Cr.) 12a 7B 13.5(weir to 7A) 10.5/(6) 10.3/(6) 10.3/(6) 10.3/(6) 10.3/(6) 11.7/(6) 10.5/(6) 10.5/(6) 10.5/(6) 10.5/(6) 9.0(W12 Ait2 2-36"culverts) (Alt 1 1-18"culvert) 13Sj 7C 10.1(culvert to 7B) 11.3/(6) 11.3/(6) 11.3/(6) 11.3/(6) 11.3/(6) 12.1/(6) 12.1/(6) 12.1/(6) 12.1/(6) 12.1/(6) 51 8 16.0(weir connected (2) (2) (2) (2) (2) (2) (2) (2) (2) (2) to Springbrook Cr.) 14 9 16.0(weir connected (2) (2) (2) (2) (2) (2) (2) (2) (2) (2) to Springbrook Cr.) 32 10 16.0(Alt 1 weir to Spbrk) (2) (2) (2) 10.2/(3) 10.2/(3) (2) (2) (2) 11.6/(3) 11.7/(3) 6.0(W32 Alt 2 weir to Spbrk) 4 11a 14.0(weir connected 14.62/(3)(11) 14.1/(3) 13.7/(3) 14.1/(3) 13.8/(3) 14.63/(3)(11) 14.1/(3) 13.8/(3) 14.1/(3) 13.8/(3) to Rolling Hills Cr.) 4 llb 13.5(Alt1 culvert to 11a) 14.55/(3)(11) 14.1/(3) 13.7/(3) 14A/(3) 13.7/(3) 14.57/(3)(11) 14.1/(3) 13.8/(3) 14.1/(3) 13.8/(3) 12.3(other alts-see notel2) 4 11 20.3(weir to Panther Cr.) 14.55/(3)(11) 14.1/(3) 13.7/(3) 14.1/(3) 13.7/(3) 14.571(3)(11) 14.1/(3) 13.8/(3) 14.1/(3) 13.8/(3) 13.5(weir to 11 b) 13Nb-Nd 12 (1) (1) (1) (1) (1) (1) (1) (1) (1) (t) (1) For notes see the following page. Notes For Table 8-3 (1) See notes in Table 6-4 and/or Table 7-4. (2) Wetland is not inundated during flood event. (3) Constantly inundated throughout simulation. (4) Wetland modeled as channel overbank. Duration of inundation is not available. However, duration would be short lived based on comparison with duration of inundation for other wetlands. See note 13. (5) Simulated elevation in the 60" storm drain conveying Rolling Hills Creek was approximately 9.2. This is only 0.2 feet higher that the outlet elevation for the wetland and would be for only a very short duration based on comparison with duration of inundation for other wetlands. (6) Inundation reflects local subbasin inflows rather than overflows from Springbrook Creek. Therefore, simulation reflects constant inundation from local inflows. (7) This alternative includes Wetland 12: Alternative 2, Wetland 7N: Alternative 1: Wetland 32 Alternative 1. (8) This alternative includes Wetland 12: Alternative 2, Wetland 7N: Alternative 1: Wetland 32 Alternative 2. (9) See R. W. Beck 1996a, Table 6, for more detailed information on hydraulic connections. See also Table 6-4 this document. (10) Based on simulated elevation of flow in 60" storm drain conveying Rolling Hills Creek. (11) Note that these elevations would be lower and similar to the other alternatives if the Washington State Department of Transportation performed maintenance of the existing poorly functioning culverts crossing SR-167 to restore them to function at full capacity. (12) 13.5 was used for no action alternative. 12.3 was used for other action alternatives based on field survey by City staff on 6/19/95 (surface water utility field book). (13) Wetland modeled as off-channel storage with weir connection to the channel for the no action alternatives only. For other alternatives, the wetland was modeled as channel overbank. (14) Elevation is controlled by local inflows through wetland. Springbrook Creek does not inundate wetland. (15) Elevation is controlled by local inflows through wetland. Springbrook Creek elevation increases to 10.2 for short period of time. R. W. Beck 10/30/96 X1159121.801 Table 8-4. Summary of Impacts for Hydraulics by Alternative Factors Analyzed' Alternative Peak Flows/Water Levels Flooding/Flood Storage Springbrook Creek Alternatives SC1 - No Action ■ Peak flows in Springbrook Creek would increase by Flooding problems in Springbrook Creek and 40% for 100-year flood at SW 43rd Street, resulting tributary systems would become more frequent and in water level increase of 1.3 feet more severe ■ High stream velocities upstream of SW 16th Street would result in continued bank erosion ■ High water levels in Springbrook Creek would continue to create backwater conditions in tributaries SC2 - Localized ■ 100-year Springbrook Creek water levels would SW 34th Street and Oakesdale Avenue flooding Improvements to decrease between SW 19th Street and SW 43rd would be corrected for up to 100-year event Springbrook Creek Street (ranging from approximately 0.6 to 2.5 feet Flood storage in Wetlands 11 and 12 would be depending on location) reduced by approximately 225 acre-feet due to ■ Reduced wetland flood storage would result in lower Springbrook Creek water levels (100-year increased downstream flows exceeding the current event) capacity of the BRPS; no additional flooding problems expected, but additional pumps would need to be brought online ■ Lower Springbrook Creek water levels would reduce backwater conditions in tributaries ■ More potential for sediment accumulation than SO due to lower high flow benches (similar to existing accumulations downstream of SW 16th Street) SC3 - Springbrook Creek ■ Springbrook Creek water levels upstream of SW Flood storage in Wetlands 11 and 12 would be Greenway Improvements 19th Street would decrease, as with SC2 greater than with SC2, slightly reducing downstream ■ 100-year water levels at SW 43rd Street would be peak flows reduced approximately 0.6 feet more than with SC2 due to box culvert at Oakesdale ■ Tributary backwater conditions would be reduced, as with SC2 ■ Less concern for sediment accumulation than with SC2 because high flow benches are higher Table 8-4. Continued Factors Analyzed' Alternative Peak Flows/Water Levels Flooding/Flood Storage Panther Creek Alternatives PC1 - No Action ■ Flooding of the EVR system would continue PC2 - High Flow Bypass to ■ EVR system flooding would be corrected assuming Panther Creek Wetland SC2 or SC3 is implemented PC3 - Maintain Existing Flow Potential for PC3 improvements not to be fully ■ Same as PC2 into the 34th Street System utilized in future if Panther Creek changes course to Panther Creek Wetland through alluvial fan SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action ■ EVR flooding would continue due to downstream conveyance restrictions along SW 23rd Street and lack of reliable outlet from Panther Creek Wetland to the SW 23rd Street channel 23ST2 - Minor Conveyance Improvements at Olympic Pipeline crossing would ■ Well defined outlet from Panther Creek Wetland at Improvements eliminate conveyance restriction, lowering 100-year SW 23rd Street would help reduce flooding of EVR upstream water levels by approximately 0.5 to 1 foot system; some loss of flood storage from Wetland (assuming SC2 or SC3 is implemented) W-8N 23ST3 - Major Conveyance Channel deepening/widening would lower water ■ Reduced flooding similar to 23ST2 Improvements levels at EVR approximately 0.4 to 0.7 feet more ■ Greater loss of wetland storage from W-8N than than 23ST2 23ST2 Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action ■ Western cell of Wetland 12 would continue to provide off-channel storage if SC1 implemented; if SC2 or SC3 implemented, little flood storage would be provided W12-2 - Culvert Replacement By providing additional flood storage, downstream ■ Flood storage in Wetland 12 would probably double peak flows would be reduced over W12-1 (assuming SC2 or SC3 is implemented) to 100 acre-feet for 100-year flood Table 8-4. Continued Factors Analyzed' Alternative Peak Flows/Water Levels Flooding/Flood Storage W32-1 - No Action ■ Wetland 32 would continue to be isolated from Springbrook Creek for floods up to and including the 100-year event W32-2 - Mitigation Downstream peak flows would be attenuated; peak ■ Approximately 65 acre-feet of additional flood Bank/Excavate Large Off- flows at pump station would be reduced storage would be provided for the 100-year event Channel Storage W7N-1 - No Action ■ Flood storage in Wetland 7N would continue to be limited W7N-2 - Culvert By providing additional flood storage, downstream ■ Approximately 15 acre-feet of additional flood Replacement peak flows would be reduced storage would be provided Pipe System Improvements PSI - No Action ■ Flooding along SW 43rd Street and EVR would continue and worsen with future development, even if SC2/SC3 and 23ST2/23ST3 were implemented PS2 - Pipe System ■ Flooding problems would be corrected if PS-2 were Improvements implemented in combination with Springbrook Creek and SW 23rd Street alternatives 1 All flood event references are associated with future land use condition flows. Table 8-5. Summary of Impacts for Wetlands by Alternative Factors Analyzed Alternative Wetland Hydrology' Biological Resources Ordinance Consistency Springbrook Creek Alternatives SC1 - No Action ■ Increases in water elevations Higher water elevations could Consistent with Policy EN-11 ranging from 7 inches to 15 result in minor modification to inches caused by increased vegetation and wildlife habitat development SC2 - Localized • Based on current conditions No significant change in Consistent with Wetland Improvements to 2-year event, lowered water vegetation structure or species; Ordinance, policies, and Springbrook Creek levels in creek under SC2 would potential impact to 0.10 acre of objectives; regional stormwater not affect wetland surface or Wetland W-9a, 0.03 acre of facilities are an allowable use groundwater hydrology W-10N, and 0.23 acre of W-16b SC3 - Springbrook Creek Same as SC2 ■ Same as SC2 ■ Same as SC2 Greenway Improvements Panther Creek Alternatives PC1 - No Action ■ No significant impacts; greater ■ No significant change in ■ Consistent with Wetland inflows caused by increased vegetation structure or species Ordinance and policies and development objectives PC2 - High Flow Bypass to ■ 2-year water elevation in W-4 ■ Minor changes in species - Same as PC1 Panther Creek Wetland' approx. 0.5 ft lower than PC1; composition and dominance with slight reduction in wetted area in change in inflow; may reduce W-4; more frequent flow reed canarygrass, a benefit; contributions to wetland when greater amount of water could Panther Creek >5 cfs; normal lengthen time mosquito breeding water elevation in Panther Creek habitat is available (probably Wetland same as current offset by reduced stagnation and elevation; small area impacted to slight decrease in wetted area for install structure; eliminates 2-year event) Panther Creek inflows into W-48f, but as a roadside ditch W-48f will still receive local inflow Table 8-5. Continued Factors Analyzed Alternative Wetland Hydrology' Biological Resources Ordinance Consistency PC3 - Maintain Existing Flow No impact except possibly to ■ No impact ■ Same as PCl into the 34th Street System W-53 if channel is widened SW 23rd Street Drainage Channel Alternatives 23ST-1 - No Action No significant impacts; water ■ Insignificant impact to W-8N, ■ Consistent with Wetland elevations 0.2 ft higher in W-8N W-10N and W-48d and e; Ordinance and policies and than current conditions; reduction in hydrology in W-4 objectives maintenance of culverts would could cause trend toward reduce the water elevations in vegetation tolerant of drier Panther Creek Wetland, thereby conditions and may reduce modifying the hydroperiod, but mosquito breeding habitat increase storm flows to W-48d/e, W-8N, and W-10N 23ST-2 - Minor Conveyance Reduced contribution to W-48e Potential changes in vegetative Evaluated in land use analysis Improvements3 from W-4 caused by plugging species composition and (Volume 2, Appendix A-7) culverts; minor modification to dominance in W-4, W-8N, and W-48e from construction of W-48e with change in inflow; conveyance channel between some seasonal shift in wildlife SR-167 culvert and East Valley use of W-8N; may reduce Road; 2-year water elevation in mosquito breeding habitat; W-8N about 2 feet lower than construction of conveyance 23ST1 due to relocation of the channel from SR-167 culvert to Olympic Pipeline; minor loss of EVR would impact 0.05 acre of Panther Creek Wetland to install wetland; impact at culvert inlet new SR-167 culvert and inlet anticipated to be less than structure; reduced 2-year water 4,000 square feet elevations in Panther Creek Wetland (would be lessened if PC2 implemented) Table 8-5. Continued Factors Analyzed Alternative Wetland Hydrology' Biological Resources Ordinance Consistency 23ST-3 - Major Conveyance Same as 23ST2; also includes Same as 23ST2; also includes Evaluated in land use analysis Improvements' conversion of 1.7 acres of W-8N conversion of 1.7 acres of W-8N and 0.8 acre of W-10N scrub- and 0.8 acre of W-10N scrub- shrub wetland to open channel shrub and emergent wetland to a storage and conveyance; channel having a combination of potential lowering of open water, emergents and groundwater adjacent to the shrub channel Wetland Mitigation Bank and Wetland Enhancements W12-1 - No Action Increase in elevation of overbank Higher stormflow water Consistent with Wetland flooding from Springbrook elevations could improve habitat Ordinance Creek to W-12b from current for aquatic wildlife and 10.3 ft to 11.54 ft under future vegetation tolerant of wet conditions; local flows would conditions also increase with local development W12-2 - Culvert Replacement ■ Only slight reduction in current Only slight change, if any, to Consistent with Wetland 2-year water elevations in resources Ordinance W-12a; normal hydrology unaffected W32-1 - No Action ■ No impact No impact ■ Consistent with Wetland Ordinance W32-2- Mitigation ■ Long-term beneficial impact by Beneficial impacts to biological ■ Consistent with Wetland Bank/Excavate Large OK- restoring historic hydrology and values Ordinance Channel Storage surface water storage W7N-1 - No Action ■ No impact No impact ■ Consistent with Wetland Ordinance W7N-2 - Culvert ■ Larger culvert would restore the Incremental increase in ■ Consistent with Wetland Replacement function of surface water storage biological values for water- Ordinance related species Table 8-5. Continued Factors Analyzed Alternative Wetland Hydrology' Biological Resources Ordinance Consistency Pipe System Improvements PS1 - No Action ■ Surface ponding of areas drained ■ No impacts Consistent with Wetland by undersized pipe systems Ordinance would have minor impacts to wetlands PS2 - Pipe System ■ Negligible impacts on wetland ■ No adverse impacts Consistent with Wetland Improvements hydrology Ordinance ' Unless otherwise stated, all references to flood elevation comparisons are associated with the 2-year event. z Assumes either 23ST2 or 23ST3 is implemented, or WSDOT performs maintenance of the existing culverts between approximately SW 23rd Street and SW 34th Street (23ST1). The resulting decrease in 2-year water elevation and wetted area is thought to be similar for each of these alternatives. s The impact to the Panther Creek Wetland with the Panther Creek Alternative 2 diversion is presented in the analysis for the Panther Creek alternatives. Table 8-6. Summary of Impacts for Surface Water and Sediment Quality by Alternative Factors Analyzed Alternative Water Quality' Sediment Quality Springbrook Creek Alternatives SC1 - No Action • Poor water quality in Springbrook Creek would ■ Not applicable continue and worsen due to flooding, erosion/ sedimentation, lack of shade cover, and increased impervious surfaces from development SC2 - Localized ■ Water quality in Springbrook Creek would improve ■ Sediments removed during stream channel Improvements to through increased flow capacity of stream channel, maintenance or widening may be contaminated; Springbrook Creek reduced flooding, and improvement of riparian testing would be required to determine special habitat handing/disposal requirements ■ Potential for short-term erosion/sedimentation during channel widening and maintenance ■ Public trails would provide opportunity to educate users about water quality SC3 - Springbrook Creek ■ Similar to SC2, but greater water quality benefit due Same as SC2 Greenway Improvements to more extensive riparian habitat improvements ■ Erosion/sedimentation potential similar to SC2, but channel maintenance program would be less rigorous ■ Public trails would provide opportunity to educate users about water quality Panther Creek Alternatives PC1 - No Action ■ Water quality problems in EVR system would Not applicable continue and may worsen with development in upper Panther Creek Basin as well as higher downstream water levels in Springbrook Creek PC2 - High Flow Bypass t0 ■ Water quality would improve as flooding in EVR Not applicable Panther Creek Wetland system is reduced ■ High flows diverted into Panther Creek Wetland would receive natural settling and biofiltration Table 8-6. Continued Factors Analyzed Alternative Water Quality' Sediment Quality PC3 - Maintain Existing Flow Water quality would improve with reduction in - Not applicable into the 34th Street System flooding SW 23rd Street Drainage Channel Alternatives 23ST1 - NO Action ■ Flooding of EVR system and associated degradation ■ Not applicable of water quality would continue to worsen as flows increase 23ST2 - Minor Conveyance ■ Reduced flooding and increased water quality of ■ Sediments removed during construction may be Improvements EVR system would occur contaminated; testing would be required to ■ Installation and maintenance of culverts would determine special handing/disposal requirements result in temporary increased turbidity 23ST3 - Major Conveyance - Water quality benefits similar to 23ST2; channel ■ Similar to 23ST2, with greater construction impacts Improvements deepening/widening would also reduce stagnation due to more extensive conveyance improvements and increase dissolved oxygen during low flow ■ Wider, deeper channel would require less frequent maintenance, with fewer episodes of increased turbidity Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action ■ Underutilization of western portion of Wetland 12 ■ Not applicable for water quality treatment would continue W12-2 - Culvert Replacement ■ More water could be temporarily stored within ■ Not applicable wetland system, resulting in additional settling/ biofdtration, reduced flooding, and improved water quality in Springbrook Creek W32-1 - No Action No water quality benefits would occur ■ Not applicable Table 8-6. Continued Factors Analyzed Alternative Water Quality' Sediment Quality W32-2 - Mitigation Bank/ ■ Improved water quality in Springbrook Creek due to ■ Sediments removed during construction of Excavate Large Off-Channel reduction in flooding and increased biofiltration/ connection to creek may be contaminated; testing Storage settling would be required to determine special handing/ disposal requirements W7N-1 - No Action ■ Limited flood storage and water quality benefits of ■ Not applicable wetland would continue W7N-2 - Culvert ■ Increased flood storage in wetland, resulting in ■ Not applicable Replacement improved water quality in Springbrook Creek Pipe System Improvements PSI - No Action ■ Water quality problems related to flooding would ■ Not applicable continue PS2 - Pipe System ■ Water quality would improve due to reductions in . Not applicable Improvements flooding ■ Construction would cause temporary turbidity increase in affected systems ' Water quality data suggest that Springbrook Creek, the dominant drainage system in the valley, is severely degraded. It is important to recognize that water quality of Springbrook Creek is an overall watershed and multi-jurisdictional problem and that the valley area makes up only a small portion of the watershed. The major factor in improving water quality in Springbrook Creek will be through implementation of water quality improvement recommendations contained in the Black River Water Quality Management Plan (R.W. Beck/Herrera 1993) for the Renton portion of the basin and the City of Kent Five Year Water Quality Program, 1992-1996 (Resource Planning Associates 1991) as the City of Kent and King County make up the majority of the basin. Most of the improvements to water quality, where noted in the table, should be considered relatively minor. Table 8-7. Summary of Impacts for Fisheries by Alternative Factors Analyzed Alternative Fish Habitat Fish Passage Water Quality for Fish Springbrook Creek Alternatives SCt - No Action Erosion and sediment deposition Potential for further restricting Water quality in Springbrook would continue to reduce upstream passage of adult Creek would not improve and juvenile fish food sources (e.g., salmon and stranding of would likely worsen with higher benthic invertebrates) in juveniles during high flows peak flow rates and runoff Springbrook Creek volumes SC2 - Localized Temporary reduction in benthic Long-term improvement of fish Potential for temporary increase Improvements to organisms during sediment passage in turbidity during construction, Springbrook Creek removal and temporary increase in water ■ Long-term benefit to habitat for temperature due to loss of both juvenile and adult fish vegetation during bank modifications ■ Long-term water quality improvement SC3 - Springbrook Creek ■ Short-term impacts similar to Long-term improvements similar . Short-term impacts similar to Greenway Improvements SC2 to SC2; use of three-sided box SC2 ■ Long-term habitat improvement culvert at Oakesdale Avenue ■ Long-term improvements similar similar to SC2, with greater would provide better fish to SC2 benefit due to more intensive passage than smaller culverts bank plantings and reduced proposed under SC2 channel maintenance program Panther Creek Alternatives PC1 - No Action As development occurs, See PCl, fish habitat; potential Current water quality problems increased runoff rates for storm for juvenile salmon to be carried would remain and probably events and potential reductions into Panther Creek Wetland and worsen due to higher flows in base flows would reduce fish lost during storms could increase resulting from future habitat and passage development Table 8-7. Continued Factors Analyzed Alternative Fish Habitat Fish Passage Water Quality for Fish PC2 - High Flow Bypass to ■ No improvement or adverse With Element 1, downstream Potential for temporary increase Panther Creek Wetland impact to fish habitat anticipated migration of fish through EVR in turbidity during construction system during low flows would continue; diversion of high flows into wetland would probably lead to greater entrainment of juvenile salmonids ■ Element 2 would probably have no long-term adverse impact on small salmonids moving downstream PC3 - Maintain Existing Flow Same as PC2 ■ Fewer fish would likely be • Temporary construction impacts into the 34th Street System diverted into wetland during high similar to PC2 flows than with PC2 SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action I3abitat would remain poor ■ Passage upstream and Water quality would remain downstream would remain poor and likely worsen with restricted; lack of well defined increased flooding exit from Panther Creek Wetland likely results in mortality of fish entering wetland during high flows 23ST2 - Minor Conveyance Removal of beaver dam at ■ Culvert improvements at ■ Potential for temporary increase Improvements confluence of SW 23rd Street Olympic Pipeline crossing would in turbidity during construction channel and Springbrook Creek improve fish passage - Drop from weir outlet of would allow fish passage into Panther Creek Wetland would channel and increase potential increase dissolved oxygen rearing habitat concentration Table 8-7. Continued Factors Analyzed Alternative Fish Habitat Fish Passage Water Quality for Fish 23ST3 - Major Conveyance Channel widening and deepening Channel widening and deepening Greater benefit than 23ST2; Improvements would result in significant short- would result in short-term loss creation of positive grade in term loss of plantings and cover, of cover, but long-term channel would likely improve but long-term improvement of improvement of fish passage water quality rearing habitat (greater benefit than 23ST2) Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action No significant impact Slight increased potential for No significant impacts to fish; stranding of juvenile salmonids see Table 8-6 in Wetland 12 west cell during flood events as development continues W12-2 - Culvert Replacement ■ No significant impact ■ Slight increase in ability of fish Slight improvement to to enter and exit wetland west Springbrook Creek water quality cell during floods W32-1 - NO Action ■ No impact ■ No impact No impact W32-2 - Mitigation ■ No impact, except wetland may ■ No impact if connection between Slight improvement to Bank/Excavate Large Off- provide off-channel refuge excavated wetland and Springbrook Creek water Channel Storage during high flows Springbrook Creek is designed quality; see Table 8-6 to prevent fish stranding in wetland as flows recede W7N-1 - No Action No impact No impact No impact Table 8-7. Continued Factors Analyzed Alternative Fish Habitat Fish Passage Water Quality for Fish W7N-2 - Culvert No impact expected No impact as long as Rolling Slight improvement in Replacement Hills Creek does not support downstream water quality; see fish; if creek has rearing Table 8-6 salmonids in future, fish could become entrained in Wetland 7N during storm events Pipe System Improvements PS1 - No Action ■ No impact expected No impact expected No impact expected PS2 - Pipe System ■ With Element 3, culvert removal With Element 3, culvert removal No direct impact expected; Improvements would return stream to more would facilitate fish passage into reduction in flooding would also natural state (Rolling Hills Rolling Hills Creek reduce corresponding water Creek) quality problems Table 8-8. Summary of Impacts for Vegetation and Wildlife by Alternative Factors Analyzed Alternative Vegetation and Wildlife Habitat/Use' Springbrook Creek Alternatives SC 1 - No Action ■ Riparian vegetation would remain dominated by current mix of native and non-native vegetation - Flood-related degradation of riparian habitat would continue during major storm events SC2 - Localized ■ Removal of accumulated sediments would result in temporary reduction in benthic prey and shift in habitat Improvements to use by waterfowl and wading birds currently using shallow areas created by the sediments Springbrook Creek ■ About 5.2 to 6.1 acres of riparian habitat between SW 16th Street and SW 23rd Street would be removed during channel construction and replaced with habitat plantings and, in selected reaches, a pedestrian trail; riparian corridor would eventually provide habitat values equal to or greater than current values SC3 - Springbrook Creek ■ Sediment removal impacts similar to SC2 Greenway Improvements ■ 9.5 to 10.4 acres of riparian habitat would be removed between SW 16th Street and SW 23rd Street, and SW 30th Street to SW 40th Street and replaced with habitat plantings and, in selected reaches, a pedestrian trail; riparian corridor would eventually provide habitat values equal to or greater than current values Panther Creek Alternatives PC - No Action ■ No change to vegetation or wildlife habitat PC2 - High Flow Bypass to ■ Some temporary and permanent loss of vegetation due to construction of diversion structure Panther Creek Wetland PC3 - Maintain Existing Flow ■ Some temporary loss of vegetation due to potential construction of a widened channel between East Valley into the 34th Street System I Road and SR-167 SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action ■ No change to vegetative structure or wildlife habitat in SW 23rd Street area 23ST2 - Minor Conveyance ■ Temporary, less-than-significant loss of vegetation and wildlife habitat during construction; small permanent Improvements loss of vegetation due to SR-167 culvert inlet structure 23ST3 - Major Conveyance ■ Temporary, less-than-significant loss of vegetation and wildlife habitat during construction, but more extensive Improvements than 23ST2 ■ Small permanent loss of vegetation due to SR-167 culvert inlet structure ■ Structure and composition of vegetation along SW 23rd Street channel would change due to channel widening/deepening, with no significant impact on wildlife; less maintenance-related disturbance than 23ST2 Table 8-8. Continued Factors Analyzed Alternative Vegetation and Wildlife Habitat/Use' Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action Some disturbance of wildlife would occur during periodic culvert maintenance ■ Ongoing removal of vegetation around ends of the culvert would not disturb mature native plant communities W12-2 - Culvert Replacement ■ Because this alternative helps in attenuating flows in Springbrook Creek, less clearing/grading may be required under the Springbrook Creek Alternatives to provide needed capacity; this could indirectly reduce temporary loss of habitat ■ No effect on open water features and wildlife values of west cell of wetland/South Marsh W32-1 - No Action • No impacts on vegetation or wildlife; vegetation communities and wildlife values would continue to increase W32-2 - Mitigation ■ Wetland restoration would result in shift in wildlife habitat type (from upland to emergent wetland); overall Bank/Excavate Large Off- value of site as wildlife habitat would increase Channel Storage W7N-1 - NO Action ■ No impacts on vegetation or wildlife W7N-2 - Culvert ■ Culvert replacement would for short periods of time increase high water levels; plant communities not Replacement expected to change significantly Pipe System Improvements PS1 - No Action ■ No direct effect on plant or animal communities; influence of seasonal flooding would continue but without significant changes in vegetation PS2 - Pipe System ■ Temporary disturbance of vegetation would occur during pipe system replacement Improvements ■ Element 3 culvert removal would provide long-term benefit to native plants and animals ' This analysis addresses primarily direct impacts due to construction. Indirect impacts due to changes in water levels are addressed in Volume 2, Appendix A-2 of the draft plan and EIS (City of Renton 1996). See also Table 8-5. TABLE 8-9 Summary of Cost Estimates by Alternative Construction Land Alternative and Alternative Elements Cost Admin. Acquisition Total (Intl.Cont.)(1) Cost(2) Cost Cost SPRINGBROOK CREEK ALTERNATIVES ALTERNATIVE 2-LOCALIZED IMPROVEMENTS SC2-Element I-improvements at Roadway A. Remove Bridge North of SW 27th Street $38,000 $11,000 $1,000 $50,000 B. SW 27th Street Culvert Improvements $708,000 $283,000 $0 S992,000 C. SW 34th Street Culvert Improvements $681,000 $272,000 $0 $954,000 D. Oakesdale Avenue Culvert Improvements $290,000 $116,000 $0 $406,000 SC2-Element 2-Channel Improvements from SW 16th to SW 23rd $2,153,000 $861,000 $175,000 $3,199,000 SC2-Element 3-Channel Maintenance Program $145,000 $43,000 $0 $188,000 SC2-Element 4-Improve Riparian Habitat/Selective Plantings $96.000 29 000 to 125 000 SC2 Total $4,111,000 $1,615,000 $176,000 $5,904,000 ALTERNATIVE 3-GREENWAY IMPROVEMENTS SC3-Element I-Improvements at Roadway Crossings A. Bridge North of SW 27th Street(Same as under SC2-Element 1) $38,000 $11,000 S1,000 S50,000 B. SW 27th Street(Same as under SC2-Element 1) $708,000 $283,000 $0 $992,000 C. SW 34th Street(Same as under SC2-Element 1) $681,000 $272,000 $0 $954,000 D. Oakesdale Avenue Culvert Improvements $739,000 $296,000 so $1 035 000 SC3-Element 2-Channel Improvements A. Channel Improvements from SW 16th to SW 23rd $1,964,000 $746,000 $200,000 $2,809,000 B. Channel Improvements from SW 30 to SW40 $715 000 $286,000 $0 $1,002,000 SC3-Element 3-Channel Maintenance Program $145,000 $43,000 $0 $188,000 SC3-Element 4-Improve Riparian Habitat/Extensive Plantings 22$ 600 $68,000 L0 29$ 4.000 SC3 Total $5,116,000 $2,005,000 $201,000 $7,324,000 PANTHER CREEK ALTERNATIVES ALTERNATIVE 2-HIGH FLOW BYPASS TO PANTHER CREEK WETLAND PC2-Element I-Modify Existing Flow Split at SR-167 with New Structure $49,000 $14,000 $0 $62,000 PC2-Element 2-SW34th Street Drainage Improvements 65E 9.00 $263.000 Vo $921,000 PC2 Total $706,000 $277,000 $0 $983,000 ALTERNATIVE 3-MAINTAIN EXISTING FLOW INTO SW 34TH ST $1,186,000 $475,000 $0 $1,661,000 SW 23RD STREET CHANNEL ALTERNATIVES ALTERNATIVE 2-MINOR CONVEYANCE IMPROVEMENTS 23ST2-Element I-Replace SR 167 Culv.Crossings w/New Crossing at SW 23rd $365,000 $146,000 $0 $511,000 23ST2-Element 2-Olympic Gas Line Relocation/Culvert Improvements 69 000 28 000 50 9$ 7.000 23ST2 Total $434,000 $174,000 $0 $608,000 ALTERNATIVE 3-MAJOR CONVEYANCE IMPROVEMENTS 23ST3-Element 1-Replace SR 167 Culv.Crossings w.New Crossing at SW 23rd $365,000 $146,000 $0 $511,000 23ST3-Element 2-Olympic Gas Line Relocation/Culvert Improvements $69,000 $29,000 $0 $97,000 23ST3-Element 3-Channel Widening and Deepening 56$ 9,000 28 000 50 79$ 7.000 23ST3 Total $1,003,000 $402,000 $0 $1,405,000 WETLAND MITIGATION BANK AND WETLAND HYDRAULIC MODIFICATIONS WETLAND I2: ALTERNATIVE 2-CULVERT REPLACEMENT $8,000 $2,000 $0 $10,000 WETLAND 7N. ALTERNATIVE 2- CULVERT REPLACEMENT $26,000 $8,000 $0 $34,000 WETLAND 32. ALTERNATIVE 2-MITIGATION BANK/ $1,739.000 $249,0010 $0 $1,988,000 EXCAVATE LARGE OFF-CHANNEL STORAGE PIPE SYSTEM IMPROVEMENTS ALTERNATIVE 2-PIPE SYSTEM IMPROVEMENTS Element I-SW 43rd Street System Improvements $2,203,000 $881,000 $5,000 $3,089,000 Element 2-East Valley Road(S of SW 23rd St) $783,000 S313,000 $0 $1,096,000 Element 3-Remove Rolling Hills Creek Culvert at Springbrook Cr. 19 000 $6 000 $_0 $25.000 Total $3,005,000 $1,200,000 $5,000 $4,210,000 Notes (1)Includes 30%construction contingency. (2)Includes either 300/6 or 400/,administrative cost depending on complexity of project. Administrative costs include state sales tax,design,permitting,project administration/management,and construction engineering. Table 8-10. Summary of Impacts for Aesthetics by Alternative Factors Analyzed Alternative Aesthetics Springbrook Creek Alternatives SC1 - No Action ■ Visual quality of Springbrook Creek area would diminish slightly due to loss of vegetation/erosion from increased flooding SC2 - Localized ■ Visual impacts from flooding would be reduced; temporary visual changes associated with construction; long- Improvements to term improvement in visual quality Springbrook Creek SC3 - Springbrook Creek ■ Visual impacts from flooding would be reduced; long-term improvement in visual quality of creek area would Greenway Improvements be greater than with SC2 because of additional planting Panther Creek Alternatives PC1 - No Action ■ No changes to aesthetics PC2 - High Flow Bypass to ■ Temporary views of construction activities; no long-term changes to views or aesthetic quality of area Panther Creek Wetland PC3 - Maintain Existing Flow ■ Same as PC2 into the 34th Street System SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action ■ No changes to aesthetics 23ST2 - Minor Conveyance ■ No significant long-term visual impacts; some improvement possible with channel replanting Improvements 23ST3 - Major Conveyance ■ Same as 23ST2 but greater degree of change than with 23ST2 Improvements Table 8-10. Continued Factors Analyzed Alternative Aesthetics Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action - No aesthetic impacts W12-2 - Culvert Replacement ■ No aesthetic impacts W32-1 - No Action ■ No aesthetic impacts W32-2 - Mitigation ■ Temporary visual changes associated with construction; long-term improvement in visual quality Bank/Excavate Large Off- Channel Storage W7N-1 - No Action ■ No aesthetic impacts W7N-2 - Culvert ■ No aesthetic impacts Replacement Pipe System Improvements PS1 - No Action ■ No aesthetic impacts PS2 - Pipe System ■ No aesthetic impacts except for more open views resulting from removal of Rolling Hills Creek culvert Improvements (Element 3) Table 8-11. Summary of Impacts for Land Use by Alternative Factors Analyzed Alternative Land Use Consistency with Plans and Policies Springbrook Creek Alternatives SC1 - No Action ■ Flooding and associated problems would continue Would not be consistent with city policies and worsen as development continues encouraging public access into open space areas; flood protection and flood storage; rehabilitation of degraded channels; and other policies SC2 - Localized ■ Reduced flooding; beneficial land use impacts Consistent with city policies and the Shoreline Improvements to ■ Some additional right-of-way required Master Program Springbrook Creek SC3 - Springbrook Creek ■ Reduced flooding Same as SC2 Greenway Improvements ■ Beneficial land use impacts similar to SC2, with increased wildlife habitat and fish cover ■ Increased need for right-of-way acquisition to develop greenway concept Panther Creek Alternatives PC1 - No Action ■ Flooding and associated problems would continue ■ Not consistent with applicable city policies (same as and worsen as development continues SCl) PC2 - High Flow Bypass to . Reduced flooding and beneficial land use impacts ■ Consistent with city policies and the Shoreline Panther Creek Wetland Master Program PC3 - Maintain Existing Flow - Same as PC2 ■ Same as PC2 into the 34th Street System Table 8-11. Continued Factors Analyzed Alternative Land Use Consistency with Plans and Policies SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action ■ Flooding and associated problems would continue ■ Not consistent with applicable city policies (as SCl) and worsen as development continues 23ST2 - Minor Conveyance ■ Reduced flooding and beneficial land use impacts ■ Consistent with city policies and the Shoreline Improvements Master Program 23ST3 - Major Conveyance ■ Same as 23ST2 ■ Same as 23ST2 Improvements Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action Wetland 12 would remain as open space; flooding ■ Not consistent with applicable city policies (as SCl) and associated problems would continue and worsen as development continues W12-2 - Culvert Replacement Flows in Springbrook Creek would be attenuated, ■ Consistent with city policies and the Shoreline resulting in beneficial land use impacts Master Program W32-1 - NO Action Wetland 32 would remain as open space; no off- ■ Not consistent with applicable city policies (as SCl) channel storage would be provided W32-2 - Mitigation Similar to W12-2 ■ Consistent with city policies and the Shoreline Bank/Excavate Large Off- Master Program Channel Storage W7N-1 - No Action Flooding and associated problems would continue ■ Not consistent with applicable city policies (as SCl) and worsen as development continues W7N-2 - Culvert Similar to W12-2 ■ Consistent with city policies Replacement Table 8-11. Continued Factors Analyzed Alternative Land Use Consistency with Plans and Policies Pipe System Improvements PS1 - No Action ■ Flooding and associated property damage would ■ Not consistent with applicable city policies (as SC1) continue and worsen with future development PS2 - Pipe System ■ Reduced flooding; beneficial land use impacts to ■ Consistent with city policies and the Shoreline Improvements surrounding properties Master Program Table 8-12. Summary of Impacts for Operations and Maintenance by Alternative Factors Analyzed Alternative Operations and Maintenance Springbrook Creek Alternatives SC1 - No Action ■ Existing O&M programs of city and Drainage District No. 1 would be continued to maintain conveyance capacity SC2 - Localized ■ Less O&M effort and frequency than SC1 Improvements to Springbrook Creek SC3 - Springbrook Creek ■ Less O&M effort and frequency than SC2 Greenway Improvements Panther Creek Alternatives PC1 - No Action ■ Existing O&M programs would be continued to maintain conveyance capacity PC2 - High Flow Bypass to ■ Slightly less O&M required than with PCl, assuming no fish screening device is used Panther Creek Wetland PC3 - Maintain Existing Flow ■ O&M similar to PC1 into the 34th Street System SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action ■ Existing O&M programs of city, WSDOT, and others would be continued to maintain conveyance capacity 23ST2 - Minor Conveyance ■ Less O&M effort and frequency than 23ST1 Improvements 23ST3 - Major Conveyance ■ Less O&M effort and frequency than 23ST2 Improvements Table 8-12. Continued Factors Analyzed Alternative Operations and Maintenance Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action ■ Existing O&M program of city would be continued to maintain conveyance capacity W12-2 - Culvert Replacement ■ Significantly reduced or eliminated need for maintenance W32-1 - No Action ■ No maintenance required W32-2 - Mitigation ■ Would require regular maintenance program for minimum of 3 years to ensure wetland mitigation plan Bank/Excavate Large Off- objectives are achieved Channel Storage ■ Infrequent maintenance may be needed to maintain storage capacity and desired habitats, such as open water W7N-1 - No Action ■ Existing O&M program of private property owner would need to be continued to maintain culvert conveyance capacity W7N-2 - Culvert ■ Significantly reduced need for maintenance Replacement Pipe System Improvements PS1 - No Action ■ Existing O&M programs would be continued to maintain culvert conveyance capacity PS2 - Pipe System ■ Slightly less O&M required than with PS1 for SW 43rd Street and East Valley Road pipe systems Improvements ■ Little if any maintenance required for open channel resulting from removal of existing culvert on Rolling Hills Creek just upstream of Springbrook Creek Table 8-13. Summary of Impacts for Implementing and Financing by Alternative Factors Analyzed Alternative Right-of-Way (ROW) Acquisition Funding' Permits3 Springbrook Creek Alternatives SC1 - No Action' Not applicable Maintenance of previously Permits would be required for improved channels (downstream significant maintenance such as of SW 16th Street) may be removal of sediment funded by multiple jurisdictions accumulation ■ Potential for city to be subject to claims related to flooding SC2 - Localized Additional ROW, permanent Some improvements related to Clean Water Act (CWA) Improvements to easements, and/or coordination flood protection would be Section 404; CWA Section 401; Springbrook Creek with other agencies required at eligible for NRCS funding; WDOE Temporary Water several locations property acquisition and portions Quality Modification; WDFW of structures related to road Hydraulic Project Approval; City improvements not eligible of Renton Shoreline Substantial ■ DD No. 1 may also fund channel Development Permit; WDOE maintenance NPDES SC3 - Springbrook Creek Similar to SC2, but channel Additional ROW cost may be Same as SC2 Greenway Improvements improvement between SW 16th partially offset by NRCS funding and SW 23rd Streets would have of Oakesdale Avenue wider cross section, requiring improvement under Element 1 more ROW acquisition Panther Creek Alternatives PC1 - No Action ■ Not applicable ■ No impacts other than potential Not applicable for city to be subject to claims related to flooding PC2 - High Flow Bypass to ■ WSDOT approval required for ■ City could solicit WSDOT Same as SC2 except NPDES, Panther Creek Wetland construction of control structure funding for SR-167 control Shoreline at SR-167 culvert crossing; structure since financial shoulder widening and/or assistance from NRCS would be vehicle turn-out may be required unlikely Table 8-13. Continued Factors Analyzed Alternative Right-of-Way (ROW) Acquisition Funding' Permits' PC3 - Maintain Existing Flow Permanent easement may be Federal funding unlikely Same as SC2 except NPDES into the 34th Street System required for channel improvements between SR-167 and East Valley Road SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action Not applicable No impacts other than potential ■ Not applicable for city to be subject to claims related to flooding 23ST2 - Minor Conveyance Additional ROW could be WSDOT has committed to ■ Same as SC2 except NPDES Improvements required for channel provide funding for Element 1 improvement between SR-167 Element 2 will be funded by and East Valley Road Olympic Pipeline Company ■ Coordination with Olympic Pipeline Company required ■ Coordination with City of Seattle required to prevent impacts to Cedar River Pipeline 23ST3 - Major Conveyance Similar to 23ST2 Similar to 23ST2; NRCS may ■ Same as SC2 except NPDES Improvements provide funding for Element 3 Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action • Not applicable ■ No impacts expected ■ Not applicable W12-2 - Culvert Replacement ■ Changes to hydrologic regime in ■ NRCS funding may be available ■ Same as SC2 except HPA, western cell of wetland would if project is considered as NPDES, WDOE Temporary require permission from mitigation for other flood control Water Quality Modification property owner of inventoried improvements Wetland W-13Sj W32-1 - No Action Not applicable No impacts expected Not applicable Table 8-13. Continued Factors Analyzed Alternative Right-of-Way (ROW) Acquisition Funding' Permits' W32-2 - Mitigation ■ No additional property ■ Much of cost may be reimbursed ■ Same as SC2 Bank/Excavate Large Off- acquisition required by private sector as developers Channel Storage use mitigation bank in future W7N-1 - No Action ■ Not applicable ■ No impacts expected ■ Not applicable W7N-2 - Culvert ■ No additional property ■ NRCS funding may be available • Same as SC2 except HPA, Replacement acquisition required if project is considered as NPDES, WDOE Temporary mitigation for other flood control Water Quality Modification improvements Pipe System Improvements PS1 - No Action ■ Not applicable ■ No impacts other than potential ■ Not applicable for city to be subject to claims related to flooding PS2 - Pipe System ■ For Element 1, easement would ■ NRCS funding would not be ■ Element 1: Same as PO Improvements probably be required where new available for Element 1; City of ■ Element 2: Same as W7N-2 pipeline would discharge to Kent may be a funding source ■ Element 3: Same as SC2 except Springbrook Creek at SW 39th ■ NRCS funding would not be NPDES Street available for Element 2 ■ No property acquisition required ■ Element 3 may be eligible for for Element 2 NRCS funding if it can be ■ For Element 3, minor property considered as mitigation for acquisition and coordination with other flood control elements DD No. 1 required ' Potential contributors for individual alternative elements are listed in Table 9-1. s Although no capital projects are included under the no action alternative, the city is under obligation with NRCS to perform maintenance of the channel from SW 16th Street to the BRPS forebay. a Permit requirements for each project element may vary. Permit listings may not be all inclusive, and additional permits may be required. Table 8-14. Summary of Impacts for Utilities by Alternative Factors Analyzed Alternative Utilities Springbrook Creek Alternatives SC1 - No Action ■ Continued/increased risk of flooding, resulting in impaired access to utility systems, utility damage, and creation of unsafe conditions (e.g., electrical hazards) SC2 - Localized ■ Reduced risk of impacts listed for SC1 Improvements to ■ Utility conflicts may require temporary or permanent relocation of impacted utility Springbrook Creek SC3 - Springbrook Creek ■ Similar to SC2, but potentially greater impact at Oakesdale Avenue crossing and along proposed channel Greenway Improvements widening from SW 30th to SW 40th Street Panther Creek Alternatives PC - No Action - Continued/increased risk of flooding, resulting in impaired access to utility systems, utility damage, and creation of unsafe conditions (e.g., electrical hazards) PC2 - High Flow Bypass to ■ Reduced risk of impacts listed for PC1 Panther Creek Wetland ■ High potential for utility conflicts with proposed pipe improvements; may require temporary disruption/ relocation of some utility services ■ Potential impacts from excavation unless mitigated PC3 - Maintain Existing Flow ■ Similar to PC2, but greater potential for utility conflicts and service disruption into the 34th Street System SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action ■ Continued/increased risk of flooding, resulting in impaired access to utility systems, utility damage, and creation of unsafe conditions (e.g., electrical hazards) 23ST2 - Minor Conveyance ■ Minor or no impact except at Olympic Pipeline crossing, where portions of pipeline system could be Improvements temporarily taken out of service 23ST3 - Major Conveyance - Similar to 23ST2 Improvements Table 8-14. Continued Factors Analyzed Alternative Utilities Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action ■ No impact expected W12-2- Culvert Replacement ■ No impact expected W32-1 - No Action ■ No impact expected W32-2 - Mitigation Bank/ ■ Possible impact to 12-inch water line extending and terminating across Springbrook Creek from SW 39th Excavate Large Off-Channel Street cul-de-sac Storage - Possible impact on future replacement for 8-inch sanitary sewer line crossing south corner of site ■ Possible impact to utilities during dewatering, especially King County sewer interceptors in Oakesdale Avenue W7N-1 - No Action ■ No impact expected W7N-2 - Culvert ■ Minor impacts, if any, during construction Replacement Pipe System Improvements PSI - No Action ■ Continued/increased risk of flooding, resulting in impaired access to utility systems, utility damage, and creation of unsafe conditions (e.g., electrical hazards) PS2 - Pipe System ■ Reduced risk of impacts listed for PSI Improvements ■ High potential for utility conflicts with proposed pipe improvements; may require temporary disruption/ relocation of some utility services • Potential impact from excavation unless mitigated Table 8-15. Summary of Impacts for Transportation by Alternative Factors Analyzed Alternative Transportation Facilities Springbrook Creek Alternatives SC1 - NO Action No impacts during construction ■ Negative impacts due to flooding will continue and worsen as development in watershed continues SC2 - Localized ■ Short-term impacts during construction Improvements to ■ Negative impacts reduced after construction Springbrook Creek SC3 - Springbrook Creek ■ Short-term impacts during construction would be slightly greater than with SC2 Greenway Improvements ■ After completion, negative impacts on transportation facilities would be reduced as with SC2 Panther Creek Alternatives PC1 - No Action ■ No impacts during construction ■ Negative impacts due to flooding would continue and worsen as development in watershed continues PC2 - High Flow Bypass to ■ Shoulder widening and/or vehicle turnout may be required off of northbound SR-167 Panther Creek Wetland ■ Temporary traffic disruptions during construction ■ After construction, negative impacts on transportation facilities would be reduced PC3 - Maintain Existing Flow ■ Temporary disruption of traffic during construction would be moderately greater than with PC2 into the 34th Street System ■ After construction, negative impacts on transportation facilities would be reduced as with PC2 SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action ■ No impacts during construction ■ Negative impacts due to flooding would continue and worsen as development in watershed continues 23ST2 - Minor Conveyance ■ Occasional disruptions to traffic during construction for Element 2 and for Element 1 if trenchless methods Improvements are used to cross SR-167; potentially significant impact to traffic if SR-167 open cut to install the culvert for Element 1 ■ After construction, negative impacts on transportation facilities due to flooding would be reduced Table 8-15. Continued Factors Analyzed Alternative Transportation Facilities 23ST3 - Major Conveyance ■ Due to the addition of Element 3, occasional disruptions to traffic during construction could be slightly Improvements greater than for 23ST2 - After construction, there could be a slightly greater reduction in negative impacts on transportation facilities due to a slightly greater reduction in flooding problems Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action ■ No impacts during and after construction W12-2 - Culvert Replacement ■ Minor occasional disruptions during construction; no impact following construction W32-1 - No Action ■ No impacts during and after construction W32-2 - Mitigation ■ Minor occasional disruptions during construction; no impact following construction Bank/Excavate Large Off- Channel Storage W7N-1 - No Action ■ No impacts during and after construction W7N-2 - Culvert ■ Minor occasional disruptions during construction; no impact following construction Replacement Pipe System improvements PS1 - No Action - No impacts during construction ■ Negative impacts due to flooding would continue and worsen as development in watershed continues PS2 - Pipe System ■ Short-term impacts anticipated during construction of Elements 1 and 2, especially on SW 43rd Street; Improvements cumulative impacts could be minimized by staging construction ■ After construction, Elements 1 and 2 would reduce negative impacts on transportation facilities due to flooding 8 Element 3 would have no impacts during or after construction Table 8-16. Summary of Impacts for Groundwater by Alternative Factors Analyzed Alternative Groundwater Flow Springbrook Creek Alternatives SC 1 - No Action ■ Continued and worsened flooding would cause periodic rise in local groundwater table, resulting in possible expansion of wetland areas SC2 - Localized ■ Slight and infrequent lowering of local groundwater levels through reduction in flooding could cause a minor Improvements to reduction in the amount of area with wetland hydrology; effect may be offset by increase in local surface Springbrook Creek inflow to wetlands resulting from development in the local area draining to the wetland SC3 - Springbrook Creek ■ Similar to SC2; more extensive channel improvements could result in greater (although still minor) impacts on Greenway Improvements shallow groundwater levels and floodplain wetlands and increased rate of seepage from exposed banks Panther Creek Alternatives PC1 - No Action ■ Generally little change to groundwater conditions in vicinity of Panther Creek; local groundwater table may slightly and periodically rise with increased flooding frequency PC2 - High Flow Bypass to ■ Greater inflow into Panther Creek Wetland could result in slight elevation of groundwater levels in area of Panther Creek Wetland wetland PC3 - Maintain Existing Flow ■ No effect on shallow groundwater flows into the 34th Street System SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action ■ Maintenance of existing SR-167 culverts likely result in slightly reduced groundwater levels in Panther Creek Wetland; effect may be offset by increases in local surface inflow to the wetland from development in the local area draining to the wetland or if PC2 is implemented; local groundwater downstream of SR-167 may be elevated as flooding worsens 23ST2 - Minor Conveyance ■ Effect on groundwater levels in Panther Creek Wetland similar to 23ST1; local groundwater may be slightly Improvements lowered between SR-167 and Olympic Pipeline crossing due to improvements to the Olympic Pipeline crossing Table 8-16. Continued Factors Analyzed Alternative Groundwater Flow 23ST3 - Major Conveyance Similar to 23ST2; also potential for localized groundwater losses near deepened SW 23rd Street channel Improvements Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action ■ Increase in shallow groundwater levels with ongoing and increased flooding W12-2 - Culvert Replacement ■ With SC1, could result in slight increases in shallow groundwater levels in areas surrounding the wetland; with SC2 or SO, increase in shallow groundwater levels in areas surrounding the wetland due to increases in local inflow could be offset by reduction in overbank flooding and increased efficiency of the culvert connecting the cells of W12, resulting in no expected impacts to groundwater as a result of Alternative W12-2 W32-1 - No Action ■ No effect on groundwater W32-2 - Mitigation ■ Short-lived local rise of groundwater in areas surrounding wetland Bank/Excavate Large Off- Channel Storage W7N-1 - No Action ■ Little or no change to shallow groundwater levels W7N-2 - Culvert ■ Would increase local groundwater levels slightly Replacement Pipe System Improvements PS1 - No Action ■ Little or no effect on shallow groundwater PS2 - Pipe System ■ Potential for slight lowering of local groundwater along new or deepened pipeline alignment Improvements Table 8-17. Summary of Impacts for Recreation by Alternative Factors Analyzed Alternative Recreation Springbrook Creek Alternatives SC1 - No Action ■ Flooding of Springbrook Trail at key intersections would increase, resulting in more trail closures and potential trail damage - Conflicts between motorists and trail users at existing at-grade intersections would increase SC2 - Localized - Flooding at roadway intersections along Springbrook Trail would be reduced Improvements to ■ Potential below-grade trail crossings at SW 27th and SW 34th Streets would improve the safety of the trail Springbrook Creek ■ Trail construction on high flow bench would be subject to more frequent inundation than if constructed at top of bank, requiring more frequent maintenance, repair, and trail closure ■ Riparian plantings would provide for increased visual interest and opportunity for interpretive facilities along trail ■ Wider bench required if it is to accommodate a recreational trail SC3 - Springbrook Creek ■ As with SC2, potential below-grade crossings at key intersections would improve trail safety Greenway Improvements ■ Additional length of improved channel cross section, wider trail area, and more extensive riparian plantings would further enhance trail users' experience ■ Additional channel improvements may allow for future construction of a trail on the high flow bench between SW 30th Street and SW 34th Street Panther Creek Alternatives PC1 - NO AetiOn ■ No immediate impact to city's ability to construct Panther Creek Trail; in the long term, continued sediment buildup east of SR-167 may redirect Panther Creek, making trail construction more difficult PC2 - High Flow Bypass to ■ Flow diversion into wetland, plus 23rd Street channel improvements, would have little if any impact on the Panther Creek Wetland future Panther Creek Trail PC3 - Maintain Existing Flow - Similar to PC1 into the 34th Street System Table 8-17. Continued Factors Analyzed Alternative Recreation SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action ■ No impacts expected 23ST2 - Minor Conveyance ■ No impacts expected Improvements 23ST3 - Major Conveyance ■ No impacts expected Improvements Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action ■ No impacts expected W12-2 - Culvert Replacement ■ No impacts expected W32-1 - No Action ■ No impacts expected W32-2 - Mitigation ■ No direct impacts; proximity of existing Springbrook Trail would allow potential interpretive opportunities Bank/Excavate Large Off- Channel Storage W7N-1 - No Action ■ No impacts expected W7N-2 - Culvert ■ No impacts expected Replacement Pipe System Improvements PS 1 - No Action ■ No impacts expected PS2 - Pipe System ■ No impacts expected Improvements C: � CZ Table 8 - 18 a� � m occ 0 o 0 Matrix Evaluation Summary oCU :D E � Q o Q Q � o 1- 3 cn cn ii > U ¢ � O � CZ CD cc Alternative Summary Description Springbrook Creek Alternatives SC1-No Action No changes to existing drainage system as development continues in the o o © c=� (2) o ca c=b NA o a o 0 watershed. SC2 - Localized Improvements Remove bridge north of 27th, new box culverts at 27th and 34th, sliplinning 40 o o o $5,900 0 40 o Q o o m existing culverts and add 2 new culverts at Oakesdale, channel improvements 16th to 23rd, channel maintenance, and habitat improvements SC3- Springbrook Creek Greenway ® o co r ® $7,320 0 ® o ® o CD Improvements Remove bridge north of 27th, new box culverts at 27th, 34th, and Oakesdale, channel improvements 16th to 23rd and 30th to 40th, channel maintenance, and more extensive habitat improvements than SC2 Panther Creek Alternatives PC -No Action No changes to existing drainage system as development continues in the o o C:31 o o (2) o NA o o watershed. PC2- High Flow Bypass to Panther New diversion structure at SR-167 culverts to divert flow>5 cfs to wetland ` o 0 0 0 $980 0 ob o o 0 0 0 Creek Wetland to reduce flows in EVR/34th system. Also includes minor improvements along 34th PC3- Maintain Existing Flow to SW No changes to SR-167 crossings. Pipe replacements and minor channel .M o o e o $1,660 0 CZD ® CW o 0 34th Street System improvements along EVR and 34th between SR-167 and Springbrook Creek SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action No changes to existing drainage system as development continues in the © o © o o (2) o c":p c3b NA o c, o 0 watershed 23ST2- Minor Conveyance Replace SR-167 culverts with new crossing at 23rd. Olympic gas line o 0 0 0 0 $610 o w. o ca ® o 0 Improvements relocation or culvert replacement 23ST3- Major Conveyance 4ft o 0 0 0 $1,410 0 .. Am o ® o 0 Improvements 23ST-2 improvements plus channel widening and deepening. Wetland Mitigation Bank and Wetland Hydraulic Modifications W12 Alternative 1 - No Action No changes to existing drainage system as development continues in the v o Cap o o (2) o 0 o NA o 0 0 0 watershed W12 Alternative 2 -Culvert Culvert replacement to increase flow capacity connection between wetland c20 ® o 0 0 $10 o c-D 4 o 0 0 0 Replacement and Springbrook W32 Alternative 1 - No Action No changes to existing drainage system as development continues in the CZD o 0 0 0 (2) o CD o NA o 0 0 0 watershed W32 Alternative 2-Wetland Mitigation Expand and enhance existing wetland to provide wetland mitigation bank c2o 4. o o <ZIP $2,010 <30 <2V o C o 0 0 0 Bank site W7 Alternative 1 -No Action No changes to existing drainage system as development continues in the CMD o 0 0 0 (2) NA o 0 0 0 watershed W7 Alternative 2-Culvert Culvert replacement to increase flow capacity connection between wetland Co © o 0 0 $34 o CD dw C o 0 0 0 Replacement and 19th system (Rolling Hills Creek) Pipe System Improvements P1 - No Action No changes to existing drainage system as development continues in the o o cm o o (2) o c:) o NA cm, + o 0 watershed P2 Pipe System Improvements Pipe improvements to 43rd system, EVR system (south of 23rd), and o 0 0 0 $4,210 0 j aro ca;- C ® ® o 0 removing Rolling Hills Culvert at Springbrook Creek Notes Legend o Significant Negative Impact C7 More Difficult Alternative to Implement 1)Overall evaluation is based upon anticipated long-term impacts with mitigation if necessary. ® Negative Impact C7 No Significant Difference Between Alternatives Mitigation measures, if any, are identified in EIS Tables 1-1 to 1-10. o Minor Negative or No Impact M Easiest Alternative to Implement 2)Although not estimated,there is a negative cost impact associated with flooding and the o Minor Beneficial Impact greater level of maintenance under the no action alternatives. ® Beneficial Impact Greatest Beneficial Impact PUMP STATION FOREBAY BLACK RIVER r PUMP STATION TO GREEN DUWAMISH i RIVER soo' o soo' loon' ® f �SCALE ti ; S Renton Wag.M i n _ SC2_1A 3ST3 1 S —TA F r _ � h a� 1 LEGEND �..� Project Boundary Existing Storm Drain SC - �B - p Pipe System Improvement 3: i __, 6 SCE 1C ■ ■ Channel Improvement SC3-1C _ P '371 _111111111 Channel Maintenance...,..-.. / 32`2 Project-Sediment Removal r +a� a� !, �Plug Existing Culvert �. • r© Brid a/Culvert Removal -,' _ _� _ T and)or Improvements f 5 ��l/i SC2-1 D i Mitigation Bank r urs., I iV t - �SC3-1 D 1i I; t -. SC2-1C Spnngbrook Creek , �r t-r '1��T •�-' -' l Alt. 2-Element 1C t sit - 'PS2 1 );� `,a,!l..� PS2-1 Pipe System a " ij F� a t h `MILL CREEK t 1 PC2-1 Par�her creek z N tom. 23ST3-2 southwest 2&d Street;•_.__-_�, y n ! W7N-2 Wetland Modification t --' !,a ._.. t._ !� Wetlands , ffllo , Wetland Mitigation f ,� Figure 8-1 Combined Project Alternatives City of Renton East Side Green River Watershed Project i PUMP STATION FOREBAY z iit ' BLACK RNER PUMP STATION rr �i� F F �uat J TO GREEN- _: DUWAMISH $ v e q RIVER ..j a pn - � - • 1 r r y- '�� -' i #.{t.� ..jyT�' iIII 4S ' s' yi i. ' t r SC3 500' 0 500' 1000' 2 t 3 f Sit fiabv Vl°vi t_ ® Q 5 Raton NYgp H SCALE t/1 r t -Z- .......'� f .:, �'/� _.;.. -•'-.� 1 '`*`. Cis.: r r� r v r SC3 r 4 B } sr SC2-1 C — LEGEND -SC3-1 C Project Boundary f : J ZZ r�Lp � D Existing Storm Drain i:''. w t , • JCj __-, ■ Channel Improvement 1/11/1111 -�- 1 • Channel Maintenance Protect 12 Sediment Removal fs .fit SC2-1 D } Q Brdge/Culvert Removal t- SC3-1 and/or Improvements Wetland31- Mitigation Wetland � I ��C ..._ `. . .. .. ,_...,_ r T 3 MILL CREEK SC2-1 C Springbrook Crk Alt. 2-Element 1C 1 i -._ ir ^r 9 15 97 Figure 8-2 Springbrook Creek (SC) Alternatives City of Renton East Side Green River Watershed Project Alternative 2 - Element 2 Improved Section Between SW 16th & SW 23rd 20 . � 15 \ Approximate. /. z Existing Channel � -- 41 New Channel O �\ j w 1L n, 5 3 a � 0 10' 1�1 O a 3 a 0 . . . . 12': . . . . . . . . . : . Q -560 80 100 120 140 160 180 200 220 Approximate Horizontal Distance Ft Notes, Dimensions are approximate. Q Low flow channel. Q3 Approximate future land use condition 2 year water surface elevation ® Disturbance of low flow channel will be avoided where feasible 10/11/96 Figure 8-3 Springbrook Creek Alternative 2 — Typical Cross Section 60' 4' 6 — Area to be Excavated _ �/ T1.7 �a 4 — /�% %// Q / /// �Ti� Original Channel 2 — jj j/ Construction 0 Cl a 0 — N / / Low Flow g Channel SECTION A-A N.T.S. Access Road IIII 1 1 ' 1 11 1 (Metro Treatment I III III IIII �? I IIII Plant) I III III 11III / \ I IIII \ II 1 �/ /I IIII III II I 1 ►IIII I I � / IIIIIII 1111 \ \ IIIIIII 1 /��Iillllll I111 \ 1 II I IIII 13 / / 11111111 ) \IJ / / II I IIII I� / / I General Schematic `� I of Contour Lines I (typical) / / /�111 I I li ll I ed l l l 1111 �1 \ d.r O11/,l I II11 j Xx/�l 1 i t I I I I \ /oo f / I I I ICI ) I III II I I aI/ill III I/ \ Maintenance Bern/ Springbrook Creek Trail North End III Grady Way Box Culvert SEDIMENT REMOVAL PLAN 10/11/96 1'=100' Figure 8-4 Springbrook Alternative 2—Element 3 / Alternative 3—Element 3 Alternative 3 - Element 2A Between SW 16th and SW 23rd 25 >20 LD 15 Existing .Channel. . �-- -- W 13 O� New Plantings Q3 � ; 10 - New . . . . \ . £_ Channel X \ aVaries � 1 Varies Q 5 10/ IT Flow High g 1 ' High Flow Bench 3 Bench 00 20 40 60 80 100 120 140 160 Approximate Horizontal Distance ft Notes, O Dimensions are approximate, © Approximate future land use condition 2 year water surface elevation Q3 Alternative allows for dense plantings between low flow water levels and high flow bench, 10/11/96 Figure 8-5 Springbrook Creek Alternative 3 — Typical Cross Sections Cross Section Plot 6958.00 Alternative 3 - Element 2B SW 30th to SW 40th 25 ca >20 z Existing Channel 0- 15 New Planting (I / w 3 n' 10 1 x ,_ `t a 25 30, 1� 3 a High Flow Bench 5 1�20 1740 1760 1780 1800 1820 1840 1860 1880 Approximate Horizontal Distance Ft Notes: Q Dimensions are approximate, Approximate future land use condition 2 year water surface elevation 0 Alternative allows for dense plantings between low flow water levels and high flow bench, ® Potential transition to symmetric channel (shelf on each side) downstream of SW 34th Street, 11/14/96 Figure 8-5 (cont) Springbrook Creek Alternative 3 — Typical Cross Sections Cross Section Plot 11735.00 PUMP STAAON FOREBAY BLACK RIVER i\ f l I *l , ��. �r PUMP STAT&, s �^ r .� - <✓r 1, ~ 1 1,s TO GREEN DUWAMISH ` = A C ..iv i'G. { RIVER cf/ <J`1 _fd f _• y - t 1t 'r `_ TJ /1 yt, •�� J h 1-1 i 500' 0 500' 1000' j1� I i II y L r15xirSvY a !( , 1 SCALE r y. j 8mt�va)e9e p y-y T. t,- ray/n f j� F �?'^ ."` � !!"-_-'•�— i' t-"- r t Ck^ iFj 1 ! l` 3ST3 1 Mr �Y14 1 I r nn f {�ll ee jj!}�{}1JJ``�lr1 ,..---I MT rh .r 36 LEGEND I ` f It Project Boundary 4 i \, f( i e ! x1 n 1 ^ -,._...,.„.,,e.' / — I i �.� • 1 �.mil Existing Storm Drain ;!/ + r ; �i �� f ..._ t- \r• '`a t Pipe System Improvementpv ■ ■ ( Channel ImprovementJ/_ of f O Culvert Removal and/or I Improvements _'::�.� � I -36• • L_-__.__..._i'/ C -.- tt' 0% Plug Existing Culvert :` g ' ��i•• - -� -i t—Wetland r �I _.�•( �� 4 ... .'_^!r C-'---f-----.1_.__:� 't�F..�.�1 f� j-a.L. TT it lt'•`i�j!� ! �r : ;, f i //,• r+_-_.L-_+i�_ 1 — Mitigation Wetland i�"j I`'t I _ MILL CREEK •.,�.-r.�,...L_i r � Or s 07 30 97 Figure 8-6 Panther Creek (PC) and Southwest 23rd Street (23ST) Alternatives City of Renton East Side Green River Watershed Project t ,'.I. ,•'I� i a,if 1 New Box 167 Culvert ,� �', ° ' New Culvert Wet[and t1J 7S) 1 q; Wetland - -- - -=- -- -- I — - r (W 4} - _.. l ..-- - .�..�_... -s „�.�..._._ ._.:.�.�,.:-:-, �-�..,�.•T T- '' , �' '� � (Panther Creek f W- tta )e nd .�i - :I •.I" ti JC i� 1: u, /•. - Co f' on r. {. t 1- 1- �tru' - t ctu E 0 Il - I.. ; re _ , - lti. r _ Wetland (W-8N) Wetland: (W-lOfV3 ; -' - _ - , 7 gut; W-48e Exist. Olympic EL 19± PLAN El. 26_ Gas Crossing APPROX. SCALE: 1"=200' - Channel Im rovements -- ___.-_ Lines, Depth to New Culvert Varies (2) Exist, 60" Culverts ELEMENT 2 Remove Existing A. Replace Exist: Ex. (2) 9 xl4 Arch, Culverts CMP Risers on Culverts wo New Culvert Inlets Remove Abandoned 10' wide by 3' Approx. Exist, Grade Beaver Dam deep Box Culvert -- (1' buried) New Control ELE�r MENT 1 Culvert 72" (or equiv,) Manhole With New Adjustable Weir PROFILE (84" required if fish Control 7/30/97 APPROX, SCALE! HV=200' V:1"=5' passage necessary) Figure 8-7 SW23RD Alternative 2 — Schematic Plan and Profile �' ' 1 !• e `� il!, wit I,t4 1 t Vi I New Box Culvert !'' ' �' ,IN 167 New . W-48d Q1 '�r � .f _ 1 . Cu v er �- -, T L .'S z, Wetla - = and _ - - __ - _ nd (W'7S) �r r_iv�.. . ,. T e , (W-4) --�--- (Panther Cree:k. �I*- 1: i tl f'---- We and) it ! t 1 I i 1 'N 1� .1 : r - /C: nt C 1_ f a r fl l 4' � ��1:0- 1.- i_ 1 j Structur X j - � ,,P. .. 1. Wetiarid: (W 8N) Wetland {W-10N1IL ai i r N J. 4 W4. -48e li Lai +. i� Exist, Olympic El. 19± PLAN El. 26± Gas Crossing -- APPROX. SCALE; 1'=200' - Lines, Depth ELEMENT 3 Varies Channel Improvements Entire Length (2) Exist, 60" Culverts •ELEMENT 2 - Remove Existing Replace Exist, Ex, (2) 9'x14' Arch, Culverts CMP Risers on �u-v erEs - W-- - — --- -.. -- ----- ---- --------emu vT e r t_-_Isi es— -- -- - - - - Remove Abandoned 10' wide by 3' Approx, Exist, Grade _ deep Box Culvert Beaver Dare (1' buried) I _ New Grade /"% ��'�'/\/� / ELEMENT 1 New Control New Culvert 72" (or equiv,) Manhole With Adjustable Weir PROFILE (84" required if f ish 7/30/97 Control APPROX, SCALE: H:I'=200' V:1'=5' passage necessary) Figure 8-8 SW23RD Alternative 3 — Schematic Plan and Profile SW23RD Alternative 3 - Element 3 Looking Upstream 25 >20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LD 41 (4- Existing Channel C .915 — . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .'I., . . . . . . . Ile L'i Gi 10 '- . . . . . . . . . . . . . . . . . . . . . .—4.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 C5 oNew Channel - . . . . . . . . . . . 5 - 3 10, %0 100 150 200 250 300 350 400 450 Approximate Horizontal Distance Ft Notes: (1) Approximate future (and use condition 2 year water surface elevation (2) Current monitored elevation in wetland W-8N for an estimated 2-yr event. (2) Width of wetland varies 10/11/96 Figure 8-9 S.W. 23rd Alternative 3 — Typical Cross Section Cross Section Plot 1550.00 PUMP STATION FOREBAY BUCK RIVER �✓ ! 4T `i, ` ��tT wL 1' C`: `1 Ir ;,`�' PUMP STATION' TO GREEN ..��—• - i+ I,' r. \ � •` - ' �: DUWAMISH RIVER .I + ii._-�'_—.__,�� {, i(-4ice`„-�--� � `t' ..� j. �I t' q L_._-r_ 500' 0 500, 1000' L \ ' t1 SCALE - � Z �i ri"y�� ", ^p l'4Sr ,('`1`f�"` \ �G--•-. J' La, 01 E�-'�'i �I .71 I W12-2 ��= f 24 .. U1 dr c" trtEA ,�� f ! t �'� �4 t ° a_ 1.``_ ,.� -�r --'� t"'�-!t• J -Il i�rZ�.T .271 ¢rTLZZ �! �( ' � � ?�+ �� .' �•s-� 3 ,i6� I i— �---ram--E�'-u`_'�u,*;_ LEGEND � I f •• Project Boundary r � f 1 7 32j2 ,s% ,� = � n ExistingStorm Drain / ` , F ' I ' . ....ram r-� "t p 0 Culvert Removal and/or Improvements t2' s T"_�'�• Mitigation Bank Wetlands=:4t�� _' w�- ` 36• — i r (` n( " Mtigation Wetland ' I / ! r t i 't MILL CREEK j 07 30 97 Figure 8-10 Wetland Mitigation Bank and Wetland Hydraulic Modifications City of Renton East Side Green River Watershed Project i PUMP STATION FOREBAY M i � �` ", a4{/ t' ••�� _ �i t ft'r BLACK' RIVER, i i u� * ' "r �.�-�`• '' \ .� .•-�.�r � ,.G 4 "�_ PUMP STATION 1 ✓'S' f Ar" a tom: TO GREEN- DUWAMISH RIVER 4 • !�i�.� t, if of-'I Lr 500' 0 500' 1000' JV ® vv..r Pi SCALE TT JTP it -------------- it 11 .. Mir Cm I yp — i ' LEGENDit �..�� Project Boundary Y. /r '. r""rr/ •, L` ' " Existing Storm Drain ��--- a r { Pipe System OCulvert Removal L Wetland ' 1 • t f Mitigation Wetland ; {-L r - - ".i__.J It F Ih Ili `---'4— I . PS21- i/ f ! / t_H 4 MILL CREEK FA s left. if if 07 30 97 ___-_)t_ \\.__1I�. Figure 8-11 Pipe System Improvements (PS) City of Renton East Side Green River Watershed Project ' SECTION 9 RECOMMENDED PLAN 1 1 1 1 1 1 1 1 SECTION 9 RECOMMENDED PLAN 9.1 INTRODUCTION As a part of the ESGRWP Plan and EIS, the ESGRWP flood control alternative measures were identified and evaluated in detail as summarized in Sections 1 and 8 of the Plan and Sections 1 and 2 of the FEIS. The preferred alternative (recommended plan) selected by the City is described in Section 1.6 of the Plan (and Section 1.5 of the FEIS). This section of the Plan identifies potential opportunities for funding or project assistance by various affected jurisdictions and organizations for the preferred alternative elements and describes the process for determining the schedule of implementation. 9.2 PROJECT ELEMENT SUMMARY AND POTENTIAL CONTRIBUTORS There are many jurisdictions, organizations, and property owners that are affected by the current flooding problems. There are several jurisdictions within the ESGRW that contribute runoff to the Valley area and thereby contribute to the current flooding. There are also those that will benefit from the flood control measures. It is unlikely that the City of Renton Storm Water Utility will have adequate financial resources to solely implement the overall program. One of the major project goals is to seek grants and other funding options to minimize cost impacts to the City, its residents and rate payers. The City fully desires to maintain the funding assistance from NRCS, however, much of the project alternatives or components of alternatives will be ineligible for funding assistance from NRCS (e.g., land acquisition, roadway crossing structures, and utility relocations). Therefore, the City will continue to pursue other options for assistance including grants, loans, and participation with affected jurisdictions, organizations, and possibly property owners. Table 9-1 provides a summary of the preferred alternative elements and potential contributors identified by the City. The form of participation could vary significantly, for example ranging from volunteer assistance in planting projects to cost sharing on large capital improvements. Table 9-1 also provides the estimated cost of the individual project elements. X0011592.112 SECTION 9 9.3 PROJECT IMPLEMENTATION AND PHASING Specific elements of the project will be implemented in multiple phases over a period of 5 to 15 years commencing in 1997, depending upon available funding. The program for implementation and long-term maintenance and operation of the ESGRWP improvements will be made through the City's annual budgeting process with guidance from the Surface Water Utility's 6-year capital improvement program and Comprehensive Plan (see Section 4.1.7). Springbrook Creek improvements will likely be implemented starting downstream and working to the upstream end of the project area. For instance, the SW 27th Street crossing may not be replaced without first widening the Springbrook Creek channel between SW 16th Street and SW 23rd Street. However, one or more of the road crossing improvements may need to be implemented prior to downstream channel improvements if funding from the NRCS for the more costly channel work is not available in the desired timeframe. The channel improvement element from SW 30th Street to SW 40th Street and the sediment removal element downstream of SW Grady Way may also vary from the downstream to upstream sequence. Unless needed sooner because of environmental reasons, such as to improve fish passage, it is intended that removal of sediments downstream of Grady Way be delayed until other upstream Springbrook Creek improvements are completed. This is because hydraulic analysis indicates that the sediments downstream of Grady Way as yet have a limited effect on conveyance capacity, while other upstream improvements will significantly increase conveyance capacity and greatly reduce upstream flooding levels. The channel improvements from SW 30th Street to SW 40th Street, however, may be accelerated to be constructed in conjunction with the adjacent wetland mitigation bank project (Alternative W32-2) and potentially prior to,but allowing for, the SW 34th Street culvert replacement. The timing of the channel improvements largely depends upon the availability of NRCS funding, and the need for establishing the wetland mitigation bank as a source of mitigation credits for wetland impacts of other public and private projects. The phasing of the ESGRWP improvements other than the Springbrook Creek elements may not necessarily occur starting in the downstream end of the project area and working upstream. For instance, the pipe system improvements PS2 may occur prior to wetland hydraulic modification alternative W7N-2, although the PS2 improvements are farther upstream on Springbrook Creek. Alternatives may be implemented prior to downstream main stem Springbrook Creek improvements if it is determined that the upstream improvement will not result in an unacceptable increase in 100-year flows or flood elevations in the downstream system. This comparison may be made considering historic flooding levels prior to previously constructed flood control projects, such as those on Springbrook Creek downstream of SW 16th Street, in determining whether there is in fact an increase. This is because previous flood control improvements were intended to not only reduce flood levels below historic 9-2 R. W. Beck x0011592.112 RECOMMENDED PLAN ' conditions that existing prior to their implementation, but to also allow for increases in flows that would result from upstream development and future ' flood control improvements, such as proposed in the ESGRWP. Again, development of an implementation program for the ESGRWP improvements would be done in conjunction with the City's annual budget and the Surface Water Utility's 6-year comprehensive planning process. X0011592.112 R. W. Beck 9-3 SECTION 9 ' TABLE 9-1 SUMMARY OF PREFERRED ALTERNATIVE ELEMENTS AND POTENTIAL CONTRIBUTORS ' Potential Alternative/ Project Cost ($) Contributors ' Element Description Benefit (in Thousands) (See Legend) Springbrook Creek SC3-lA Remove. Flooding, $50 City SWU; DD #1 , bridge N of Habitat 27th SC3- 1B 27th St Flooding, $992 City SWU; DD#1 ' Culvert Imp. Habitat SC3-1C 34th St. Flooding, $954 City SWU; DD#1 ' Culvert Imp. Habitat SC3- 1D Oakesdale Flooding, $1,035 City SWU; DD#1, Culvert Imp. Habitat City of Kent ' SC3-2A Channel- Flooding, $2,809 City SWU,Parks; 16th to 23rd Habitat, NRCS; Property Water Owners/ , Quality Developers; DD#1; KCD; Friends of Black , River SC3-2B Channel- Flooding, $1,002 City SWU; NRCS; 30th to 40th Habitat DD#1; KCD; Friends of Black River SC3-3 Channel Flooding, $188 City SWU; City of ' Maintenance Habitat Kent; King County; City of Tukwila; DD#1; , KCD; Friends of Black River SC3-4 Riparian Habitat, $294 City SWU, Parks; ' Habitat and Water NRCS; Property Plantings Quality Owners/ Developers; ' DD#1; KCD; Friends of Black River ' X0011592.112 R. W. Beck , RECOMMENDED PLAN TABLE 9-1 (CONTINUED) Potential Alternative/ Project Cost($) Contributors (See Element Description Benefit (in Thousands) Legend) SW 23rd Street Drainage Channel Alternatives 23ST3-1 Replace Flooding, $511 WSDOT,City SR-167 Mosquitoes, SWU Crossing Maintenance 23ST3-2 Olympic Flooding, $97 Olympic Pipeline Pipeline Habitat Co.; City SWU Crossing Improve- ments 23ST3-3 Channel Flooding, $797 City SWU,NRCS, Habitat KCD, Friends of Black River Panther Creek Alternatives PC2-1 Modify Ex. Flooding, $62 City SWU; Flow Split Mosquitoes, WSDOT etc. PC2-2 34th St Imp. Flooding $921 City SWU Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-2 Culvert Flooding $10 City SWU Replacement W32-2 Wetland Bank Flooding, $1,988 City SWU and Habitat other City funds; Bank Participants W7N-2 Culvert Imp. Flooding $34 City SWU R. W.Beck X0011592.112 SECTION 9 I TABLE 9-1 (CONTINUED) Potential Alternative/ Project Cost($) Contributors(See Element Description Benefit (in Thousands) Legend) Pipe System Improvements PS2-1 43rd St. Imp. Flooding $3,089 City SWU; City of Kent PS2-2 E. Valley Flooding $1,096 City SWU Road Imp. PS2-3 Remove Flooding, $25 City SWU Culvert Habitat Legend: SWU-Renton Surface Water Utility NRCS-Natural Resources Conservation Service Parks- Renton Parks Department WSDOT-Washington State Department of Transportation DD#1 -King County Drainage District No.1 KCD-King Conservation District Note: Possible funding options for the City SWU include: grants,loans,local improvement districts, basin surcharges,utility rates,and others. Cost sharing of road crossing improvements may be made with the City's Transportation Systems Division. i X0011592.112 R. W. Beck SEcriory 10 REFERENCES 1 1 ' SECTION 10 REFERENCES t Adams, G. 14 February 1990. Personal communication (phone by Dr. Walter Trial,Jr.). Seattle Audubon Society, Seattle, WA. Adams, G. 1989. Black River field trip observations of 11 March 1989. Seattle Audubon Society, Seattle,WA. Adamus, P. R. and L. I. Stockwell. 1983. A method for wetland functional assessment. Volume 1, Critical review and evaluation concepts. U. S. Department of Transportation,Federal Highway Administration. Beak Consultants, Inc. 1990. Final Report of Wetland Surveys Conducted at the tPanther Creek Wetland Complex. Kirkland, WA. Prepared for the City of Renton, WA. ' Beak Consultants, Inc. 1991. City of Renton Mosquito Abatement Program Wildlife Survey. July. Prepared for City of Renton, WA. Converse. 1989. Report Mill Creek Environmental Assessment (Kent, WA). Converse ' Geoenvironmental Services Project No. 88-45556-01 for R. W. Beck and Associates. ' Department of the Army Environmental Laboratory. 1987. Corps of Engineers Wetlands Delineation Manual. Technical Report Y 87-1. Vickburg, Mississippi. Erwin, K. L. 1990. Wetland evaluation for restoration and creation. J. A. Kusler and M. E. Kentula (eds.): Wetland creation and restoration: the status of ' science. FEMA. See "Federal Emergency Management Agency." Federal Emergency Management Agency. 1980. Flood Insurance Study, City of Renton, King County, WA. November 5 Federal Emergency Management Agency. 1989. Flood Insurance Study, King ' County, WA, and Incorporated Areas,Volumes 1, 2,and 4. September 29. Federal Emergency Management Agency. 1995. Flood Insurance Rate Map, ' No. 53033C0976F, 53033C0977F, 53033C0978F, and 53033C0979F, King County,WA, and Incorporated Areas. May 16. ' Federal Emergency Management Agency. 1996. Flood Insurance Study, King County,WA, and Incorporated Areas,Volumes 1, 2, and 3. May 20. Federal Highway Administrative. 1983. Visual impact assessment for highway ' projects. (Contract DOT-FH-11-9694.) Washington, D.C. Franze, Delbert, 1994. Unsteady Flow Solutions, Notes for Short Course on FEQ and ' Unsteady Flow. X0011592.112 SECTION 10 Gardner Consultants. 1992. City of Tukwila Southeast Central Business District ' Drainage Study. GRBP. See "Green River Basin Program." ' Green River Basin Program. 1980. Environmental Mitigation Program. King County,WA. Green River Basin Program, 1986. Pump Operations and Procedures Plan. Sponsors: King County, Cities of Auburn,Kent, Renton, and Tukwila. Green River Basin Program, 1992. Green River Interlocal Agreement. Sponsors: King ' County, Cities of Auburn, Kent, Renton, and Tukwila. Hammond, Collier & Wade-Livingstone Associates, Inc. 1992. City of Tukwila ' Nelson Place/McLeod/Boeing CSTC Storm Drainage Technical Report. Harza. 1995. Comprehensive Fisheries Assessment of the Mill Creek, Garrision Creek ' and Springbrook Systems. June. Prepared for City of Kent, Kent, WA. HDR Engineering, Inc. 1995 Draft. City of Renton Surface Water Utility , Comprehensive Plan. Bellevue, WA. City of Renton. Jones & Stokes Associates, Inc. 1988. Final Report, Adequacy Determination 1979 Final Environmental Impact Statement, Eastside Watershed Project. ' December 2. Bellevue, WA. Prepared for City of Renton, WA. Jones & Stokes Associates. 1991. Critical Areas Inventory—City of Renton Wetlands ' and Stream Corridors, City of Renton, WA. Jones & Stokes Associates. 1992. City of Renton Black River Water Quality Management Plan Wetland Inventory Report. September 22. USA 91-094- ' 003.) Bellevue, WA. Prepared for R. W. Beck, Seattle, WA. Jones & Stokes Associates. 1994. Longacres Office Park. Draft Environmental , Impact Statement. August 22. USA 91-129.) Bellevue, WA. Prepared for City of Renton Planning/Building/Public Works Department, Renton,WA. Jones & Stokes Associates. 1996. City of Renton Wetland Inventory Update. City of , Renton, Washington. King County. 1987. King County Basin Reconnaissance Plan, Vols., I-III. King , County Department of Public Works, Seattle, WA. King County. 1990. Surface Water Design Manual. King County,WA. , King County. 1993. Flood Hazard Reduction Plan. King County, WA. King County. 1995. Hydrologic Monitoring Report, Volume 1, Containing Data for ' Water Years. 1988-1994. King County. 1995a. Panther Lake and Panther Creek Fish Use. July 20. Letter to City of Renton,Renton, WA. ' 10-2 R.W. Beck X0011592.112 REFERENCES King County Drainage District No. 1. 1994. Comprehensive Plan for Springbrook Creek and Mill Creek. March 31. Prepared by Barghausen Consulting ' Engineers, Inc., for District No. 1. Kramer Chin and Mayo. 1988. City of Tukwila Nelson Place/Longacres Way Storm Drainage System Preliminary Design Report. ' Krom, S. 14 February 1990. Personal communication (phone by Dr. Walter Trial,Jr.). Citizens for Renton Wildlands Preservation. Krom, S. 1990. Renton Heron Rookery Bird and Mammal Count of 14 February 1990. Seattle Audubon Society. ' Metro. 1989. Quality of Local Lakes and Streams: 1987-1988 Status Report. Municipality of Metropolitan Seattle, Water Resources Section, Water Pollution Control Department, Seattle, WA. Metro, King County Environmental Division, and Washington Department of Ecology. 1991. Green-Duwamish Watershed Non-point Action Plan, Final ' Plan. Seattle, WA. NHC. See "Northwest Hydraulic Consultants." Northwest Hydraulic Consultants Inc., 1992. BRPS Pump Performance Test. Report prepared for the City of Renton. Northwest Hydraulic Consultants Inc., 1995. BRPS Pump Performance Tests on ' Pumps P3 and P8, December 1994. Report prepared for the City of Renton. Northwest Hydraulic Consultants Inc., 1996. ESGRWP Hydrologic Analysis. City ' of Renton. Puget Sound Water Quality Authority. 1994. 1994 Puget Sound Water Quality Management Plan. Seattle, WA. R. W. Beck and Associates. 1989. Panther Creek Wetland/P-9 Channel Design, Draft Interim Preliminary Engineering Report. City of Renton. ' R. W. Beck and Associates. 1993. Black River Basin Water Quality Management Plan - Volumes 1, 2, and 3. May. Seattle, WA. In association with Herrera ' Environmental Consultants and Jones & Stokes Associates. Prepared for City of Renton, Renton, WA, and Washington Department of Ecology, Olympia, WA. ' R. W. Beck and Associates. 1994. Mill Creek Stormwater Management Analysis. Draft Phase I Report. In association with Northwest Hydraulic Consultants, Inc. Prepared for the City of Kent, Kent, WA. R. W. Beck, 1995a. ESGRWP Technical Memorandum, Hydraulic Modeling of Flood Control Alternatives. Submitted to the City of Renton. ' R. W. Beck, 1995b. ESGRWP Design Criteria Memorandum. Submitted to the City of Renton. ' X0011592.112 R. W. Beck 10-3 SECTION 10 , R. W. Beck, Incorporated. 1996a. East Side Green River Watershed Project - Hydraulic ' Analysis Report - Existing Drainage System. City of Renton. R. W. Beck, Incorporated. 1996b. Draft SW 7th Street, Hardie Avenue, and Lake ' Avenue South Drainage Investigations. City of Renton. Renton, City of. 1981. City of Renton Wetlands Study—A Reconnaissance Study of , Selected Wetlands in the City of Renton. February. Prepared with the Assistance of Northwest Environmental Consultants, Inc. Renton, City of, City of Tukwila. 1986. Interlocal Agreement Regarding Reciprocal Annexations. Renton File No. CAG-86-046. Renton, City of. 1990. Trails Master Plan. Renton, City of. 1992. Comprehensive park, recreation, and open space plan. Renton, WA. 'Renton, City of. 1995. East Side Green River Watershed Plan. FEQ Modeling of Alternatives, Clarification of Design Criteria and Alternative Definitions. June 28. ' Renton, City of. 1995a. Comprehensive Plan Renton, City of. 1996. East Side Green River Watershed Project, Draft Plan and ' Environmental Impact Statement. Prepared by R. W. Beck in association with Jones & Stokes, Associates, Northeast Hydraulic Consultants and Herrera Environmental Consultants. ' Renton, City of. 1997 Pending. Wetland Mitigation Banking Program and Plan. Resource Planning Associates. 1991. City of Kent Five-Year Water Quality Program. ' City of Kent, Washington. SCS. See "U.S. Department of Agriculture, Soil Conservation Service." ' Shapiro and Associates. 1993. Mosquito Abatement Program-1993 Survey and Final Report. Prepared for the City of Renton Public Works Department. ' Renton, WA. U. S. Department of Agriculture, Soil Conservation Service. 1965. East Side Green River Watershed Work Plan. ' U. S. Department of Agriculture, Soil Conservation Service, 1972. Black River Pumping Plant, O & M Manual, Book 1. Green River Flood Control Zone ' District, King County,Washington. U. S. Department of Agriculture, Soil Conservation Service. 1974. Environmental Mitigation Agreement. June 3. Spokane, WA. Agreement with City of ' Auburn, City of Kent, City of Renton, City of Tukwila, Green River Flood Control Zone District, King County Conservation District, and King ' County, WA. U. S. Department of Agriculture, Soil Conservation Source. 1978. ESGRWP Revised Watershed Plan , 10-4 R. W. Beck X0011592.112 , REFERENCES U. S. Department of Agriculture, Soil Conservation Service. 1979. East Side Green River Watershed Plan, Final Environmental Impact Statement. ' Spokane, WA. U. S. Department of Agriculture, Soil Conservation Service. 1981. East Side Green River Watershed Plan, Amplification of Final Environmental Impact ' Statement. Spokane,WA. U.S. Department of Agriculture, Natural Resources Conservation Service. 1995. ' East Side Green River, Existing Channel Capacity in the Vicinity of the P-9 Channel Enhancement Project. ' U. S. Environmental Protection Agency. 1988. Hydrologic Simulation Program, FORTRAN. USEPA Environmental Research Laboratory. Athens, Georgia. Washington State Department of Ecology. 1991. Mean Annual Flow Determination for Springbrook Creek. March 25. Olympia. WA. Yake, W. E. 1985. Impact of Western Processing on Water Quality in Mill Creek ' (Kent, WA). Washington State Department of Ecology, Olympia,WA. 1 1 x0011592.112 R. W. Beck 10-5 E I S East Side Green River Watershed Project Final Environmental Impact Statement September 1997 Prepared for: City of Renton Planning/Building/Public Works Department 200 Mill Avenue South Renton, Washington 98055 Prepared by: Jones &- Stokes Associates, Inc. 2820 Northup Way, Suite 100 Bellevue, Washington 98004-1419 In association with: R.W. Beck 1001 Fourth Avenue, Suite 2500 Seattle, Washington 98154-1004 CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT FACT SHEET Title East Side Green River Watershed Project File LUA-95-205 ECF Description of preferred and Preferred Alternative other alternatives The Preferred Alternative includes the following project elements: SC3- Springbrook Creek Greenway Improvements Element 1 - Improvements at Roadways A. Remove Bridge North of SW 27th Street B. SW 27th Street Culvert Improvements C. SW 34th Street Culvert Improvements D. Oakesdale Avenue SW Culvert Improvements Element 2 - Channel Improvements A. Channel Improvements from SW 16th Street to SW 23rd Street B. Channel Improvements from SW 30th Street to SW 40th Street Element 3 - Channel Maintenance Program Element 4 - Improve Riparian Habitat/Extensive Planting Panther Creek Alternative 2 (PC2) -High Flow Bypass to Panther Creek Wetland Element 1 -Modify Existing Flow Split at SR-167 with New Structure Element 2 -SW 34th Street Drainage Improvements SW 23rd Street Channel Alternative 3 (23ST3) -Major Conveyance Improvements Element 1 - Replace SR-167 Culvert Crossings with New Crossing at SW 23rd Street Element 2- Olympic Pipeline Relocation/Culvert Improvements Element 3 -Channel Widening and Deepening 09/97c JSA 1 CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT Wetland Mitigation Bank and Wetland Hydraulic Modifications Wetland 12 Alternative 2 - Culvert Replacement Wetland 7N Alternative 2 - Culvert Replacement Wetland 32 Alternative 2 - Mitigation Bank/Excavate Large Off- Channel Storage Pipe System Improvements Alternative 2 (PS2) Element 1 - SW 43rd Street System Improvements Element 2 - East Valley Road (South of SW 23rd Street) Element 3 - Remove Rolling Hills Creek Culvert at Springbrook Creek Other Alternatives Considered Spring-brook Creek (SC) Alternatives SCI -No Action SC2 -Localized Improvements to Springbrook Creek Element 1 - Improvements at Roadway Crossings A. Bridge North of SW 27th Street B. SW 27th Street C. SW 34th Street D. Oakesdale Avenue Element 2 - Channel Improvements from SW 16th to SW 23rd Street Element 3 - Channel Maintenance Program Element 4 - Improve Riparian Habitat/Selective Plantings Panther Creek (PC) Alternatives PC1 -No Action PC3-Maintain Existing Flow into the 34th Street System SW 23rd Street (23ST) Drainage Channel Alternatives 23ST1 - No Action 09/97e JSA ii CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT 23ST2- Minor Conveyance Improvements Element 1 - Replace SR-167 Culvert Crossings with New Crossing at SW 23rd Street Element 2 - Olympic Pipeline Relocation or Culvert Replacement Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 - No Action W32-1- No Action 1+7N--1 -No Action Pine System (PS) Improvements PS1 -No Action Location of site The project area, located in Renton,Washington, generally includes Springbrook Creek from SW 7th Street to Interstate 405 and most of the Renton Valley between Interstate 405 to the north; SW 43rd Street to the south; the Renton- Tukwila city line to the west; and east to and including the Panther Creek Wetland,just east of SR-167. Proposal's sponsor City of Renton Planning/Building/Public Works Department, Surface Water Utility Date of implementation Specific elements of the project will be implemented in multiple phases over a period of 5 to 15 years commencing in 1997, depending upon available funding. Lead agency City of Renton Planning/Building/Public Works Department Surface Water Utility Responsible official City of Renton Environmental Review Committee List of possible permit, U.S. Army Corps of Engineers approval, and license ■ Section 404, Clean Water Act requirements Washington Department of Ecology ■ Section 401 Certification, Clean Water Act ■ National Pollutant Discharge Elimination System Permit ■ Temporary Water Quality Modification Permit Washington Department of Fish and Wildlife ■ Hydraulic Project Approval City of Renton ■ Shoreline Substantial Development Permit Authors and principal Jones & Stokes Associates, Inc. contributors to EIS 2820 Northup Way, Suite 100 Bellevue, WA 98004-1419 (425) 822-1077 09/97e JSA 111 CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT R.W. Beck 1001 Fourth Avenue, Suite 2500 Seattle, WA 98154-1004 (206) 695-4700 Northwest Archaeological Associates, Inc. 5416-1/2 - 20th Avenue NW Seattle, WA 98107 (206) 781-1909 Herrera Environmental Consultants 2200 Sixth Avenue, Suite 601 Seattle, WA 98121-1820 (206) 441-9080 City of Renton Planning/Building/Public Works Department Community Services Department 200 Mill Avenue South Renton,WA 98055 (425) 235-2550 Draft EIS issue date December 17, 1996 Final EIS issue date September 30, 1997 Additional environmental Detailed permitting review would be conducted by the City of Renton for review each development phase of the project. Location of prior EIS related City of Renton to this proposal, EIS Planning/Building/Public Works Department technical reports, 200 Mill Avenue South background data, adopted Renton,WA 98055 documents, and materials (425) 235-255 incorporated by reference for this EIS Jones & Stokes Associates, Inc. 2820 Northup Way, Suite 100 Bellevue, WA 98004 (425) 822-1077 Cost of copy to public Final Plan and EIS - $20.00 plus tax 09/97e JSA iv CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT DISTRIBUTION LIST Federal Agencies U.S. Army Corps of Engineers Seattle District Office Cyrus M. McNeely/Karen Northup - Environmental Resources Section Tom Mueller - Regulatory Ann Uhrich - Regulatory Gail Terzi - Regulatory U.S. Department of Agriculture Natural Resources Conservation Service Rod DenHerder, Renton Field Office Lynn Brown, State Office U.S. Department of HUD U.S. Department of Transportation Department of Highways District 1 U.S. Environmental Protection Agency Linda Storm U.S. Fish and Wildlife Service Dennis Carlson U.S. National Marine Fisheries Service Ben Meyer Native American Tribes Duwamish Tribal Offices Muckleshoot Indian Tribe Rod Malcom, Fisheries 09/97e JSA v CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT State Agencies Department of Natural Resources Puget Sound Water Quality Authority Abbot Raphael Hall Washington State Department of Ecology SEPA Register Keith Phillips Elizabeth J. Phinney Northwest Regional Office Environmental Review Section John H. Glynn Eric Stockdale Shorelands - Permit Coordinator Washington Department of Fish and Wildlife Phil Schneider Ted Muller Washington State Department of Transportation, Northwest Region Vickie Erickson, Developer - Services Section Sam Richard, Local Programs Don Willis, Environmental Rumina Suafoa, Design Mohammad Saleem, Design Regional Agencies King Conservation District Jack Davis King County Department of Natural Resources Water Pollution Control Division Kathryn McKee MS 120 Gregory M. Bush MS 92 Erik Davison MS 117 Surface Water Management Division Nancy Hanson Andy Levesque 09/97e JSA vi CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT Department of Development and Environmental Services Land Use Services Division Mark Carey King County Courthouse EIS Review Coordinator Puget Sound Air Pollution Control Agency Puget Sound Regional Council Seattle-King County Health Services Department City of Renton City Council Development Services Fire Department Long Range Planning Mayor Maintenance Services Division Parks & Recreation Plan Review Planning Commission Police Department Transportation Systems Division Local Agencies City of Kent Bill Wolinski 09/97e JSA vii CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT City of Tukwila Ross Ernst Phil Phaser Steve Lancaster Utilities/Services Olympic Pipeline Company Bill Mulkey Puget Sound Energy Seattle Public Utilities, Water Department Real Estate Services Division Shirley Lukhang Libraries Renton Public Library Main Branch Highlands Branch Other Public and Private Organizations Citizens for Renton Wildlands Preservation Suzanne Krom Friends of the Black River Jerry Holmes Ted Mallory Tom Malphrus Trudy Thomas King County Drainage District No. 1 Jack Nelson, Attorney Giles Hulsmann, Engineer Rainier Audubon Society Debbie Fisher Jim Flynn 09/97e JSA viii CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT Seattle Audubon Society Gerry Adams University of Washington Tom Leschine Valley Medical Center Washington Environmental Council Darlene Madenwald Parties of Record Joseph S. Alhadeff Benaroya Capital Co., LLC Ome Almeda Valley Medical Center Douglas Bonner Vyzis Company Bart Brynestad Opus Northwest LLC Jim Douma Group Health Stacy Elrod John Robertson Trammell Crow Company Don Gallagher Stephan Goetz Pacific Resources Group William Hale Tom Malphrus Richard McCann Perkins Coie 09/97e JSA ix CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT Dana Mower DBM Consulting Engineers James G. Peterson/Warren Pugh Austin Company Lori Pitzer/Rick Ford The Boeing Company Tim Puryear/J. Randy Kyte Winmar Metro, Inc David Radabaugh Jim Routos Martin Seelig 3300 Company Bernadine Shultek Don Tatro Allen Tosch Hunter Douglas, Inc. Velecia Williams Rhonda Younker 09/97e JSA x CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT TABLE OF CONTENTS CHAPTER 1. SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1.1 INTRODUCTION AND BACKGROUND . . . . . . . . . . . . . . . . . . . . . . . . 1-1 1.2 FORMAT AND USE OF THIS FINAL EIS . . . . . . . . . . . . . . . . . . . . . . 1-2 1.3 HISTORY AND PURPOSE OF THE PROPOSED PROJECT . . . . . . . . . 1-3 1.3.1 Project History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 1.3.2 Purpose of the Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 1.4 SUMMARY OF ALL ALTERNATIVES . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 1.5 RECOMMENDED PREFERRED ALTERNATIVE . . . . . . . . . . . . . . . . . . 1-5 1.6 ISSUES TO BE RESOLVED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 1.7 SIGNIFICANT IMPACTS, MITIGATION MEASURES, AND UNAVOIDABLE ADVERSE IMPACTS . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 CHAPTER 2. ADDITIONAL FACTUAL INFORMATION . . . . . . . . . . . . . . . . . 2-1 2.1 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2.2 PREFERRED AND OTHER ALTERNATIVES . . . . . . . . . . . . . . . . . . . . 2-1 2.3 EXISTING CONDITIONS, IMPACTS, AND MITIGATION . . . . . . . . . . . . 2-1 2.3.1 Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2.3.2 Groundwater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2.3.3 Surface Water Quantity/Quality . . . . . . . . . . . . . . . . . . . . . . . 2-1 2.3.3.1 Water Quantity . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1 2.3.3.2 Water Quality 2-2 2.3.4 Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3 2.3.5 Terrestrial and Aquatic Resources . . . . . . . . . . . . . . . . . . . . . 2-4 2.3.5.1 Fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4 2.3.6 Hazardous Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 2.3.7 Land Use and Recreation . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5 2.3.8 Cultural Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6 2.3.9 Public Services and Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6 2.3.10 Transportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 2.3.11 Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 CHAPTER 3. COMMENTS AND RESPONSES . . . . . . . . . . . . . . . . . . . . . . . 3-1 3.1 LIST OF COMMENTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 APPENDIX A. PUBLIC HEARING RECORD AND ATTENDANCE . . . . . . . . . A-1 APPENDIX B. DETAILED DESCRIPTION OF ALTERNATIVES . . . . . . . . . . . B-1 LIST OF ACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . precedes back cover 09/97e JSA xi CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT LIST OF TABLES TABLE 1-1 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR EARTH BY ALTERNATIVE TABLE 1-2 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR GROUNDWATER BY ALTERNATIVE TABLE 1-3 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR SURFACE WATER QUANTITY/QUALITY BY ALTERNATIVE TABLE 1-4 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR WETLANDS BY ALTERNATIVE TABLE 1-5 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR TERRESTRIAL AND AQUATIC RESOURCES BY ALTERNATIVE TABLE 1-6 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR HAZARDOUS MATERIALS BY ALTERNATIVE TABLE 1-7 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR LAND USE AND RECREATION BY ALTERNATIVE TABLE 1-8 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR CULTURAL RESOURCES BY ALTERNATIVE TABLE 1-9 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR PUBLIC SERVICES AND UTILITIES BY ALTERNATIVE TABLE 1-10 SUMMARY OF IMPACTS AND MITIGATION MEASURES FOR TRANSPORTATION BY ALTERNATIVE TABLE 1-11 DESCRIPTION OF ALTERNATIVES CONSIDERED FOR EAST SIDE GREEN RIVER WATERSHED PROJECT TABLE 2-1 WETLANDS WITHIN AND IMMEDIATELY DOWNSTREAM OF THE EAST SIDE GREEN RIVER PROJECT AREA LIST OF FIGURES FIGURE 1-1 PROJECT AREA MAP FIGURE 2-1 WETLANDS MAP - EAST SIDE GREEN RIVER WATERSHED PROJECT 09/97e JSA xii CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT FOREWORD This Final Environmental Impact Statement (EIS) has been prepared to comply with the State Environmental Policy Act (SEPA Chapter 43.21C RCW), and the City of Renton's SEPA Policy. A Draft EIS for the East Side Green River Watershed Project was published on December 17, 1996 and distributed to federal and State agencies, to affected tribes, and to a variety of local agencies and interest groups (see Distribution List on page v of this Final EIS). At the request of reviewers of the Draft EIS, the initial 45-day review/comment period was extended through February 7, 1997. As advertised in the transmittal letter for the Draft EIS, a public meeting was held at the Renton City Council chambers on January 16, 1997 and was attended by 9 people. The meeting included a brief description of the proposed action, alternatives and impacts, and verbal comments from members of the audience. This Final EIS includes this Foreword; Chapter 1 -Summary; Chapter 2 -Additional Factual Information based on review comments; and Chapter 3 - Comments and Responses. The public hearing record and attendance are included in Appendix A. FINAL EIS PROCESS AND SCHEDULE Following issuance of this Final EIS, the City will prepare a Mitigation Document which will set forth the mitigation measures for the proposed East Side Green River Watershed Project. 09/97e JSA xiii Chapter 1 ' SUMMARY CHAPTER 1 SUMMARY 1 .1 INTRODUCTION AND BACKGROUND The City of Renton Surface Water Utility proposes to resolve existing and prevent future flooding problems and improve environmental resources in the Renton Valley portion of the East Side Green River Watershed (ESGRW) (Figure 1-1). The project area for the East Side Green River Watershed Project (ESGRWP), shown in Figure 1-1, generally includes Springbrook Creek from SW 7th Street to SW 43rd Street and most of the Renton Valley between Interstate 405 to the north;SW 43rd Street to the south; the Renton - Tukwila city line to the west; and east to and including the Panther Creek Wetland, just east of State Route 167 (SR-167). The City of Renton is both project proponent and lead agency for the environmental review. During May 1995, and as a part of the planning and State Environmental Policy Act (SEPA) EIS process, the City held public and agency workshops to present the history of the project, to explain the alternatives evaluation and selection process, and to describe the project alternatives. Information from those meetings was used to refine and further formulate project goals and alternatives. In January 1996, the City of Renton issued a Determination of Significance (DS) for the proposed ESGRWP under SEPA (WAC 197-11-360). This determination was based upon a finding that the proposed project may cause significant adverse impacts to the environment (RCW 43.21C.020[2]), unless mitigation measures are identified. A summary of the scoping process and public comments received during scoping was published in April 1996. In December 1996, the Draft ESGRW Plan and Environmental Impact Statement (EIS) were issued for public review. The Draft Plan and EIS did not identify a Preferred Alternative so that review comments from the public, agencies, businesses, and others could be an integral part of the Preferred Alternative selection process. The comment period for the Draft Plan and EIS began December 17, 1996. A public hearing on the Plan and EIS was held at the Renton City Council chambers on January 16, 1997, during which a description of the project alternatives was presented and public comments received. The public comment period for the Draft Plan and EIS was originally scheduled to close on January 31, 1997, but was extended to February 7, 1997, a 52-day comment period, to allow additional public review time. The City received nine comment letters. Comments and responses are included in this Final EIS. 09/97e JSA 1-1 CHAPTER 1 Changes were made to the alternatives and mitigation measures as a result of review comments received on the Draft EIS. These changes included: ■ Possibility that the SR-167 culvert/control structure proposed for the Panther Creek Wetland (Alternatives 23ST2 and 23ST3, Element 1) would be constructed in an open trench across SR-167 versus the jacking method analyzed in the Draft EIS. ■ Design of the SR-167 culvert/control structure proposed for the Panther Creek Wetland (Alternative 23ST2/3-1) will allow for future fish passage into the wetland from the SW 23rd Street channel. Additional mitigation measures were also identified and are included in the summary tables at the end of this chapter. 1 .2 FORMAT AND USE OF THIS FINAL EIS Chapter 1 of this Final EIS includes a description of the Preferred Alternative, summary of other project alternatives, and issues to be resolved. Environmental elements, impacts, and mitigation measures required by regulation or established as a result of project-related impacts to the environment have been identified in Tables 1-1 through 1-10. i All mitigation measures identified in the Final EIS will be reviewed by the City of Renton's Environmental Review Committee, which will produce a separate Mitigation Document setting forth those measures judged adequate to protect the environment as a result of regulations and/or identified impacts. Identified potential mitigation measures are intended to minimize impacts of the alternatives. Many of the measures are tied to City of Renton regulations or policies. Other non-City of Renton permits (e.g., Washington Department of Ecology Water Quality Certification, Washington Department of Fish and Wildlife Hydraulic Project Approval, U.S. Army Corps of Engineers Clean Water Act Section 404 Permit) may require mitigation specific to those permit requirements. Chapter 2 of this Final EIS includes any additional factual information on existing conditions, impacts and mitigation measures identified during this Final EIS process. Chapter 3 presents the comments received and the responses to those comments. Appendix A includes the public hearing agenda, public hearing attendance record, and testimony received during the hearing, as well as responses to hearing comments. 1-2 JSA 09/97e SUMMARY Copies of the Draft EIS, appendices, and supporting technical reports and background data incorporated by reference and used in the EIS are available for review at the following location: City of Renton City Hall Third Floor, Customer Service Counter 200 Mill Avenue South Renton, WA 98055-2189 1 .3 HISTORY AND PURPOSE OF THE PROPOSED PROJECT 1 .3.1 PROJECT HISTORY This section summarizes the history and purpose of the proposed project. More detailed information is included in Section 3 of the Final ESGRWP Plan. During the ESGRW planning effort, which has been ongoing for several years, the City has coordinated closely with the Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service (SCS), and a number of other resource and regulatory agencies. The watershed planning process has also been closely tied to the City of Kent's stormwater planning. Runoff from Kent contributes to Springbrook Creek, which flows through the Renton Valley planning area (see Figure 1-1). The NRCS has a long history of involvement with flood control planning and implementation in the Green River Valley. The current ESGRWP is a continuation of initial planning that the NRCS (at that time called the Soil Conservation Service) began during the 1960s. Initial flood control planning efforts began after the Cities of Auburn, Kent, Renton, and Tukwila, along with King County, the Green River Flood Control Zone District, and the King Conservation District, passed a resolution requesting flood protection from the federal government under the Watershed Protection and Flood Prevention Act (Public Law 566). This initial effort led to the construction of the Black River Pump Station, the first component of the recommended flood control system. The City of Renton assumed lead-agency responsibility for the project within Renton in 1982. The City, with assistance from the NRCS, coordinated the construction of the Black River Pump Station Floodwater Storage Pond, the P-1 Channel from the pond to SW 16th Street, the Grady Way Box Culvert, and the Interstate 405 Box Culvert. In 1988, the City initiated a process for further construction of the P-1 Channel south of SW 16th Street to SW 43rd Street. In response to public and agency comments, the City conducted an Adequacy Determination Study of the ESGRW planning and environmental review information. The Adequacy Determination Study identified specific deficiencies in the previous planning efforts with respect to impacts on wetlands, streams, wildlife habitat, 09/97e JSA 1-3 CHAPTER 1 fisheries, and water quality south of SW 16th Street. The identification of these deficiencies led to the current ESGRW planning effort. 1.3.2 PURPOSE OF THE PROJECT Detailed project goals are described in Section 2.3 of the ESGRWP Plan. Generally, the purpose of the ESGRWP is to: ■ develop a multi-benefit, comprehensive surface water improvement proposal that minimizes impacts to environmental resources and, if possible, enhances these resources while providing flood protection; ■ ensure the protection of existing private and public property, infrastructure, and environmental resources; and ■ protect these resources under future development conditions within the watershed consistent with the City's comprehensive land use plan and the land use plans of other jurisdictions within the watershed boundaries. Specific elements of the project will be implemented in multiple phases over a period of 5 to 15 years commencing in 1997, depending upon available funding. 1.4 SUMMARY OF ALL ALTERNATIVES The alternatives developed for solving current and future flooding problems and improving environmental resources in the Renton Valley area of the ESGRW were developed from detailed engineering and environmental studies prepared by the City of Renton Surface Water Utility staff; the NRCS; the project consultant team; and others. Input from public and agency workshops on May 16 and May 18, 1995, respectively, and other public/agency reviews were also used in formulating alternatives. The alternatives include the following major categories: ■ Springbrook Creek Alternatives ■ Panther Creek Alternatives ■ SW 23rd Street Drainage Channel Alternatives ■ Wetland Mitigation Bank and Wetland Hydraulic Modifications ■ Pipe System Improvements Table 1-11 summarizes the alternative descriptions contained in Section 8 of the ESGRWP Plan and in Appendix B of this Final EIS. More information on the alternative development process is included in Section 8.2 of the ESGRWP Plan. 1-4 JSA 09/97e SUMMARY 1 .5 RECOMMENDED PREFERRED ALTERNATIVE The recommended Preferred Alternative consists of alternatives selected from the five project categories previously described. The Preferred Alternative consists of the following (see Table 1-11): ■ Springbrook Creek Alternative 3 (SC3) - Greenway Improvements ■ Panther Creek Alternative 2 (PC2) - High Flow Bypass to Panther Creek Wetland ■ SW 23rd Street Channel Alternative 3 (23ST3) - Major Conveyance Improvements ■ Wetland Mitigation Bank and Wetland Hydraulic Modifications Alternative 2 ■ Pipe System Improvements Alternative 2 (PS2) For detailed descriptions of these alternatives, see Appendix B of this Final EIS. The first phase of improvements is scheduled to begin during 1997. More information on project implementation and phasing is contained in Section 9.3 of the Final ESGRWP Plan. Further discussion of the selection of the Preferred Alternative is included in Section 1.6 of the Final Plan. 1.6 ISSUES TO BE RESOLVED SEPA Rule WAC 197-11-440 states that the Final EIS summary shall include a discussion of any issues to be resolved relative to the alternatives. No such issues have been identified. 1.7 SIGNIFICANT IMPACTS, MITIGATION MEASURES, AND UNAVOIDABLE ADVERSE IMPACTS Tables 1-1 through 1-10 at the end of this chapter summarize the impacts and mitigation measures for each of the alternatives. Substantive changes to the tables since publication of the Draft EIS are shown in italics and strikeout font. If the mitigation measures described in the EIS are implemented, no significant unavoidable adverse impacts are expected from the action alternatives. If no action is taken, the following significant unavoidable adverse impacts would likely occur: ■ Earth. Continued channel erosion in Springbrook Creek and washoff/deposition during high flows would occur, as well as continued maintenance associated with those problems. • Surface Water Quantity/Quality. Flooding and associated water quality impacts will continue to become more severe as the area of impervious surfaces in the watershed increases with development. 09/97e JSA 1-5 CHAPTER 1 ■ Land Use. The frequency and severity of flooding would continue to increase within the watershed, adversely affecting existing land uses and damaging property and potential land uses. ■ Public Services and Utilities. The risk of flooding would continue, with the problems of impaired access, possible damage, and creation of unsafe conditions including disruption of public services. ■ Transportation. Flooding would continue to become more severe with resulting impacts due to disruption of vehicular and pedestrian traffic, including impairment of emergency access. I I 1-6 JSA 09/97e Table 1-1. Summary of Impacts and Mitigation Measures for Earth by Alternative Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Springbrook Creek Alternatives SC1 - No Action Channel erosion during high flows would continue,especially Continued maintenance would be required to maintain upstream of SW 16th conveyance capacity,some maintenance activities may require mitigation similar to SC2,Element 1 SC2-Localized Improvements to Springbrook Creek Element 1-Improvements at Roadway Potential for minor,local increase in soil erosion during • Do not use inwater excavation (dredging)unless it cannot be Crossings construction at roadway crossings avoided or the potential for discharging sediment-laden water A. Bridge North of SW 27th Street into the downstream system is minimal and the dredging activity B. SW 27th Street is allowed by state and federal permits(0) C. SW 34th Street D. Oakesdale Avenue As applicable,comply with state Hydraulic Code Rules and HPA Permit constraints,such as limit disturbance area,provide erosion protection within 7 days of project completion,perform construction during low flow periods,and bypass flow around and isolate work areas(R) • Minimize soil erosion by using best management practices per the King County Surface Water Design Manual and Renton Storm and Surface Water Drainage Ordinance and through implementation of the provisions set forth in the City of Renton Standard Specifications for Municipal Construction(R) • Comply with Renton Land Clearing/Tree Cutting and Mining/ Excavation/Grading Ordinances for vegetation clearing and earthwork(R) • Control dust during construction(R) Unstable soils are prone to liquifaction,differential settlement ■ Seismic hazards shall be mitigated by proper structure and or intense shaking during earthquakes pipeline construction practices,such as those presented in the Uniform Building Code(R) Element 2-Channel Improvements ■ Channel improvements from SW 16th to SW 23rd would,in the ■ None needed from SW 16th to SW 23rd Street long term,reduce stream velocity and soil erosion during floods (if modified channel is stabilized before high flows occur) Table 1-1. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document • Excavated slopes may be prone to sloughing Use biostabilization techniques,flatter slopes,and/or other stabilization measures(0) • During construction,potential for erosion of exposed soil prior Utilize same measures as defined for SC2,Element 1 to revegetation/stabilization Element 3-Channel Maintenance • Stream channel and bottom temporarily destabilized immediately Utilize same measures as defined for SC2, Element 1 Program following sediment removal Element 4-Improve Riparian Habitat/ • Selected plantings would reduce potential for bank erosion None needed Selective Plantings during high flows SC3-Springbrook Creek Greenway Improvements Element 1-Improvements at Roadway ■ Similar to SC2,Element 1 • Utilize same measures as defined for SC2,Element 1 Crossings Element 2-Channel Improvements • Similar to SC2,Element 2; more extensive channel • Utilize same measures as defined for SC2,Elements 1 and 2 improvements and plantings could further reduce bank erosion A. SW 16th to SW 23rd Street B. SW 30th to SW 40th Street Element 3-Channel Maintenance • Same as SC2,Element 3 Utilize same measures as defined for SC2, Element 1 Program Element 4-Improve Riparian Habitat/ • Similar to SC2,Element 4; more extensive plantings could None needed Extensive Plantings further reduce erosion Panther Creek Alternatives PC1 -No Action • Continued washoff and erosion and deposition in culverts/ • Similar to SC1 ditches during high flows PC2- High Flow Bypass to Panther Creek Wetland Element 1-Modify Existing Flow Split • Reduced risk of flooding would reduce potential for erosion and • Utilize same measures as defined for SC2, Element 1 at SR-167 washoff during floods Table 1-1. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the Citys Environmental Review Committee as an element of the EIS mitigation document Potential for minor local increase in soil erosion during - Utilize same measures as defined for SC2,Element 1 construction Element 2-SW 34th Street System ■ Similar to PC2,Element 1 but greater potential for erosion - Utilize same measures as defined for SC2,Element 1 Improvements during construction PC3-Maintain Existing Flow Into - Similar to PC2,Element 2 • Same as PC2,Element 2 the 34th Street System SW 23rd Street Drainage Channel Alternatives 23ST1 -No Action - Continued washoff and erosion;some erosion to Olympic - Similar to SC1 Pipeline berm 23ST2- Minor Conveyance Improvements Element 1-Replace SR-167 Culvert - Similar to SC2,Element 1 - Same as measures defined for SC2,Element 1 Crossings with New Crossing at SW 23rd Street Element 2-Olympic Pipeline - Similar to PC2, Element 1 - Same as SC2,Element 2 Relocation or Culvert Replacement 23ST3-Major Conveyance Improvements Element 1-Replace SR-167 Culvert - Same as 23ST2,Element 1 - Same as 23ST2,Element 1 Crossings with New Crossing at SW 23rd Street Element 2-Olympic Pipeline - Same as 23ST2,Element 2 - Same as 23ST2,Element 2 Relocation or Culvert Replacement Element 3-Channel Widening and • Short-term increase in erosion caused by exposure of 2.5 acres - Same as SC2,Element 2 Deepening of soil during construction; no significant long-term impacts - Excavated slopes may be prone to sloughing Table 1-1. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 -No Action ■ Ability to reduce flooding and associated washoff and erosion • Similar to SCl impacts impaired W12-2-Culvert Replacement • Increased ability to reduce flooding and associated washoff and • Similar to SC2,Element 1, but at much smaller scale erosion impacts W32-1 -No Action • Similar to W12-1 • None W32-2-Mitigation Bank/Excavate • Similar to W12-2 except temporary exposure of nearly 14 acres • Similar to SC2,Element 2 Large Off-Channel Storage of soil resulting in short-term impact from erosion W7N-1 -No Action • Similar to W12-1 • Similar to SCl W7N-2-Culvert Replacement . Similar to W12-2 • Similar to SC2, Element 1,but at much smaller scale Pipe System Improvements PS1 - No Action • Continued washoff and erosion • Similar to SCl PS2- Pipe System Improvements PS2-1-SW 43rd Street System . Potential for soil erosion in areas of clearing and grading until • Same mitigation as defined for SC2 Improvement soils are stabilized; reduced risk of flooding would reduce potential for erosion and washoff PS2-2-East Valley Road System ■ Similar to PS2-1 . Same as PS2-1 Improvements PS2-3-Rolling Hills Culvert ■ Similar to PS2-1 • Same as PS2-1 Table 1-2. Summary of Impacts and Mitigation Measures for Groundwater by Alternative Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Springbrook Creek Alternatives SC1 - No Action No adverse impacts expected;potential for expansion of None boundaries of wetlands adjacent to Springbrook Creek SC2-Localized Improvements to SC2 improvements combined would lower storm flow elevations None needed Springbrook Creek in Springbrook Creek and may result in very slight lowering of local groundwater levels along the creek and in hydrologically linked wetlands during the wet season;should have little effect on wetland hydrology, also increases in local surface inflows to wetlands with development and resulting infiltration may offset any potential lowering due to lowered storm flow elevations Element 1-Improvements at Roadway • Potential release of pollutants during construction Accidental releases of hazardous materials during construction Crossings shall be reported to the DOE and City of Renton; the site may A. Bridge North of SW 27th Street be subject to cleanup under applicable regulations(R) B. SW 27th Street C. SW 34th Street • Temporary dewatering may be required for construction, As applicable,plans for dewatering would be required and could D. Oakesdale Avenue lowering local groundwater elevations include measures to decrease iron loading in discharge water,to prevent impacts to existing improvements,and/or to monitor existing improvements for possible settlement(0) Element 2-Channel Improvements • Similar to SC2,Element 1 Same as SC2,Element 1 from SW 16th to SW 23rd Street Element 3-Channel Maintenance • Similar to SC2,Element 1 Same as SC2,Element 1 Program Element 4-Improve Riparian Habitat/ - Transpiration from Springbrook Creek riparian plantings would None needed Selective Plantings slightly reduce local shallow groundwater and increase water- holding capacity of floodplain soils SC3-Springbrook Creek Greenway • Combined effect of SC3 in lowering groundwater levels during None needed Improvements the wet season may be slightly greater than SC2,but still have little effect on wetland hydrology Element 1-Improvements at Roadway • Similar to SC2,Element 1 Same as SC2,Element 1 Crossings Element 2-Channel Improvements • Similar to SC2,Element 1 Same as SC2,Element I A. SW 16th to SW 23rd Street B. SW 30th to SW 40th Street Table 1-2. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Element 3-Channel Maintenance Similar to SC2,Element 1 • Same as SC2,Element 1 Program Element 4-Improve Riparian Habitat/ Same as SC2, Element 4,but to potentially greater extent • None needed Extensive Plantings Panther Creek Alternatives PC1 -No Action No adverse impacts ■ None PC2- High Flow Bypass to Panther Creek Wetland Element 1-Modify Existing Flow Split Similar to SC2,Element 1;also higher tloodflow volumes to • Same as SC2,Element 1; none needed for elevation of at SR-167 Panther Creek Wetland could result in local,minor elevation of groundwater in Panther Creek Wetland groundwater levels for a few days during and after flooding Element 2-SW 34th Street System Similar to SC2,Element 1 • Same as SC2,Element 1 Improvements PC3- Maintain Existing Flow Into Similar to SC2,Element 1 • Same as SC2,Element 1 the 34th Street System SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action Maintenance of poorly functioning SR-167 cross culverts could • None result in lower groundwater levels in Panther Creek Wetland during and for some time following the 2-year storm event; increases in local surface inflows if PC2 is implemented,and with development and resulting infiltration may offset any potential lowering due to lowered storm flow elevations 23ST2-Minor Conveyance Improvements Element 1-Replace SR-167 Culvert • Similar to SC2,Element 1;also installation of culvert/weir could • Same as SC2,Element 1;none needed for potentially lowered Crossings with New Crossing at result in lower groundwater levels in Panther Creek Wetland groundwater related to 2-year storm event SW 23rd Street during the 2-year storm event;similar to under 23S`Fl Element 2-Olympic Pipeline • May lower local groundwater level since overbank flooding of • None proposed Relocation or Culvert Replacement Wetland 8-N would be less frequent and to lesser depth Table 1-2. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document 23ST3-Major Conveyance Improvements Element I-Replace SR-167 Culvert • Same as 23M,Element 1 • Same as 23M,Element 1 Crossings with New Crossing at SW 23rd Street Element 2-Olympic Pipeline • Same as 23ST2, Element 2 • Same as 23ST2, Element 2 Relocation or Culvert Replacement Element 3-Channel Widening and • Lower storm flow elevations potentially resulting in slight • None needed Deepening reduction in local groundwater levels during extreme wet periods • Channel widening/deepening along 23rd between SR-167 and • During design,conduct additional groundwater monitoring along Springbrook Creek could lead to ground subsidence depending the channel alignment to confirm long-term effect on on location of peat (if any exists)and existing/projected groundwater of deepening the channel; if significant impacts to groundwater levels wetland or existing improvements would result from lowered groundwater,then could install impervious membrane liner to prevent lowering(0) Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 -No Action • Greater volume of local inflows with development could increase None infiltration in western cell of Wetland 12 which could cause slight local increases in groundwater levels W12-2-Culvert Replacement • Potential release of pollutants during construction Accidental releases of hazardous materials during construction shall be reported to the DOE and City of Renton; the site may be subject to cleanup under applicable regulations(R) • Slight reduction in storm flow elevations due to increased None needed efficiency of proposed culverts may slightly reduce infiltration; however,this may be offset by increases in local inflow volumes with development W32-1 -No Action ■ No adverse impacts None W32-2-Mitigation Bank/Excavate ■ Similar to SC2,Element 1;slight increase in groundwater level Same as SC2,Element 1 Large Off-Channel Storage associated with Wetland 32-2 because it would allow overflows from the creek into the wetland Table 1-2. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document W7N-1 - No Action • No adverse impacts None W7N-2-Culvert Replacement • Potential increase in groundwater levels in the wetland during None needed floods • Potential release of pollutants during construction Accidental release of hazardous materials during construction shall be reported to the DOE and City of Renton; the site may be subject to cleanup under applicable regulations(R) Pipe System Improvements PS1 - No Action • No adverse impacts None PS2-Pipe System Improvements PS2-1 -SW 43rd Street System • Similar to SC2, Element 1; also potential for slight lowering of • Same as SC2,Element 1 Improvement local groundwater along new or deepened pipeline alignment PS2-2-East Valley Road System • Similar to PS2-1 • Same as PS2-1 Improvements PS2-3-Rolling Hills Culvert • Similar to SC2,Element 1 • Same as PS2-1 Table 1-3. Summary of Impacts and Mitigation Measures for Surface Water Quantity/Quality by Alternative Note: All flood events referenced are associated with future land use condition flows. Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Springbrook Creek Alternatives SC1 -No Action Water Quantity-Springbrook Creek would be subject to ■ Continued maintenance would be required to maintain increases in peak flows and runoff volumes,resulting in conveyance capacity;some maintenance activities may require increased flooding; for 100-year flood at SW 43rd,peak flows mitigation similar to SC2,Element 1 would increase by 40%,resulting in water level increase of 1.3 feet • Capacity of several Springbrook Creek tributaries would be reduced due to backwater conditions ■ High stream velocities upstream of SW 16th could lead to streambank erosion • Water Quality-Water quality in Springbrook Creek would continue to be poor; flooding-related impacts would continue SC2-Localized Improvements to Water Quantity-SC2 improvements combined would reduce Design and analysis of conveyance improvements must be Springbrook Creek 100-year water levels upstream of SW 19th Street by 0.6 to consistent with King County Surface Water Design Manual,as 2.5 feet and increase inflows to the BRPS by about 40%; lower adopted by the City of Renton and other city,state,and federal Springbrook Creek water levels would reduce tailwater regulations(R) conditions on tributary systems,thereby increasing their capacity Element 1 -Improvements at Roadway ■ Water Quality-Potential for temporary increase in suspended As applicable,comply with state Hydraulic Code Rules and Crossings solids,turbidity,nutrients in Springbrook Creek during HPA Permit constraints,such as limit disturbance area,provide A. Bridge North of SW 27th Street construction;construction in streambed would require permits erosion protection within 7 days of project completion,perform B. SW 27th Street from WDFW and DOE;reduction in water quality problems construction during low flow periods,and bypass flow around C. SW 34th Street associated with flooding and isolate work areas(R) D. Oakesdale Avenue ■ Minimize soil erosion by using best management practices per the King County Surface Water Design Manual and Renton Storm and Surface Water Drainage Ordinance and through implementation of the provisions set forth in the City of Renton Standard Specifications for Municipal Construction(R) • The time of disturbance is to be kept to a minimum(0) • Construction would likely require Temporary Water Quality Modification from DOE(R) Table 1-3. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document - If dewatering is necessary,define measures to decrease discharge of iron loading to receiving water(0) Vegetation and earthwork shall be subject to the Land Clearing and Tree Cutting Ordinance and Mining, Excavation,and Grading Ordinance(Title IV,Chapter 9 and 10)(R) See Table 1-5 for additional measures ■ Sediments potentially contaminated at construction locations - As warranted,sample stream sediments prior to excavation to determine contamination; remediate or dispose of contaminated sediments at an appropriate,approved facility(R) Element 2-Channel Improvements - Water quality impacts similar to SC2,Element 1,but to - Same as SC2,Element 1;also do not use in-water excavation from SW 16th to SW 23rd Street potentially greater level; reduced channel erosion (dredging)unless it cannot be avoided or the potential for discharging sediment-laden water downstream is minimal and dredging is allowed by state and federal permits(0) NPDES permit required from DOE for clearing greater than 5 acres(R) Increased insolation and water temperatures until planted - Plant fast-growing shrubs and trees and revegetate streambanks vegetation becomes established immediately following construction (0) Element 3-Channel Maintenance - Water Quality-Potential for temporary increase in suspended - Same as SC2, Element 2; also develop detailed maintenance Program solids,turbidity,nutrients in Springbrook Creek during plans of each project element so that regular maintenance construction; construction in streambed would require permits activities,if needed,are agreed upon and recognized as part and from WDFW and DOE parcel of the project for it to function as intended through its life(0) Element 4-Improve Riparian Habitat/ - Riparian plantings would improve water quality by reducing - None needed Selective Plantings temperature and helping to increase dissolved oxygen SC3-Springbrook Creek Greenway ■ Water Quantity-Similar to SC2,except for 100-year water level - Same as SC2 Improvements at SW 43rd would be further reduced by about 0.6 foot more than with SC2;the inflows at BRPS would be increased 10%less than SC2;and water levels at SW 27th would be about 0.3 foot higher than SC2 Element 1-Improvements at Roadway - Similar to SC2,Element 1 - Same as SC2,Element 1 Crossings Table 1-3. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Element 2-Channel Improvements • Similar to SC2,Element 2,but to a greater extent • Same as SC2,Element 2 A. SW 16th to SW 23rd Street B. SW 30th to SW 40th Street Element 3-Channel Maintenance • Similar to SC2,Element 3;less maintenance required than for • Same as SC2,Element 3 Program SC2 upstream of Grady Way Element 4-Improve Riparian Habitat/ • Water Quality-Similar to SC2,but with increased benefit due • None needed Extensive Plantings to more extensive plantings Panther Creek Alternatives PC1 -No Action • Water Quantity-Flooding of East Valley Road would continue • Same as SC1 • Water Quality-Water quality impacts due to flooding would continue PC2-High Flow Bypass to Panther • Water Quantity-East Valley Road flooding problem would be • Same as SC2;periodic maintenance required to maintain Creek Wetland corrected assuming either SC2 or SC3 is implemented capacity/function(see SC2,Element 3) • Flow through SR-167 culvert would be about 7 cfs for 100-year storm Element 1-Modify Existing Flow Split • Water Quality-Beneficial impact overall to water quality in • Same as SC2,Element 2 at SR-167 Panther Creek and Springbrook Creek; increased pollutants entering Panther Creek Wetland during high flows would largely settle out in south end of wetland; reduction in water quality impact associated with flooding;potential for temporary impacts during construction Element 2-SW 34th Street System Pipe replacement could result in temporary increase in Same as SC2,Element 2 Improvements suspended solids and turbidity downstream; construction in streambed would require permits from WDFW and DOE; reduction in water quality problems associated with flooding PC3- Maintain Existing Flow Into Water Quantity-East Valley Road flooding problem would be Same as PC2 the 34th Street System corrected assuming either SC2 or SC3 is implemented;flows crossing SR-167 would be approximately 31 cfs(2-year)and 38 cfs(100-year);potential for larger pipe system not to be fully utilized if Panther Creek naturally changes course over time Table 1-3. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document • Water Quality-Similar to PC1,reduced flow to Panther Creek Same as SC2,Element 2 Wetland would result in less pollutant removal,and greater pollutant load reaching downstream areas; temporary impacts similar to PC2,Element 2,but more extensive; reduction in water quality problems associated with flooding SW 23rd Street Drainage Channel Alternatives 23ST1 - No Action Water Quantity-East Valley Road flooding would continue Same as SCl; assumes WSDOT performs maintenance of existing,poorly functioning SR-167 culverts to restore them to full capacity if 23ST2 or 23S-0 is not implemented • Water Quality-Flooding and associated water quality degradation would continue 23ST2-Minor Conveyance Water Quantity-Outlet from Panther Creek Wetland at • Same as PC2 Improvements SW 23rd Street would replace existing poorly functioning SR-167 culverts and help correct East Valley Road system flooding(in combination with Pipe System Improvements); Panther Creek Wetland water levels would be determined by an inlet control structure on the proposed culvert,designed to maintain 100-year flooding levels in the wetland similar to 23ST1;eliminating conveyance restriction at Olympic Pipeline crossing would lower 100-year upstream water levels by approximately 0.5 to 1 foot (assuming either SC2 or SC3 is implemented) Element 1-Replace SR-167 Culvert • Water Quality-Temporary water quality impacts during ■ Same as SC2, Element 2 Crossings with New Crossing at construction; reduction in water quality impacts associated with SW 23rd Street flooding Element 2-Olympic Pipeline • Water Quality-Similar to 23ST2,Element 1;construction in • Same as SC2,Element 2 Relocation or Culvert Replacement streambed would require permits from WDFW and DOE 23ST3-Major Conveyance ■ Water Quality-Similar to 23ST2,except 100-year upstream • Same as PC2,but less maintenance required to maintain Improvements water levels would be lowered beyond 23ST2 by about 0.4 to 0.7 capacity/function than 23ST2 foot; this would reduce extent of pipe system improvements required in East Valley Road(PS2-2) Element 1-Replace SR-167 Culvert • Water Quality-Same as 23ST2 • Same as SC2,Element 2 Crossings with New Crossing at SW 23rd Street Table 1-3. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Element 2-Olympic Pipeline Water Quality-Same as 23Sn Same as SC2,Element 2 Relocation or Culvert Replacement Element 3-Channel Widening and Water Quality-Similar to 23M,but greater area susceptible to Same as SC2,Element 2 Deepening erosion during construction;positive grade would reduce stagnation and improve water quality; less maintenance-related water quality impacts than 23M Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 -No Action Water Quantity-Impact would depend on which Springbrook Same as SC1 Creek alternative is selected:with SC1,western cell of Wetland 12 and Welland 13Sj would continue to function as off- channel storage;with SC2 or SC3,this area would provide very little flood storage with 18-inch culvert only hydraulic connection for Springbrook Creek overflow • Water Quality-Potential water quality treatment function of • None west cell of Wetland 12 underutilized W12-2-Culvert Replacement • Water Quantity-Western cell of Wetland 12 and Wetland 13Sj • None needed would provide approximately 100 acre-feet of flood storage for 100-year flood(assuming SC2 or SC3 is implemented); this would likely double the flood storage available with W12-1 • Water Quality-Increases water quality treatment function in • None needed west cell of Wetland 12; reduced water quality impacts associated with flooding W32-1 - No Action • Water Quantity and Quality-Wetland 32 would continue to be • None isolated from Springbrook Creek during flooding and offer no direct water quality benefits to Springbrook Creek W32-2-Mitigation Bank/Excavate • Water Quantity-Approximately 65 acre-feet of new flood • None needed Large Off-Channel Storage storage would be provided during 100-year event and peak flows at BRPS would be reduced by about 60 cfs • Water Quality-Similar to SC2;provide additional water quality • Same as SC2 treatment function for flows stored on the site W7N-1 -No Action • Water Quantity and Quality-Wetland 7N would continue to • None provide little or no flood storage and limited water quality benefits Table 1-3. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document W7N-2-Culvert Replacement • Water Quantity-Approximately 15 acre-feet of additional flood • None needed storage for 100-year event • Water Quality-Potential for temporary increase in suspended • Construction may require temporary water quality modification solids and turbidity downstream during construction; increases from DOE(R) water quality function and reduces water quality impacts associated with flooding • Minimize soil erosion by using best management practices per the King County Surface Water Design Manual and Renton Storm and Surface Water Drainage Ordinance and through implementation of the provisions set forth in the City of Renton Standard Specifications for Municipal Construction(R) Pipe System Improvements PS1 - No Action Water Quantity-flooding would continue along SW 43rd and Same as SCl East Valley Road even if SC2/SC3 and 23STM/23M are implemented; flooding would become more frequent and severe as watershed continues to develop • Water Quality-Flood-related water quality problems would None continue PS2- Pipe System Improvements Water Quantity- Improvements would correct flooding Same as PC2 problems(in combination with Springbrook Creek and SW 23rd drainage channel alternatives) PS2-1 -SW 43rd Street System Water Quality-Flooding and associated roadway pollutants • Same as SC2,Element 1 Improvement would be reduced;potential for erosion of exposed soil during construction;no adverse impacts if culverts are replaced during dry season PS2-2-East Valley Road System Water Quality-Similar to PS24 • Same as SC2,Element 1 Improvements PS2-3- Rolling Hills Culvert Water Quality-Potential for temporary increase in suspended • Same as SC2,Element 2 solids and turbidity downstream during construction; construction in Rolling Hills Creek would require permits from WDFW and DOE Table 1-4. Summary of Impacts and Mitigation Measures for Wetlands by Alternative Note: As groundwater may be related to wetland hydrology, see also Table 1-2 for impacts and mitigation for groundwater. Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Springbrook Creek Alternatives SC1 -No Action • Surface flows to wetlands would increase over time with • None development(this also true for other alternatives) SC2-Localized Improvements to • Based on 2-year event,lowered water levels under SC2 in the • None needed to mitigate for wetland impacts due to minor Springbrook Creek creek would have little effect on wetland hydrology/vegetation water level changes Element 1-Improvements at Roadway • No adverse impacts to wetlands at any of the roadway crossings; • Activities affecting wetlands or streams likely subject to Crossings some work within ordinary high water mark of the creek Sections 401 and 404 of the Clean Water Act(R) A. Bridge North of SW 27th Street B. SW 27th Street C. SW 34th Street D. Oakesdale Avenue Element 2-Channel Improvements Potential direct impact of widened channel to 0.10 acre of Activities affecting wetlands or streams likely subject to from SW 16th to SW 23rd Street Wetland W-9a,0.06 acre of W-10N,0.26 acre of W-13Na and Sections 401 and 404 of the Clean Water Act(R) W-16b combined,and an additional 0.2 acre of W-16b from trail construction; some work within ordinary high water mark of the creek • Prepare a wetland mitigation plan consistent with the requirements of Wetland Management Ordinance(Title IV, Chapter 32)(R) • Conduct wetland monitoring and maintenance in accordance with the Wetland Management Ordinance(R) • Explore the options of enhancing habitat values of degraded City-owned wetlands(0) Element 3-Channel Maintenance No wetlands would be adversely impacted;some work within Activities affecting wetlands or streams likely subject to Program ordinary high water mark of the creek Sections 401 and 404 of the Clean Water Act(R) • Temporary modification to vegetation in the Black River • None needed floodwater storage pond as a result of temporary drawdown in water elevation in the pond Element 4-Improve Riparian Habitat/ No adverse impact; net benefit to biological resources;some • Activities affecting wetlands or streams likely subject to Selective Plantings work within ordinary high water mark of the creek Sections 401 and 404 of the Clean Water Act(R) Table 1-4. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document SC3-Springbrook Creek Greenway - Similar to SC2 in terms of lowered 2-year water levels - None needed to mitigate for impacts due to minor water level Improvements changes Element 1-Improvements at Roadway - Similar to SC2,Element 1 - Same as SC2,Element 1 Crossings Element 2-Channel Improvements A. SW 16th to SW 23rd Street ■ Similar to SC2,Element 2 - Same as SC2,Element 2 B. SW 30th to SW 40th Street - No wetlands lie within approximately 3,000 feet of channel;some - Same as SC2,Element 1 work within ordinary high water mark of creek Element 3-Channel Maintenance - Similar to SC2,Element 3; less maintenance than SC2 upstream - Same as SC2,Element 3 Program of Grady Way Element 4-Improve Riparian Habitat/ - Similar to SC2,Element 4; greater benefit to biological - Same as SC2,Element 4 Extensive Plantings resources than SC2 Panther Creek Alternatives PC1 -No Action ■ Same as SC1 ■ None PC2-High Flow Bypass to Panther Creek Wetland Element 1-Modify Existing Flow Split - Water elevations in floodplain portion of W4 OS foot lower - None needed to mitigate for impacts due to minor water level at SR-167 during 2-year storm event than under PCl assuming either changes 23M or 23M is implemented or WSDOT performs maintenance of existing SR-167 culverts between SW 23rd Street and SW 34th Street(23ST1); more frequent flow to W4 when Panther Creek >5 cfs; normal water elevation in W4 same as current elevation - Impact 0.01 acre of riparian portion of W4 as a result of - Similar to SC2,Element 2 installing flow diversion control structure on Panther Creek at SR-167 - Reduction in flow to W48f if SR-167 culvert closed - None needed - Minor changes in vegetative composition in W4,possibly - None needed reducing reed canarygrass - Not expected to increase mosquito breeding in W4 - None needed Table 1-4. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Element 2-SW 34th Street System • No adverse impacts to wetlands; some work within ordinary high • Same as SC2,Element 1 Improvements water mark of creek PC3-Maintain Existing Flow Into • Similar to PC2,Element 2,except to W-53 if channel reach is • Similar to SC2,Element 2 the 34th Street System widened SW 23rd Street Drainage Channel Alternatives 23ST1 -No Action • Reduction in water elevation in Panther Creek Wetland(W4) • None by WSDOT maintenance of poorly functioning SR-167 culverts, but increased water elevations of Wetlands W-8N,W-10N,and W-48d and e • Surface flow volumes to wetlands would increase with development(this also true for other alternatives) • Minor change in wetland vegetation in response to higher stormwater levels in W-8N,W48d and a and lower stormwater levels in W4 23ST2-Minor Conveyance Improvements Element 1-Replace SR-167 Culvert Removal of less than 4,000 sq ft of wetland at the western edge • Activities affecting wetlands or streams likely subject to Crossings with New Crossing at of the Panther Creek Wetland as a result of culvert construction; Sections 401 and 404 of the Clean Water Act (R) SW 23rd Street impact to OAS acre of north end of W-48e for new conveyance channel from SR-167 culvert to East Valley Road • Prepare a wetland mitigation plan consistent with the requirements of Wetland Management Ordinance(Title IV, Chapter 32)(R) • Conduct wetland monitoring and maintenance in accordance with the Wetland Management Ordinance(R) • Explore the options of enhancing habitat values of degraded City-owned wetlands(0) • Potential change in vegetation composition in W-48e from • None needed reduced surface flows as a result of modifying SR-167 culverts • Reduced 2-year water elevations in Panther Creek Wetland; • Monitor water elevations in Panther Creek Wetland and potential change in vegetation composition;reduction in 2-year coordinate with Corps of Engineers to determine adjustments to levels would be reduced if PC2 were implemented the low flow device and/or flood control weir(0) Table 1-4. Continued Akernative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document • May reduce mosquito breeding habitat - None needed Element 2-Olympic Pipeline Temporary disturbance of Wetland W-10N during pipeline • Similar to 23ST2 Element 1 Relocation or Cuiveti Replacement relocation or culvert replacement • Reduction in 2-year storm surface elevations in W-8N by • Explore the option of the City purchasing and covenaniing approximately 24 inches as a result of removing the flow W-8N as open space and wetland habitat(0) obstruction(two 18-inch culverts);potential change in vegetation composition in W-8N 23ST3-Major Conveyance Improvements Element 1-Replace SR-167 Culvert Same as 23ST2 Element 1 Same as 23ST2 Element 1 Crossings with New Crossing at SW 23rd Street Element 2-Olympic Pipeline Same as 23ST2 Element 2 Same as 23SU Element 2 Relocation or Culvert Replacement Element 3-Channel Widening and 1.7 acres of scrub-shrub and emergent wetland in W-8N and • Same as 23ST2,Element 2;consider removing portions or all of Deepening 0.8 acre of similar habitat in W-10N would be replaced with the berm separating Wetlands W-12a and W-12b as a potential widened and deepened channel;greater reduction in storm flow mitigation site(0) elevations and overbank flooding than 23ST2 ■ Seek exception to NRCS criteria to allow steeper channel side slopes(0) - Limit construction to what can be accomplished from the existing access road where feasible(0) See also 23ST3, Element 3 in Table 1-2 Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 -No Action • Same as SCl • None W12-2-Culvert Replacement - Only slight reduction in current 2-year water elevations in ■ None needed; may be subject to Sections 401 and 404 of the W-12a;normal hydrology unaffected Clean Water Act(R) W32-1 -No Action I - No adverse impact;W32 remain isolated I - None Table 1-4. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document W32-2- Mitigation Bank/Excavate - About 6.7 acres of existing wetland on fill would be excavated • Similar to SC2, Element 2 Large Off-Channel Storage and replaced and expanded,resulting in an increase in wetland habitat and functional value; hydrologic connection to Springbrook Creek restored W7N-1 - No Action • No adverse impacts; W7N would remain isolated • None W7N-2-Culvert Replacement Higher stormwater elevations in the wetland and potentially Similar to W12-2 increased duration of hydroperiod Pipe System Improvements PSI -No Action • Surface ponding of areas drained by undersized pipe systems None would have minor impact to wetlands PS2-Pipe System Improvements PS2-1-SW 43rd Street System • No adverse impacts to wetlands, may require some minor work • None needed;outfall may be subject to Sections 401 and 404 of Improvement within ordinary high water mark of Springbrook Creek to install the Clean Water Act(R) outfall PS2-2-East Valley Road System • No adverse impacts to wetlands; may require some minor work • Similar to PS2-1 Improvements within ordinary high water mark of SW 23rd Street drainage channel PS2-3-Rolling Hills Culvert • No adverse impacts; removal of culvert would create wetland/ • None needed;work likely subject to Sections 401 and 404 of the stream habitat;some minor work may be required within Clean Water Act(R) ordinary high water mark of Springbrook and Rolling Hills Creeks This page left blank intentionally. Table 1-5. Summary of Impacts and Mitigation Measures for Terrestrial and Aquatic Resources by Alternative Note: The vegetation and wildlife analysis primarily addresses direct impacts due to construction. See Table 1-4 for impacts due to changes in water levels and for mitigation for direct impacts to wetland vegetation. Sediment quality considerations are included in Table 1-6. Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Springbrook Creek Alternatives SC1 - No Action • Continued maintenance would be required to maintain capacity, Some maintenance activities may require mitigation similar to flood-related impacts to vegetation and wildlife would continue SC2,Element 1 • Fish-Water quality and habitat in Springbrook Creek would degrade during high flow rates due to erosion and sedimentation SC2- Localized Improvements to Springbrook Creek Element 1 -Improvements at Roadway Crossings A. Bridge North of SW 27th Street Vegetation and Wildlife-Temporary,localized vegetation Comply with Renton Land Clearing/Tree Cutting and Mining/ B. SW 27th Street disturbance would occur during construction; mature vegetation Excavation/Grading Ordinances for vegetation clearing and C. SW 34th Street would become reestablished within 10 years of project earthwork(R) D. Oakesdale Avenue completion; reduction in flooding would provide long-term benefit to vegetation and wildlife • Fish-Potential for temporary increase in turbidity during As applicable,comply with state Hydraulic Code Rules and construction; in-channel work subject to approval by WDFW; HPA Permit constraints,such as limit disturbance area,provide improved fish passage and habitat;water quality improvement erosion protection within 7 days of project completion,perform through reduced flooding construction during low flow periods,and bypass flow around and isolate work areas(R) • See additional mitigation measures in Table 1-3 under SC2 Element 2-Channel Improvements Vegetation and Wildlife-About 5.2 to 6.1 acres of riparian Develop a revegetation plan during the design phase which from SW 16th to SW 23rd Street habitat would be removed during channel construction and includes riparian vegetation and habitat improvement features; replaced with habitat plantings and a pedestrian trail;plantings and consider installing temporary irrigation system to ensure would not be as intensive as SC3 below the level of the 100-year that vegetation becomes established; coordinate with adjacent flood property owners on compatibility of landscaping(0) ■ Alternative element SC2-4 should be implemented prior to or concurrent with SC2-2(0) • See also SC2,Element 1 Table 1-5. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document • Potential temporary reduction in downstream wildlife use due to Where feasible,limit channel modifications to a single bank in water quality impairment during construction of Springbrook any segment and incorporate existing beneficial vegetation into Creek channel the new channel design;where feasible,minimize disturbance to the low flow channel while enhancing vegetation and in-stream habitat(0) • Without a control program,invasive plant species would become Similar to as is required for wetlands,monitoring and established in the new channel maintenance of other plantings not in wetlands will be conducted to ensure that plant establishment and survival rates achieve desired performance goals;explore implementing DOE guidelines as an option for the control of invasive species(0) • Fish-Potential short-term impact on fish due to increased See above measures turbidity,loss of streamside cover,and reduced dissolved oxygen during channel widening; lower flow velocity would benefit water quality and fish passage over long term Element 3-Channel Maintenance Vegetation and Wildlife- Removal of accumulated sediments Similar to SC2, Element 1 Program and selected vegetation downstream of Grady Way would result in a temporary reduction in benthic prey and shift in habitat use by wildlife currently using the area;vegetative maintenance needs below the elevation of the 100-year floodplain would be similar to that required under SCI for upstream of SW 23rd Street • Fish-Potential for temporary impact on fish due to increased Similar to SC2,Element 1 turbidity and reduced dissolved oxygen during channel maintenance (sediment removal); lower flow velocity would benefit water quality and fish over long term Element 4-Improve Riparian Habitat/ • Vegetation and Wildlife-Habitat would be improved over the Similar to SC2,Element 2 Selective Plantings long term along portions of Springbrook Creek • Fish -Placing instream rootwads and planting riparian Similar to SC2,Element 2 vegetation would benefit fish habitat Table 1-5. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document SC3-Springbrook Creek Greenway Improvements Element 1 -Improvements at Roadway Crossings A. Bridge North of SW 27th Street - Similar to SC2,Element 1;greater improvement of fish passage - Same as SC2,Element 1 B. SW 27th Street at Oakesdale Avenue due to use of three-sided box culvert C. SW 34th Street D. Oakesdale Avenue Element 2-Channel Improvements - Vegetation and Wildlife-Similar to SC2 Element 2 ercept 9.5 to - Same as SC2,Element 2 A. SW 16th to SW 23rd Street 10.4 acres of riparian habitat would be removed during channel B. SW 30th to SW 40th Street construction and replaced with habitat plantings and a pedestrian trail (between about SW 19th Street and SW 24th Street); riparian corridor would eventually provide habitat values equal to or greater than current values - Alternative Element SC3-4 should be implemented prior to or concurrent with SC3-24 (0) Fish-Similar to SC2,but greater long-term benefit - Same as SC2,Element 2 Element 3-Channel Maintenance - Vegetation,Wildlife and Fish-Similar to SC2,but less - Same as SC2,Element 1 Program maintenance required than for SC2 upstream of Grady Way Element 4-Improve Riparian Habitat/ - Additional planting would provide a greater diversity of - Similar to SC2,Element 2 Extensive Plantings vegetation and wildlife habitat than with SC2 Fish-More natural riparian corridor and greater stream shading - Similar to SC2,Element 2 would further improve fish habitat and increase input of fish prey(terrestrial insects) Panther Creek Alternatives PC1 -No Action - Vegetation and Wildlife-No change to vegetation or wildlife - None habitat - Fish-Water quality,low stream flow,and other factors would continue to limit fish production potential of Panther Creek; potential for stranding in braided channel of Panther Creek and in Panther Creek Wetland would continue Table 1-5. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document PC2-High Flow Bypass to Panther Creek Wetland Element I-Modify Existing Flow Split - Vegetation and Wildlife-Some temporary and permanent loss - Same as SC2,Element 1 at SR-167 of vegetation due to c.,.,.....ction of diversion structure Fish-Increased turbidity during construction;potential increase - During the design phase,work with WDFW to determine need in stranding of fish in Panther Creek Wetland during high flow for fish exclusion device; high level of maintenance required if (>5 cis)diversion (note: Panther Creek flows would be at or exclusion devices used(R) below 5 cfs for 70 to 80010 of the time with overflows typically occurring during the wet season when Panther Creek Wetland - /f Element 23ST2 or 23ST3 is implemente4 then a possible option water levels are high) may be to create an 'overflow channel"through use of vegetation maintenance to facilitate fish reaching standing water in the wetland(0) Diversion structure could be designed to include physical means (such as series of weirs)to add oxygen to water as it is diverted into the Panther Creek Wetland(0) Element 2-SW 34th Street System - No significant adverse impacts to vegetation or wildlife - None needed Improvements Fish-Potential for temporary increase in turbidity during - Same as SC2, Element I construction; no long-term adverse impact PC3- Maintain Existing Flow Into - Vegetation and Wildlife-Some temporary loss of vegetation if - None needed for pipe;same as SC2, Element 2 for channel the 34th Street System channel between SR-167 and Fast Valley Road is widened; portion replacement of pipe system would not impact vegetation and wildlife Fish-Similar to PCl;construction impacts similar to PC2, - Same as SC2,Element 1 for pipe;same as SC2,Element 2 for Element 2 channel portion SW 23rd Street Drainage Channel Alternatives 23ST1 -No Action - Vegetation and Wildlife-No change to vegetation or wildlife ■ Some maintenance activities may require mitigation similar to habitat SC2,Element 1 Fish-Continued restriction of fish use in channel due to poor water quality and obstructions; flood related problems would continue;continued maintenance would be required to maintain capacity Table 1-5. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document 23ST2- Minor Conveyance • Maintenance of channel would be similar to 23ST1;new SR-167 • Some maintenance activities may require mitigation similar to Improvements culvert and Olympic Pipeline crossing improvements would SC2,Element 1 require less frequent maintenance than 23ST1 Element 1- Replace SR-167 Culvert • Vegetation and Wildlife -Temporary loss of vegetation due to • Same as SC2,Element 1 Crossings with New Crossing at construction;small permanent loss of vegetation to install SW 23rd Street SR-167 culvert inlet stfaetura ■ Fish-Culvert to be designed to allow future fish passage into the - None needed Panther Creek Wetland Increase in oxygen concentrations with new weir outlet from • The SR-167 culvert and inlet control structure could be designed Panther Creek Wetland to include vertical drop to add oxygen to the water prior to entering the 23rd Street channel (0) Potential for temporary increase in turbidity during construction • Similar to SC2,Element 1 Element 2-Olympic Pipeline • Vegetation and Wildlife-Temporary loss of vegetation due to • Similar to SC2,Element 1 Relocation or Culvert Replacement construction • Fish-Removal of obstructions would allow passage into channel • Similar to SC2,Element 1 and increase potential rearing habitat 23ST3- Major Conveyance Improvements Element 1-Replace SR-167 Culvert - Same as 23ST2 ■ Same as 23ST2 Crossings with New Crossing at SW 23rd Street Element 2-Olympic Pipeline • Same as 23ST2 • Same as 23ST2 Relocation or Culvert Replacement Element 3-Channel Widening and - Vegetation and Wildlife-Temporary loss of vegetation and • Similar to SC2,Element 2 Deepening wildlife habitat during construction; more extensive than 23ST2; structure/composition of vegetation would be changed due to channel widening/deepening; less maintenance-related disturbance than 23ST2 • Fish-Short-term loss of cover and increased solar insolation; Similar to SC2,Element 2 improved water quality,fish passage,and rearing habitat (greater than 23ST2) Table 1-5. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Wetland Mitigation Bank and Wetland Hydraulic Modifications Fw12-1 -No Action No adverse impacts to vegetation or wildlife ■ None • Fish-Sirdnding of fish may occur during floods and increase as development continues W12-2-Culvert Replacement Vegetation and Wildlife-No adverse impacts • None needed • Fish-Greater conveyance capacity between wetland cells could • None needed improve ability of fish to enter and exit Wetland W-12a during floods W32-1 -No Action Vegetation,Wildlife,and Fish-No impact;vegetation • None communities and associated wildlife values would increase over time as the vegetative structure matures W32-2-Mitigation Bank/Excavate Vegetation and Wildlife-Temporary loss of vegetation and • Similar to SC2,Element 2 Large Off-Channel Storage wildlife habitat during construction;with planting,wetland vegetation and associated wildlife values would increase; upland habitat would be replaced by water-related vegetation and wildlife • Fish-Should not strand fish as hydraulic connection between None needed wetland and Springbrook Creek would be configured to ensure that fish can move into the creek as water elevations recede in the wetland;wetland would provide off-channel refuge during high flows W7N-1 -No Action Vegetation,Wildlife,and Fish-No adverse impacts None W7N-2-Culvert Replacement Vegetation and Wildlife-Plant communities would not change None needed significantly • Fish-No adverse impact as long as Rolling Hills Creek does not None needed support fish; if creek has rearing salmonids in future,fish could become entrained in W7N during storm events(greater than 2 year) Table 1-5. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Pipe System Improvements PSI - No Action • Vegetation and Wildlife-No adverse impacts • None Fish-Flooding would continue; PSI would have no direct impact on fish or instream environment PS2-Pipe System Improvements PS2-1 -SW 43rd Street System • Vegetation and Wildlife-Any vegetation within the pipe • Similar to SC2,Element 1 Improvement alignment would be removed during construction • Fish-Potential for temporary increase in turbidity during • Similar to SC2,Element 1 construction PS2-2-East Valley Road System • Vegetation,Wildlife,and Fish-Similar to PS2-1 • Same as PS2-1 Improvements PS2-3- Rolling Hills Culvert • Vegetation,Wildlife,and Fish- Restoration of stream channel • Similar to SC2,Element 1 would be a benefit to the resource over long term;potential for temporary increases in turbidity during construction This page left blank intentionally. Table 1-6. Summary of Impacts and Mitigation Measures for Hazardous Materials by Alternative Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document All Alternatives Potential accidental release of hazardous materials during Prevention and cleanup of construction-related contaminants construction should be in accordance with City of Renton Standard Specifications for Municipal Construction and other local,state, and federal regulations(R) Springbrook Creek Alternatives SC1 - No Action • Maintenance might involve removal or disturbance of sediments As warranted,sample stream sediments prior to excavation to which may be contaminated;potential temporary increase of determine contamination; remediate or dispose of contaminated contaminants in the water column in Springbrook Creek during sediments at an appropriate,approved facility(R) sediment removal; long-term benefit by removal of these substances(impact applies to all elements of SC2) SC2- Localized Improvements to Springbrook Creek All Elements • Similar to SCI; low potential for hazardous materials in local Same as SC1;as much as possible,conduct construction groundwater that could occur during dewatering activities when flows and groundwater levels are low(0) SC3- Springbrook Creek Greenway Improvements All Elements I Same as SC2 Same as SC2 Panther Creek Alternatives PC1 - No Action No impacts expected None PC2- High Flow Bypass to Panther Creek Wetland All Elements • No impacts expected for any elements of PC2 except low As much as possible,conduct construction activities when flows potential for hazardous materials in local groundwater that could and groundwater levels are low(0) occur during dewatering(Element 2 only) PC3- Maintain Existing Flow Into • Similar to PC2 Same as PC2 the 34th Street System Table 1-6. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the Citys Environmental Review Committee as an element of the EIS mitigation document SW 23rd Street Drainage Channel Alternatives 23ST1 -No Action Similar to SCl Same as SC1 23ST2-Minor Conveyance Improvements All Elements Similar to 23ST1 Mitigation measures same as 23ST1 23ST3-Major Conveyance Improvements All Elements Similar to 23ST2,except greater potential for removal of • Same as SCI contaminated sediments under Element 3,channel widening and deepening Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 -No Action No adverse impacts • None needed W12-2-Culvert Replacement No adverse impacts • None needed W32-1 -No Action No adverse impacts • None needed W32-2-Mitigation Bank/Excavate Connection of mitigation bank site to Springbrook Creek may • Same as SC2 Large Off-Channel Storage involve removal/disturbance of contaminated sediments W7N-1 -No Action No adverse impacts • None needed W7N-2-Culvert Replacement No adverse impacts • None needed Pipe System Improvements PSI -No Action No adverse impacts • None needed PS2- Pipe System Improvements All Elements Potential disturbance of sediments that may be contaminated in • Same as SC2 Rolling Hills Creek and where storm drainage outfalls will be installed Table 1-7. Summary of Impacts and Mitigation Measures for Land Use and Recreation by Alternative Note: See also Tables 1-9 and 1-10 for mitigation measures for possible public services/utilities and transportation impacts that may also affect surrounding land uses such as business operations. Alternative/Project Element I Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Springbrook Creek Alternatives SC1 - No Action • Flooding would worsen as development continues None • Would not be consistent with city policies encouraging public access into open space areas; flood protection and flood storage; maintenance of stream courses in a natural state and rehabilitation of degraded channels;and other policies SC2-Localized Improvements to • Elements of SC2 would help reduce flooding,thereby providing None needed for beneficial impact;all elements would require Springbrook Creek a beneficial land use impact; all elements would be subject to Shoreline Substantial Development Permit(R) the Shoreline Master Program Element 1-Improvements at Roadway • Roadway crossings may allow sufficient headroom for below- Incorporate trail location and design considerations in the Crossings grade trail crossings design for the flood control improvements;provide temporary alternative routes when possible for trail users if existing trail is impacted by construction(R) A. Bridge North of SW 27th Street • Would require permission from property owners on both sides Obtain permission as needed(R) of creek and Drainage District No. 1 B. SW 27th Street • Would require additional right-of-way downstream of SW 27th Acquire additional right-of-way as needed(R) culvert improvements C. SW 34th Street • Additional right-of-way or easement may be needed Acquire additional right-of-way as needed(R) D. Oakesdale Avenue • Additional right-of-way or easement likely required upstream of Acquire additional right-of-way/easement as needed (R) Oakesdale Avenue improvements Element 2-Channel Improvements • Public access trail from about SW 19th to SW 24th would Incorporate trail location and design considerations in the from SW 16th to SW 23rd Street provide recreational benefit; some portions of existing trail south design for the flood control improvements;provide temporary of SW 16th Street may need to be relocated alternative routes when possible for trail users if existing trail is impacted by construction(R) • Additional right-of-way required between SW 16th and SW 19th Acquire additional right-of-way as needed(R); coordinate with Street on the west side of the channel;develop right-of-way all adjacent property owners regarding compatibility of plantings agreement with Drainage District No. 1 with adjacent landscape schemes(0) Table 1-7. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Coordination with Seattle Water Department required to cross . Coordinate with Seattle Water Department as needed (R) Cedar River Pipeline right-of-way at SW 23rd Street Element 3-Channel Maintenance . Coordination with Drainage District No.1 and some adjacent . Coordinate with affected property M,metY as.needed(P.) Program property owners would be required Element 4-Improve Riparian Habitat/ - Coordination with Drainage District No. 1 required;plantings - Coordinate and obtain permission as needed(R);also Selective Plantings may require obtaining permission from property owners in some coordinate with regard to compatibility of landscaping schemes areas;plantings increase opportunity for enjoyment of trail uses (0) SC3-Springbrook Creek Greenway . Elements of SC3 would help reduce flooding,thereby providing . None needed for beneficial impact;all elements would require Improvements beneficial land use impact;all elements would be subject to the Shoreline Substantial Development Permit(R) Shoreline Master Program Element 1-Improvements at Roadway . Similar to SC2 Element 1,but more extensive improvement at . Same as SC2,Element 1 Crossings Oakesdale may accommodate below-grade trail crossing Element 2-Channel Improvements A. SW 16th to SW 23rd Street . General land use impacts similar to SC2,with more wildlife . Similar to SC2,Element 2;obtain additional right-of-way as habitat and fish cover provided and more right-of-way required needed(R) under SC3 Public access trail impacts similar to SC2 with greater . Same as SC2,Element 2 opportunity for enjoyment of trail users B. SW 30th to SW 40th Street . May allow for future trail on high flow bench between SW 30th . Incorporate trail location and design considerations in the Street and SW 34th Street design for the flood improvements(R) Element 3-Channel Maintenance . Similar to SC2,Element 3 . Same as SC2,Element 3 Program Element 4-Improve Riparian Habitat/ - Similar to SC2,Element 4 . Same as SC2,Element 4 Extensive Plantings Table 1-7. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Pipe System Improvements PSI - No Action • Flooding and associated property damage would worsen in a None future as development continues • Not consistent with applicable city policies;similar to SCl PS2- Pipe System Improvements • All elements of PS2 would help reduce flooding and provide • None needed for beneficial impacts; all elements would require beneficial land use impacts;all elements would require working Shoreline Substantial Development Permit(R) within 200 feet of Springbrook Creek PS2-1 -SW 43rd Street System • Easement would likely be required at west end of SW 39th • Obtain easement as needed(R) Improvement Street • Temporary construction impact to existing recreational trail • Provide temporary alternative routes when possible for trail where pipe system would outfall to Springbrook Creek users if existing trail is impacted by construction(R) • Coordination with Drainage District No. I would be required at • Coordinate as required(R) the outfall PS2-2-East Valley Road System • No additional property acquisition required • None needed Improvements PS2-3- Rolling Hills Culvert • Minor property acquisition may be required;coordination with • Obtain property as needed and coordinate with Drainage Drainage District No. 1 would be required District No.1 (R) This page left blank intentionally. Table 1-7. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Panther Creek Alternatives PC1 - No Action - Flooding and associated property damage would worsen in - None future as development continues;not consistent with applicable city policies; similar to SC1 PC2- High Flow Bypass to Panther - All elements of PC2 would help reduce flooding and provide - None needed Creek Wetland beneficial land use impacts Element 1 -Modify Existing Flow Split - Approval from WSDOT would be required for control structure - Obtain approval as needed(R) at SR-167 at SR-167 crossing Element 2-SW 34th Street System - No adverse impacts - None needed Improvements PC3- Maintain Existing Flow Into - PC3 would help reduce flooding and provide beneficial land use - Obtain approval as needed and apply for Substantial the 34th Street System impacts;permanent easement may be required for channel Development Permit(R) improvements between SR-167 and East Valley Road;Shoreline Substantial Development Permit required for work within 200 feet of Springbrook Creek SW 23rd Street Drainage Channel Alternatives 23ST1 -No Action - Flooding and associated property damage would worsen in - None future as development continues Not consistent with applicable city policies;similar to SCI 23ST2-Minor Conveyance - Elements of 23ST2 would reduce flooding,resulting in beneficial - None needed Improvements land use impact Element 1- Replace SR-167 Culvert - Coordination with Olympic Pipeline,Seattle Water Department, - Coordinate and obtain permission as needed(R) Crossings with New Crossing at and WSDOT would be necessary SW 23rd Street - Additional right-of-way or easement may be needed between - Acquire additional right-of-way/easement as needed(R) SR-167 and East Valley Road Element 2-Olympic Pipeline ■ Similar to 23ST2,Element 1;Shoreline Substantial Development - Similar to 23ST2,Element 1;apply for Shoreline Substantial Relocation or Culvert Replacement I Permit required I Development Permit(R) Table 1-7. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document 23ST3-Major Conveyance Land use benefits greater than 23M None needed Improvements Element 1-Replace SR-167 Culvert • Same as 23M, Element 1 • Same as 23ST2,Element 1 Crossings with New Crossing at SW 23rd Street Element 2-Olympic Pipeline • Same as 23M, Element 2 • Same as 23SI2,Element 2 Relocation or Culvert Replacement Element 3-Channel Widening and • No additional right-of-way required;Shoreline Substantial • Apply for Shoreline Substantial Development Permit(R) Deepening Development Permit required Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 -No Action • Flooding and associated property damage would worsen in • None future as development continues ■ Not consistent with applicable city policies;similar to SCl W12-2-Culvert Replacement • Permission from property owner would be required for changes • Obtain permission as needed;apply for Shoreline Substantial in hydrologic regime of west cell of Wetland 12 and W-13Sj; Development Permit(R) Shoreline Substantial Development Permit required;beneficial land use impact due to reduction of flooding W32-1 -No Action • Wetland would remain isolated from Springbrook Creek and • None provide no off-channel flood storage • Not consistent with applicable city policies;similar to SCl W32-2-Mitigation Bank/Excavate • Shoreline Substantial Development Permit required;beneficial • Apply for Shoreline Substantial Development Permit(R) Large Off-Channel Storage land use impact due to reduction of flooding • Coordination with Drainage District No. 1 may be required for • Obtain permission as needed(R) constructing the connection to the creek W7N-1 -No Action • Similar to W12-1 • None W7N-2-Culvert Replacement •Apply for Shoreline Substantial Shoreline Substantial Development Permit required;beneficial Development Permit(R) land use impact due to reduction of flooding Table 1-8. Summary of Impacts and Mitigation Measures for Cultural Resources by Alternative Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Springbrook Creek Alternatives SC1 - No Action No impacts • None SC2- Localized Improvements to Springbrook Creek Element I -Improvements at Roadway • Potential adverse impact;excavating may unearth and expose • Contact OAHP if archaeological sites are discovered; monitor Crossings cultural resources previously unknown,and operation of earth- site during construction;stop work if archaeological site is found A. Bridge North of SW 27th Street moving equipment may damage or shift the position of artifacts and evaluate need for further treatment in consultation with B. SW 27th Street along Springbrook Creek state OAHP and other parties(R) C. SW 34th Street D. Oakesdale Avenue Element 2-Channel Improvements • Same as SC2,Element 1 • Same as SC2,Element 1 from SW 16th to SW 23rd Street Element 3-Channel Maintenance • No adverse impacts . None needed Program Element 4-Improve Riparian Habitat/ • No adverse impacts • None needed Selective Plantings SC3-Springbrook Creek Greenway Improvements Element 1-Improvements at Roadway • Same as SC2, Element 1 • Same as SC2,Element 1 Crossings Element 2-Channel Improvements • Same as SC2,Element 1 • Same as SC2,Element 1 A. SW 16th to SW 23rd Street B. SW 30th to SW 40th Street Element 3-Channel Maintenance • No adverse impacts • None needed Program Element 4-Improve Riparian Habitat/ • No adverse impacts • None needed Extensive Plantings Table 1-8. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Panther Creek Alternatives PCt - No Action No impacts PC2- High Flow Bypass to Panther Creek Wetland Element 1-Modify Existing Flow Split No impact unless new excavation of native soils required,then Same as SC2 if impacts occur(contact OAHP if archaeological at SR-167 impacts would be same as SC2(excavating may unearth and sites are discovered; monitor site during construction;stop work expose cultural resources previously unknown,and operation of if archaeological site is found and evaluate need for further earth-moving equipment may damage or shift the position of treatment in consultation with state OAHP and other parties) artifacts along Springbrook Creek) (R) Element 2-SW 34th Street System Same as PC2,Element 1 Same as PC2,Element 1 Improvements PC3-Maintain Existing Flow Into Same as PC2, Element 1 Same as PC2,Element 1 the 34th Street System SW 23rd Street Drainage Channel Alternatives 23ST1 -No Action • No impacts None 23ST2-Minor Conveyance Improvements Element 1-Replace SR-167 Culvert • Same as PC2,Element 1 Same as PC2,Element 1 Crossings with New Crossing at SW 23rd Street Element 2-Olympic Pipeline ■ Same as PC2,Element 1 Same as PC2,Element 1 Relocation or Culvert Replacement 23ST3-Major Conveyance Improvements Element 1- Replace SR-167 Culvert • Same as PC2,Element 1 Same as PC2,Element 1 Crossings with New Crossing at SW 23rd Street Table 1-8. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Element 2-Olympic Pipeline • Same as PC2,Element 1 . Same as PC2,Element 1 Relocation or Culvert Replacement Element 3-Channel Widening and • Same as PC2,Element 1,with increased probability of damage • Same as PC2,Element 1 Deepening to cultural resources due to channel widening and deepening Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 -No Action No impacts • None W12-2-Culvert Replacement No impacts expected • None needed W32-1 -No Action No impacts • None W32-2-Mitigation Bank/Excavate Similar to SC2,Element 1 • Same as SC2,Element 1 Large Off-Channel Storage W7N-1 -No Action No impacts • None W7N-2-Culvert Replacement No impacts unless native soils are disturbed during construction, • Same as SC2,Element 1,if impacts occur then impacts would be similar to SC2, Element 1 Pipe System Improvements PSI -No Action No impact • None PS2-Pipe System Improvements PS2-1-SW 43rd Street System No impacts unless native soils are excavated,then impacts would • Same as SC2,Element 1,if impacts occur Improvement be same as SC2,Element 1 PS2-2-East Valley Road System • No impacts unless native soils are excavated,then impacts would • Same as SC2,Element 1,if impacts occur Improvements be same as SC2,Element 1 PS2-3-Rolling Hills Culvert • No impacts unless native soils are excavated,then impacts would • Same as SC2,Element 1,if impacts occur be same as SC2, Element 1 This page left blank intentionally. Table 1-9. Summary of Impacts and Mitigation Measures for Public Services and Utilities by Alternative Note: See also Table 1-2 for impacts potentially caused by changes in groundwater levels, including mitigation measures. Alternative/Project Element I Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Springbrook Creek Alternatives SCt - No Action - Risk of flooding would continue with the problems of impaired - None possible without project implementation access,possible damages and creation of unsafe conditions including disruption of public services SC2-Localized Improvements to - Less flood impacts to utilities and less disruption of public - None needed Springbrook Creek services due to reduction in flooding levels Element 1-Improvements at Roadway Crossings A. Bridge North of SW 27th Street - No adverse impacts - None needed B. SW 27th Street - Temporary or permanent relocation of gas,power,phone,water, - The City of Renton Standard Specifications for Municipal storm drain outfalls would be required Construction require the protection of all private and public utilities from damage by construction activities; the specifications also include requirements for coordination with utility purveyors,notifications to affected parties of temporary disruptions in service,and contacting the One-Call utility locate service prior to any excavation(R) Coordinate with utility purveyors during design to identify potential conflicts and need for relocation of utilities if necessary and/or if other mitigation measures are needed (0) C. SW 34th Street - Similar to SC2,Element 113;sewer line relocation may not be - Similar to SC2,Element 113 possible,and sewer service may need to be provided from existing sewer in Lind Avenue D. Oakesdale Avenue - Temporary or permanent relocation of gas,power,phone,and - Similar to SC2,Element 1B water lines would be required Element 2-Channel Improvements - Relocation of electrical power pole and potential modification to - Same as SC2,Element 113 from SW 16th to SW 23rd Street five storm drain outfalls Element 3-Channel Maintenance - No adverse impacts - None needed Program Table 1-9. Continued Alternative/Project Element Impacts Mitigation Measures Element 4-Improve Riparian Habitat/ - No adverse impacts • None needed Selective Plantings SC3-Springbrook Creek Greenway • Less flood impacts to utilities and less disruption of public • None needed Improvements services due to reduction in flooding levels Element 1 -Improvements at Roadway - Similar to SC2; potential for needing to relocate utilities for • Same as SC2,Element 1 Crossings Oakesdale Avenue crossing is greater than with SC2 • Potential for impacts to King County sewer interceptors at - Same as SC2,Element 1 Oakesdalc Avenue crossing is greater than with SC2 due to greater support loadings and erosive flows in natural-bottom culvert Element 2-Channel Improvements A. SW 16th to SW 23rd Street • Similar to SC2 Same as SC2,Element 1B B. SW 30th to SW 40th Street • Potential impact on 12-inch water main at SW 39th (line may • Same as SC2,Element 1B need to be relocated); three storm drain outfalls may be affected Element 3-Channel Maintenance • No adverse impact • None needed Program Element 4-Improve Riparian Habitat/ • No adverse impact • None needed Extensive Plantings Panther Creek Alternatives PC1 -No Action • flooding problems would continue and worsen,resulting in • None possible without project implementation disrupted access to utility systems,possible damage,and potential creation of hazardous conditions,including disruption of public services PC2-High Flow Bypass to Panther • Less flood impacts to utilities and less disruption of public • None needed Creek Wetland services due to reduction in flooding levels Element 1-Modify Existing Flow Split • Potential for impact to King County and City sewer lines • Same as SC2,Element 113 at SR-167 Element 2-SW 34th Street System • Potential for temporary disruption and/or relocation of gas, - Same as SC2,Element 1B Improvements phone,power,sewer,and water utilities; mitigation may be required to prevent impacts from excavations Table 1-9. Continued Alternative/Project Element Impacts Mitigation Measures ■ Side sewer crossing to parcel at NW corner of Lind Avenue/ ■ Same as SC2,Element 113 SW 34th Street may require use of low head structure to pass under the sewer PC3-Maintain Existing Flow Into • Similar to PC2 but greater construction-related utility impacts • Similar to PC2 the 34th Street System due to larger,more extensive drainage system replacement SW 23rd Street Drainage Channel Alternatives 23ST1 -No Action • Flooding problems would continue and worm,resulting in • None possible without project implementation disrupted access to utility systems,possible damage,and potential creation of hazardous conditions,including disruption of public services 23ST2-Minor Conveyance ■ Less flood impacts to utilities and less disruption of public • None needed Improvements services due to reduction in flooding levels Element 1-Replace SR-167 Culvert • Excavation of jacking pits for SR-167 culvert may impact ■ Same as SC2,Element 113 Crossings with New Crossing at Olympic Pipelines SW 23rd Street Element 2-Olympic Pipeline ■ Installation of a new culvert under the pipelines may impact ■ Same as SC2,Element 113 Relocation or Culvert Replacement operation of the pipelines; relocation of the pipelines under the channel would require staggered shutdown of all three lines 23ST3-Major Conveyance • Less flood impacts to utilities and less disruption of public ■ None needed Improvements services due to reduction in flooding levels Element 1-Replace SR-167 Culvert ■ Similar to 23ST2,Element 1 • Same as SC2,Element 1B Crossings with New Crossing at SW 23rd Street Element 2-Olympic Pipeline • Similar to 23ST2,Element 2 • Same as SC2,Element 1B Relocation or Culvert Replacement Element 3-Channel Widening and ■ Potential reduction in lateral confinement pressure along the south ■ In coordination with the City of Seattle,further geotechnical Deepening side of Seattle's 60-inch water line may induce soil movement and studies may be conducted during the design phase to identify allow the water line to shift potential impacts on Seattle's 60-inch water line and to define mitigation measures as needed(0) Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 -No Action ■ Similar to SCl Similar to SC1 W12-2-Culvert Replacement ■ No impacts None needed Table 1-9. Continued Alternative/Project Element Impacts Mitigation Measures W32-1 -No Action - Similar to SCl - Similar to SCl W32-2-Mitigation Bank/Excavate - Possible temporary impact on utilities in and adjacent to - Similar to SC2,Element 113 Large Off-Channel Storage Oakesdale Avenue along west site boundary during dewatering Potential impact on 12-inch water line across from SW 39th cul- - Similar to SC2,Element 113 de-sac during excavation;line would need to be located below proposed grade of off-channel storage area if line is extended across mitigation bank site Creating wetlands above 8-inch sewer line may affect future - Similar to SC2,Element IB sewer replacement projects W7N-1 -No Action - Similar to SCl - Similar to SC1 WIN-2-Culvert Replacement - May need to relocate 16-inch water line that crosses over ■ Similar to SC2,Element 113 existing culvert,or water line may limit size of replacement culvert Pipe System Improvements PS1 - No Action - Similar to SC1 - Similar to SC1 PS2-Pipe System Improvements PS2-1 -SW 43rd Street System - Possible temporary disruption and/or relocation of gas - Same as SC2,Element 113 Improvement distribution pipelines,power and phone systems,sewer lines,and water services PS2-2-East Valley Road System - Potential disruption and/or relocation of gas,electrical power, - Same as SC2,Element 1B Improvements telephone,sanitary sewer and water along alignment PS2-3- Rolling Hills Culvert - No impacts - None needed Table 1-10. Summary of Impacts and Mitigation Measures for Transportation by Alternative Alternative/Project Element77 Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Springbrook Creek Alternatives SC1 -No Action • Flooding would continue to disrupt vehicular and pedestrian • None traffic at several locations and would worsen as development continues SC2-Localized Improvements to • Elements 1,2,and 3 of SC2 would help control flooding, • None needed Springbrook Creek improve traffic operations,and reduce emergency access disruption/accident potential Element 1 -Improvements at Roadway Crossings A. Bridge North of SW 27th Street • Minor construction-related delays on SW 27th Street • Comply with applicable City of Renton,WSDOT,and other appropriate agency provisions for traffic control and construction techniques to maintain optimum safety and travel conditions(R) B. SW 27th Street • Temporary disruption of vehicular and/or pedestrian traffic • If possible,stage construction of SW 27th crossing so that it expected does not occur simultaneously with extension of Oakesdale Avenue from SW 16th to SW 27th(0) • Limit construction activity during peak travel periods(0) • Maintain access to local businesses and coordinate with affected businesses before disrupting access points(0) • Comply with applicable City of Renton, WSDOT, and other appropriate agency provisions for traffic control and construction techniques to maintain optimum safety and travel conditions(R) C. SW 34th Street Similar to SC2,Element 1B • Stage construction of SW 34th crossing so that it does not occur simultaneously with construction of Oakesdale Avenue crossing of Springbrook Creek(0) • Where applicable,accommodate pedestrian traffic during construction(0) • Comply with applicable City of Renton, WSDOT, and other appropriate agency provisions for traffic control and construction techniques to maintain optimum safety and travel conditions(R) D. Oakesdale Avenue • Similar to SC2,Element 1B ■ Same as SC2,Element 1C Element 2-Channel Improvements • No impacts expected • None needed from SW 16th to SW 23rd Street Table 1-10. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Element 3-Channel Maintenance Occasional minor disruptions of traffic on SW Grady Way west - Similar to SC2,Element 1A Program of Oakesdale Avenue during movement of construction vehicles and equipment EIe ,.t 4-I:;prove Riparian Habitat/ No ad:^ ._puts ■ None needed Selective Plantings SC3-Springbrook Creek Greenway - Elements 1,2,and 3 of SC3 would help control flooding, - None needed Improvements improve traffic operations,and reduce emergency access disruption/accident potential Element 1-Improvements at Roadway - Similar to SC2,Element 1,but more extensive improvements - Similar to SC2,Element 1 Crossings could require full closure of Oakesdale Avenue during construction; impacts would be minor if SW 34th is available as alternative route Element 2-Channel Improvements A. SW 16th to SW 23rd Street ■ No impacts expected ■ None needed B. SW 30th to SW 40th Street - Occasional minor disruption of traffic on SW 34th during - Similar to SC2,Element 1C movement of construction vehicles and equipment Element 3-Channel Maintenance - Same as SC2,Element 3 - Same as SC2,Element 3 Program Element 4-Improve Riparian Habitat/ - No impacts expected ■ None needed Extensive Plantings Panther Creek Alternatives PC1 -No Action - Flooding would continue to disrupt vehicular and pedestrian traffic and would worsen as development continues PC2-High Flow Bypass to Panther - Elements of PC2 would help reduce flooding and improve traffic ■ None needed Creek Wetland operations and reduce emergency access disruption/accident potential Element 1 -Modify Existing Flow Split - Potential for occasional disruption of northbound traffic on - Comply with applicable City of Renton,WSDOT,and other at SR-167 SR-167 and closure of road shoulder during construction appropriate agency provisions for traffic control and construction techniques to maintain optimum safety and travel conditions(R) - Limit construction activity during peak travel periods(0) Table 1-1o. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Element 2-SW 34th Street System Vehicular and pedestrian traffic would be disrupted during • Same as PC2,Element 1;maintain access to local business and Improvements construction,but impacts would not be significant coordinate with affected businesses before disrupting access points(0) • Where applicable,accommodate pedestrian traffic during construction(0) • Potential temporary disruption of railroad service north of SW • Coordinate with the owners of the railroad during design to 34th Street during construction minimize impacts to rail service(0) PC3- Maintain Existing Flow into • PC3 would help reduce flooding and improve traffic operations ■ None needed the 34th Street System and reduce emergency access disruption/accident potential • Other impacts similar to PC2,Element 2 • Same as PC2,Element 2 SW 23rd Street Drainage Channel Alternatives 23ST1 -No Action • Flooding would continue to disrupt vehicular and pedestrian • None traffic and would worsen as development continues 23ST2-Minor Conveyance • All elements of 23ST2 would help reduce flooding,improve • None needed Improvements traffic operations and reduce emergency access disruption/ accident potential Element 1-Replace SR-167 Culvert • Occasional disruption of northbound traffic on SR-167 and on • Similar to PC2,Element 1 Crossings with New Crossing at East Valley Road during construction if trenchless methods are SW 23rd Street used to cross SR-167;potential significant impact to traffic if SR-167 open cut to install the culvert Element 2-Olympic Pipeline • Occasional disruption of Lind Avenue traffic during • Similar to PC2,Element 1 Relocation or Culvert Replacement construction; impacts not considered significant 23ST3-Major Conveyance • All elements of 23ST3 would help reduce flooding,improve • None needed Improvements traffic operations,and reduce emergency access disruption/ accident potential Element 1-Replace SR-167 Culvert • Same as 23ST2 • Same as 23ST2 Crossings with New Crossing at SW 23rd Street Element 2-Olympic Pipeline • Same as 23ST2 • Same as 23ST2 Relocation or Culvert Replacement Element 3-Channel Widening and • Occasional disruption of Lind Avenue and East Valley Road • Similar to PC2,Element 1 Deepening traffic during construction; impacts not considered significant Table 1-10. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the City's Environmental Review Committee as an element of the EIS mitigation document Wetland Mitigation Bank and Wetiand Hydraulic Modifications W12-1 -No Action No impacts associated with construction expected • None W12-2-Culye► Rep!ae-ement Orracinnal rdiSrgptinnc of traffir on SW 27th and pm d {Jr)V . Similar to PC2 Element 1 _r.___..._..- pose__-� facility(if operating)during movement of construction vehicles and equipment W32-1 -No Action No impacts associated with construction expected • None W32-2- Mitigation Bank/Excavate ■ Occasional disruptions of traffic on Oakesdale Avenue during • Similar to PC2,Element 1 Large Off-Channel Storage movement of construction vehicles and equipment W7N-1 - No Action • No impacts associated with construction expected • None W7N-2-Culvert Replacement • Impacts similar to the proposed storm drain replacement in SW • Same as PC2,Element 2 34th Street as discussed in PC2,Element 2,except no potential for impact to railroad Pipe System Improvements PS1 - No Action • hooding would continue to disrupt vehicular and pedestrian • None traffic at several locations and would worsen as development continues PS2-Pipe System Improvements • All elements of PS2 would help reduce flooding,improve traffic • None needed operations,and reduce emergency access disruption/accident potential PS2-1-SW 43rd Street System • Lane closures and detours during construction would result in • Stage construction at the intersection of SW 43rd Street and Improvement short-term traffic impacts and disruption of local property access Lind Avenue so that it does not occur simultaneously with along SW 43rd,Lind Avenue,and SW 39rh construction at the intersection of SW 43rd Street at Oakesdale Avenue(0) ■ Comply with applicable City of Renton,WSDOT,and other appropriate agency provisions for traffic control and construction techniques to maintain optimum safety and travel conditions(R) • Maintain vehicular access to local businesses during construction and coordinate with businesses before disrupting access points(0) • Limit construction during peak travel periods(0) Table 1-10. Continued Alternative/Project Element Impacts Mitigation Measures R = Mitigation required by federal,state,or local regulations O = Other mitigation that could be required by the Citys Environmental Review Committee as an element of the EIS mitigation document Potential disruption of pedestrian traffic • Where applicable,accommodate pedestrian traffic during construction(0) • Possible disruption of rail service east of Lind Avenue and north • Coordinate with the owners of the railroad during design to of SW 39th Street during construction of the pipe system on minimize impacts to rail service(0) SW 39th Street and Lind Avenue PS2-2-East Valley Road System • Lane closures and detours during construction would result in • Similar to PC2,Element 2,except no impact or mitigation Improvements short-term traffic impacts and disruption of local property access related to railroad service along East Valley Road; potential disruption of pedestrian traffic PS2-3- Rolling Hills Culvert • No impacts expected ■ None needed This page left blank intentionally. Table 1-11. Description of Alternatives Considered for East Side Green River Watershed Project Part of Alternative/Project Element Description Preferred Alternative Springbrook Creek Alternatives SCt -No Action ■ Flood control improvements would not be implemented;existing maintenance programs for vegetation No management and sediment removal would continue. SC2-Localized Improvements to No Springbrook Creek Element 1-Improvements at Roadway ■ Improvements at four Springbrook Creek roadway crossings that currently restrict conveyance: Crossings A. Bridge North of SW 27th Street B. SW 27th Street C. SW 34th Street D. Oakesdale Avenue Element 2-Channel Improvements • Widening and restoration of approximately 3,400 linear feet of Springbrook Creek between SW 16th Street from SW 16th to SW 23rd Street and SW 23rd Street to increase capacity(a public access trail would be provided from about SW 19th Street to SW 24th Street). Element 3-Channel Maintenance • A channel maintenance program for vegetation management and sediment removal along Springbrook Creek. Program Element 4-Improve Riparian Habitat/ • Plantings to improve riparian habitat. Selective Plantings SC3-Springbrook Creek Greenway Includes many of the same improvements as SC2;improvements to Springbrook Creek would be more extensive, Yes, Improvements creating a greenway concept. Element 1 -Improvements at Roadway Improvements at four Springbrook Creek roadway crossings that currently restrict conveyance: Crossings A. Bridge North of SW 27th Street B. SW 27th Street C. SW 34th Street D. Oakesdale Avenue Element 2-Channel Improvements Widening and restoration of Springbrook Creek between: A. SW 16th to SW 23rd Street B. SW 30th to SW 40th Street A public access trail would be provided from about SW 19th Street to SW 24th Street. Element 3-Channel Maintenance A channel maintenance program for vegetation management and sediment removal along Springbrook Creek; Program program would be reduced and the City would need to perform less frequent maintenance compared to SC2. Element 4-Improve Riparian Habitat/ More intensive plantings near the low-flow channel to create wildlife habitat and improve fish habitat. Extensive Plantings Table 1-11. Continued Part of Alternative/Project Element Description Preferred Alternative Panther Creek Alternatives PC1 -No Action No flood control improvements would be implemented. Existing maintenance programs would continue. No PC2-High Flow Bypass to Panther ya Creek Wetland Element 1-Modify Existing Flow Split - Block one SR-167 culvert and install a structure at the other of the southerly SR-167 culverts near SW 39th at SR-167 Street to pass low flows to the existing system and divert excess flows into the Panther Creek Wetland(the structure would be designed to allow downstream migration of fish). Element 2-SW 34th Street System Replace an existing 36-inch-diameter concrete pipe system in SW 34th Street with a 48-inch-diameter system Improvements or larger from approximately East Valley Road to Lind Avenue. PC3-Maintain Existing Flow Into Maintain Panther Creek low and moderate flows through the two southerly SR-167 culvert crossings No the 34th Street System described in PC2,but improve the entire downstream drainage system from SR-167 to Springbrook Creek by (1) replacing the existing pipe system along the East Valley Road and SW 34th Street with a new larger system; (2)channel improvements between the outlet of the two southerly SR-167 culverts and the East Valley Road; and(3) intermittent maintenance of vegetation as needed to maintain channel performance. SW 23rd Street Drainage Channel Alternatives 23ST1 -No Action No flood control improvements would be implemented. Intermittent vegetation management,sediment No removal,and other maintenance would be necessary. The poorly functioning SR-167 culverts between the southerly culverts described in PC2 and SW 23rd Street would be cleaned to restore them to full capacity. 23ST2-Minor Conveyance No Improvements Element 1-Replace SR-167 Culvert • Plugging the poorly functioning SR-167 culverts and replacing them with a new SR-167 crossing at SW 23rd Crossings with New Crossing at Street,and implementing minor channel improvements between the new SR-167 culverts and the East Valley SW 23rd Street Road culvert crossing. Element 2-Olympic Pipeline • Replacing the two existing 18-inch culverts that carry the SW 23rd Street drainage channel flows underneath Relocation or Culvert Replacement the existing Olympic Pipeline crossing west of Lind Avenue with a larger box culvert,or relocating the petroleum pipelines and restoring the crossing to an open channel. Intermittent vegetation management and sediment removal would also be necessary. ................................ . .. 23ST3-Major Conveyance Similar to 23ST2 with addition of channel widening and deepening. 1'rs Improvements Element 1-Replace SR-167 Culvert Plugging the poorly functioning SR-167 culverts and replacing them with a new SR-167 crossing at SW 23rd Crossings with New Crossing at Street,and implementing minor channel improvements between the new SR-167 culverts and the East Valley SW 23rd Street Road culvert crossing. Table 1-11. Continued Part of Alternative/Project Element Description Preferred Alternative Element 2-Olympic Pipeline Replacing the two existing 18-inch culverts that carry the SW 23rd Street drainage channel flows underneath Relocation or Culvert Replacement the existing Olympic Pipeline crossing west of Und Avenue with a larger box culvert,or relocating the petroleum pipelines and restoring the crossing to an open channel. Intermittent vegetation management and sediment removal would also be necessary. Element 3-Channel Widening and The existing drainage channel between Springbrook Creek and SR-167 would be widened and deepened to Deepening provide a positive grade through the system and reduce maintenance. Wetland Mitigation Bank and Wetland Hydraulic Modifications W12-1 -No Action Wetland 12 would remain as open space and would continue to function as off-channel storage for No Springbrook Creek;periodic maintenance of the 18-inch culvert through the berm that bisects the wetland would be necessary to prevent plugging. W12-2-Culvert Replacement The existing 19-inch culvert in the berm bisecting the wetland would be replaced with two or three 36-inch Yes culverts,or with an open channel or weir,in order to restore the hydraulic connection between Springbrook Creek and the area west of the berm. W32-1 -No Action Wetland 32 would be preserved as open space; the site would remain isolated from Springbrook Creek and No provide no off-channel flood storage capacity. W32-2-Mitigation Bank/Excavate Wetlands would be created/enhanced and used as mitigation to compensate for offsite wetland impacts of Yes Large ON-Channel Storage other public and private projects;the hydraulic connection between Wetland 32 and Springbrook Creek would be restored. W7N-1 -No Action Wetland 7N would remain isolated from Rolling Hills Creek and provide little off-channel storage. No W7N-2-Culvert Replacement The existing 12-inch culvert between the wetland and the 60-inch storm drain in SW 19th Street that conveys Yet: Rolling Hills Creek would be replaced with a minimum 36-inch culvert in order to restore the hydraulic connection of the wetland with the adjacent drainage systems. Pipe System Improvements PS1 -No Action No pipe system improvements would be implemented. No PS2-Pipe System Improvements yes PS2-1-SW 43rd Street System Replace short segment of 36-inch pipe with 54-inch pipe in SW 43rd Street system at Oakcsdale Avenue and Improvement construct new minimum 72-inch system from SW 43rd Street north along Lind Avenue and west along SW 39th Street to Springbrook Creek. PS2-2-East Valley Road System System improvements(pipe enlargements)in East Valley Road from approximately SW 29th Street to the Improvements discharge at the existing channel along SW 23rd Street. PS2-3-Rolling Hills Culvert Remove an existing culvert that carries Rolling Hills Creek between Springbrook Creek and Raymond Avenue(along SW 19th Street)and restore it as a channel. This page left blank intentionally. Black River Pump Station 1-5 Renton k Valley Area Panther Creek I-405 Wetlands o 0 j I3tt II t xI Tukwila T kwilQ Kent —t zc I '.1s + Black River Water Quality Management Plan Study Area t 1W.' 41rd ", . St,/ I Panther Creek ►� I a i r Renton i ESGR 181 I I .King County � Watershed Boundary I-5 1 Upper Panther Lake �t c S rin br k k \ �o I reek S_ 212th St, CS t Garrison Creek \ t % 1 •�� V oc, Kent�...� �... W I_�.. Lagoons I / \ King Co. I Kent 167 � I --- King—County — I I . Kent j r— I I I I I L_AI \ I I 08/20/97 ------I Figure 1-1 Project Area Map This page left blank intentionally. i Chapter 2 ADDITIONAL FACTUAL INFORMATION CHAPTER 2 ADDITIONAL FACTUAL INFORMATION 2.1 INTRODUCTION This chapter presents additional factual information on existing conditions, impacts, and mitigation measures in response to comments received on the Draft EIS. For a majority of the elements evaluated in the Draft EIS, no additional factual information was required. 2.2 PREFERRED AND OTHER ALTERNATIVES The Natural Resources Conservation Service (NRCS)requested a more complete discussion of the reasons for not including the original Soil Conservation Service P-1 Channel alignment as a feasible alternative. A discussion of the process whereby the use of the original P-1 Channel alternative was eliminated from consideration is included in Section 8.2 of the Final Plan. 2.3 EXISTING CONDITIONS, IMPACTS, AND MITIGATION 2.3.1 EARTH No additional information is needed for this element. 2.3.2 GROUNDWATER No additional information is needed for this element. 2.3.3 SURFACE WATER QUANTITY/QUALITY 2.3.3.1 Water Quantity Table 8-2 of the ESGRWP Plan presents a summary of hydraulic modeling for the 2-year, 25-year and 100-year conveyance events water elevations upstream of the Black River Pump Station (BRPS). Under current conditions, the inflow elevation to the floodwater storage pond is 4.0 ft (533 cfs) for a 2-year storm event. Under future conditions without the project (No Action), the projected elevation would be 4.2 ft (728 cfs), or 0.2 ft higher than current conditions. Under the 2-year storm event, inflow water elevation with the proposed project (as defined in Chapter 1 of this Final EIS) at the inlet to the pond is calculated to be 4.3 ft (773 cfs), or 0.1 ft higher than future conditions without the project (No Action). This increase of 0.1 ft elevation, which would occur primarily during the winter months, would not adversely affect the wetland and wildlife use of the pond. The increase in inflow to the 09/97e JSA 2-1 CHAPTER 2 pond under future conditions would result in a change in the frequency of pumping at the BRPS. The greater volume of water entering the pond would require more frequent pumping, pumping of a longer duration, and/or more pumps operating at one time. 2.3.3.2 Water Quality In addition to the Panther Creek water quality information provided in Table 6-5 of the Draft Plan, lower Panther Creek is well vegetated and provides thermal cover that helps to moderate high water temperatures during the summer and fall. Floodwater Storage Pond Water Quality Impacts Comments were received from the Friends of the Black River and the Citizens for Renton Wildlands Preservation regarding the potential impact of the project alternatives on the floodwater (P-1) storage pond located outside of the project area and downstream of the proposed flood control improvements. The pond was constructed by NRCS in 1984 as a regional stormwater detention facility and totals approximately 18 acres at elevation 5.0. The adjacent Black River riparian forest (see W-5 in Table 2-1) and three other small wetlands that would be unaffected by the proposed projects (W-5a, 5b, and 5c) occur adjacent to the pond but at higher elevations (see Figure 2-1). The hydrologic condition and water elevations in the pond are controlled by the BRPS operated by King County. Table 8-3 in the Final Plan has been revised to include the floodwater storage pond. Potential impacts of the proposed projects on the flood control pond would be primarily water quality-related and associated with project construction. The project elements having the greatest likelihood of impacting the water quality in the floodwater storage pond include Springbrook Creek Greenway Improvements (SC3) and SW 23rd Street Channel Alternative 3 (23ST3). These projects will require excavation within or immediately adjacent to the channel. The timing of construction will be determined by the Washington Department of Fish and Wildlife (WDFW) as part of the Hydraulic Project Approval (HPA), and by the Washington Department of Ecology as part of the Temporary Modification of Water Quality Criteria allowed for during the construction period. During the construction period (est. June 15 - September 15), the water elevation could be drawn down to elevation 0 to reduce the pool (open water) in the pond for the purpose of limiting the area of the pond affected by the silty water to the main channel in the pond and the pool behind the pump station. This would result in a temporary reduction in wetted area and more exposed mud flats during the construction period. Exposure of the mud flats, in turn, will result in temporary changes to vegetative cover. Wetland plants such as spikerush and smartweed will grow on the exposed areas, providing an additional food supply for waterfowl during the fall when the water elevation is increased. Temporary drying or drawdown of water elevations in wetlands (those having water control structures) is a recognized management technique on wildlife refuges throughout the United 2-2 JSA 09/97e ADDITIONAL FACTUAL INFORMATION States (U.S. Fish and Wildlife Service 1964; Smith 1989). The modification of water elevations during the construction period would not adversely impact great blue heron use of the nesting colony since a majority of the heron foraging activity occurs elsewhere in the Green River Valley. (See Response No. 18 to Citizens for Renton Wildlands Preservation in Chapter 3 of this Final EIS.) Construction activities in Springbrook Creek and the SW 23rd Street channel could result in temporary water quality impairment in the flood storage pond. These impacts could include increased turbidity, reduced dissolved oxygen in the water column, and possibly increased nutrients and sediment pollutants (i.e., metals, petroleum hydrocarbons). Allowable water quality changes during construction will be defined in the Temporary Modification of Water Quality Criteria permit. Measures to minimize the impacts to water quality would include those previously defined in Sections 5.4.1 and 5.4.2 of the Draft EIS and shown in Chapter 1 of this Final EIS. 2.3.4 WETLANDS SW 23rd Street Channel Mitigation As a result of continents received from the WDFW, the following mitigation measures are included for consideration by the City of Renton Environmental Review Committee: ■ To minimize impacts to Wetlands 8-N and 10-N, an exception to NRCS channel design criteria to allow steeper side slopes and a narrower channel bottom should be evaluated during the design phase for the SW 23rd Street channel deepening and widening element. ■ Deepening and widening of the SW 23rd Street channel should be limited as much as feasible to that which may be conducted from the existing access road to the north side of the channel. Floodwater Storage Pond Wetland Impacts The lowering of water elevations in the pond as proposed for Alternatives SC2/3-3 would have some temporary impacts on the wetland resources in the floodwater storage pond located immediately upstream of the BRPS. The temporary drawdown would result in temporary reduction in wetted area and more exposed mud flats during the construction period. Exposure of the mud flats, in turn, will result in temporary changes to vegetative cover. Wetland plants such as spikerush and smartweed will grow on the exposed areas, providing an additional food supply for waterfowl during the fall when the water elevation is increased. Temporary drying or drawdown of water elevations in wetlands (those having water control structures) is a recognized management technique on wildlife refuges throughout the United States (U.S. Fish and Wildlife Service 1964; Smith 1989). The modification of water 09/97c JSA 2-3 CHAPTER 2 elevations during the construction period would not adversely impact great blue heron use of the nesting colony since a majority of the heron foraging activity occurs elsewhere in the Green River Valley. (See Response No. 18 to Citizens for Renton Wildlands Preservation in Chapter 3 of this Final EIS.) Addition of Wetland 13Na Figure 6-1 of the Draft EIS did not include a narrow in-channel wetland (Wetland 13Na) within Springbrook Creek immediately south of SW 16th Street. This wetland has been added to Figure 2-1 of this Final EIS as a result of a wetland delineation for the Oakesdale Avenue EIS (City of Renton 1997) and confirmation of the wetland by the Corps of Engineers. Widening of Springbrook Creek would impact that wetland (approximately 0.26 acre) and would require mitigation as defined in Chapter 6 of the Draft EIS and in Chapter 1 of this Final EIS. 2.3.5 TERRESTRIAL AND AQUATIC RESOURCES 2.3.5.1 Fish The WDFW raised issues about fish habitat, passage, and stranding. These have been addressed by including fish passage features in the Preferred Alternative and adding mitigation measures, as described below. According to the WDFW, the lower portion of Panther Creek, downstream of Talbot Road, can be considered potential spawning habitat for anadromous fish, even though anadromous fish do not have access at this time. Also, beginning in 1984, channel improvements to the Springbrook Creek channel downstream of SW 16th Street were made by the NRCS and the City of Renton. The section of creek downstream of SW Grady Way has developed an excellent overstory that provides thermal protection for most of the day. Similar good thermal protection and excellent riparian habitat exist from SW 16th Street to north of SW 23rd Street. The WDFW requested that the proposed SR-167 culvert crossing and water control structure (Alternative 23ST2/3-1) be designed to not preclude fish passage in the future. This feature will now be included as an element of the 23ST3-1 Preferred Alternative. For the PC2-1, high flow diversion of Panther Creek, the WDFW suggested that an overflow channel be constructed downstream of the diversion structure to minimize fish stranding and to allow fish to move into the Panther Creek Wetland. This feature will now be included as an element of the PC2-1 Preferred Alternative. 2-4 JSA 09/97` ADDITIONAL FACTUAL INFORMATION The following mitigation measures have been added for consideration as part of the City's formal environmental review process: ■ Riparian plantings proposed under Alternative SC2-4 should be implemented prior to or concurrent with Alternative SC2-2 (channel widening - SW 16th to 23rd Street) to help mitigate for the temporary loss of habitat resulting from the channel widening. Similarly, Alternative SC3-4 should be implemented prior to or concurrent with Alternative SC3-2a (channel widening - SW 16th to 23rd Street) if the Springbrook Creek greenway alternative concept is implemented. ■ An overflow "channel' from the Alternative PC2-2 Panther Creek diversion structure to the nearest standing water in the Panther Creek Wetland should be created by mowing/cutting a path through the existing reed canarygrass and planting willows and cottonwoods (where conditions are suitable) on each side of the mowed path to provide cover and habitat diversity. 2.3.6 HAZARDOUS MATERIALS No additional information is needed for this element. 2.3.7 LAND USE AND RECREATION The following discussion includes additional analysis of the proposed action relative to the City's Shoreline Master Plan. The City of Renton's Shoreline Master Program (City of Renton, Title IV, Chapter 19) includes several policies of the Conservation Element (Section 4.02) that apply to the Springbrook Creek project alternatives (Springbrook Creek from the BRPS to SW 43rd Street is subject to the Shoreline Regulations). These policies include: ■ Policy A.1 - Water quality and water flow should be maintained at a level to permit recreational use, to provide suitable habitat for desirable forms of aquatic life, and to satisfy other human needs. ■ Policy A.2 -Aquatic habitats and spawning grounds should be protected, improved and if feasible, increased. ■ Policy A.3 -Wildlife habitats should be protected, improved and, if feasible, increased. Evaluation: The Springbrook Creek SC2 and SC3 alternatives would, in the long term, be consistent with the above policies by improving aquatic and wildlife habitats along those portions of Springbrook Creek proposed for channel widening. Under existing conditions, much of Springbrook Creek is lacking in habitat structure for aquatic life (e.g., boulders, large woody debris, overhanging trees and shrubs). In the long term, the proposed channel widening and planting program would increase habitat suitable for fish, other aquatic life, and riparian-dependent wildlife species. 09/97e JSA 2-5 CHAPTER 2 ■ Policy B - Existing and future activities on all shorelines and wetlands within the City of Renton should be designed to minimize adverse impacts on the environment. Evaluation: Construction of the Springbrook Creek SC2 and SC3 alternatives would cause short term impacts to the natural environment (as defined in the Draft EIS), but would, in the long term, maintain or increase the habitat conditions of Springbrook Creek and associated wetlands. Adverse impacts to the environment would be minimized during the construction phase by employing Best Management Practices as defined in the Draft EIS. ■ Policy F- . . . that portion of Springbrook Creek beginning from SW 27th Street on the north to SW 31st Street on the south, abutting City-owned wetlands in this area, and for that portion of the west side of the Creek in the vicinity of SW 38th Street abutting the City's recently acquired Wetlands Mitigation Bank should be left in an undeveloped natural state as much as possible. Evaluation: As indicated in the Draft EIS, much of the aquatic and wildlife habitat along Springbrook Creek lacks diversity and structure. The proposed SC2 and SC3 projects would improve those conditions; reestablish more natural conditions, and maintain an undeveloped natural condition (i.e., one of a natural stream channel and adjacent riparian habitat). Once completed, habitat conditions would be improved over the current conditions. Additionally, excavation of the wetland mitigation bank site, with hydrologic connection to Springbrook Creek, would further improve the natural conditions. 2.3.8 CULTURAL RESOURCES No additional information is needed for this element. 2.3.9 PUBLIC SERVICES AND UTILITIES Comments received from the City of Seattle indicated a concern for potential impacts caused by construction of the SW 23rd Street (23ST3) project. Specifically, the concern was for (1) potential impacts for lowered groundwater levels that could occur when deepening the SW 23rd Street channel or from temporary dewatering activities during construction,and (2) the potential reduction in lateral confinement pressure along the south side of Seattle's 60-inch-diameter waterline that might induce soil movement and allow the waterline to shift. The following mitigation measure has been added to avoid the potential impact identified above: ■ In coordination with the City of Seattle, further geotechnical studies may be conducted during the design phase to identify potential impacts on the 60-inch waterline and to define mitigation measures as needed. 2-6 JSA 09/97c ADDITIONAL FACTUAL INFORMATION 2.3.10 TRANSPORTATION Chapter 12 of the Draft EIS presented the potential transportation impacts of the project. Since that time, the Washington State Department of Transportation has begun the design process for construction of the SR-167 culvert crossing and control structure (Alternative Elements 23ST2-1/23ST3-1). The Draft EIS had indicated that a jacking construction technique would be used to install the culvert; however, results of the design studies have indicated that an open cut trench method will probably be necessary due to geotechnical problems associated with jacking. Further geotechnical studies will determine the final construction method. In the event trenching is required, some lane restrictions, with the attendant vehicular traffic delays, would be required during the construction period. Measures to mitigate those impacts would include the following: ■ Provide traffic control with maintenance of three lanes (10 ft minimum width) of traffic in each direction, where possible. For mid-road construction, one lane would be separated from the other two. ■ WSDOT would prepare a detailed traffic control plan with advance public notice of the planned traffic revisions. Page 12-2 of the Draft EIS, SW 27th Street discussion, noted that SW 27th Street would, in the future, provide local access to the Boeing Longacres Office Park. SW 27th Street currentlyprovides only local access. Also, in addition to the future SW 27th Street transportation facilities defined on page 12-3, the extension of Oakesdale Avenue SW is a proposed improvement (the Final EIS was recently completed). Page 12-5, Oakesdale Avenue crossing of Springbrook Creek, references SW 41st Street as an alternative route during construction for local traffic north of the crossing. However, the primary alternative route would be along Lind Avenue and SW 34th Street. Additionally, the last paragraph in that section ("The improvements under Element 1 . . .") should be replaced with the following statement: "Temporary lane closures during construction would have minimal impacts on local access and through traffic using Oakesdale Avenue SW". 2.3.11 LITERATURE CITED The following should be added to the citations list: Smith, L. M. 1989. Habitat management for migrating and wintering waterfowl in North America. Texas Tech University Press. Lubbock, Texas. 560 pp. U.S. Fish and Wildlife Service. 1964. Waterfowl tomorrow. Joseph Linduska, Editor. Washington, D.C. 770 pp. 09/97c JSA 2-7 CHAPTER 2 This page left blank intentionally. 2-8 JSA 09/97` Table 2-1. Wetlands within and Immediately Downstream of the East Side Green River Project Area Wetland Inventory Potentially Numberl Acreage category, Impacted by Plan W-3 10.3 2 W-4 59 1 X w-53 34.7 1 W-5a3 0.1 3 W-5b3 1.14 3 W-50 0.7 3 W-6 1.2 3 W-7N 12.3 1 X W-7S 3.3 3 W-8N 9.6 2 X W-8S 1.3 3 W-9a 2.1 3 X W-9b 0.8 3 W-10N 8.6 2 X W-10S 2.9 2 X W-11 24.2 2 X W-12a 22.2 1 X W-12b 12.7 2 X W-13Na 0.26 3 X W-13Nb 4.6 3 W-13Nc 1.5 3 W-13Nd 8.9 3 X W-Ma 0.08 3 W-13Sb 2.21 3 W-13Sc 0.04 3 W-13Sd 0.09 3 W-13Se 0.18 3 W-13Sf 0.08 3 W-13Sg 0.71 3 W-13Sh 0.38 3 W-13Si 0.31 3 W_13S' 10.92 2 X Table 2-1. Continued Wetland Inventory Potentially Number Acreage Category, Impacted by Plan W-14 2.58 3 W-16a 4.2 3 X W-16b 9.9 3 X W-16c 0.87 3 W-16d 2.0 3 W-18 0.59 3 W-19 2.3 3 W-22 18.78 3 W-28 0.4 3 W-32 6.69 3 X W-33a 1.06 3 W-33b 0.63 3 W-33c 3.0 3 W-44 0.08 3 W-45 28 3 W-48a 0.11 3 W-48b 0.04 3 W-48c 0.6 3 W-48d 0.6 3 X W-48e 3.66 3 X W-48f 0.26 3 X W-48g 0.02 3 W-48h 0.03 3 W49 0.1 3 X W-51 0.48 3 W-53 0.2 3 X W-54a 1.8 2 W-54b 5.2 2 Total Wetlands = 58 Total Acres = 329.02 'Wetland inventory numbers are City of Renton Wetland Inventory identification numbers. 'Per City of Renton Ordinance No. 4346 3 Wetlands outside the East Side Green River Project Area f to Black Rive Pump Stgum m • S ra e 0 IL , } 500' 0 500' 1000' W-21 ® S am VkP A SCALE -6 W-13M W-1 13N � - MeW-1 W-13Sg �:. W-13Sh all _ g w .,ON w-i • �... 10S i w W w �„R : .►W-14 � Q9� LEGEND w © —1e � 32 � w33a w w t FrI � N kW-34 5,8m St W-1 9 15 97 I--'�\ ' s Inw St Figure 2-1 Wetlands Map City of Renton East Side Green River Watershed Project Chapter 3 COMMENTS AND RESPONSES 1 i ' 1 i 1 CHAPTER 3 COMMENTS AND RESPONSES This chapter presents the letters of comment received during the 54-day review period for the Draft EIS and the responses to those comments. Nine letters of comment were received, two from federal agencies, one from state agencies, one from city/county/regional agencies and tribes, and the five remaining letters from companies, interest groups and citizens. Comments for each letter are numbered in the right margin, with responses to those comments presented on the pages following the letter. Responses, when appropriate, include reference to sections in the Draft EIS,reference to additional information presented in Chapter 2 of this Final EIS, or reference to responses to similar comments elsewhere in this chapter. 3.1 LIST OF COMMENTORS Commentor Date Federal Agencies ■ U.S. Army Corps of Engineers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 02/07/97 j ■ Natural Resources Conservation Service . . . . . . . . . . . . . . . . . . . . . . . . . 01/31/97 State Agencies ■ Washington Department of Fish and Wildlife . . . . . . . . . . . . . . . . . . . . . 01/31/97 City/County/Regional Agencies and Tribes ■ City of Seattle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01/16/97 Companies/Interest Groups/Citizens ■ Boeing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01/31/97 ■ Citizens For Renton Wildlands Preservation . . . . . . . . . . . . . . . . . . . . . . . 02/07/97 ■ Friends of the Black River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 02/06/97 ■ David Radabaugh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 02/07/97 ■ 3300 Company . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 02/07/97 09/97e JSA 3-1 CHAPTER 3 This page left blank intentionally. 3-2 JSA 09/970 COMMENTS AND RESPONSES DEPARTMENT OF THE ARMY SE FEB i ATTLE DISTRICT. CORPS OF ENGINEERS �551 P.O. BOX 3 SEATTLE,WASHINGTON 98124-2255 4:,..: PUBLIC DORY;B;,�r�glW. XC.L TO ATTE—..or Planning Branch Mg 1 1 19F Gregg Zimmerman, Administrator Planning/Building/Public Works Department Renton Municipal Building 200 Mill Avenue South Renton, Washington 98055 Dear Mr. Zimmerman: We have reviewed the draft environmental impact statement (EIS) for East Side Green River Watershed Project with respect to the U.S. Army Corps of Engineers' areas of special expertise and jurisdiction by law as designated by the President' s Council on Environmental Quality on December 21, 1984. Implementation of any of the project alternatives which require work in waters of the U.S. will likely to be subject to: Section 10 of the Rivers and Harbors Act of 1899, for work in navigable waters. For example, the Duwamish River is a navigable water from its mouth to the head of navigation at the mouth of the Black River. • Section 404 of the Clean Water Act, for work in waters of the U.S. For example, the Duwamish River, the Green River, Springbrook Creek, Rolling Hills Creek, SW 23rd Street Channel, Panther Creek, and other rivers, lakes, ponds, and streams, including intermittent creeks, are waters of the U.S., as are special aquatic sites such as wetlands and riffle/pool complexes. Work includes structures, fills, dredging or excavation, grading, and mechanized land clearing. Fill in waters or wetlands for water control structures, fill or excavation in wetlands for stormwater detention basins, and excavation or mechanized land clearing in wetlands during restoration or enhancement are examples of activities that would likely require authorization from the Corps. Depending on the ultimate location and extent of such work, it may be covered with Nationwide permit(s) or may require standard Individual permits. If you have questions or desire further information, please contact the Regulatory Branch at (206) 764-3495. 09/97e JSA 3-3 CHAPTER 3 -2- Thank you for the opportunity to review this statement. Sincerely, Cy �Sm. McNeely, Acti g Chief Environmental Resources Section I 3-4 JSA 09/97e COMMENTS AND RESPONSES Response to Comments from the Seattle District Corps of Engineers 1. Comment noted. The City of Renton will coordinate with the Corps of Engineers during the Section 404 permitting process. The project does not propose any work in navigable water and is therefore not subject to Section 10 requirements. 09/97e JSA 3-5 CHAPTER 3 This page left blank intentionally. 3-6 JSA 09/97c COMMENTS AND RESPONSES Un D� United States Natural 316 W.Boone Ave, Suite 450 JDepartment of Resources Spokane,WA 99201-2348 Agriculture Conservation Service Phone 509-353-2348 Fax 509-353-2354 Date: January 31, 1997 Ron Straka, P.E. City of Renton j I', S;�1 ._•, '' 200 Mill Avenue South J r,+ f •' 'J Renton, WA 98055 F B 1 Re: East Side Green River Project, DRAFT Plan and Environmental Impact Statement CI i :,F r=NT,'Di L�c r.ce1•c.,J �n.1L Dear Ron: The Natural Resources Conservation Service (NRCS) appreciates the opportunity to comment on the Draft Environmental Impact Statement (EIS) and Plan for the East Side Green River Watershed Project (ESGRWP)within the City of Renton. This plan provides for the following: • Works of improvement to reduce flooding in the valley; • Eliminate erosion in the Springbrook Creek upstream of SW 16th Street; • Increased fish habitat within Springbrook Creek; • Increased riparian habitat along Springbrook Creek; • Potentially restore salmon runs to the upper areas of Panther Creek. Specific comments and our recommendation for the preferred alternatives are listed on the attached addendum. We are looking forward to continued cooperation with the City of Renton in the construction of the East Side Green River project in Renton. If you have any questions, feel free to give Rod D nHerder or Joe Henry, of our Renton Field Office, a call at: (206) 764-3325. �n�9�� L NN A. BROWN State Conservationist Attachment cc: Ron Shavlik, NRCS, Olympia, WA Joe Henry, NRCS, Renton FO Rod DenHerder, NRCS, Renton FO Larry Cooke, NRCS, Spokane SO The Natural Resources Conservation Service works hand-In-hand with the American people to conserve natural resources on private lands AN EQUAL OPPORTUNITY EMPLOYER stnks:msaworddn 09/97e JSA 3-7 CHAPTER 3 EAST SIDE GREEN RIVER WATERSHED DRAFT PLAN AND ENVIRONMENTAL IMPACT STATEMENT A. RECOMMENDED ALTERNATIVES Springbrook Creek: Alternative 3 Elements 1 through 4, Channel Improvements, Road Crossing Improvements and Enhanced Vegetation. 1 This alternative is recommended because of the opportunity to enhanced riparian vegetation on the channel banks and provide in-stream fish habitat components while building in adequate flood flow capacity for the 100-year event. Improvements to the road crossings will solve flow restrictions and prevent blocking problems associated with trash and debris. This alternative will also reduce the maintenance required to maintain flood flow capacity. SW 23rd Channel (SCS Plan P-9 Channel): Alternative 3 Elements 1 through 3 Channel Improvements, Hwy 167 Pipe Crossing and Olympic Pipeline Improvement. Providing a single, large pipe crossing under Highway 167 will provide a known positive outlet from the southern part of Panther Creek Wetland. This will be easier to maintain and also provide for future fish passage into and through Panther Creek Wetland, if desired in the future. Panther Creek Wetland Altemative 2 Element 1 High Flow Bypass into Panther Creek Wetland. Since it is possible for Panther Creek to divert into the wetland in the future on its own, it does not make sense to develop an enhanced pipe outflow system through the 34th system. It makes good use of an existing wetland to bypass flood flows into it. It may still be desirable to enhance the wetland values in the future as previously proposed by NRCS. Plan Section 8.3.2: In the discussions of the Panther Creek Wetland altematives, it strongly suggests that therE)will be no fish passage now or in the future through the wetlands. However, as discussed in this document, there is a high potential for natural changes to the flow of Panther Creek due to the bed load in the creek building the alluvial fan just upstream from Highway 167. Therefore, it seems reasonable in the choice of alternatives to at least provide the opportunity for future fish passage through Panther Creek Wetland and the restoration of Panther Creek along the SW 23rd corridor. This would include the design of the culvert under Highway 167, the high flow diversion (Panther Creek Alternative 2), and design of culverts under the Olympic pipelines. Until the upstream problems are resolved that cause the high gravel bed loads, there are no assurances that Panther Creek will continue to flow through the Highway 167 culverts and through the 34th pipe system. 3-8 JSA 09/97e COMMENTS AND RESPONSES Wetlands: Although NRCS will not be participating financially, our recommendation is for the action alternatives to enhance and hydraulically improve the use and function of the wetlands, both for flood storage and environmental values. In the mitigation agreement of 1980, it called for preservation of open space. By enhancing and enlarging wetlands in contiguous locations, it would be better than small green spaces around parking lots. Pipe Improvements: The purpose of the ESGRWP is flood control; therefore, the pipe improvement alternatives to I 6 improve flood flow into the channels is recommended. Table 9-01: Alternative Element Contributors: Generally, the items showing NRCS participation appear reasonable although final decisions will be made during the preliminary design. Because Springbrook Creek Element No. 3 of Alternative No. 3 (SCS-3) is a maintenance element, it probably will not be eligible for NRCS financial participation. General Comments: Table 9-01: Alternatives Eliminated: A more complete discussion regarding the reasons for not including the original SCS P-1 Channel alignment as an alternative should be included in this document. Although the 8 reasoning for not including this alignment, which is that it runs along the railroad tracks at the west side of Renton, may be included in other documents, it should also be included because it has been the preferred alternative for almost 25 years. 09/97e JSA 3-9 CHAPTER 3 This page left blank intentionally. 3-10 JSA 09/97e COMMENTS AND RESPONSES Response to Comments from USDA, Natural Resources Conservation Service 1. The City's Preferred Alternative includes Springbrook Creek Alternative 3 as recommended by NRCS. 2. Section 7 of the Draft EIS noted that the proposed culvert through SR-167 at SW 23rd Street would not be designed for fish passage primarily because of environmental impacts and costs associated with providing fish passage through the Panther Creek Wetland upstream of the culvert. However, in response to comments from NRCS and the Washington Department of Fish and Wildlife (WDFW), the City's Preferred Alternative includes designing the proposed culvert under SR-167 at SW 23rd Street so as to not preclude fish passage into the Panther Creek Wetland in the future. 3. The bypass of additional water into the Panther Creek Wetland from Panther Creek would increase the feasibility of modifying wetland water levels to enhance the wetland as part of a separate, future project proposal. Water levels could be modified through changes to the inlet control structure for the culvert across SR-167 at SW 23rd Street proposed under the Preferred Alternative Element 23ST3-1. Wetland enhancements could include expanding the area of open water available in the wetland and increasing the diversity of wetland vegetation by drowning out the invasive reed canarygrass. 4. As noted in the response to NRCS Comment No. 2, the City's Preferred Alternative includes designing the proposed culvert under SR-167 at SW 23rd Street so as to not preclude fish passage into the Panther Creek Wetland in the future. The culverts under the Olympic pipelines will also be designed to allow for fish passage. Use of a high flow bypass at Panther Creek would not facilitate fish passage through the Panther Creek Wetland in the future. For upstream fish passage to be provided through the Panther Creek Wetland in the future, all Panther Creek flow would need to be diverted into the wetland, including low flows. Therefore, design of the high flow bypass at Panther Creek is not related to future fish passage through the wetland as the comment suggests. Instead, the diversion design is intended to reduce flooding of the developed land west of SR-167 while continuing to allow low flows and downstream migrating fish to pass through the existing pipe system in East Valley Road and SW 34th Street into Springbrook Creek. It is unclear what upstream problems NRCS is referring to with regard to the high gravel bed loads. Stream bed erosion and movement of gravels is a natural process and implementing measures to completely stop movement of gravels into the alluvial fan upstream of SR-167 is not feasible. There will always be the potential for channel changes in the alluvial fan area unless a sediment maintenance removal program were instituted to keep the stream in a specific channel. It is evident from 09/97e JSA 3-11 CHAPTER 3 the size of the alluvial fan that significant deposition of material has historically occurred upstream of SR-167. 5. Comment noted. 6. Comment noted. 7. Comment noted. 8. A brief discussion regarding the process whereby use of the original SCS alignment as an alternative was eliminated from consideration was included in Section 8.2 of the Draft Plan. This discussion has been expanded in the Final Plan as requested. 3-12 JSA 09/97` COMMENTS AND RESPONSES 1 FEB 5 - 1991 State of Washington CITY OF F1L,\t UN DEPARTMENT OF FISH AND WILDLIFE PUBLIC WORKSADMI?j. Mailing Address: 600 Capitol Way N•Olympia,WA 98501-1091•(360)902.2200.TDD(360)902-2207—_ Main Office Location: Natural Resources Building•1111 Washington Street SE•Olympia.WA Mr . Greg Zimmerman January .3] 1997 City of Renton I ' " Planning/Building/Public Works Department fE Renton Municipal Building, 3rd Floor 200 Mill Avenue South Renton, Washington 98055 En *::.`r:r:rc Dept. SUBJECT: DRAFT PLAN AND ENVIRONMENTAL IMPACT STATEMENT (DEIS) FOR THE CITY OF RENTON'S PROPOSED EAST SIDE GREEN RIVER WATERSHED PROJECT (ESCRWP) FOR SPRINGBROOK AND PANTHER CREEK. Dear Mr. Zimmerman: The Department of Fish and Wildlife (WDFW) has a long history of being involved in the various phases of this project. We recognize the flooding problem that you are trying to correct and compliment the city on the scope of your project goals that includes goals that benefit fish and wildlife resources through wetland protection and habitat enhancement. The following are my comments and concerns: 1. Page 6-25, 6. 8. 2 .1 Springbrook Creek (SC)- We would include Panther Creek as potential spawning areas, especially the lower section between Talbot Road and SR 167 even though anadromous fish do not have access at this time . 2. Page 6-26, paragraph 2- The section of SC downstream from Grady Way is developing an overstory that provides thermal protection for most of 2 the day and the section from SW 16th to just north of the SW 23rd Street has an excellent riparian area with. larger trees and provides good thermal protection. 3. Table 6-5, Panther Creek, Water Quality-Other- The sections of Panther Creek I observed seem to well vegetated and would help moderate I high water temperatures. 4. Page 7-8, 7 .4 .2 - Paragraph 2 - granted future high flows may I restrict salmon passage however its not unusual that fish are delayed during high flow events. 5. Page 8-6 Springbrook Alternatives (SC2 and SC3s) A. Element 1 , Roadway Crossing - upgrading these crossings with bridges or bottomless culverts would be a benefit for fish passage . Every effort should be attempted to install a new culvert or bridge at Oaksdale and get rid of the multiple culvert system that is there now. The multiple culvert system is not conducive to fish passage and is more likely to catch debris and cause flooding and block fish passage. The day I looked at this location deb>r•i5 was blocking the culvert. 09/97e JSA 3-13 CHAPTER 3 Mr. Greg Zimmerman Page 2 January 31, 1997 B. Element: 2 SC2 and Element 3 SC3- both of these elements have the potential to cause the most short term construction impacts and long term impact to SC for both fish and wildlife as recognized in this document . The riparian area between SW 16th and SW 23rd Street the most diverse and established riparian area on SC and the loss of this area even temporary will / severely impact wildlife . As mitigation for this impact an (� aggressive and immediate replanting of other areas of SC should be an :important component of this plan. In addition wherever possible existing trees and shrubs should remain along the low flow channel. The cross section shown on Figure 8-5 for SW 30th to SW40 would be best for maintaining existing riparian for SW 16st and SW 23rd. Another important design component is the incorporation woody debris which we would recommend a minimum of one piece per two channel width and explore the possibility to meandering the channel or providing deflectors to create the meanders . The latter comments would also apply to the dredging proposal downstream of Grady Way. I believe the original design for this proposal had wood or boulders in this section that are now covered with sediment. 6. P8-19, Panthher Creek Alternative 2 (PC)- With either of these two alternatives 'the culvert at SW 23rd St. should be installed first . Since fish are planted and there seems to be some natural reproduction of resident trout there should be some strategy to minimize stranding or entrainment in the Panther Creek Wetland. One option could include maintaining a channel to the standing water areas by combination of cutting the canary grass with planting willow and cottonwood to provide shading to prevent further growth of the canary grass. With the addition of woody debris this could provide fish better access downstream. The fish concerns at this time is for out migration and I agree that a channel improvements at this time would be difficult both from a construction and a regulatory standpoint due to wetland impacts of such a project . However, I still recommend that the new culvert at SW 23rd St. be installed so it will be passable to fish so we don 't preclude options in the future . It looks as though the lower section of Panther Creek has the potential for spawning. 7 . Page 8-17 through 8-20, SW 23rd Street Alternative 2 and 3 . A. See Comments above concerning the culvert. 3-14 JSA 09/97c COMMENTS AND RESPONSES Mr . Greg Zermmerman Page 3 January 31, 1997 B. I am concerned about the potential impact to wetland 8-N and 1ON if the NRCS channel criteria are used if the same results can be obtained with the option that would least impact the Q wetland. The goal of avoiding and minimizing impacts to environmentally sensitive areas should apply for this element of this alternative . I would encourage the city to discuss the possibility of exemption to NRCS channel criteria in this instance . 8. Page 8-25, Rolling Hills Culvert- I encourage the city to remove this stream from this culvert . This will have benefits for water quality and fish and wildlife . 9 . The goal of recreation and education is commendable goal for this proposal . However, the development of a pedestrian and bike trail within the riparian area of this stream is an impact to wildlife habitat that is not necessary. The present setbacks from buildings and parking lots along Springbrook are marginal for the protection of fish ^ and wildlife . WDFW recommends 300 foot buffers for wildlife and 100 L foot buffers for fisheries protection. The addition of the trail will further compromise wildlife habitat in the buffer . I would recommend that where the existing trail at the Boeing Facility ends, an interpretive area and is set up to explain this project and the benefits for wildlife by not having further intrusion of the trail into buffer area of SC. Other interpretive or wildlife observation areas could be developed in appropriate areas along the SC or its associated wetlands. I would like to thank you for the opportunity comment on this project and I hope my comments have been helpful . I will be looking forward to working with you for the Hydraulic Project Approval for this project. If you have any questions please call me at ( 206) 391-4365. I would also like to thank you for your cooperation in our efforts to protect and enhance our states fish and wildlife resources. Yours truly, Philip 'Schneider Habitat Biologist cc Ted Muller Rod Malcomb, Mulkelshoot Tribe Trudy Thomas, Friends of the Black River Olympia- Habitat 09/97e JSA 3-15 CHAPTER 3 This page left blank intentionally. 3-16 JSA 09/97° COMMENTS AND RESPONSES Response to Comments from the Washington Department of Fish and Wildlife 1. Panther Creek would be suitable for anadromous fish spawning if access to the creek is restored in the future. Section 6.8.2.2 of the Final Plan has been expanded to identify Panther Creek as a potential spawning area. However, based on field study findings, spawning and rearing habitat restoration measures would be needed in addition to restoring access if the creek were to support a viable, self-perpetuating fishery. 2. This information has been added to Section 2.3.5 of this Final EIS and Section 6.8.2.1 of the Final Plan. 3. This information has been added to Section 2.3.3 of this Final EIS. Table 6-5 of the Final Plan has also been revised to clarify that high temperatures in base flows may potentially be from solar insolation at Panther Lake at the headwaters of the creek, not the lack of vegetation along the creek downstream of the lake. 4. This information has been added to Section 7.4.2 of the Final Plan. 5. The proposed culvert replacements at SW 27th Street and SW 34th Street will be bottomless three-sided culverts which provide a natural substrate for fish habitat. The City's Preferred Alternative includes Springbrook Creek Alternative 3 which proposes replacing the existing culverts at Oakesdale Avenue SW with a bottomless box culvert similar to SW 27th Street and SW 34th Street. 6. Comment noted. Design of the widened channel between SW 16th Street and SW 23rd Street will consider opportunities to minimize disturbance to the low flow channel and existing riparian vegetation where feasible. Revegetation of disturbed areas of Springbrook Creek will be accomplished immediately as a part of the channel construction. One of the goals of the project is to improve riparian habitat in the project area. Measures to improve riparian habitat along the entire creek were proposed with each of the alternatives presented in the Draft Plan and EIS. Although not acknowledged in the Draft Plan and EIS, it has been the City's intent to implement the planting restoration measures as soon as possible in the reaches not planned for widening because plantings take many years to mature. Section 9.3 of the Plan has been expanded to specifically clarify the City's commitment to early implementation of riparian plantings. Also, the following mitigation measure has been noted in Section 2.3.5 of the Final EIS as an additional measure that could be required as part of the City's formal environmental review process: ■ Riparian plantings proposed under Alternative SC24 should be implemented prior to or concurrent with Alternative SC2-2 (channel widening - SW 16th to SW 23rd Street) to help mitigate for the temporary loss of habitat resulting from the channel widening. Similarly, Alternative SC3-4 should be implemented prior 09/97c JSA 3-17 CHAPTER 3 to or concurrent with Alternative SC3-2a (channel widening - SW 16th to SW 23rd Street) if the Springbrook Creek greenway alternative concept is to be implemented. It is important to clarify that Springbrook Creek Alternative 3 plantings within the floodway may need to be delayed until after the plantings outside of the floodway. This is because plantings within the floodway will reduce the conveyance of the reach in which they are installed. It is important to carefully schedule the implementation of plantings within the floodway so that the compensating capacity improvements are in place prior to any loss of conveyance due to the extensive floodway plantings. For example,the Oakesdale Avenue SW road crossing improvement(Alternative SC3-1d) should be completed before the conveyance capacity of the reach upstream of the crossing to SW 43rd Street is allowed to be affected by extensive plantings within the floodway. The feasibility of limiting construction to a single bank between SW 16th Street and SW 23rd Street will be determined during the design phase. 7. Comment noted. If Alternative SO is implemented, both the existing and widened portions of the creek will be improved with the addition of instream structures, such as boulders and large woody debris. If Alternative SC2 is implemented, instream structures would not be incorporated into reaches that will not be widened to prevent reducing their conveyance capacity. The feasibility of incorporating low flow meanders will be determined during the design phase. The original design for the widened channel downstream of Grady Way did not include instream structures. The City will work with the WDFW and NRCS to explore the feasibility of incorporating instream structures and creating low flow meanders in the previously widened reaches of the channel when the proposed sediment removal project is implemented. 8. The City concurs with your recommendation that the SW 23rd Street culvert at SR-167 be installed first (before Element PC2-1). The culvert under SR-167 is scheduled to be one of the first project elements designed and constructed. The following mitigation measure has been noted in Section 2.3.5 of the Final EIS as an additional measure that could be required as part of the City's formal environmental review process: ■ An overflow "channel' from the Alternative PC2-2 Panther Creek diversion structure to the nearest standing water in the Panther Creek Wetland should be created by mowing/cutting a path through the existing reed canarygrass and planting willows and cottonwoods on each side of the mowed path to provide shading and prevent further growth of the canarygrass. 3-18 JSA 09/97° COMMENTS AND RESPONSES 9. Comment noted. See response to NRCS Comments Nos. 2 and 4. 10. Comment noted. It is true that increasing the conveyance capacity of the SW 23rd Street channel is not necessary to achieve the desired level of flood protection. The additional capacity provided under Alternative 23ST3 should be noted as a secondary benefit of the proposal to deepen the channel, rather than it being implied as the primary reason through use of the title "Major Conveyance Improvements". The primary purpose of deepening the channel is to provide positive drainage over its length, reducing maintenance needs and reducing stagnation that negatively impacts the quality of water in the channel. For the channel to be deepened it must also be widened. If the channel is to be modified, then mitigation measures should be considered that minimize impacts to Wetlands 8-N and 10-N from the construction and operation of the deepened and widened channel. During construction,impacts to the wetlands should be minimized by widening the channel only from the north (access road) side of the channel, thereby eliminating the need to move construction equipment into the wetlands on the south side of the channel. This would also reduce the amount of impact to the scrub-shrub and emergent wetland. The feasibility of modifying or exempting the NRCS channel criteria should also be evaluated during the design phase. The following mitigation measures have been noted in Section 2.3.4 of the Final EIS as additional measures that could be required as part of the City's formal environmental review process. Other measures for mitigating wetland impacts have already been defined in the Draft EIS. ■ An exception to NRCS channel design criteria to allow steeper side slopes and a narrow channel bottom should be evaluated during the design phase for the SW 23rd Street channel deepening and widening element. ■ Deepening and widening of the SW 23rd Street channel should be limited as much as feasible to that which may be conducted from the existing access road on the north side of the channel. 11. Comment noted. The City recently acquired the right-of-way needed to remove the culvert. This culvert would likely be removed as part of the Springbrook Creek channel widening project from SW 16th Street to SW 23rd Street currently scheduled for 1998/1999. 12. On November 20, 1996, the City of Renton issued a shoreline permit for the Hunter Douglas project (City file LUA-96-104, SM; formerly Raymond Avenue Center West). The Hunter Douglas project site lies adjacent to and west of the reach of Springbrook Creek between SW 19th Street to SW 23rd Street. The Hunter Douglas proposal includes constructing a building and associated improvements on the northern portion of their site, keeping a 50-foot setback from the 40-foot-wide Drainage District No. 1 property that follows the alignment of the creek. A permit 09/97c JSA 3-19 CHAPTER 3 condition of the Hunter Douglas project was to install a pedestrian trail within the 50-foot setback area along the length of the creek adjacent to their site. All land use permits for the project are now final. The ESGRWP Draft EIS was in the final stages of being prepared for printing and distribution when the shoreline permit for the Hunter Douglas project was issued. The Draft EIS was thus issued on December 17, 1996,without clarifying that the trail from SW 19th Street to SW 23rd Street was actually an element of the Hunter Douglas project, intending instead to make the clarification in this ESGRWP Final Plan and EIS. The approximately 200-foot segment south of SW 23rd Street that will connect the Hunter Douglas trail with the trail previously installed by the Allpak project remains the responsibility of the City. This missing trail link will likely be constructed as part of the Springbrook Creek channel widening project from SW 16th Street to SW 23rd Street. Construction of this link will be the final segment of a continuous trail system extending along the creek from SW 27th Street to the Oakesdale Avenue SW crossing north of SW 7th Street, a distance of approximately 8,000 ft. 3-20 JSA 09/97e COMMENTS AND RESPONSES �► City of Seattle DEVELOPMENT PLANNING Norman B. Rice. Mayor CITY OF RENTON Seattle Public Utilities Diana Gale,Director JAN 2 2 1°97 RECEIVED January 16, 1997 Development Service Division Planning/Building/Public Works Department Attn.: Mark R. Pywell,AICP 200 Mill Ave. So. Renton,Washington 98055 Re: Draft Environmental Impact Statement—City of Renton East Side Green River Watershed Project-City of Renton File No. LUA-95-205.ECF Gentlemen: In Reviewing the above referenced project Seattle Public Utilities (Water Department) request that the City of Renton include in its"Contract Plans"all of Seattle Public Utilities existing pipeline facilities, if applicable. It is additionally requested and required that when any work or proposed use of Seattle Public Utilities fee owned right of way is planned or scheduled near pipeline facilities precise 1 Construction Plans be submitted to Seattle Public Utilities for review and approval prior to any construction or use activity.A Use Permit will be required from Seattle Public Utilities for any such usage. As Built Construction Plans are available from Seattle Public Utilities(Water Department) upon request. More directly in response to the"Draft Environmental Impact Statement'for the City of Renton East Side Green River Watershed Project, Seattle Public Utilities (Water Department) is of the opinion that Section 8 page 8-19 sub-section SW 23RD Street Altemative 3 (23ST3)-Major Conveyance Improvements and section PS 2-3 may have significant adverse impact on Seattle Public Utilities sixty inch(60") Cedar River Pipeline No. 4. Seattle Public Utilities respectfully request that the City of Renton include into the final Impact statement a more precise and direct description of the projects impact on Seattle Public Utilities facilities, Your consideration and cooperation in this matter is very greatly appreciated. Should you have any further question please feel free call me at 386-9754. Sincerely Shirley Lukhang, Real Estate Services wpc Dexter Horton Building, 1 Oth floor 710 Second Avenue, Seattle WA 98104 Tel: (206) 684-5851, TTY/TDD (206) 233-7241, FAX: (206) 684-4631 An equal-employment opportunity, affirmative action employer.Accommodations for people with disabilities provided on request. 09/97e JSA 3-21 CHAPTER 3 CITY OF RENTON ..0 Planning/Building/Public Works Department Jesse Tanner,Mayor Gregg Zimmerman P.E.,Administrator January 30, 1997 Shirley Lukhang City of Seattle Real Estate Services Dexter Horton Building-RM 1 11 l 710 Second Ave Seattle, WA 98104 SUBJECT: EAST SIDE GREEN RIVER WATERSHED PROJECT DRAFT PLAN AND ENVIRONMENTAL IMPACT STATEMENT(EIS) Dear Ms.Lukhang: Thank you for you recent comment letter on the above-referenced project. As we discussed over the phone, I believe that Chapter I I of the Draft EIS, Public Services and Utilities, should have included a reference to Chapter 4, Groundwater, for additional analysis of potential impacts that the SW 23rd Street Alternative 3 may have on the surrounding area, including the City of Seattle's 60"Cedar River Pipeline No.4. Without the reference,reviewers may not have be aware of the additional analysis. If possible, I would really appreciate if the reviewers within Seattle Public Utilities would look at Chapter 4 of the Draft EIS to see if it includes the more precise and direct description of impacts that they were expecting. Even more detailed information on groundwater conditions and potential impacts of the SW 23rd Street Alternative 3 is included in Volume 2 of the Draft EIS,Appendix A-12. If upon further review it is found that the Draft EIS does address the concerns of Seattle Public Utilities,then I would appreciate a supplemental comment letter so noting. If it is still thought that more direct analysis is needed, then it would be helpful if the supplemental comment letter could specifically list what element of the proposed action Seattle Public Utilities believes may have significant impact to the 60"pipeline,such as dewatering activities during construction. With regard to Pipe System Improvement Alternative 2-3 (PS2-3, Rolling Hills Culvert) listed in your recent letter, it is unclear to me how removal of a culvert at SW 19th Street would have an effect as far south as SW 23rd Street. I very much appreciate consideration of this request, as it will help us respond better to your comments on the Draft EIS and facilitate preparation of the Final EIS. You will also be getting a separate letter regarding a 7-day extension of the deadline for the Draft EIS comment period from 5 PM January 31, 1997,to 5 PM on Friday,February 7, 1997. I hope this is sufficient time for the additional review I am requesting in this letter. Thank you for your help. If you have any questions, please contact me at 277-5547. Sincerely, Scot Woodbu �roject Manager t ry� 1 9 Surface Water Utility H:DOCS:97-076:SW CC: File LUA-95-205.ECF 200 Mill Avenue South - Renton, Washington 98055 3-22 JSA 09/97e COMMENTS AND RESPONSES �► City of Seattle Norman B.Ricc,Mayor Seattle Public Utilities r Diana Gale,Director April 10, 1997 APR 117997 C.J Cpgnt "r; �PPfv Scott Woodbury City of Renton,Public Works Dept. 200 Mill Ave. South Renton,WA 98055 Subject: East Side Green River Watershed Project Draft Plan and Environmental Impact Statement Dear Mr. Woodbury: The City of Seattle,Seattle Public Utilities(formerly Seattle Water Department) would like to state that there is no longer a concern about Pipe System Improvement Alternative 2-3 (PS2-3, Rolling Hills Culvert). The concern,however,on 23ST3 are still valid.Any widening or deepening at this channel next to the transmission pipeline could cause the underlying peat and soft soils to move. This could allow the pipe to shift. The pipe is slip joint and requires straight alignment and side support to stay together and in place. If you have any questions please call be at 386-9754 or Dave Garrison at 684-5903. Sincerely, S irleY Lukhat Real Estate Services Dexter Horton Building, 1 Oth floor 710 Second Avenue, Seattle WA 98104 Tel: (206) 684-5851,TTY/TDD (206)233-7241, FAX: (206)684-4631 An equal-employment opportunity, affirmative action employer.Accommodations for people with disabilities provided on request. to 09/97e JSA 3-23 CHAPTER 3 This page left blank intentionally. 3-24 JSA 09/97C COMMENTS AND RESPONSES Response to Comments from the City of Seattle 1. Comment noted. 2. A more detailed description of the potential impacts of the SW 23rd Street Alternative 3 (23ST3) is included in this Final EIS in Section 2.3.9. Mitigation measures related to the 60-inch pipeline and Alternative 23ST3 are also listed. Pipe System Alternative PS2-3 was noted as no longer of concern in a subsequent comment letter from the City of Seattle dated April 10, 1997. 09/97e JSA 3-25 CHAPTER 3 This page left blank intentionally. 3-26 JSA 09/97e COMMENTS AND RESPONSES Boeing Commercial Airplane Group P.O.Box 3707 Seattle.WA 98124-=7 CITY OF RENTON t RECEIVED January 31, 1997 JAN 31 1997 6-8A9F-RF-97-002 E BUILDING DfVISION Mr. Mark Pywell, Senior Planner City of Renton Development Services Division 200 Mill Avenue South Renton,Washington 98055 Subject: East Side Green River Watershed Project BOE//VG Project No. LUA-95-205, ECF Dear Mr.Pywell: I am writing in response to the issuance of a Plan and Environmental Impact Statement Volume 1 (Draft), dated December 1996, for the East Side Green River Watershed Project(ESGRWP) . As you know, Boeing owns the property on the western bank of Springbrook Creek from SW 16'h Street to SW 19`s Street, as if it were extended. The Boeing property is the location of the Customer Services Training Center building and the future BCAG Headquarters Building. A.letter dated February 29, 1996 addressed to you from Liz Warman identified concerns and issues we had as a result of reviewing the EIS Scoping Summary,dated April 1996,for the subject project. Based on the review of the description of the project and the alternates,we offer the following comments. We would reinforce how important phasing and timing of the ESGRWP improvements are. We realize that starting downstream and working up would be the ideal way to do a project of this sort as recognized in the EIS,but we also realize potential exceptions will exist. Our concern lies in the possibility of implementing non- Springbrook Creek improvements prior to downstream main stem Springbrook Creek improvements. This should only be done if it is determined that the upstream improvement will not result in an unacceptable increase in 100-year flows or flood elevations in he downstream system. For example, removing upstream flow restrictions would lessen the flooding condition south of the Boeing property,however, this potential could simply be transferred to downstream property owners. Of the alternatives proposed for Springbrook Creek improvements,we could support the third. It is the widest in terms of the amount of physical space that it will take, but it is the most attractive in terms improved aesthetic appearance,improved fish and wildlife habitat and it would be the most compatible with the appearance created along the Creek with native plants that we previously installed. Note, right-of-way acquisition discussions have not taken place at the writing of this letter. 09/97e JSA 3-27 CHAPTER 3 Project mitigation discussed in Chapter 7 of the EIS mentions the control, eradication or replacement of the Reed Canary grass as necessary mitigation. We feel it would be mutually beneficial to the City and Boeing, coordinating efforts at eradicating this noxious weed. As you know,the City is developing an Oakesdale Avenue extension project. Sections of the proposed road will be over or very near Springbrook Creek. It would be cost effective for the work on the Oakesdale and Springbrook Creek projects,which potentially could disturb the same area, to be coordinated and completed along a similar timeline. BOE/A/G If you have any questions or comments regarding this information,please do not hesitate to call either Lori Pitzer(544-5259) or myself. Sincerely Richard J. Ford Permit Administrator 544-5362 M/S 2R-26 Cff` OF REXI TOu RECEIVE D 11997 UILDING DIVIV Ste_ 3-28 JSA 09/97e COMMENTS AND RESPONSES Response to Comments from the Boeing Commercial Airplane Group 1. Comment noted. Section 9.3 of the Plan has been revised to clarify that even the road crossing improvements may be implemented before downstream channel widening, subject to the determination that the upstream improvement will not result in an unacceptable increase in 100-year flow or flood elevations in the downstream system. None of the improvements identified in the Plan will cause flood elevations to exceed those identified in the current FEMA flood insurance study (FEMA 1996). 2. Comment noted. The City will coordinate with Boeing regarding the necessary right- of-way acquisition. 3. This project will offer an opportunity for Boeing and the City to jointly address the control of reed canarygrass along that portion of Springbrook Creek abutting Boeing property. 4. The work of coordinating the Springbrook Creek widening from SW 16th Street to SW 23rd Street with the Oakesdale Extension Project is ongoing. However, much of the Springbrook Creek widening is contingent upon receiving grant funding from the NRCS which may not be available in the timeframe needed to allow both projects to be constructed in the same construction season. 09/97e JSA 3-29 CHAPTER 3 This page left blank intentionally. i 3-30 JSA 09/97e COMMENTS AND RESPONSES Errata copy RECEIVED Suzanne (Susan) Krom,President Citizens For Renton Wildlands Preservation FEB 13 1997 4715 1/2-36th Avenue SW, Seattle WA 98126 phone/fax: 933-0222;e-mail: szkrom@aol.com DEVELOPMENT PLANNING CITY OF RENTON February 11, 1997 City of Renton Development Services Division Plan=* gBuilding/Public Works Dept. 200 Mill Avenue South Renton,WA 98055 Attn:Mark Pywell Subject: DEIS for the East Side Green River Watershed Project Dear Mr. Pywell, I represent the Citizens for Renton Wildlands Preservation.The group has been active since 1989 and our primary focus is the Black River heron colony, which includes the P-1 Pond (forebay)and adjacent wetlands and wildlife habitat. The East Side Green River Watershed Project DEIS as is currently stands is inadequate in several respects, which I address below.These points require further study before the City moves forward with the project. As a general comment that applies throughout my letter,wherever studies are requested, they should be included in the FEIS, along with their results. The new information should then be made available to applicable agencies and the public,allowing adequate time for evaluation and a comment period regarding the new information.The new information should be approved and finalized prior to moving forward with this project in any way. In addition, I have a number of concerns with specific areas of the proposed project. Incidentally, thank you for agreeing to accept my comments today, as Scott and I discussed last Friday. Overall Concern: City of Renton as Lead Agency for Multijurisdictional Project 1. Although I am directing my comments to the City of Renton,my strong desire is that the entire project be overseen by WDOE.It was my impression that during the initial scoping process for this project,WDOE was in fact identified as the lead agency. Whether or not this is true, clearly, the impacts are multijurisdictional,affecting Renton,Kent,Tukwila, and unincorporated King County,along with all other jurisdictions that share and arc impacted by this watershed.Because this project must be designed, evaluated, and conducted as whole, it 1 must be fully coordinated aud connected between all affected jurisdictions. The lead agency must have the ability to design and implement this project knowing and understanding the larger picture, not just the immediate needs of one affected community. At this point,does each jurisdiction plan to work relatively independently,coordinating only as necessary?Please include WDOEs response to these concerns in the FEIS (or whatever the next step turns out to be). If their response is not included, explain why. Also, explain why WDOE is not the lead agency overseeing the entire project, including but limited to Tukwila, Kent,unincorporated King County, and Renton. 09/97e JSA 3-31 CHAPTER 3 Issues Requiring, Further Study 2. Regarding the proposed use of deeper channels: Has the technology regarding the use of deeper channels proven to be successful and effective over the short and long terns?If so, where and for what specific projects? How did it affect the hydrology of its affected area?Did these valleys have equivalent conditions and environmentally sensitive areas, and if so,were the environmentally sensitive areas altered in=way after construction of the deeper channels?Describe thoroughly the effects on the environmentally sensitive areas,both short and long term. Provide photographs, if available, of the effects both before and after the work was conducted showing the impacts to wetlands as a result of using the deeper channels. I have serious concerns about the impacts of the use of deeper channels: By increasing the depth of the channels,there is a likelihood of changing the hydrology of the valley by severely interfering with the movement of groundwater across the valley floor. The deep cuts across the valley floor may segregate the movement of water across the valley in ways that will result in additional, unanticipated problems,and could result in significant and adverse impacts to existing wetlands,underwater streams, and other groundwater throughout the valley. We estimate that this could result in damaging between 15% to 25%of the existing wetlands, which would not only affect the ground's ability to handle large volumes of water,but also will significantly and ,adversely affect the habitat ecology of the animals that inhabit the affected wetlands, including amphibians,fish,birds, and other animals. It is absolutely reasonable to expect that the impacts could be significantly higher than the 2517o figure estimated here. Additionally, to attempt to mitigate for any resulting damage to existing wetlands by "enhancing" them after the damage has been done will be expensive in at least two ways: a. First, the impacts were avoidable. With thorough and appropriate planning, the damage would not have occurred in the first place, and b. Second,technologically "enhanced" or man-made wetlands are never equivalent to those that are naturally occurring.To come close to the effectiveness of a naturally occurring wetland,the man-made wetlands need be significantly larger than the ones that they replace. This scenario was also avoidable. With thorough and appropriate planning,the damage would not have occurred in the first place. What other methods-- other than the deeper channels --could be employed that have a track record of success and that do not alter the hydrology of a flood-prone valley?What studies 5. have been conducted, both successful and unsuccessful, on the use of deeper channels/dredgir►g projects?What are the potential long-term impacts of the use of deeper channels? I believe that the City must endeavor to not change the hydrology of the valley/watershed in any significant way.Does the City agree?Could this project affect the recharging of groundwater and aquifers? Note item#4, below,which relates to the environmental consequences of the release of currently capped toxins into the waterways when the existing channels are disturbed.These two related concerns represent potentially highly significant and severe impacts to the (� environmental safety, health,and integrity of the entire ecosystem throughout the watershed, affecting all surface and groundwater throughout the valley. How will the City address these issues and protect the ecosystem at the same thee? What studies have been done in anticipation of this project to determine the extent of damage that may occur to existing wetlands as a result of using deeper channels?If no studies have 1 been conducted, then they should have been conducted,and they,with their results should have been included in this DEIS.They require evaluation and comment,meaning that when 3-32 JSA 09/97e COMMENTS AND RESPONSES they are included in the FEIS, that comments should be solicited, with commenters being provided adequate review and comment time(as mentioned in the intro paragraph). This issue relates to item#l, above:If this project had been designed by WDOE in the first place,and if this was the DEIS that reflected the comprehensive overview pertaining to all the affected jurisdictions, then the deeper channels may have been rendered unnecessary, as all jurisdictions would be working together to create a comprehensive plan. How would this project be different if it had been scoped,evaluated, and presented by WDOE as a comprehensive program that included all affected jurisdictions,and was being designed, managed, and overseen by WDOE? Your response to this question should be fully comprehensive. Be sure to include information concerning the use of the normal,shallower channels, as opposed to the deeper channels that arc proposed, if this project had been comprehensively designed. Two example alternatives to the deeper channels/dredging approach are as follows. Instead of going into the environmentally sensitive areas to address the flooding problems: • Can the City install larger pipes in the flood-prone streets?And/or • Can the City raise the flood-prone streets as opposed to lowering the channels? Either approach would preclude the dredging/channeling of the waterways and achieve the same or similar results with regard to resolving the flooding issue. Is the City willing to use these methods (or others)which would not have the severe impacts to environmentally sensitive areas, in all or most of the areas that are identified in the DEIS? If not,why not? If other alternatives to the above bulleted suggestions are identified in the FEIS, they should be fully described,including but not limited to their environmental impacts and comparing their effectiveness against the suggested alternatives. Is a motivating factor for this project a desire on the part of the City to develop flood-prone land into use,so that the valley can be developed far more extensively than it is already developed? If so, then why shouldn't the proponents to this development be the ones who pay for it instead of using public(local and federal) funds (taxes)?Could this project be funded in a way that is similar to the LID projects, where the local population that stands to benefit from this project pays for it?If not, why not? 3. Regarding the accuracy of the City of Renton Wetland Inventory Update map:Is the Black River heron colony site, along with all the other wetlands affected by the project,included in the City's Wetland Inventory Update? If yes, do the descriptions of the sites, including Black River, agree with the curren delineations defined by WDW,WDOE, ACE, and other appropriate agencies? I believe that it was WDWs description of the Black River site that was revised last year to reflect the wetland delineations. Does the City's mapping match all other agency maps?Is the City's updated wetlands mapping in every way complete and accurate? Which independent agency/agencies have verified its accuracy and completeness? If the City's wetlands maps are not fully accurate and complete, then the City's maps should be revised to fully reflect the accurate,current, and comprehensive status of its wetlands, and these should be published in the FEIS as revised maps. A comprehensive description of how the new information will affect the entire project must accompany the revised maps. The project should not move forward in any way, including the release or approval of the FEI , before this mapping is finalized and approved by all appropriate agencies and parties. This is important because of the likelihood of the hydrology of the valley being affected if the deeper channels are used.In fact, it is important regardless of the use of deeper channels. Without accurate mapping of wetlands of the watershed area and valley,the City,neighboring jurisdictions, and other agencies cannot know and understand the current conditions, nor can 09/97e JSA 3-33 CHAPTER 3 they evaluate the effectiveness of the project once it is completed, or understand and resolve unanticipated impacts. How will the City accurately and fully address this essential issue? 4. Highly toxic debris;has settled and been capped throughout the entire stream system of the valley basin/watershed area. For example, this basin contains discharge from such highly toxic contributors as Western Processing,which is high on the list of Federal Superfund sites. For the record,the Kent Lagoons were found to contain toxic materials that may have been dumped in the water in the 1960s. Unfortunately,there are significant toxic pollutants entering the system every day,even today. Any work in these channels will release these toxins back into the waterways, aquifer, groundwater, wetlands,etc. Disruption of these toxins have an extremely high probability of having a very significant and adverse impact on the strum environment, including the killing off, weakening, and/or mutating of animals,fish, amphibians, vegetation, etc.The effects of any disruption of these streambeds must be studied and evaluated thoroughly before the FEIS is released The results of those studies and impacts must be included in the FEIS. How will the City of Renton address this very serious problem? 5. Regarding the proposed use of clay to line the channels: Has clay proven to be a fully effective block for water seepage?Please provide examples of this method being used successfully. Also include examples of this method being used unsuccessfully, the resulting impacts,and the replacement technologies that were used to correct the deficiencies. What other means should 13 be considered for this project that will provide an effective barrier,and that will have no significant envirorunental impact,including but not limited to its effect on water quality?What studies have been done in anticipation of this project related to this issue?If no studies have been conducted, then they should be conducted, and they,along with their results, should be included in the F1:-1S, allowing adequate time for comment (see intro paragraph). 6. The section addressing the Panther Creek mosquito abatement program is unclear. Please clarify-- are you referring to the continued use of bioagents? Or of modifying habitat so that bioagents aren't needed? In either case,you will get the same results, which is that you will ultimately have no mosquitoes. No mosquitoes -no wildlife that depends on them for food (swallows, bats,fish, frogs,amphibians),which is in direct conflict with your stated goal on pale 2-4, Goal number 5, "Improve Riparian Habitat Attain and maintain diverse and self-sustaining habitats that support aquatic and terrestrial species..." Insects are an essential pan of the ecosystem. Without the mosquitoes,you will succeed only in eliminating the insectivore populations — swallows,bats,fish,frogs, and amphibians -- in the immediate affected areas, thus reducing overall populations of these species, and severely reducing or eliminating all species that depend on those insectivores because they too have lost their food sources.This includes great '1 G blue herons, hawks, bald eagles,waterfowl, etc. all through the food chain. In addition, we are concerned by your stated findings of the safety and acceptance of the proposed mosquito abatement methods,specifically, with the use of Altosid, a growth inhibitor. During a SEPA appeal by Chris Clifford four to six years ago,Gerry Adams provided the manufacture's own literature describing the known adverse impacts to aquatic life. Please check the Hearing Examiner's file re the mosquito abatement issue for the written records of this appeal and provide in the FEIS the information that Gerry presented regarding the known adverse impacts to aquatic life. (Note: If the City intends to use this bioagent,can it make the claim drat there are no adverse impacts to aquatic life?) Re Section 4.1.3 on page 4-3, " A primary goal of the ESGRWP is to design project improvements for multiple benefit Where possible,the ESGRWP will incorporate features to reduce mosquito breeding in the Panther Creek Wetland to lessen the need for the application of 3-34 JSA 09/97e COMMENTS AND RESPONSES insecticides." Does this paragraph refer to altering the wetland by creating islands and pools, water depth, or other changes to the topography of the wetland? Clearly mosquitoes are a nuisance insect for humans. However,as mentioned earlier, they play an important role in our ecosystem, providing an essential food source for the insectivores -- including birds, bats,fish, frogs, and amphibians --which in turn, provide food for those animals that prey on the insectivores.We are well aware that mosquitoes do not contribute to the personal comfort of a community. At the same time,if the integrity of the ecosystem is to be maintained,it is important that the mosquito population not be impacted in any way that has an adverse impact on the animals and fish that dcpcnd on them for food. To address the overabundant mosquito population, a balance between the insects and insectivores needs to be established. A healthy ecosystem is evident in a balance between prey and predator. An overpopulation of mosquitoes is evidence that there is an imbalance.The most effective long-term environmentally sound solution that will achieve a balance (and thus reduce the mosquito population) is to promote populations of native fish and wildlife that depend on the insects for their diets. To simply address the mosquito overpopulation by throwing bioagents or other chemicals at the problem is being shortsighted. Is the City of Renton willing to commit to the long-term environmental health of Renton's ecosystem (which means that a watcrbody will be rich in abundance and variety of wildlife), including but not limited to Panther Creek? If so, then the approach should be obvious. It is also not expensive nor does it require much if any maintenance(the regular application of chemicals,etc. would require an ongoing commitment). Is the City willing to encourage the nesting of all locally occurring swallow species and the colonizing of bats,both of which depend on mosquitoes and other insects for their diets, by installing swallow nest boxes and bat boxes to encourage these species to populate and feed at the mosquito infested areas,such as Panther Creek?Also, is the City willing to promote the tree frog population (not the invasive bullfrog population,if at all possible),and stock the creek with native fish that depend on mosquitoes as part of their diet?The City should work with WDW and other appropriate agencies to determine effective natural,nontoxic,nonchcmical solutions that satisfy the needs of the community as well as support the existing ecosystem. A balance of mosquitoes to their predators should be pursued, meaning that the City needs to increase the number of insectivores to carrying capacity. Does the City of Renton agree that it is possible for the program to be successful if only natural predators are used? If so, is the City willing to commit to a program of encouraging natural predators to achieve the balance they seek, and not use bioagents or other artificial or chemical means?What do studies show with regard to the success of the use of natural predators in maintaining a balance within an ecosystem without the use of chemicals, bioagents, and other insecticides?Is the City willing to commit to a program of natural predation to address the mosquito abatement issue? Incidentally, there likely isn't a legitimate reason not to use the naturally occurring insectivores to successfully achieve the desired results. Also, are there studies comparing the effects of use of wetlands by wildlife other than the insectivores when bioagents or other chemical insect controls are used, with the use of wetlands by wildlife where the insect population is healthy and thriving?If so,please include them in the FEIS, along with a reference to your stated goal number 5 on page 24 of the DEIS. If the answer to any of the above yes/no questions in item#6 is no,explain why not. General concerns regarding the DEIS 09/97e JSA 3-35 CHAPTER 3 7. The 2%landscape sec-aside program that currently is in place, requiring that vegetation be planted specifically, for wildlife habitat, is proposed to be eliminated. This will result in further reduction of habitat and will have a significant environmental impact. Additionally, this was pan of a larger protective package that was approved under SEPA,and removing it undermines the original purpose and intent for which it was deemed necessary.Why would you consider eliminating a program that was (a) Approved under SEPA, and (b) Provides even this minimal level of effort to provide some support to wildlife? 6 We urge you to keep this program ' lace.The elimination of this program quietly eliminates something that underwent scrutiny of the SEPA review process. If you can justify removing this sec-aside program,what replacement is being provided in lieu of its removal that provides equal or greater protection of habitat and open space? How can you abandon an environmental program that has been approved by the SEPA process -- especially when that particular portion was part of a large.protective package that was under SEPA review at the same time? 8. Regarding wetlands mitigation banldn;,has this been proven to be effective?Please provide at least four examples of places where this approach has bcon used successfully and explain why they were successful. Also, identify mitigation sites that will be used by Renton's mitigation bank. Jr7 The highest success rates with regard to mitigation banking involve the integral participation of private foundations,such as the Seattle-King County Land Conservancy. Is the City of Renton going to require the full and active participation of a private land trust or land conservancy, which includes aacepting their recommendations,in order to help give this program every chance of success'? If not, why not? 9. It is proposed that the County drop the water level in the P1 Pond/forebay to 0 level from its current minimum of 2 feet.'Ibis will have a severe and significant adverse environmental impact on the Black River site,affecting the entire ecosystem, from fish and animals, to amphibians, to vegetation, to insects. Additionally, the draw-down will cause even more sihadon than already occurs without the draw-down. There is already a significant problem with sediment accumulating at the bottom of P1 Pond (forebay). We strongly urge you to retain the current water levels,which means retaining the minimum 2 foot level during the summer months (and throughout the rest of the ycar). What is the l� operating plan for the Pump Station? It should have been spelled out in this DEIS. If there is no operating plan, then one needs to be established 1l&to embarking on this project. When responding to this question, please keep in mind all items related to this issue in this letter.This is another example of a direct conflict with the stated goals of this DEIS: Section 2.3,Goal number 5, Improve Riparian Habitat. Attain and maintain diverse and self-sustaining habitats that support aquatic and terrestrial species by improving fish rearing habitat...,reducing erosive flows... protecting and enhancing wetlands." I want to emphasize and clarify the seriousness of this proposed action in hopes that this issue of drawing down the water level in the Black River heron colony PI Pond/forebay will finally be put to rest with the result being that the forcbay will contain a minimum of 2 feet of water throughout the year. Significant and highly adverse impacts to the entire ecosystem at this location&W result in the drawing down of the water level during the summer(or any other time of year) to 0--or any level that alters the existing ecosystem. Be aware that these impacts WILL occur. To:imply or say that these impacts may occur is absolutely false and misleading. 3-36 JSA 09/97e COMMENTS AND RESPONSES I will provide a straightforward and accurate example of what the impacts will be on the great blue heron population,which, as you are well aware, live and breed at this site,if the water level is drawn down to any level that affects the overall ecosystem at the site--I am=calling about a 0 level here,just a reduction from its current minimum 2 foot level.Fish and frogs make up close to 100% of the great blue herons' diet. The adult herons depend on the currently abundant supply of fish and frogs for food(last September I watched as an adult great blue heron caught and ate eight to ten fish within 1-1/2 minutes, and he had been very successfully hunting for quite some time before I started counting the number of fish he caught within a limited period of time), and in addition, this is what they feed their young,which they raise here at the Black River pond/forebay.There are two fundamental reasons the herons choose the Black River site: a. Safety and Protection:The surrounding water provides safety and protection from many potential predators and other disturbances (such as people who would otherwise be inclined to get too close to their nesting area), and b. Readily Available Food:The site provides a convenient and plentiful source of fish and frogs,which, as I stated, make up close to 100% of their diet. Herons depend on all the thin s that a lake or pond provide in the way of food and protection. The water source cannot simpy be nearby.It must be in the exact place where they nest and raise their young.The proximity and volume of water, along with all the living things that the water contains and attracts, are fundamental and crucial to the herons choosing this site to live, breed,and rear their young. A reduction of the water level to 0 will fully eliminate as a nesting ground all of those species that depend on the water for food or shelter or both-- this includes the great blue herons and green herons,as well as the year-around populations of fish, also frogs,snakes, amphibians,waterfowl, and all those animals that prey on these animals and aquatic life,such as hawks, 18 bald eagles,and coyotes. These species can depend on the site only when there is an dependable and adequate year-around supply of water that supports their basic survival needs. Let's not kid ourselves by attempting to soft pedal this part of the plan. This will destroy the site as a great blue heron breeding ground, eliminating one of the most important places in the Puget Sound region for their continued success. And although we shine the light on the herons and their young and their continued glorious and healthy presence at this site,the fact is this is a remarkably rich ecosystem that supports an extraordinary variety of wildlife. This refuge is Renton's shining star, and to destroy it, or risk even a moderate reduction in the rich complexity of life that it supports will be a tremendous loss for those of us who love the site, as well as the animals who depend on it for their survival. As I mentioned, if the water is drawn down as proposed, it will fully eliminate the fish population that depends on this pond/forcbay (390 adult Coho salmon used the fish ladder last year, according to WDW-- which does not include the significant numbers of fish that were eaten by the herons.WDW may also have numbers for cutthroat trout, which have also used the waterway in years past.);severely alter the vegetation of the site; and eliminate the habitat for nesting waterfowl and other birds that depend on the water,such as green herons and plover.This action is in direct conflict to the City's general and stated policies of protecting the heron's habitat at this site, and the goals stated in this DEIS. What is the logic of this proposed action? Do you really believe that it is worth the price?Are you willing to severely jeopardize the environmental integrity of this site--not)'ust risk imposing significant and adverse impacts on all wildlife living at the site,but actually destroy it?And are you willing to risk creating yet another mosquito bog as you disrupt the natural and health ecos stem at the Black River site (which incidentally,has taken years to mature and develop?(Related information and questions in items 10 and 11,below.)If the answer to any of the above questions in item#9 is yes, explain why. 09/97e JSA 3-37 CHAPTER 3 10. Related to item#9, above, the Black River site is not described in any way except to view it as a floodwater storage area.The entire Black River wetland area needs to be defined fully, including but not limited to its terrain and ecosystem, which includes (but is not limited to) wildlife and fish populations, vegetation, and the breeding and spawning seasons of the 19 wildlife and fish based on such sources of information as WDW,Rainier Audubon Society, Seattle Audubon Society, Friends of Black River, and Citizens for Renton Wildlands Preservation, among others who are familiar with the environmental aspects of this specific site. 11. Related to item#9, above, the City, in collaboration with other agencies and several citizen's groups,has committed tremendous time and millions of dollars to preserving the Black River heron colony,which includes the Black River,P1 Pond/Forebay, and the associated section of Springbrook Creels. The City has been working to preserve this highly environmentally sensitive site since the mid-1980s.We urge you to continue your long-term commitment to the site and not compromise its existing environmental integrity in any way, whether the subject is 2� drawing down the water level of the P1 forebay to any level below a minimurn of 2 feet, conducting work(luring the breeding and nesting seasons for the wildlife that live at the site (which is addressed in item#14,below),or any other action that could potentially have an adverse impact on the site. Is the City willing to agree to do everything it can to maintain or improve the existing environmental integrity of the Black River site.If not,why not?If yes, how will the City accomplish this? 12. What is the current capacity of the PI forebay?Isn't it reasonable to consider using the abutting 1 wetlands in the Black River site for additional flood storage? Shouldn't this be included in the 2 plan before commencing with the project? Specifically,how will using these abutting wetlands impact the overall plan? 13. Schedule of construction and other work relative to environmental impacts:The timing of the construction and impacts of all aspects of the project must have an absolute minimum impact, if any at all. on the nesting and breeding cycles of the birds and other wildlife, as well as the spawning cycles of the fish throughout the entire area affected by the project. The herons begin their breeding cycle January 1 and the cycle lasts until August 1,when the newly fledged herons leave the site in search of nearby feeding grounds.The timing is slightly later than it was in the late 1980s and early 1990s as a result of the bald eagle predation, which has forced the herons to lay more than one clutch of eggs to replace eggs destroyed by the eagles.This 2' impacts their rearing and fledging(the time when the young herons leave their nest for the fist time) schedule by usually up to three weeks.The August 1 date provides no forgiveness on the part of the heron's nesting schedule if they are delayed by more than two weeks (which has happened in the past). Perform all work and construction-related activities after between August 1 and January 1. We are aware that the fish spawning occurs between the August 1 - January 1 window. Is the City of Renton willing to do what it takes to ensure that construction and other work has little to no impact on the breeding herons and spawning fish?If so, what does the City propose in terms of timing and methods of constuction and work(needs to be approved by WDW, EPA, Army Corps...)? 14. Pump testing of tie Black River Pump Station: Describe the tests and anticipated environmental �L impacts of those tests,including but not limited to impacts to birds, other wildlife,fish, vegetation, and water quality. Sincerely, L Suzanne Krom cc:WDOE 3-38 JSA 09/97e COMMENTS AND RESPONSES Response to Citizens For Renton Wildlands Preservation 1. The City of Renton is the designated lead agency because the City initiated the proposal (i.e., the East Side Green River Watershed Project). Under SEPA rules (WAC 197-11-926), the agency that initiates the proposal (in this case the City of Renton) is considered the lead agency. The Washington Department of Ecology (DOE) was involved earlier in the project as the lead funding agency for the Black River Basin Water Quality Management Plan (City of Renton 1993). That plan was funded, in part, by DOE Centennial Clean Water Funds. This project was undertaken by the City of Renton because, as a municipality, the City is lead agency responsible for drainage and flood control in that part of the valley under study. Also, the other sponsors to the East Side Green River Revised Watershed Plan Agreement with the NRCS (Renton File No. CAG-80-009) formally designated Renton as the lead agency sponsor of the ESGRWP on June 7, 1983, at a meeting of the Green River Basin Executive Committee. During the course of study, the City did coordinate with King County, the City of Kent, the DOE, and other agencies regarding the project. Please see Section 4 of the Final Plan for a description of the plans of others that influenced this project. No letter of comment has been received from DOE on this project. 2. The proposed channel widening would involve deepening only the SW 23rd Street channel (Alternative 23ST3) from the East Valley Road to Springbrook Creek. Springbrook Creek is proposed to be widened, not deepened,through the use of high flow benches. The bottom elevation of the Springbrook Creek channel will remain the same as the current elevation, except for removal of sediments from the previously widened reaches (Alternative SC2-3 or SC3-3) and for minor changes associated with incorporating habitat structures within the existing low flow channel. An evaluation of the impacts to groundwater and mitigation measures for SW 23rd Street Alternative 3 (23ST3) was included in the Draft EIS in Section 4. Removal of sediments from the previously widened reaches is a maintenance action that restores the channel section to the originally constructed condition. The original channel was previously approved and permitted in accordance with local, state, and federal requirements. An example of the use of deepened (and wider) channels is lower Springbrook Creek downstream of SW 16th Street, including the floodwater storage pond. Lower Springbrook Creek downstream of SW 16th Street was widened and deepened and the floodwater storage pond was constructed between 1984 and 1995 by NRCS. Prior to construction, the floodwater storage pond was a narrow stream that connected to the Black River. Pre- and post-construction drawings of the previous projects are available at the City and NRCS offices for your review. 09/97e JSA 3-39 CHAPTER 3 Table 8-3 of the Draft Plan (Table 6-2 in the Draft EIS) presented modeled current and future water elevations (with the project constructed) in wetlands throughout the valley. Additional information on wetland hydrology is presented in Attachment B of Appendix A-2 (Volume II of the Draft Plan and EIS). The crest gage and groundwater monitoring data indicate that water elevations in wetlands vary considerably monthly and annually throughout the valley, and under a 2-year storm event, few wetlands are inundated by flows from Springbrook Creek. The impacts to groundwater and wetlands were presented in Chapters 4 and 6 of the Draft EIS. 3. The impacts to groundwater, wetlands and terrestrial and aquatic resources were analyzed in Chapters 4, 6 and 7 respectively of the Draft EIS. 4. The Wetland Mitigation Bank and Wetland Hydraulic Modification Alternatives proposed as part of the Plan are for wetland systems that have been impacted in the past by human activities. Many years ago, a berm was constructed across Wetlands W-12a and W-12b, effectively modifying the hydrology of that wetland. The proposal to enlarge the culvert between the wetlands will allow for a more natural hydrologic connection between the wetlands,thereby increasing flood storage capacity and improving habitat conditions. Wetland 32 was filled in the past and excavating the fill will restore the functions of that wetland to provide flood storage and to support wetland vegetation and wildlife use. Similarly, proposed enhancements to Wetland 7N would include providing additional flood storage and flow attenuation. 5. Please see Response No. 2 above. Alternatives other than deepened channels were considered, such as the use of high flow benches for widening of Springbrook Creek. See also Chapter 4 of the Draft EIS for more information on the effect of the project on groundwater. 6. An analysis of impacts on water quality and those associated with hazardous material is presented in Chapter 5 and 8, respectively, in the Draft EIS. Mitigation measures to reduce impacts are presented in Sections 5.4 (page 5-13) and 8.4 (page 8-4) of the Draft EIS. 7. Only Alternative 23ST3 included a proposal for a deepened SW 23rd Street channel (please see Response No. 2 above). The Draft Plan and EIS, including the Volume 2 appendices, present the technical analysis associated with the 23ST3 deepening project. The hydrologic and hydraulic modeling of current and future conditions was the basis for determining the impacts of the various project alternatives, including 23ST3. No additional studies are proposed for the Final EIS. 8. See Response to Comment No. 1 above. During the course of study, the City and the consultant team coordinated with the adjoining jurisdictions regarding flows and runoff contributions that enter the City of Renton's portion of the valley. Projects such as the ESGRWP are the responsibilities of local jurisdictions and not the DOE. The DOE has been made aware of this project from the outset. In addition to being 3-40 JSA 09/97e COMMENTS AND RESPONSES a part of the Black River Water Quality Management Plan, scoping information and the Draft EIS were submitted to DOE. 9. The construction of larger pipes in streets is a component of alternatives presented in the Plan and EIS. Section 8.3.2 of the Plan describes improvements to the SW 34th Street system, and Section 8.3.5 of the Plan describes pipe system improvements at SW 43rd Street, East Valley Road, and SW 19th Street at the mouth of Rolling Hills Creek. While enlargement of existing pipes at these locations will reduce localized flood problems, flood elevations in the channels that receive the flow from the pipe systems must also be reduced to achieve the desired level of flood protection. Raising the elevations of streets is not a feasible alternative. As can be seen by the flooding pictures in the Plan (Figure 6-613), flooding problems are not limited to streets. Surrounding existing commercial and industrial developed properties are also affected. Flood control could only be achieved by raising the surface elevations of many existing developed properties in the entire valley. 10. Flooding in already developed areas of the valley is a problem under current conditions and land uses. The flooding will worsen as development in the valley and other areas of the watershed continues. Therefore, the Plan addresses these existing flooding problems and seeks to prevent future flooding from occurring as development in the watershed continues. It is not expected that the Plan will encourage development in the low-lying areas that currently provide a significant volume of floodplain storage in the valley. Many of these low-lying areas are defined as wetland in the City's wetlands inventory and are therefore protected from development under current regulations. The City also requires development projects to excavate an equivalent volume of compensatory storage to replace any floodplain storage loss that may result from a development. Furthermore, many of the significant low-lying areas are owned by the City because of the floodplain storage and other valuable functions these areas provide. Existing and future developments within Renton are required to pay monthly fees for surface water utility services that the City provides. These fees and other funding sources that will be used to implement the ESGRWP are described in Chapter 9 of the Plan. 11. An update to the City's wetland inventory was prepared as a part of this Plan and EIS. The wetland inventory update is presented in the Volume II Appendices (Attachment A to Appendix A-2 Wetlands) of the Draft Plan and EIS. The update included all of the Black River (ESGRW) basin area within Renton and its sphere of influence. The inventoried wetlands are based on aerial photo interpretation and site-specific delineations and boundary surveys that were conducted for specific projects. As is the established procedure for all projects involving the Corps of Engineers, the boundaries of the wetlands impacted by the project will be verified by the Corps during the 404 permitting process. 09/97e JSA 3-41 CHAPTER 3 Although it has developed the characteristics of a wetland since it was constructed in 1984, the floodwater storage pond south of W-5 near the Black River Pump Station is not shown as a wetland on the City's inventory maps because it is a constructed floodwater storage facility. Some of the boundaries of Wetland W-5 and W-5b, as shown on the wetland inventory map, slightly overlap into the floodwater storage pond and would be adjusted if a site specific delineation was done. The approximate nature of the W-5 and W-5b boundaries does not affect the analysis of the impacts of the ESGRWP on these wetlands. These wetlands are in fact several feet higher than the water levels in the pond and therefore are unaffected by changes in water levels within the pond. 12. The comment that toxic material has settled and been capped throughout the entire stream system does not recognize the fact that the stream bed erosion and deposition is a natural process. Many stream areas will therefore not have accumulated and capped toxic material. However, because the City recognized that contaminated sediments have been found in some reaches of the system, the EIS scope included a evaluation for hazardous materials (also, see Black River Basin Water Quality Management Plan [1993] for additional water quality information). The evaluation was included in Chapter 8 of the Draft EIS. As indicated in the Draft EIS, sediments in Springbrook Creek will be sampled during the design phase as necessary. Contaminated sediments that exceed regulatory cleanup thresholds would be removed and disposed of in an approved manner. Sediments exceeding the dangerous waste criteria would be disposed of at a licensed disposal facility. If contaminated sediments are found, their removal would, over time, improve water quality in Springbrook Creek. Much of the disturbance to the existing channel bottom as a result of the proposed ESGRWP will occur during installation of instream habitat structures intended to benefit aquatic organisms. See also Response No. 4 to the Friends of the Black River letter of comment. 13. Hydrogeologic studies will be conducted during the design phase to determine the need for lining the SW 23rd Street channel with an impervious membrane. Membranes made of synthetic materials have been approved and used successfully as impervious barriers in many critically important applications, including preventing seepage from wastewater treatment facilities and landfills. Use of a clay liner was not proposed. 14. The purpose of the section in Chapter 4 of the Plan regarding mosquitoes was to evaluate the possibilities of modifying habitat in the Panther Creek Wetland to help reduce mosquito populations and to ensure that the proposed project would not add to an existing problem. The City's current and future mosquito abatement program, including the use of the larvicide Altosid, is not an element of this EIS. The use of larvacide in the Panther Creek Wetland was abandoned after the 1993 abatement program primarily because of its high cost and questionable effectiveness. Applying 3-42 JSA 09/97e COMMENTS AND RESPONSES chemicals to water is also contrary to City policy to improve and protect the quality of the City's surface water and wetlands. As stated in the Draft Plan, a goal of the ESGRWP is to incorporate features to reduce mosquito breeding in the Panther Creek Wetland. The construction of a control structure (Alternative 23ST2-1 or 23ST3-1) on the proposed outlet from the Panther Creek Wetland will allow seasonal or intermittent adjustment of that wetland's water levels for purposes such as control of mosquito larvae or invasive vegetation. However, no such adjustment scheme is proposed in this EIS (see Plan Section 8.3.3 discussion for 23ST2, Element 1). Instead, the necessary permits and approvals for making such adjustments to the control structure would need to be obtained through a future, separate project proposal. Mosquitoes do play an important role as a prey base in the food chain of the birds, amphibians, fish and mammals mentioned in the comment letter. However, the presence of large numbers of mosquitoes is not an indication that there is an imbalance between prey and predators (in this case insectivorous birds and bats). Mosquitoes occur in natural ecosystems (e.g., Alaska) in numbers that far exceed predatory consumption. There are many historical accounts of huge populations of mosquitoes encountered by early explorers. 15. The use of measures to encourage natural predators (amphibians, birds, mammals, fish) in the valley wetlands is an excellent idea. The development of improved fish habitat (instream structures, improved riparian habitat) and the improvements to the Panther Creek Wetland and other wetlands in the valley will ultimately provide additional habitat for wildlife populations. As a part of this project, the City will promote and encourage the development of bird nesting boxes and bat boxes, and work with the Washington Department of Fish and Wildlife (WDFW) during the design phase to ensure that the project design provides habitat for insectivorous species. As a separate action from this proposal, the City worked with the Rainier Audubon Society to distribute, in April and early May of 1997, approximately 160 violet-green swallow nest boxes to residents in the vicinity of the City's mosquito abatement program in Talbot Hill. 16. The City is not trying to quietly remove the 2% landscaping requirement. Section 4.2.6 of the Draft and Final Plan provides an explanation of the background of the requirement and the justification for its removal. A future ordinance change will be necessary to eliminate the requirement from the Renton City Code. However, it should be noted that the required habitat is being provided more effectively by the habitat being created along the existing channels rather than the small plots created by individual projects. 17. Wetland mitigation banking has been successfully implemented in a number of states throughout the U.S., including Oregon. There is currently one active bank in 09/97e JSA 3-43 CHAPTER 3 Washington for Paine Field in Everett. The City of Renton has proposed only one wetland mitigation bank site in the ESGRWP Plan and EIS which is Wetland 32 adjacent to the west bank of Springbrook Creek between approximately SW 34th Street and SW 40th Street. A detailed mitigation banking program, including the approach to managing and operating the bank, is being prepared by the City of Renton (see also the discussion in Section 1.5 of the ESGRWP Plan). 18. Section 8.3.1 under Alternative SC2 Element 3 notes that King County has been operating the level of the pond at the pump plant between elevation 2 and 3 ft year- round, rather than operating a lower summer/fall water nominal elevation of 0.0 ft as defined in the pump station's operating plan. As a result, sediments from Springbrook Creek have accumulated where Springbrook Creek enters the pond rather than in the forebay immediately upstream of the pump station as designed. The forebay was designed to collect a majority of the sediments at one location, which would facilitate maintenance of the regional facility (i.e., periodic dredging from one location of the pond rather than throughout the pond). As stated in the Plan, the City does not intend for pond levels to be lowered for the proposed sediment removal activity upstream of the pond on a frequent basis or at a time that would have a significant impact on the fish and wildlife using the pond and surrounding area. We recognize the concerns regarding the operation of the BRPS relative to the wildlife use of the pond and will work with the WDFW to establish an appropriate timing for the sediment removal construction window. Sediment removal from the pond is not within the scope of this ESGRWP Plan and EIS, but will need to be addressed within the context of a comprehensive plan for the pump station and the floodwater storage pond. The City of Renton intends under a separate,future project to coordinate with King County,NRCS, WDFW, and other interested parties to review and update the management/operating plan for the BRPS and floodwater storage pond. This plan will consider such factors as hydraulic requirements, future flows, seasonal variations in flows, wildlife use (including the great blue herons), sediment loading, existing vegetation, accumulated sediments and need for dredging and other periodic maintenance, fish use, and requirements of the Green River Basin Program and Interlocal Agreement. No specific timeframe or funding for the update has been established. The following responses are intended to clarify several issues raised in Comment No. 18: A. The draw-down of water levels will not cause even more siltation than already occurs. On the contrary, the higher water level decreases flow velocities and increases the residence time for water passing through the pond, affording more time for suspended material to settle out of the water column. B. The water level may be temporarily reduced at a time that will not have a significant impact to wildlife, including migratory fish and nesting herons. The 3-44 JSA 09/97e COMMENTS AND RESPONSES impact to wildlife nesting and rearing and salmonids can be avoided or minimized through use of a summer window established in coordination with the WDFW. An appropriately timed temporary water level reduction also would not negatively impact the vegetation of the site. C. Resident fish populations in the pond and channels in the vicinity upstream were found to be limited according to a comprehensive fisheries report by Harza in 1995. Such limited populations would not be sufficient to support the size of the heron colony found in the Black River Riparian Forest, indicating that the herons are not solely dependent upon the pond as a food source. Foraging herons generally range several miles in search of food. 19. Section 6.8.3 of the Plan includes a discussion of the Black River Wetland area. Table 8-2 of the ESGRWP Plan presents a summary of hydraulic modeling for the 2-year, 25-year and 100-year conveyance event water elevations upstream of the Black River Pump Station (BRPS). The significant storage volume available in the pond (more than 100 acre-feet) was accounted for in the modelling effort. Under current conditions, the peak elevation at the inlet to the floodwater storage pond is modeled at 4.0 ft (533 cfs) for a 2-year storm event. Under future conditions without the project (No Action), the modeled elevation is 4.2 ft (728 cfs), or 0.2 ft higher than current conditions. Under the 2-year future conditions storm event, inflow water elevation with the proposed project (as defined in Chapter 1 of this Final EIS) at the inlet to the pond is calculated to be 4.3 ft (764 cfs), or 0.1 ft higher than future conditions without the project (No Action). This increase of 0.1 ft elevation, which would occur primarily during the winter months, would not adversely affect the wetland and wildlife use of the pond. The increase in inflow to the pond under future conditions would result in a change in the frequency of pumping at the BRPS. The greater volume of water entering the pond would require more frequent pumping, pumping of a longer duration, and/or more pumps operating at one time. Table 8-3 has been revised in the Final Plan to include the floodwater storage pond area. The evaluations of the pond and surrounding area in the Final Plan and EIS are considered adequate to determine the impact of the alternatives being considered under the ESGRWP. As a part of the future update to the management/operating plan for the pump station and pond, the resources of the floodwater pond and surrounding area would be evaluated to the level of detail commensurate with potential impacts (see Response No. 18). It is important to note that the wetlands adjacent to the floodwater storage pond would not be inundated by overflows from Springbrook Creek even under the 100-year, future conditions, storage event (when the pump plant is required to shut down by high flows in the Green River) modeled at elevation 13.0 ft under the No Action alternative. 09/97c JSA 3-45 CHAPTER 3 20. Please see Responses No. 18 and 19. 21. Please see Response No. 19. 22. The construction of the ESGRWP will occur in phases over several years (please see Chapter 1 of this Final EIS for a description of the Preferred Alternative). The scheduling of work will be established by the WDFW through the Hydraulic Project Approval permit. No other time requirements are anticipated during construction. 23. The pump testing of the BRPS can only be conducted when the Green River downstream of the pump station is high (near elevation 14 ft). While the pump tests are not part of the proposal being evaluated in the ESGRWP, it is interesting to note that the temporary increase in water levels upstream of the pump station necessary to conduct the test is on the order of several feet less than what the water elevations would be if the pump station did not prevent Green River flows from flooding into Springbrook Creek. As with any project, it is important to conduct the pump tests so as to minimize any potential environmental impacts. 3-46 JSA 09/97e COMMENTS AND RESPONSES February 6, 1997 Development Services Division Planning/Building/Public Works Department ATTN: Mark R. Pywell, ACIP 200 Mill Ave. S. Renton WA 98055 RE: Comments on Draft Environmental Impact Statement for the East Side Green River Watershed Plan We the undersigned are responding to the East Side Green River Watershed Project DEIS and represent the following environmental organizations: Friends of the Black River, Rainier Audubon Society and Citizens For Renton Wildlands Preservation. We believe the following Alternatives are the best choices to maximize the effectiveness and use of wetlands in the watershed. However, we have several concerns and feel that they should be addressed in the final Plan. SPRINGBROOK CREEK ALTERNATIVE 3 (SC-3): This alternative would lead to an improved channel with increased vegetation and riparian habitat. However, this alternative has significant deficiencies: 1. The amount of sediment that would be deposited in the Black River Wetland (BRW) 1 would greatly degrade the already marginal quality of this wetland. 2. The drawdown of the water level in the Black River Wetland to allow for work in Springbrook Creek will leave NO habitat for the many waterfowl that use this wetland. The period from January I -August 1 is an important breeding time in the wetland. 3. Although not mentioned in the Plan or DEIS, the "Black River Pump Station Storage Pond" is a significant wildlife habitat and constitutes a wetland. Consideration of this 3 fact has not been incorporated in the Plan or the DEIS although we had provided comments at the scoping session and had submitted written comments. a. Dredging of Springbrook Creek north of SW Grady Way We are concerned with the City of Renton's plan to dredge the portion of Springbrook Creek that lies downstream of the SW Grady Way box culvert. This section of L�- Springbrook Creek contains some of the best wildlife habitat in the valley stretch of the creek. Islands have formed in the stream bed, creating prime wildlife habitat, and 09/97o JSA 3-47 CHAPTER 3 maturing red alders line the stream bank, protecting the stream from solar heating. Dredging will result in the loss of this prime wildlife habitat and the loss of a large number of the red alders that line the stream. The City of Renton acknowledges that dredging this section of Springbrook Creek will have little impact on reducing upstream flooding (ESGRWP, Plan and Environmental Impact Statement, Volume 1, Section 9.3). In addition, the Comprehensive Fisheries Assessment of Mill Creek Garrison Creek and Springbrook System (Harza, 1995) recommends that dredging in the low gradient portion of the Springbrook Creek watershed should be minimized in order to decrease turbidity and improve the fish 4 resource within the watershed. Considering the costs associated with dredging 800 feet of I stream channel (permit fees, staff time, consultant costs and construction costs), the damage that will be inflicted on valuable wildlife habitat, and that the benefit obtained from the dredging will be minimal, is it prudent for the City of Renton to dredge this portion of Springbrook Creek? In light of the issues raised above, we ask that the City of Renton remove from the ESGRWP Plan, the portion of the Plan that deals with the dredging of Springbrook Creek downstream of SW Grady Way. This will provide time for all interested parties to explore and develop options regarding the sediment buildup in this section of the creek. The City can then revisit this issue when it prepares a DEIS for the planned dredging of the Black River Pump Station Forebay, as appropriate. b. Sediment Control With sediment loading in Springbrook Creek an acknowledged problem, now and into the foreseeable future, should the City of Renton explore the option of constructing a sediment trap in the FEIS? Once constructed, regular maintenance of a sediment trap would have significantly less impact on wildlife habitat than periodic(10-15 year) dredging of the creek. In addition, regular maintenance of a sediment trap would be a cost efficient alternative to periodic dredging. One logical place to consider building a sediment trap is at the outlet of the SW Grady Way box culvert. A trap at this location would slow sediment deposition in that portion of the channel downstream of SW Grady Way that the City now proposes to dredge. If needed, an additional trap can be constricted at the SW 16th Street crossing. Would it not be prudent for the City of Renton to consider building a sediment trap in Springbrook Creek in order to minimize the need to dredge the creek every 10-15 years? 3-48 JSA 09/97° COMMENTS AND RESPONSES C. Scheduling of Work Every consideration should be given to tinting of the work in the watershed to times that (o will cause the least disruption to wildlife breeding activities. d. Penalties for Contractors In an effort to minimize impacts to fish and wildlife and to ensure compliance with the schedule, consider assessing penalties for contractors who do not comply with the schedule. Include this information in the Plan if appropriate. e. Box Culvert at Oakesdale Av. The Plan does not specifically commit to or state that the box culvert, at the Oakesdale Av., crossing will be placed at the lowest possible elevation. Placement at the lowest 8 possible elevation would allow for adult salmon passage during low water flow. The Plan should be modified to state that the box culvert will be placed at the lowest possible elevation. f. SW 16th to SW 23rd St. In order to maintain wildlife habitat, can the stream improvements for flood control in the stretch of Springbrook Creek from SW 16th to SW 23rd St. be achieved by working only on the east side of the stream, leaving the vegetation on the west side of the stream intact? 9 Doing this would reduce impact on the mature wildlife habitat that lines the stream and would maintain solar screening of the stream. Waiting ten years for newly planted habitat to mature will significantly reduce wildlife use of this area. Lack of shading of the stream will cause increases in water temperature and contribute to water quality problems. g. Drawdown of Black River Wetland The period from January I - August I is an important breeding time in the wetland. Is it possible to avoid drawdown of the wetland during this period? What reasonable alternatives are available that preclude the necessity to drawdown the wetland. h. Significance of Black River Wetland The City of Renton and various citizen organizations have worked hard to preserve this highly sensitive area. We hope that the City continues its long term commitment to maintaining the environmental integrity of this site. The FEIS needs to address how the project will impact the wetland and its wildlife, and how these impacts will be addressed. 09/97e JSA 3-49 CHAPTER 3 PANTHER CREEK ALTERNATIVE 2 (PC2): We have concern with the use of insecticides in the wetlands in this area. There are many ways of natural control for mosquitoes, including using fish, birds and bats. Use of insecticides may have non-target effects. An insecticide mentioned in the Plan, Alsid, is methoprene and is being investigated as the agent causing the explosion of frog deformities in the Midwest and other areas. See attached article. An investigation of the ,{ amphibian populations in the areas where this insecticide has been used should be 1 thoroughly investigated. Also, research into biocontrols for mosquito such as bats, fish, birds, etc. should be incorporated in the plan. We discourage the use of all insecticides and other toxins. We encourage the continued collaboration between the City of Renton and Rainier Audubon Society in promoting the violet-green swallow nest box program. Scheduling of construction activity in this area should be scheduled so as to not impact wildlife breeding and rearing activity. This time period may not be the same as that for scheduling of construction activity in streams. SW 23RD ST. ALTERNATIVE 3 (23ST3): Please request an exception from NRCS to change the channel design criteria. This will 1,3 reduce the impacts of this alternative on adjacent wetlands and may result in reduced construction costs. WETLAND ALTERNATIVES: Wetland 12 Alternative 2 (W12-2) Wetland 32 Alternative 2 (W32-2) Wetland 7N Alternative 2 (W7N-2) We recognize that Wetlands 12A, 12B, and 54B are heavily used by nesting waterfowl. In fact, they may be some of the most heavily used wetlands in the watershed. Scheduling of construction activity in all wetlands should be scheduled so as to not impact wildlife breeding and rearing activity. The schedule will not be the same as that for scheduling of construction activity in streams. PIPESYSTEM IMPROVEMENTS ALTERNATIVE 2 (PS2): Reduced flooding of streets and property may result in improved water quality. 3-50 JSA 09/97e COMMENTS AND RESPONSES GENERAL COMMENTS: Invasive Species Disruption of riparian habitat during construction may cause an increase in invasive species. Sites newly planted with native species are vulnerable to takeover by invasive 16 species. Programs for control of invasive species should be addressed and should include long-term plans for the control of invasive species on newly planted sites. The controls should be non-chemical. How does the City plan to control invasive species? Does this plan include control over the long term, and if so, how long? Maintenance of Project How does the City plan to maintain the project once it is completed? What effect will the ( 1 maintenance program have on the wildlife? Scheduling of Work We request that construction be scheduled to minimize impacts to fish and wildlife. How 8 does the City propose to schedule construction in order to minimize impacts to fish and wildlife? Contaminated Sediments Results of sediment and water quality testing for the Black River Basin Water Quality Management Plan showed considerable contamination with heavy metals, including cadmium, zinc, lead, and other metals including copper, and organic chemicals and hydrocarbons. In section 8.2 it states that sediment samples surpass DOE sediment 19 guidelines for some of these contaminants and are high enough to be toxic to aquatic 1 organisms. Several of the alternatives will involve disruption of sediments and increase in contaminated sediments moving downstream. We are concerned about toxic sediment being redistributed throughout the waterway. Ultimately this will impact the BRW which already is highly contaminated. How does the City propose to minimize these impacts? Impacts To Wildlife Because of the importance of this watershed for wildlife and the need to maintain urban n 0 wildlife, we request that the City perform an assessment of the effects of this project on L wildlife. How does the City propose to minimize impacts to wildlife? Inwater Excavation We oppose the use of inwater excavation methods because of the significant negative impacts that increased sediment loading will have on downstream wildlife. Stream flows 2 should be temporarily bypassed around in-stream construction to prevent increased sediment loading of downstream waters. 09/97e JSA 3-51 CHAPTER 3 Thank you for the opportunity to comment on the DEIS. Tom Malphrus Friends of the Black River 231 1/2 Garden Ave.N. Renton WA 98055 Phone: 277-8219 Trudy Thomas Friends of the Black River 4600 51 st Av. S. Seattle WA 98118 Jerry Holmes Friends of the Black River 408 Index PI NE Renton WA 98056 Ted Mallory Friends of the Black River 7524 S. 135th St. Seattle WA 98178 Suzanne(Susan)Krom Citizens for Renton Wildlands Preservation 4715 1/2 -36th Av. SW Seattle WA 98126 Phone/fax: 933-0222 e-mail: szkrom@aol.com Jim Flynn Rainier Audubon Society 462 Lind NW Renton WA 48055 3-52 JSA 09/97c COMMENTS AND RESPONSES Fro Deformities grow where one should bc.In sonic cas- es,parasites cairn also lead to the ahscncc ncc of a limb.Increased numbers of parasites are probably coming from increases in Pose A M sue snail populations,which act as a host for y ry parasites,he says. But Michael J. Lannoo of Ball State University in Muncie,Ind.,says the range Scrious deformities in frogs have 1750, "it's just not normal to see such of limb deformities seen in the Minne- been reported in 56 out of 87 high percentages of deformed animals," sota frogs is beyond that reported for counties in Minnesota. They also says Tictge. David M. Iloppe,a licrpetol- parasites. have been found in Wisconsin, South ogist from the University of Minnesota, Martin OUellct, a veterinarian and Dakota, Vermont,Japan, and the Cana- Morris, who along with another wildlife graduate student at McGill University's dian provinces of Ontario and Quebec. biologist has been sampling frogs in Min- Redpath Museum in Montreal,thinks ag- So far, deformities have been seen in nesota for the past 20 years, says it ricultural chemicals could be the cause. six frog species and appear to be more wasn't until 1994 that they found a sig- In studies in Quebec, he says, he found common in those that spend more time nificant number of deformities. that in ponds contaminated with pesti- in water. Tliere are two layers of concern about tides, about 12% of frogs have dcfornmi- In late September, the Environmental frog deformities, says Tictge. "If it is ties compared with only 1 or 2% in Protection Agency held a meeting of fed- demonstrated to have a cause that would ponds in relatively pristine areas. oral,state,and Canadian officials and sci- pose a risk to Human Health, then obvi- Lannon also speculates that the cause entists to discuss possible causes and ously, it's going to create more concern must be sonic kind of chemical contanii- begin design of a research program to and attention," he says. Even "if it's not nation. He points to methoprcnc as a address the problem. The attendees de- a health issue,we should not ignore it," possible candidate. Methoprene, a syn- cided that parasites or some kind of he adds, pointing out that frogs arc an thetic analog of a natural insect juvenile chemical contamination is the most like- important part of ecosystems and frog hormone, came into widespread use in ly cause,says Joseph E.Tictge,a research populations with high levels of deformi- the mid-1980s on ponds and wetlands to biologist at EPA's Midcontinent Ecology ties will likely decline over time. keep juvenile mosquitoes from maturing, Division, Duluth, Minn., who organized Genetic causes of the deformities have and in dogs and cats to control (Jets. It the meeting. been more or less ruled out.Debra L Carl- does not have any known adverse effects The deformities, which usually occur son of Augustana College in South Dakota on mammals. in the frogs' Hindquarters, include extra has been analyzing the chromosomes in The structure of methoprcnc is very legs,missing legs,misshapen legs,and legs tissues of deformed frogs and so far has similar to that of retinoic acid. "If rctino- sticking out from the body at odd places. found no genetic mutations that correlate is acid is injected with a micropipet into Some frogs also have a missing eye or an with deformities.This means that the de- the limbs of developing frogs in the labo- eye in an unusual place such as the back velopmental abnormalities most have their story,it produces a majority of the linih of the head.Surveys this spring found the origin in the egg or tadpole stage. deformities we're seeing in nature," Lin- percentage of deformed frogs in many Stanley K.Sessions,a professor of vet- noo says. "But it has not been shown Minnesota ponds ranging from a low of erinary medicine at Hattwick College, that you can repeat the rctinoic acid ex- 10%to a high of 95%.The surveyed ponds Oneonta, N.Y., believes the problem is periment with methoprene and obtain are located in both agricultural regions and parasites. In a study on frog deformities the same results,nor has it been shown fairly pristine vacation areas. in Northem California, he found that that methoprene has been applied to the While isolated occurrences of de- cysts form around parasites after they en- wetlands where the frog deformities are formed frogs have been observed since ter a tadpole and cause multiple legs to showing up." Methoprene caused no problems when tested on frogs in the lab, says John 11. Hopley, toxicologist at Sandoz Agro, Des Plaines,Ill.,which is one of two manufac- a tuners of the chemical.As is common U.S. practice, these tests employed an African o species in which 30%of the DNA diflers s from that in U.S. species. However, S:ui- a doz is concerned,Hopley says,and is"fol- '„ lowing up on a big study done in Wiscon- sin,"which looked at the effects of metho- prene on many different species. Obviously,much work remains to be done before the frog mystery is solved. Frogs have not yet been examined for parasites, nor have frogs or the spring pond water where they spawn been ana- lyzed for chemical contaminants. Frog found In Minnesota pond has extra limbs. Bette Hilenman 24 NOVEMBER 18,19%C&EN 09/97e JSA 3-53 CHAPTER 3 This page left blank intentionally. 3-54 JSA 09/97c COMMENTS AND RESPONSES Response to Comments from Friends of the Black River, Rainier Audubon Society, and Citizens For Renton Wildlands Preservation 1. The amount of sediment loading to the Black River Wetland is actually expected to decrease as a result of the ESGRWP because flow velocities that cause erosion would be reduced. Areas of the creek that are experiencing significant erosion, such as the reach from SW 16th Street to SW 23rd Street, would also be stabilized. There is potential for erosion of soils exposed during construction. However, Best Management Practices (BMPs) for erosion and sedimentation control will be used to minimize the impact of erosion and sedimentation during construction. Other mitigation measures for construction were set forth in Section 5.4 of the Draft EIS. The final mitigation measures will be defined by the City's Environmental Review Committee in the Mitigation Document. 2. The temporary lowering of water levels is only needed for removal of sediment from the previously widened reaches of Springbrook Creek and potentially for a small segment of the proposed widened channel for a short distance just upstream of SW 16th Street(approximately 100 ft)where the channel would transition from a low flood flow shelf at the SW 16th Street bridge to the proposed high flow benches. Lowering of the water levels at the pump station is not needed for other project elements. The drawdown of the water level will not completely eliminate habitat for waterfowl that use the wetland. See also Response No. 18 to Citizens for Renton Wildlands Preservation. 3. The fact that the Black River Wetland provides valuable wildlife habitat was acknowledged in Section 6.8.3 of the Draft Plan. More discussion on the potential impact of the ESGRWP on the Black River Wetland is provided in Section 2.3 of this Final EIS and in Responses No. 11, 18, and 19 to Citizens for Renton Wildlands Preservation. 4. The sediment removal element is in partial fulfillment of the City's agreement with the ESGRWP federal sponsor, the NRCS, for operation and maintenance of the previously constructed channels. This action must remain a part of the ESGRWP because of the City's obligation under the terms of the NRCS agreements and the need to maintain NRCS financial support. However,the sediment removal continues to be a low priority for the City at this time as acknowledged in Section 9.3 of the Plan. The description of the sediment removal action in the Draft Plan and EIS identified the action as an interim measure, prior to development of a comprehensive plan for the pump station's flood water storage pond and upstream reaches to SW 16th Street. However, based on the additional evaluations presented in other sections of this Final EIS, the description in the Final Plan has been revised to clarify 09/97e JSA 3-55 CHAPTER 3 that the sediment removal action is in fact separate and independent of the planned comprehensive plan in terms of its scope and environmental impact. Furthermore, the comprehensive plan is not considered a required mitigation measure for the proposed ESGRWP, but is instead a separate future planned project for which no time frame has yet been established (see also Response No. 18 to Citizens for Renton Wildlands Preservation). The primary difference between sediment in the previously construction channels and floodwater storage pond is the size of the material. The pump station is a dam to nearly all but the smallest material being transported by the creek. Larger materials (gravels, sands) that tend to settle quickly out of the water column comprise most of the sediment in the previously constructed channels, while the finer material is transported further downstream to the floodwater storage pond. With and without the sediment removal action, the larger material will continue to settle out in the previously constructed channel regardless of what water level operating scheme may be identified as part of the future comprehensive plan. This is because the significant capacity in the channels downstream of SW 16th Street results in low velocities, allowing the larger materials to settle out before reaching the pond. The sediments in the channels are also likely significantly different from the sediments in the pond in terms of their quality. The large-grained sediments, which settle out in the channel, are not likely to contain contaminants in concentrations that would be deemed hazardous. As noted by Minton(in City of Renton Comprehensive Plan 1995), because contaminants tend to bind to the smaller particles. Thus, the potential for encountering contaminants in the fine sediments of the floodwater storage pond is much higher than in the upstream channels. Even though the potential for contamination is expected to be low, sediment quality sampling would be performed prior to removal of the sediments to determine the need for removal and disposal precautions and other requirements. The City shares the Friends' concerns regarding removal of the red alders along the bank of the stream downstream of SW Grady Way. That is why the Draft Plan and EIS noted that vegetation along the banks would be left undisturbed as much as possible (see Draft Plan page 8-9, 4th paragraph, and Draft EIS page 7-7, 1st paragraph). Vegetation along the banks that are disturbed would be revegetated. Removal of the sediment "islands" would return the channel to its originally constructed grade, the original channel having been previously approved and permitted in accordance with local, state, and federal requirements. The return of the channel to the originally constructed condition would not result in a significant impact to wildlife resources. Comment No. 4 includes a reference to a report by Harza that recommends that dredging be minimized in the low gradient portion of Springbrook Creek. The ESGRWP is consistent with this recommendation. Springbrook Creek is not dredged frequently(as disclosed in the ESGRWP EIS) under the proposed sediment removal action(Section 8.3.1 of the Plan); accumulated sediments in the channel downstream 3-56 JSA 09/97e COMMENTS AND RESPONSES of SW Grady Way that was constructed in 1987 have yet to be removed. The lack of sediment removal activity is true of other areas of the Springbrook Creek channel within Renton. 5. Infrequent sediment removal may be viewed by some as causing less environmental impact than frequent, regular maintenance of a sediment trap. Regular maintenance of a sediment trap may also not be as cost effective because of the frequent mobilization and demobilization that would not be required for the infrequent sediment removal activity. The suggested locations for sediment traps do not appear to be feasible. The excavation of a trap at the outlet of the SW Grady Way box would potentially compromise the stability of the adjacent wingwalls. Also, a 108-inch-diameter King County (formerly Metro) sewer and a 20-inch-high pressure Puget Sound Energy (formerly Washington Natural Gas) natural gas crossing affect the ability to construct a trap in this location. The excavation of a trap at the SW 16th Street bridge crossing would also potentially compromise the stability of the adjacent concrete and gabion wingwalls. The depth of the trap would also be limited by the impervious membrane that was placed under the channel between SW 16th Street and SW Grady Way. The purpose of the membrane was to prevent migration of water from the channel into the adjacent Oakesdale Avenue SW underpass drainage system. The City will explore the construction and use of a sediment trap with the Washington Department of Fish and Wildlife (WDFW)when the City applies for the WDFW's Hydraulic Project Approval permit for the sediment removal activity. The use of a trap will also be considered during permitting of the proposed Springbrook Creek channel widening from SW 16th Street to SW 23rd Street. If necessary the City would amend the ESGRWP EIS to disclose the environmental impact associated with use of a trap. 6 Comment noted. 7. Comment noted. The bid and construction requirements will be defined during the design phase. 8. The box culvert at Oakesdale Avenue SW is planned to be three-sided and will therefore have a natural bottom, improving fish passage. 9. Comment noted. Please see Response to Comment No. 6 for the Washington Department of Fish and Wildlife. 10. See Response No. 18 to Citizens for Renton Wildlands Preservation. 11. See Response No. 3 above. 09/97e JSA 3-57 CHAPTER 3 12. Thank you for your comment and the article. See Response No. 14, first paragraph, to Citizens for Renton Wildlands Preservation. 13. Comment noted. See Response No. 10 to Washington Department of Fish and Wildlife. 14. Comment noted. 15. Comment noted. 16. Comment noted. Section 7.4 of the Draft EIS listed use of DOE guidelines as an optional approach to controlling invasive species. The specifics of the City's approach to handling invasive species will be developed during the design phase. The City will also coordinate with adjacent property owners on controlling invasive weeds (see Response No. 3 to The Boeing Company). 17. It is a goal of the ESGRWP to minimize maintenance needs (see Plan Section 2.3, Goal No. 4). This reduces maintenance program costs and minimizes disturbance to the environment (wildlife, etc.) of the area that would be affected by maintenance activities. Since Alternative SC3 was selected as the Preferred Alternative for Springbrook Creek, the maintenance requirements for mainstem Springbrook Creek will be minimal. Maintenance could include the removal of debris and vegetation that is presenting a restriction to flow (above that allowed for in the channel design) or is causing damage to the channel. Springbrook Creek Alternative SC3 will allow for habitat features (woody debris, etc.) in the channel and dense vegetation. Therefore, SC3 should have little need for such maintenance, but the potential need for infrequent maintenance of this type should be recognized as an attendant part of the project design. The need for sediment removal should also be recognized, particularly if a sediment trap requiring regular maintenance is included as a design feature. 18. See Responses No. 18 and 22 to Citizens for Renton Wildlands Preservation. 19. The proposed Springbrook Creek widening is designed to minimize disturbance of sediments through the use of high flow benches above the existing low flow channel. Much of the disturbance to the existing channel bottom as a result of the proposed ESGRWP will be from installation of instream habitat features intended to benefit aquatic organisms. Mitigation for potential sediment impacts was defined in Chapter 8 of the Draft EIS. See also Response No. 12 to Citizens for Renton Wildlands Preservation. 20. Please see Chapter 7 of the Draft EIS for an assessment of the ESGRWP impacts on wildlife and Sections 7.4.1 and 7.4.2 of the Draft EIS regarding mitigation measures to be implemented to minimize the impacts on wildlife. Additionally, please see Response No. 15 to Citizens for Renton Wildlands Preservation. 3-58 JSA 09/97e COMMENTS AND RESPONSES 21. Comment noted. As listed in Section 5.4.2 of the Draft EIS, inwater excavation would not be used unless (1) it cannot be avoided, (2) the potential for discharging sediment-laden water into the downstream system is minimal, and (3) inwater excavation is allowed by state and federal permits. 09/97o JSA 3-59 CHAPTER 3 This page left blank intentionally. 3-60 JSA 09/97e COMMENTS AND RESPONSES David Radabaugh P.O.Box 30684 Seattle, WA 98103 (206) 706-1323 February 7, 1997 Mr. Gregg Zimmerman FEB 1 City of Renton Planning/Building/Public Works Department - Renton Municipal Building 200 Mill Avenue South - Renton, WA 98055 RE: East Side Green River Watershed Project Draft Environmental Impact Statement Dear Mr. Zimmerman: The purpose of this letter is to provide comments on the East Side Green River Watershed Project Draft Environmental Impact Statement(DEIS). 100-Year Floodplain In reviewing the DEIS, it was not clear how much of the study area is located in the 100- year floodplain. It is reasonable to assume that location of the 100-year floodplain is �1 relevant to this study. This information is necessary to any sort of meaningful analysis of l this proposal. Some of the questions that follow from this include: 1. Does this proposal represent a policy commitment to floodplain development? ( 2 2. Are the legal requirements relating to floodplain development being met? I /1 3. How much will this proposal encourage development in floodplains? Alternatives The DEIS makes it clear future development in the stream basin is expected to increase flood flows. The DEIS makes reference to having new development follow existing drainage design rules. The implication is that existing drainage design rules are not 5 adequate to mitigate the drainage impacts of expected development. If this is the case, then an appropriate alternative would be to strengthen drainage design standards to fully mitigate drainage impacts of new development. This alternative will be useful in ascertaining to true costs of development in this area. 09/97C JSA 3-61 CHAPTER 3 Mr.Gregg Zimmerman February 7, 1997 Page 2 E=h The DEIS does not address sedimentation from new development in the basin. New development combined with the potential changes in channel characteristics, could raise a concern of serious sedimentation problems in portions of the basin with low energy stream characteristics. The DEIS must also make the impacts of channel maintenance clear. How much dredging or vegetation disturbance in anticipated to maintain the 17 project? Stream Channels The DEIS makes reference to"channel improvements." The DEIS should use more accurate language. If you mean"channel widening",then say so. For those areas where channel widening is proposed,the DEIS doesn't appear to discuss n low flow conditions. A wider channel will likely reduce water depth. The environmental y impacts of this must be fully disclosed. Thank you for the opportunity to comment on this DEIS. Please include me as a party of record for this proposal. Sincerely, avid Radabaugh 3-62 JSA 09/97e COMMENTS AND RESPONSES Response to Comments from David Radabaugh 1. The existing conditions section of Chapter 5 of the Draft EIS (page 5-1) refers to Chapters 6 and 7 of the Draft Plan and the 1996 Hydraulic Analysis Report by R.W. Beck for detailed information on surface water quantity conditions, such as the 100-year flood. Because 100-year flood conditions as modeled by the City are significantly different in much of the project area from that modeled by the Federal Emergency Management Agency (FEMA) in 1987, a map of the FEMA 100-year floodplain was not included in the Draft Plan and EIS. The City modeling results differ from FEMA primarily because several physical changes have been made to the drainage system which were not in place at the time of the FEMA analysis, the most significant of which is the increase in capacity of the Black River Pump Station. By bringing additional pumps online, the nominal installed capacity of the pump station was increased from the 875 cfs used in the 1987 FEMA analysis to 1917 cfs at the time of the City modeling. At the time of the FEMA work, the capacity of the pump station was less than the 100-year flow projections, but now the capacity exceeds the 100-year future conditions flow. Sections 4.1.9 and 7.3.2.1 of the Draft Plan specifically discuss the relationship of the ESGRWP and the FEMA 100-year floodplain. Draft Plan Table 7-3 includes a comparison of the ESGRWP 100-year flood modeling results with the flood elevations defined by FEMA. The City plans to request a comprehensive map revision from FEMA after some of the improvements in the ESGRWP Plan have been implemented. 2. The goals of the project are described in Section 2.3 of the Plan. Please also see Response No. 10 to Citizens for Renton Wildlands Preservation. 3. Whether or not the proposed project is implemented, development projects proposed for construction within the valley must meet the requirements for construction within the floodplain of Springbrook Creek and its tributaries. These requirements include, but are not limited to, the following: A. Filling within the 100-year floodplain must be offset by construction of an equal amount of compensatory storage capacity. B. Floor elevations of buildings must be elevated at least one foot above the 100-year flood elevation. C. Encroachments into the floodway are prohibited unless mitigated. Future development within the basin must also comply with runoff control and water quality requirements, including the control of erosion and sedimentation during construction to ensure that water quality is not impaired. 09/97c JSA 3-63 CHAPTER 3 4. Please see Response No. 10 to Citizens for Renton Wildlands Preservation. 5. The City of Renton requires that onsite peak rate runoff control be provided in accordance with the 1990 King County Surface Water Design Manual as adopted by the City. Generally, peak rate runoff control facilities must be designed to control up to a 10-year event with an additional 30 percent factor-of-safety. Use of more stringent standards might be of value in minimizing future increases in peak flows at some locations in the drainage basin or in minimizing localized storm drainage problems. However, flooding in the lower Springbrook Creek system is also a function of storm runoff volumes which are not reduced by detention facilities. Opportunities to control runoff volumes, such as use of infiltration systems, are limited because soil types are unsuitable for infiltration. Also, given the extent of development that has already taken place in the watershed, additional onsite control measures would not produce a significant reduction in expected valley flooding problems resulting from continued development to full build-out, or significantly reduce flood control storage requirements in the lower part of the Springbrook Creek system. The current conditions land use modeling in the Plan was based on 1989 aerial photographs, while incorporating major improvements to the drainage system that have occurred since that time (e.g., the SW Grady Way to SW 16th Street widening and the City of Kent Lagoons project). Approximately 8 years of development has occurred since 1989 so the actual difference between future and existing conditions is less than presented in the Plan. Current conditions are constantly changing as development in the watershed continues, but updating the watershed models to reflect these changes is time consuming and expensive. Therefore, current conditions in the plan and EIS were based on the 1989 land use. 6. Future development within the basin must comply with runoff control and water quality requirements, including the control of erosion and sedimentation during construction to ensure that water quality is not impaired and that soil inputs to the downstream system are minimized. 7. Please see Response No. 17 to Friends of the Black River. 8. Comment noted. 9. Please see Section 8.3.1 of the Plan for the description of Springbrook Creek Alternatives 2 and 3, Element 2, including the relationship of the proposed channel widening to the low flow channel. The Renton City Council has selected Springbrook Creek Alternative 3 for implementation,which proposes a wider stream channel for Springbrook Creek through the use of high flow benches (see Figure 8-5 of the Plan). The low flow channel width or the bottom will not be widened, thus maintaining existing low flow channel conditions, except as may result from the installation of instream habitat structures. 3-64 JSA 09/97e COMMENTS AND RESPONSES 3300 Company Seelig Family Properties 7 February 1997 Mr. Scott Woodbury,P.E.,Project Manager Surface Water Utility City of Renton 200 Mill Avenue South Renton, WA 98055 F F. RE: East Side Green River Watershed Project Comments on Draft Plan and E.I.S. ...... Dear Mr. Woodbury: We have owned the property which in located on the east side of Lind Ave. between S.E. 21"'and S.E. 23d Streets since the mid 1970's. We are definitely property owners"in for the long haul." As such we believe in designing and building infrastructure work which will last for many years to come. Unfortunately, previously built surface water utility projects in the Valley area have not always been constructed with this a long term objective as a goal. Many were either insufficiently sized to perform in their intended manner or were constructed so that they could not be effectively maintained and are now requiring replacement only a few years after installation. The consequence is that money has been wasted which could have otherwise been used to make further improvements to our surface water environment,rather than to rectify prior misjudgments. To avoid repeating mistakes of the past, we therefore favor the SW 23d St. Drainage Alternative 3 (23ST3). This design will satisfy the drainage needs of the Valley for many future years. Alternative 3 by achieving a positive grade will minimize future maintenance costs which have historically been understated and have always increased with time,thereby draining future monetary resources which could be spent on capital improvements to our environs. In the same way that public sanitary sewers replace the need for private septic systems,we favor surface water projects by the public sector which would elirrdnate the need for on-site retention systems. We urge that you consider sizing the proposed improvements to accomplish that end Large scale, Public improvements will operate more effectively than piece-meal, on site, private detention systems: they will be more easily maintainable: and most importantly they will serve our environment best. Public improvements could be of such size to have a substantial, positive benefit on wildlife and could serve as well as public amenities. Conversely, on site underground retention tanks or small above grade"cesspools," connected to a tiny orifice are subject to frequent malfunction, and cannot function as well as an area-wide public sector project. MSincerel , TIN A. SE Z ELIG Phone: 206-454-0885 Mailing Address: P.O. Box 1925, Street Address: 1309 114th SE.Suite 107, Fax: 206-451-8203 Bellevue,WA Bellevue,WA 98009 98004 09/97e JSA 3-65 CHAPTER 3 This page left blank intentionally. 3-66 JSA 09/97c COMMENTS AND RESPONSES Response to Martin Seelig, 3300 Company 1. Thank you for your comments. Please see Chapter 1 of this Final EIS for a description of the action proposed by the City. 2. Comment noted. Whether the ESGRWP improvements may be used as an alternative to providing separate onsite water quantity control requirements will be determined separately on a case-by-case basis or on a regional scale through a separate proposal in coordination with the Surface Water Utility's Comprehensive Plan. 09/97e JSA 3-67 CHAPTER 3 This page left blank intentionally. 3-68 JSA 09/97e ' Appendix A ' PUBLIC HEARING RECORD AND ATTENDANCE APPENDIX A PUBLIC HEARING RECORD AND ATTENDANCE EAST SIDE GREEN RIVER WATERSHED PROJECT DRAFT PLAN AND ENVIRONMENTAL IMPACT STATEMENT PUBLIC HEARING MEETING AGENDA JANUARY 16, 1997, 7:00 PM CITY COUNCIL CHAMBER, RENTON, WA 7:00 - 7:05 Welcome and Introductions 7:05 - 7:10 Purpose of the Hearing 7:10 - 7:25 Project Overview 7:25 - 8:50 Public Comment 8:50 - 9:00 Closure of Meeting 09/97u JSA A-1 APPENDIX A CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT DRAFT PLAN AND ENVIRONMENTAL IMPACT STATEMENT PUBLIC HEARING JANUARY 16, 1997 ATTENDANCE RECORD Check by your name if you wish to speak during the public comment period Name Affiliation Address Phone ��` �.vt-� ��.�� '.�o,ll'� ,�C_ iS�v �(Jve��kb Lye`.��:�iiE• Q2Z-/�?� �TEI/c C-pot-L :ELCI F I C (::;+°12 13-3 5,.j z c.y � j�vti�4.� 5l- \1,�3�1 $� I�y�So Z-72-5 2b ,4!�70A Wok ecuor!lz4l' !1r/ce _)/gl8 TcD -5wiDEKS WSDo% gEUTo►J wA ,2z8-.-'c (,yy A-2 JSA 09/97u PUBLIC HEARING RECORD AND ATTENDANCE Proceedings of the Public Hearing for the Draft Plan and EIS Held on January 16, 1997 A public hearing hearing for the East Side Green River Watershed Project (ESGRWP)Draft Plan and EIS was held on January 16, 1997. The meeting was recorded on audio tape. A copy of the tape is included in the project file. The hearing was opened with introductions of City and consultant staff attending the public hearing. A representative of the project's federal sponsor, the Natural Resources Conservation Service, was also introduced. After Mark Pywell of the City's Development Services Division described the purpose of the hearing, Scott Woodbury of the City's Surface Water Utility gave a brief overview of the ESGRWP. Mark Pywell then opened the hearing for public comment. Only one individual, Trudy Thomas,testified at the hearing. A transcription of her comments are included following. Trudy Thomas, Friends of the Black River, a community group who are stewards to the Black River Riparian Forest and Wetland,a valuable resource in Renton. Some of the activities of our group are to monitor the heron rookery and other wildlife in the area,to increase the community awareness of the area through field trips, brochures and to act as voice in matters that may impact the area. We strongly urge the City to purchase additional property around the wetland to preserve habitat. This property was purchased in September of 1996. In October we sponsored a field trip in conjunction with Rainier Audubon. Over 50 people attended and viewed over 30 species of birds and other wildlife in the area. Last November one of our members coordinated a tree planting event using 25 volunteers, and some of the members of our group planted over 100 trees on the Saturday before Thanksgiving in three inches of snow. Tonight I am also speaking for Citizens for Renton Wild Lands Preservation. This group has been active in the Black River site and was instrumental in obtaining the money to purchase the wetland. I am also speaking for the Rainier Audubon, who are active in watershed issues in South King County. The Black River Riparian and Forest and wetland is rich in wildlife. There is a major heron rookery on this site. There is year around habitat for water fowl, song birds, mammals, raptors and more. Mitigatory water fowls use this area. In the spring this area is very important nursery for many species of birds. Also, 355 salmon returned to the watershed to spawn last year and pass through the wetland. This is an area rich in wildlife already, but it has potential for much more. In spite of the fact that wildlife uses this area,there are significant signs of that this is a sick wetland. In the summer, duckweed has covered most of the pond area, and last summer large masses of brown algae floated in the brown soup of the pond area. On a summer's evening, the mosquitoes will eat you alive. if this were a healthy wetland,the waters would support small fish and other water dwelling creatures that would feast on mosquito larvae. The ESGRWP is an opportunity to make changes that will enhance the Black River Riparian Wetland by improving water quality conditions upstream and improve habitat in the watershed. But I've seen the work done two years ago just upstream from the wetland,a major impact occurs with any stream work. Draw down of water levels eliminate important water habitat for water fowl. Disturbance of the stream bed caused increased sediment in 09/97u JSA A-3 APPENDIX A the water, and the decreased water flows resulted in the sediment settling in the pond area. Also a disturbance of sediments in the watershed may increase the flow of contaminants into the wetland further damaging the habitat. Because of the complex issues involved, and the need to thoroughly review the documents, we request an extension of the deadline for written comments on this report. The timing of the release of the report was just prior to a major holiday season. Also many of us were Z further restricted by the unseasonable weather. We request an extra three weeks to provide adequate time to review the information and provide substantive comments. Thank you. Following Trudy Thomas' comments,the public hearing was closed. I t:DOCS:97-039:SSw:ps A-4 JSA 09/97u PUBLIC HEARING RECORD AND ATTENDANCE Response to Public Hearing Comments of Trudy Thomas 1. Thank you for your comments. The City encourages active participation by the Friends of the Black River and others in the stewardship of the Black River Riparian Forest and Wetland and other habitats in the ESGRW. Please see also the responses to comments from the Friends of the Black River, Rainier Audubon Society, and Citizens For Renton Wildlands Preservation. 2. A 7-day extension of the comment period deadline was granted by the City as noted in the attached letter dated January 30, 1997. 09/97„ JSA A-5 APPENDIX A This page left blank intentionally. A-6 JSA 09/97u PUBLIC HEARING RECORD AND ATTENDANCE CITE OF RENTON Planning/Building/Public Works Department Jesse Tanncr.Mayor Gregg Zimmerman P.E.,Administrator January 30, 1997 SUBJECT: EAST SIDE GREEN RIVER WATERSHED PROJECT DRAFT PLAN AND ENVIRONMENTAL IMPACT STATEMENT EXTENSION OF THE COMMENT PERIOD Dear Reviewer: Several individuals have requested additional time in which to submit comments on the East Side Green River Watershed Project (ESGRWP) Draft Plan and Environmental Impact Statement because of the complexity and volume of information to review. Therefore, the City has decided to extend the deadline for the comment period one additional week from 5:00 PM on January 31, 1997, to 5:00 PM on Friday, February 7, 1997. WAC 197-11-455 requires that a 30-day comment period be provided for a Draft Environmental Impact Statement (DEIS), unless extended by the lead agency. Upon request, the rules state that a lead agency may grant an extension of up to 15 days to the comment period. The ESGRWP.DEIS document was issued with an extended 45-day review and comment period because it was anticipated that reviewers would need the additional 15 days more than the 30 days required under the SEPA rules. With the 7 days added by this letter, the time allowed for the comment period is extended from 45 days to a total of 52 days. Thank you for your participation in the environmental review process. If you have any questions about the East Side Green River Watershed Project Draft Plan and Environmental Impact Statement, please do not hesitate to contact me at (206) 277-5547 or Mark Pywell, Senior Planner, at (206) 277-5586. Sincerely, ' G v"Crt�i�l�l f i� Scott Woodbury, P.E., Aroject Manager Surface Water Utility H:DOCS:97.074:SW:ps CC-. File LUA-95.205.ECF Ron Straka Mark Pywell 200 Mill Avenue South- Renton,Washington 98055 09/97u JSA A-7 Appendix B ' DETAILED DESCRIPTION OF ALTERNATIVES APPENDIX B DETAILED DESCRIPTION OF ALTERNATIVES 1 . SPRINGBROOK CREEK ALTERNATIVES A. SPRINGBROOK CREEK ALTERNATIVE 1 (SC1) - NO ACTION Under SC1, flood control improvements would not be implemented and existing flooding problems would continue. Springbrook Creek water levels would continue to rise during flood events such that the Valley area would be subject to more significant, recurring flooding. If no improvements are implemented along the mainstem of Springbrook Creek, the existing flooding problems will continue to negatively impact the Renton Valley area and will worsen in the future as development in the watershed continues. Existing maintenance programs for vegetation management and sediment removal to maintain conveyance capacity would continue. Problems with water quality, fish rearing areas, and riparian habitat in Springbrook Creek will also continue. B. SPRINGBROOK CREEK ALTERNATIVE 2 (SC2) - LOCALIZED IMPROVEMENTS TO SPRINGBROOK CREEK SC2 includes a number of localized improvements to Springbrook Creek that, when combined with other system improvements, would reduce flooding problems and improve riparian habitat. This alternative focuses on minimizing modifications to the Springbrook Creek stream channel. SC2 includes a number of discrete elements (projects): ■ SC2 - Element 1. Improvements at four Springbrook Creek roadway crossings that currently restrict conveyance: private bridge 500 feet north of SW 27th Street, SW 27th Street, SW 34th Street, and Oakesdale Avenue. ■ SC2 - Element 2. Widening and restoration of approximately 3,400 linear feet of Springbrook Creek between SW 16th Street and SW 23rd Street to increase capacity. A public access trail would be provided from about SW 19th Street to SW 24th Street. ■ SC2 - Element 3. A channel maintenance program for vegetation management and sediment removal along Springbrook Creek to maintain conveyance capacity (one specific action would be removal of sediments that have accumulated in the constructed channel downstream of SW Grady Way). ■ SC2 - Element 4. Plantings to improve riparian habitat. 09/97e JSA B-1 APPENDIX B C. SPRINGBROOK CREEK ALTERNATIVE 3 (SC3) - SPRINGBROOK CREEK GREENWAY IMPROVEMENTS SC3 includes many of the same improvements as described under SC2 (improvements at road crossings SC3 - Element 1). It differs from SC2 in that improvements to Springbrook Creek would be more extensive and would include additional reaches of channel improvement between SW 30th Street and the existing railroad bridge just north of SW 41st Street (SC3 - Element 2). Improvements at the Oakesdale Avenue crossing would also be more extensive than with SC2. The improvements would focus on a greenway concept that would incorporate more intensive plantings near the low flow channel to create wildlife habitat and improve fish habitat by providing overhanging vegetation and lower water temperatures. Under this alternative, the vegetation management program (SC3 - Element 3) would be reduced, and the channel improvements would allow for more intensive vegetation plantings along the channel banks of Springbrook Creek (SC3 - Element 4). As a result, the City would need to perform less frequent maintenance. As with SC2, a public access trail would be provided from about SW 19th Street to SW 24th Street. 2. PANTHER CREEK ALTERNATIVES A. PANTHER CREEK ALTERNATIVE 1 (PC1) - NO ACTION Under PC1, no flood control improvements would be implemented, and existing flooding problems would continue. Low and moderate flows from Panther Creek would continue to flow through the two southern SR-167 culvert crossings near SW 39th Street to enter the East Valley Road and SW 34th Street drainage systems, which were never designed to handle these flows. Note: Panther Creek may at some time in the future alter its own course to flow entirely into the Panther Creek Wetland. Should this occur, the Panther Creek alternatives presented below may become partly or completely unnecessary. B. PANTHER CREEK ALTERNATIVE 2 (PC2) - HIGH FLOW BYPASS TO PANTHER CREEK WETLAND This alternative includes maintaining Panther Creek low flows through the East Valley Road and SW 34th Street drainage systems and diverting moderate and high flows to the Panther Creek Wetland. Maintaining low flows would allow for continued downstream migration of fish through the East Valley Road drainage system. Specific elements of this alternative include: ■ PC2 - Element 1. Block one SR-167 culvert and install a structure at the other of the southerly SR-167 culverts designed to pass low flows to the existing East Valley Road system and divert excess flows into the Panther Creek Wetland (the structure would be designed to allow downstream migration of fish). B-2 JSA 09/97e DETAILED DESCRIPTION OF ALTERNATIVES ■ PC2 - Element 2. Replace an existing 36-inch-diameter concrete pipe system in SW 34th Street with a 48-inch-diameter system or larger from approximately the East Valley Road to Lind Avenue. C. PANTHER CREEK ALTERNATIVE 3 (PC3) - MAINTAIN EXISTING FLOW INTO THE 34TH STREET SYSTEM PC3 includes maintaining Panther Creek low and moderate flows through the two southerly SR-167 culvert crossings as under the no action alternative. Under this alternative, the entire downstream drainage system along the East Valley Road and SW 34th Street would be improved by (1) replacing the existing pipe system along the East Valley Road and SW 34th Street with a new larger system sized to convey Panther Creek flows and local runoff; (2) channel improvements between the outlet of the two southerly SR-167 culverts and the East Valley Road; and (3) intermittent maintenance of vegetation as needed to maintain channel performance. 3. SW 23RD STREET DRAINAGE CHANNEL ALTERNATIVES A. SW 23RD STREET ALTERNATIVE 1 (23ST1) - NO ACTION Under 23ST1, no flood control improvements would be implemented. Flooding along the East Valley Road between approximately SW 23rd Street and SW 30th Street will worsen if no improvements are made in this area. Intermittent vegetation management, sediment removal, and other maintenance would be necessary to maintain conveyance capacity. The poorly functioning SR-167 culverts between the southerly culverts described for Alternative PC2 and SW 23rd Street would be cleaned to restore them to full capacity. B. SW 23RD STREET ALTERNATIVE 2 (23ST2) - MINOR CONVEYANCE IMPROVEMENTS 23ST2 includes implementing minor improvements along the SW 23rd Street drainage channel and replacing the poorly functioning SR-167 culvert crossings with a new crossing at SW 23rd Street. Specific elements of this alternative include: ■ 23ST2 Element 1. Plugging the poorly functioning SR-167 culverts between the southerly culverts described in Alternative PC2 and SW 23rd Street and replacing them with a new SR-167 crossing at SW 23rd Street, including an inlet structure on the new crossing; implementing minor channel improvements between the new SR-167 culvert and the East Valley Road culvert crossing (the existing risers on the upstream end of the East Valley Road culverts would be removed). ■ 23ST2 Element 2. Replacing the two existing 18-inch culverts that carry the SW 23rd Street drainage channel flows underneath the existing Olympic Pipeline crossing west of Lind Avenue with a larger box culvert, or relocating the pipelines and restoring the crossing to an open channel. 09/97e JSA B-3 APPENDIX B Intermittent vegetation management and sediment removal would be necessary to maintain conveyance capacity. C. SW 23RD STREET ALTERNATIVE 3 (23ST3) - MAJOR CONVEYANCE IMPROVEMENTS 23ST3 would be similar to 23S72 except that the existing drainage channel between Springbrook Creek and SR-167 would be widened and deepened to provide a positive grade through the system and reduce maintenance. Specific elements of this alternative include: ■ 23ST3 Element 1. Replacing the SR-167 culverts with a new crossing at SW 23rd Street as described under 23ST2. ■ 23ST3 Element 2. Replacing the existing culverts under the Olympic petroleum pipelines as described under 23S72. ■ 23ST3 Element 3. Widening and deepening the existing channel along SW 23rd Street between SR-167 and Springbrook Creek to provide positive drainage. 4. WETLAND MITIGATION BANK AND WETLAND HYDRAULIC MODIFICATIONS As part of this project, the City is proposing hydraulic modifications (culvert replacements) to two wetlands, as well as a wetland mitigation bank. A. WETLAND 12 Wetland 12 Alternative 1 (W12-1) - No Action. Under W12-1, Wetland 12 would continue to function as off-channel storage for Springbrook Creek and would also attenuate local inflows. The wetland is owned by the City and would remain as open space, with a recreational trail planned for construction along Springbrook Creek at some future time under a separate proposal. Based on expected future land use conditions in the watershed, overbank flooding of Springbrook Creek will occur more frequently. Periodic maintenance of the culvert in the berm that bisects the wetland would be necessary to prevent plugging. This maintenance would include removal of sediment and vegetation in and around the culvert ends. Wetland 12 Alternative 2 (W12-2) - Culvert Replacement. Under W12-2, the existing 18-inch culvert in the berm bisecting the wetland would be replaced with two or three 36-inch culverts. The new culverts would be installed at the same elevation as the existing culvert to maintain the outlet elevation of the wetland. A second option would be to remove the existing culvert and replace it with an open channel or weir. The bottom of the channel or weir would be set to maintain the existing open water features of the wetland. The purpose of replacing the existing culvert would be to restore the hydraulic connection between Springbrook Creek and the area west of the berm. This would help to attenuate B-4 JSA 09/97e DETAILED DESCRIPTION OF ALTERNATIVES flows in Springbrook Creek and thereby reduce the extent of improvements needed on the mainstem of Springbrook Creek. B. WETLAND 32 Wetland 32 Alternative 1 (W32-1) - No Action. Under W32-1, Wetland 32 would be preserved as open space in accordance with restrictions placed on the property when it was acquired by the City. The site would remain isolated from Springbrook Creek and would provide no off-channel flood storage capacity. Wetland 32 Alternative 2 (W32-2) - Mitigation Bank/Excavate Large Off-Channel Storage. The City proposes to create wetlands and enhance Wetland 32 over the entire property. The created and enhanced wetlands would be used as mitigation to compensate for offsite wetland impacts from other projects in the same drainage basin. The hydraulic connection between the wetland and Springbrook Creek would be restored, allowing temporary floodwater storage in Wetland 32. C. WETLAND 7N Wetland 7N Alternative 1 (W7N-1) - No Action. Under W7N-1, the wetland would likely remain unaffected by development on the surrounding properties, remain isolated from Rolling Hills Creek, and provide little off-channel storage. Wetland 7N Alternative 2 (W7N-2) - Culvert Replacement. Under W7N-2, the existing 12-inch culvert between the wetland and the 60-inch storm drain in SW 19th Street that conveys Rolling Hills Creek would be replaced with a minimum 36-inch culvert at the same elevation as the existing culvert, thereby maintaining the existing dead storage and open water components in the wetland. The larger culvert would restore the hydraulic connection of the wetland with the adjacent drainage systems. For flood events greater than a 2-year event, water would be able to move more freely between the wetland and Rolling Hills Creek, thereby adding more floodwater storage to the drainage system and attenuating flows. This project is now scheduled to be constructed by private land owners (Candlewood Hotel or Hilton Garden Suites) proposing to develop adjacent properties north of the wetland. 5. PIPE SYSTEM IMPROVEMENTS A. PIPE SYSTEM IMPROVEMENTS ALTERNATIVE 1 (PS1) - NO ACTION Under PS 1, no pipe system improvements would be implemented. Even if the Springbrook Creek alternatives are implemented, flooding would be reduced but still occur at several locations. The flooding problems would become exacerbated as development continues in the watershed. 09/97e JSA B-5 APPENDIX B B. PIPE SYSTEM IMPROVEMENTS ALTERNATIVE 2 (PS2) - PIPE SYSTEM IMPROVEMENTS PS2 includes several pipe system improvements to reduce flooding in the Valley area: ■ SW 43rd Street System Improvement (PS2-1). System improvements are necessary from approximately Lind Avenue to Springbrook Creek. Preliminary sizing of this system indicates that at least an 84-inch-diameter concrete pipe system is necessary to solve flooding for the future 100-year event. Alternatively, at least a 72-inch-diameter pipe system would solve flooding for the future 25-year event. Because of traffic impact concerns on SW 43rd Street, the new pipe system will extend north down Lind Avenue to SW 39th Street and then west on SW 39th Street to Springbrook Creek. The existing system in SW 43rd Street would remain active with an approximately 55-foot length of 36-inch pipe at the Oakesdale/SW 43rd Street intersection being replaced with at least a 54-inch-diameter pipe. ■ East Valley Road System Improvements (PS2-2). System improvements are necessary from approximately SW 29th Street to the discharge at the existing channel along SW 23rd Street. This improvement will include replacing an existing 30/36-inch system with at least a 48-inch-diameter system. ■ Rolling Hills Culvert (PS2-3). This improvement includes removing an existing culvert that carries Rolling Hills Creek between Springbrook Creek and Raymond Avenue (along SW 19th Street) and restoring it as a channel. This element is not required for solving a flooding problem. The culvert serves no real purpose and removing it will result in an environmental benefit. B-6 JSA 09/97e CITY OF RENTON EAST SIDE GREEN RIVER WATERSHED PROJECT LIST OF ACRONYMS BMPs . . . . . . . . . Best Management Practices BRPS . . . . . . . . . Black River Pump Station cfs . . . . . . . . . . . . cubic feet per second DOE . . . . . . . . . . Washington State Department of Ecology DS . . . . . . . . . . . . Determination of Significance EIS . . . . . . . . . . . Environmental Impact Statement ESGRW . . . . . . . East Side Green River Watershed ESGRWP . . . . . . East Side Green River Watershed Project FEMA . . . . . . . . . Federal Emergency Management Agency ft . . . . . . . . . . . . . feet HOV . . . . . . . . . . high-occupancy vehicle HPA . . . . . . . . . . Hydraulic Project Approval NRCS . . . . . . . . . Natural Resources Conservation Service OAHP . . . . . . . . . Office of Archaeology and Historic Preservation SCS . . . . . . . . . . . Soil Conservation Service SEPA . . . . . . . . . State Environmental Policy Act SR-167 . . . . . . . . . State Route 167 WAC . . . . . . . . . . Washington Administrative Code WDFW . . . . . . . . Washington Department of Fish and Wildlife WSDOT . . . . . . . Washington State Department of Transportation 09/97e JSA 1 LIST OF ACRONYMS This page left blank intentionally. 2 JSA 09/97e