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Home My WebLink About14. L2STA-TIR Lake to Sound Trail – Segment A Draft Technical Information Report Prepared for King County April 2015 Prepared by April 2015 │ 554‐1521‐084 (A/3T200B) Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain Prepared for King County Division of Capital Planning and Development Facilities Management Division, DES King County Administration Building 500 Fourth Avenue, Room 320 Seattle, Washington 98104 Prepared by Parametrix 719 2nd Avenue, Suite 200 Seattle, WA 98104 T. 206.394.3700 F. 1.855.542.6353 www.parametrix.com CITATION Parametrix. 2015. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain. Prepared by Parametrix, Seattle, Washington. April 2015. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) CERTIFICATION The technical material and data contained in this document were prepared under the supervision and direction of the undersigned, whose seal, as a professional engineer licensed to practice as such, is affixed below. _____________________________________________ Prepared by Craig Buitrago, P.E. _____________________________________________ Checked by Julie Brandt, P.E. _____________________________________________ Approved by Jenny Bailey, Project Manager Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) i TABLE OF CONTENTS 1. OVERVIEW .................................................................................................................................. 1‐1 1.1 PROPOSED PROJECT ...................................................................................................................... 1‐1 1.2 EXISTING SITE CONDITIONS .......................................................................................................... 1‐1 1.3 DEVELOPED SITE CONDITIONS .................................................................................................... 1‐13 2. CONDITIONS AND REQUIREMENTS ............................................................................................. 2‐1 3. OFFSITE ANALYSIS ....................................................................................................................... 3‐1 3.1 STUDY AREA DEFINITION AND MAPS ........................................................................................... 3‐1 3.2 RESOURCE REVIEW ....................................................................................................................... 3‐1 3.3 FIELD INSPECTION ......................................................................................................................... 3‐1 3.3.1 TDA 1 (A‐Line Stations 1+00 to 14+82) ............................................................................ 3‐2 3.3.2 TDA 2 (C‐Line Stations 201+11to206+50) ........................................................................ 3‐2 3.3.3 TDA 3 (B‐Line Stations 101+77 to 110+00) ...................................................................... 3‐2 3.3.4 TDA 4 (B‐Line Stations 110+00 to 132+50) ...................................................................... 3‐3 3.3.5 TDA 5 (B‐Line Stations 132+50 to 143+17) ...................................................................... 3‐3 3.4 DRAINAGE SYSTEM AND PROBLEM DESCRIPTIONS ...................................................................... 3‐3 3.5 MITIGATION OF EXISTING OR POTENTIAL PROBLEMS ................................................................. 3‐3 4. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN .................................... 4‐1 4.1 EXISTING SITE HYDROLOGY (PART A) ............................................................................................ 4‐1 4.2 DEVELOPED SITE HYDROLOGY (PART B) ....................................................................................... 4‐1 4.3 PERFORMANCE STANDARDS (PART C) .......................................................................................... 4‐2 4.3.1 Flow Control ..................................................................................................................... 4‐2 4.3.2 Conveyance System ......................................................................................................... 4‐3 4.3.3 Water Quality Treatment ................................................................................................. 4‐3 4.4 FLOW CONTROL SYSTEM (PART D) ............................................................................................... 4‐3 4.5 WATER QUALITY (PART E) ............................................................................................................. 4‐4 5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN ............................................................................ 5‐1 5.1 MONSTER ROAD STORM DRAIN SYSTEMS.................................................................................... 5‐1 5.2 TDA 3 CATCH BASIN ...................................................................................................................... 5‐1 5.3 TDA 4 BOX CULVERT ..................................................................................................................... 5‐1 6. SPECIAL REPORTS AND STUDIES .................................................................................................. 6‐1 6.1 FLOODPLAIN ANALYSIS ................................................................................................................. 6‐1 6.2 STREAM DISCIPLINE REPORT ........................................................................................................ 6‐1 6.3 CRITICAL AREA STUDY (DRAFT) ..................................................................................................... 6‐1 6.4 VEGETATION AND WILDLIFE DISCIPLINE REPORT (DRAFT) ........................................................... 6‐1 Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County TABLE OF CONTENTS (CONTINUED) ii April 2015 │ 554‐1521‐084 (A/3T200B) 7. OTHER PERMITS .......................................................................................................................... 7‐1 8. CSWPPP ANALYSIS AND DESIGN ................................................................................................. 8‐1 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT .......................... 9‐1 10. OPERATIONS AND MAINTENANCE MANUAL ............................................................................. 10‐1 11. REFERENCES ............................................................................................................................. 11‐1 LIST OF FIGURES 1‐1 TIR Worksheet ............................................................................................................................ 1‐2 1‐2 Site Location ............................................................................................................................. 1‐10 1‐3 Drainage Basins, Subbasins, and Site Characteristics .............................................................. 1‐11 1‐4 Soils .......................................................................................................................................... 1‐12 LIST OF TABLES 1‐1 Effective Impervious Area Comparison.................................................................................... 1‐14 2‐1 Summary of Core and Special Requirements ............................................................................ 2‐1 4‐1 Comparison of Peak Runoff Rates.............................................................................................. 4‐4 APPENDICES A Project Design Drawings B Land Cover Area Calculations C Offsite Analysis ‐ Resource Review and Site Visit Photos D KCRTS Runoff Modeling Documentation E Box Culvert Design Calculations F Grading Within the Floodplain ‐ Cut and Fill Calculations G King County Surface Water Design Manual Operation and Maintenance Excerpts Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) iii ACRONYMS AND ABBREVIATIONS ADS Advanced Drainage Systems BMP best management practice BNSF Burlington Northern Santa Fe cfs cubic feet per second CSWPPP construction stormwater pollution prevention plan EIA effective impervious area FEMA Federal Emergency Management Agency FHWA Federal Highway Administration GIS geographic information system KCRTS King County Runoff Time Series KCSWDM King County Surface Water Design Manual M&O maintenance and operations NEPA National Environmental Policy Act NPDES National Pollutant Discharge Elimination System NRCS Natural Resources Conservation Service Renton Addendum City of Renton 2010 Amendments to the 2009 King County Surface Water Design Manual Segment A Lake to Sound Trail Segment A TIR technical information report TDA threshold discharge area Tukwila Addendum City of Tukwila Infrastructure Design and Construction Standards WSDOT Washington State Department of Transportation Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 1‐1 1. OVERVIEW 1.1 Proposed Project King County, together with the Cities of Renton and Tukwila, the Washington State Department of Transportation (WSDOT), and the Federal Highway Administration (FHWA), is proposing to develop a 1.2‐mile‐long trail segment of what will ultimately be the 16‐mile‐long Lake to Sound Trail. This trail, known as the Lake to Sound Trail Segment A (Segment A) or the Two Rivers Trail, will provide non‐ motorized access to recreation and employment centers for a variety of users such as bicyclists, pedestrians, runners, wheelchair users, and skaters. This technical information report (TIR) provides stormwater management documentation for Segment A and has been prepared in accordance with the 2009 King County Surface Water Design Manual (KCSWDM, King County 2009a). The TIR Worksheet (Figure 1‐1) provides a general overview of the components of this report. A site location map is presented in Figure 1‐2. Design drawings for the proposed project are provided in Appendix A. 1.2 Existing Site Conditions The Segment A project corridor lies within the Black River drainage basin, as shown on Figure 1‐2. The corridor extends from the Green River Trail along an informal dirt footpath south of the Black River, crosses beneath the Burlington Northern Santa Fe (BNSF) and Union Pacific railroad trestles, crosses Monster Road southeast of the Monster Road bridge, crosses over the Black River east of the Monster Road bridge, and follows an existing gravel maintenance road along the north bank of the Black River and the Black River Riparian Forest until reaching Naches Avenue SW. Five threshold discharge areas (TDAs) have been identified for the site, as shown on Figure 1‐3. Topography in the site area is relatively flat; therefore, portions of the proposed trail in TDA 1 pass through the Black River floodplain. Surface runoff from most of the site travels as sheet flow discharging directly to the Black River (TDAs 1 and 3) or to wetlands in the Black River Riparian Forest (TDAs 4 and 5). Runoff from the portion of the proposed trail that approaches and crosses the existing Monster Road (TDA 2) is collected into the storm drain systems on the north and south sides of the roadway. The north Monster Road storm drain system drains to an existing ditch that discharges to the Black River on the southeast side of the bridge. The south Monster Road storm drain system is conveyed southwest of Monster Road and continues onto private property adjacent the Black River. Northeast of the project area near the Black River Riparian Forest, a steep hillside drains towards the proposed site. There are four existing culverts in this area (TDAs 3, 4, and 5) that convey surface water flows beneath the existing gravel maintenance road. Soils in the project area (Figure 1‐4) were classified west (TDAs 1, 2, and 3) and east (TDAs 4 and 5) of Monster Road. The west area, including Monster Road, is identified as Newberg silt loam—hydrologic soil group A/B—while the east area is Woodinville silt loam—hydrologic soil group D (NRCS 2013). KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 1 1/9/2009 PART 1 PROJECT OWNER AND PROJECT ENGINEER PART 2 PROJECT LOCATION AND DESCRIPTION Project Owner King County Facilities Management Division (Jason Rich) Project Name Lake to Sound Trail Segment A Phone 206.263.7314 Green River Trail to Naches Ave SW Address 201 So. Jackson St., Rm 700 DDES Permit # N/A Seattle, WA 98104 Location Township 23 N Project Engineer Craig Buitrago Range 04 E Company Parametrix Section SE 14, S 13, and NE 23 Phone 206.394.3639 Site Address PART 3 TYPE OF PERMIT APPLICATION PART 4 OTHER REVIEWS AND PERMITS Landuse Services DFW HPA Shoreline Mgmt Subdivision/Short Subd. / UPD COE 404 Structural Building Services DOE Dam Safety Rockery/Vault/ M/F / Commercial / SFR FEMA Floodplain ESA Section 7 Clearing and Grading COE Wetlands Right-of-Way Use Other Other PART 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review: Full/ Targeted Large Site Type Full/ Targeted Large Site Date (include revision dates): July 2013 Date (include revision dates): April 2013 Date of Final April 2015 Date of Final April 2015 PART 6 ADJUSTMENT APPROVALS Type: Standard Complex Preapplication Experimental Blanket Description: (include conditions in TIR Section 2) Date of Approval: KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 2 1/9/2009 PART 7 MONITORING REQUIREMENTS Monitoring Required Yes No Describe Start Date: Completion Date: PART 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: Green River Valley Special District Overlays: None Drainage Basin: Black River, WRIA 9 Stormwater Requirements: Tukwila: Conservation/Duration Control, Existing Conditions Target Renton: Peak Rate Flow Control Standard, Existing Conditions Target PART 9 ONSITE AND ADJACENT SENSITIVE AREAS River/Stream Green & Black Rivers Steep Slope Lake Erosion Hazard Wetlands Black River Riparian Forest-Wetlands 1-6 Landslide Hazard Closed Depression Coal Mine Hazard Floodplain Green & Black Rivers Seismic Hazard Other Habitat Protection PART 10 SOILS Soil Type Slopes Erosion Potential Ng 0-4% slight Wo 0-2% slight High Groundwater Table (within 5 feet) Sole Source Aquifer Other Seeps/Springs Additional Sheets Attached KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 3 1/9/2009 PART 11 DRAINAGE DESIGN LIMITATIONS REFERENCE LIMITATION / SITE CONSTRAINT Core 2 – Offsite Analysis Sensitive/ Critical Areas Maintain wetland hydrology; no net fill in floodplains SEPA Other Additional Sheets Attached PART 12 TIR SUMMARY SHEET (PROVIDE ONE TIR SUMMARY SHEET PER THRESHOLD DISCHARGE AREA) Threshold Discharge Area (name or description): TDA 1 - A-Line Stations 1+00 to 14+20 Core Requirements (all 8 apply) Discharge at Natural Location Number of Natural Discharge Locations: 1- continuous sheet flow to Blk River Offsite Analysis: Level: 1 2 3 Dated: February 21, 2013 Flow Control (incl. facility summary sheet) Level: 1 2 3 or Exemption Number Q100 increase = 0.1cfs Small Site BMPs with basic & full dispersion Conveyance System Spill containment located at: N/A Erosion and Sediment Control ESC Site Supervisor: To be identified in construction SWPPP Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: Private Public If Private, Maintenance Log Required: Yes No Financial Guarantees and Liability Provided: Yes No Water Quality (include facility summary sheet) Type: Basic Sens. Lake Enhanced Basic Bog Or Exemption No. N/A - no pollution-generating surfaces Landscape Management Plan: Yes No Special Requirements (as applicable) Area Specific Drainage Requirements Type: CDA SDO MDP BP Shared Fac. None Name: Floodplain/Floodway Delineation Type: Major Minor Exemption None 100- year Base Flood Elevation (or range): 22.58 feet Datum: NAVD 88 Flood Protection Facilities Describe: N/A Source Control (comm./ industrial landuse) Describe: N/A Describe any structural controls: Oil Control High-use Site: Yes No Treatment BMP: Maintenance Agreement: Yes No With whom? Other Drainage Structures Describe: KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 4 1/9/2009 PART 12 TIR SUMMARY SHEET (PROVIDE ONE TIR SUMMARY SHEET PER THRESHOLD DISCHARGE AREA) Threshold Discharge Area (name or description): TDA 2 - C-Line Stations 201+11 to 206+50 Core Requirements (all 8 apply) Discharge at Natural Location Number of Natural Discharge Locations: 1- Ditch outfall to Black River Offsite Analysis: Level: 1 2 3 Dated: February 21, 2013 Flow Control (incl. facility summary sheet) Level: 1 2 3 or Exemption Number Q100 increase < 0.1cfs Small Site BMPs Conveyance System Spill containment located at: N/A Erosion and Sediment Control ESC Site Supervisor: To be identified in construction SWPPP Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: Private Public If Private, Maintenance Log Required: Yes No Financial Guarantees and Liability Provided: Yes No Water Quality (include facility summary sheet) Type: Basic Sens. Lake Enhanced Basic Bog Or Exemption No. N/A - no pollution-generating surfaces added Landscape Management Plan: Yes No Special Requirements (as applicable) Area Specific Drainage Requirements Type: CDA SDO MDP BP Shared Fac. None Name: Floodplain/Floodway Delineation Type: Major Minor Exemption None 100- year Base Flood Elevation (or range): 22.58 feet Datum: NAVD 88 Flood Protection Facilities Describe: N/A Source Control (comm./ industrial landuse) Describe: N/A Describe any structural controls: Oil Control High-use Site: Yes No Treatment BMP: Maintenance Agreement: Yes No With whom? Other Drainage Structures Describe: Four catch basins and 12-inch conveyance pipe installed to maintain Monster Road runoff collection in existing roadway conveyance system. KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 5 1/9/2009 PART 12 TIR SUMMARY SHEET (PROVIDE ONE TIR SUMMARY SHEET PER THRESHOLD DISCHARGE AREA) Threshold Discharge Area (name or description): TDA 3 - B-Line Stations 100+00 to 110+00 Core Requirements (all 8 apply) Discharge at Natural Location Number of Natural Discharge Locations: 1- continuous sheet flow to Blk River Offsite Analysis: Level: 1 2 3 Dated: February 21, 2013 Flow Control (incl. facility summary sheet) Level: 1 2 3 or Exemption Number Q100 increase < 0.1cfs Small Site BMPs with basic & full dispersion Conveyance System Spill containment located at: N/A Erosion and Sediment Control ESC Site Supervisor: To be identified in construction SWPPP Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: Private Public If Private, Maintenance Log Required: Yes No Financial Guarantees and Liability Provided: Yes No Water Quality (include facility summary sheet) Type: Basic Sens. Lake Enhanced Basic Bog Or Exemption No. N/A - no pollution-generating surfaces Landscape Management Plan: Yes No Special Requirements (as applicable) Area Specific Drainage Requirements Type: CDA SDO MDP BP Shared Fac. None Name: Floodplain/Floodway Delineation Type: Major Minor Exemption None 100- year Base Flood Elevation (or range): 22.58 feet Datum: NAVD 88 Flood Protection Facilities Describe: N/A Source Control (comm./ industrial landuse) Describe: N/A Describe any structural controls: Oil Control High-use Site: Yes No Treatment BMP: Maintenance Agreement: Yes No With whom? Other Drainage Structures Describe: Catch Basin Type 2 and 12-inch conveyance pipe (connect to existing CB) near B-Line Sta. 105+05. KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 6 1/9/2009 PART 12 TIR SUMMARY SHEET (PROVIDE ONE TIR SUMMARY SHEET PER THRESHOLD DISCHARGE AREA) Threshold Discharge Area (name or description): TDA 4 B-Line Stations 110+00 to 132+00 Core Requirements (all 8 apply) Discharge at Natural Location Number of Natural Discharge Locations: 1- continuous sheet flow to wetlands Offsite Analysis: Level: 1 2 3 Dated: February 21, 2013 Flow Control (incl. facility summary sheet) Level: 1 2 3 or Exemption Number Q100 increase < 0.1cfs Small Site BMPs with basic & full dispersion Conveyance System Spill containment located at: N/A Erosion and Sediment Control ESC Site Supervisor: To be identified in construction SWPPP Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: Private Public If Private, Maintenance Log Required: Yes No Financial Guarantees and Liability Provided: Yes No Water Quality (include facility summary sheet) Type: Basic Sens. Lake Enhanced Basic Bog Or Exemption No. N/A - no pollution-generating surfaces Landscape Management Plan: Yes No Special Requirements (as applicable) Area Specific Drainage Requirements Type: CDA SDO MDP BP Shared Fac. None Name: Floodplain/Floodway Delineation Type: Major Minor Exemption None 100- year Base Flood Elevation (or range): 18.58 feet Datum: NAVD 88 Flood Protection Facilities Describe: N/A Source Control (comm./ industrial landuse) Describe: N/A Describe any structural controls: Oil Control High-use Site: Yes No Treatment BMP: Maintenance Agreement: Yes No With whom? Other Drainage Structures Describe: Box culvert to be installed at Station 125+95. KING COUNTY, WASHINGTON, SURFACE WATER DESIGN MANUAL TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2009 Surface Water Design Manual 7 1/9/2009 PART 12 TIR SUMMARY SHEET (PROVIDE ONE TIR SUMMARY SHEET PER THRESHOLD DISCHARGE AREA) Threshold Discharge Area (name or description): TDA 5 B-line Stations 132+50 to 142+50 Core Requirements (all 8 apply) Discharge at Natural Location Number of Natural Discharge Locations: 1- continuous sheet flow to wetlands Offsite Analysis: Level: 1 2 3 Dated: February 21, 2013 Flow Control (incl. facility summary sheet) Level: 1 2 3 or Exemption Number Q100 increase < 0.1cfs Small Site BMPs with basic & full dispersion Conveyance System Spill containment located at: N/A Erosion and Sediment Control ESC Site Supervisor: To be identified in construction SWPPP Contact Phone: After Hours Phone: Maintenance and Operation Responsibility: Private Public If Private, Maintenance Log Required: Yes No Financial Guarantees and Liability Provided: Yes No Water Quality (include facility summary sheet) Type: Basic Sens. Lake Enhanced Basic Bog Or Exemption No. N/A - no pollution-generating surfaces Landscape Management Plan: Yes No Special Requirements (as applicable) Area Specific Drainage Requirements Type: CDA SDO MDP BP Shared Fac. None Name: Floodplain/Floodway Delineation Type: Major Minor Exemption None 100- year Base Flood Elevation (or range): 18.58 feet Datum: NAVD 88 Flood Protection Facilities Describe: N/A Source Control (comm./ industrial landuse) Describe: N/A Describe any structural controls: Oil Control High-use Site: Yes No Treatment BMP: Maintenance Agreement: Yes No With whom? Other Drainage Structures Describe: Burlington Northern Santa Fe (BNSF) RailwaySW 7th StMonster R d S W 68 t h Oakesd a l e A v e S W Mau le A v e SNaches Ave SWS 143rd St 80th Ave SI n t e r u r b a n A v e S S 144th St Beacon Coa l M i n e B N S F S 143rd St Martin Luther King Way S Duwamish River G re e n Ri verTrailGre en River CITY OFRENTONCITY OFTUKWILA UNINC.KING COUNTY Black RiverPump StationBlackRiver EndProject BeginProject Proposed Rest Area ProposedRetaining Wall Proposed Culvert ConcreteRecyclingPlant S p ri ngbrookCreekBR 5 3 1/2 Complex 6 4 7 Proposed Rest Area 0 600300Feet Figure 1-2Site Location Project Area LakeWashington 90 5 405 5 99 509 599 518 S E A T T L E R E N T O N B E L L E V U E S E A T A C T U K W I L A Legend: Proposed Trail Existing Trail City Boundary Railroad Black River Riparian Forest WetlandsPath: U:\PSO\Projects\Clients\1521-KingCo\554-1521-084 L2ST\99Svcs\GIS\MapDocs\Fig1-2TIR-Vic-8x11Apr2015.mxdParametrix Sources: King County, City of Renton, WDFW 2014, WSDOT. Lake to Sound Trail --- Segment A BeginProject TDA 2 Ditch outfallto Black River S p r i ngbrookCreekBlack RiverProposed Rest Area Proposed Rest Area Burlington Northern Santa Fe (BNSF) RailwaySW 7th StMonster R d S W 68 t h Oakesd a l e A v e S W Mau le A v e SNaches Ave SWS 143rd St 80th Ave SI n t e r u r b a n A v e S S 144th St Beacon Coa l M i n e B N S F S 143rd St Martin Luther King Way S Duwamish River G re e n Ri verTrailGre en River CITY OFRENTONCITY OFTUKWILA UNINC.KING COUNTY Black RiverPump Station EndProject ProposedRetaining Wall Proposed Culvert ConcreteRecyclingPlant Springbrook 18Black River Basin Springbrook 17Black River Basin Springbrook 17Black River Basin Lower Green River - West Basin DuwamishRiverBasin 7 5 3 1/2 Complex 6 4 BR Copyright:© 2013 National Geographic Society, i-cubed 0 600300Feet Figure 1-3Drainage Basins, Subbasins,and Site CharacteristicsPath: U:\PSO\Projects\Clients\1521-KingCo\554-1521-084 L2ST\99Svcs\GIS\MapDocs\Fig1-3TIR-Drn-8x11Apr2015.mxdParametrix Sources: King County, City of Renton, WDFW 2014, WSDOT. Lake to Sound Trail --- Segment A Legend: TDA 1a-Tukwila TDA 1b-Renton TDA 2 TDA 3 TDA 4 TDA 5 Existing Trail City Boundary Railroad Wetlands Black River Riparian Forest Floodway Floodplains (100-year) Subbasin Burlington Northern Santa Fe (BNSF) RailwaySW 7th StMonster R d S W68 th Oakesd a l e A v e S W Mau l e A ve SNaches Ave SWS 143rd St 80th Ave SI n t e r u r b a n A v e S S 144th St Beacon Co a l M i n e B N S F S 143rd St Duwamish River G re e n Ri ver Trail G reen River Spr i ngbrookCreek CITY OFRENTON CITY OFTUKWILA UNINC.KING COUNTY Black RiverPump StationBlackRiver EndProject BeginProject Proposed Rest Area ProposedRetaining Wall Proposed Culvert ConcreteRecyclingPlant Proposed Rest Area ! ! Wo PyUr BeD Ur Wo Ng BeC PITS Ur Ur BeC BeD Tu Ur BeC BeC Pu Pu BeD 0 600300Feet Figure 1-4Soils´Legend: TDA 1a-Tukwila TDA 1b-Renton TDA 2 TDA 3 TDA 4 TDA 5 Existing Trail City Boundary Railroad Hydrologic Soil Group A/B C DPath: U:\PSO\Projects\Clients\1521-KingCo\554-1521-084 L2ST\99Svcs\GIS\MapDocs\Fig1-4TIR-Soils-8x11June2013.mxdParametrix Sources: King County, City of Renton, WDFW 2011, WSDOT, NRCS Soils. Lake to Sound Trail --- Segment A Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 1‐13 1.3 Developed Site Conditions The proposed Segment A trail is designed to integrate into the existing landscape with as little alteration as possible. As previously stated, the paved trail will follow an existing dirt path and maintenance road. The trail will generally follow existing contours and maintain the current surface water flow patterns and discharge locations. Specific elements that will be included in the Segment A project are:  Constructing a 12‐foot‐wide asphalt pavement trail with 2‐foot‐wide shoulders and 1‐foot‐wide clear zones from the edge of the pavement (approximately 2.9 acres of impervious surface)  Performing minor grading to construct the trail (approximately 1,410 cubic yards of cut and 2,980 cubic yards of fill, disturbing an area of approximately 0.72 acres outside the proposed trail footprint).  Performing ground improvements, which will disturb an area of approximately 0.17 acres, to mechanically improve the physical properties of weak soils in the vicinity of the proposed trail bridge footings.  Constructing an undercrossing feature (a fenced canopy supported by posts) beneath two railroad bridges to protect trail users from potential falling debris  Installing a new trail bridge over the Black River to the east of the existing Monster Road Bridge, which cannot be improved to safely accommodate the envisioned trail use  Installing a pedestrian‐actuated signal crossing of Monster Road south of the bridge  Installing approximately 250 feet of sidewalk improvements at the southwest approach to Monster Road  Building a retaining wall near the south approach to Monster Road  Building three retaining walls north of the proposed trail bridge over the Black River to minimize fill impacts to adjacent areas  Constructing up to two 10‐foot by 20‐foot pull‐out rest areas (one at the northern perimeter of the Black River Riparian Forest and one just west of the Black River Pump Station)  Installing one box culvert and five new catch basins  Building two retaining walls, one on each side of the box culvert to avoid impacts to adjacent wetlands  Installing split‐rail fencing and plantings to minimize the potential for disturbance to sensitive wildlife  Restoring the remaining disturbed areas with native plantings and soil amendments The Segment A alignment and profile will be adjusted and walls may be designed to minimize cut and fill impacts. Table 1‐1 provides a comparison of the existing and proposed effective impervious area (EIA) for each TDA within the project site. Dispersion best management practices (BMPs) will be used along the trail to maintain the existing sheet flow stormwater patterns wherever possible. The effective impervious fractions applied to the actual total impervious areas within each TDA are 0 percent of total impervious for portions where full dispersion is applicable, 50 percent of total impervious where basic Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County 1‐14 April 2015 │ 554‐1521‐084 (A/3T200B) dispersion will be used, and 100 percent of total impervious where no dispersion is feasible. A detailed summary of impervious area calculations for each TDA is provided in Appendix B. Table 1‐1. Effective Impervious Area Comparison TDA1 Station Length (mile) Total Area (acre) EIA2 (acre) Discharge Location Start End Existing Proposed Tukwila Green River Trail to Monster Road (A‐Line Segment) 1a 1+00 7+65 0.13 0.36 0.01 0.13 Sheet flow to Black River Renton Green River Trail to Monster Road (A‐Line Segment) ‐ continued 1b 7+65 14+20 0.12 0.42 0.03 0.18 Sheet flow to Black River Monster Road Bridge (C‐Line Segment) 2 201+11 206+50 0.10 1.05 0.85 0.87 Ditch outfall to Black River Monster Road to Naches Avenue (B‐Line Segment) 3 101+77 110+00 0.16 0.52 0.12 0.07 Sheet flow to Black River 4 110+00 132+50 0.43 1.36 0.14 0.07 Sheet flow to wetlands 5 132+50 143+17 0.20 0.64 0.05 0.15 Sheet flow to wetlands Total Project 1.20 1.47 1 TDA = Threshold Discharge Area 2 EIA = effective impervious area Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 2‐1 2. CONDITIONS AND REQUIREMENTS Both the City of Tukwila and the City of Renton have adopted the KCSWDM with jurisdictional addenda. Therefore, the Segment A trail stormwater design follows the guidelines provided in the KCSWDM, the City of Renton 2010 Amendments to the 2009 King County Surface Water Design Manual (Renton Addendum, Renton 2010), and the City of Tukwila Infrastructure Design and Construction Standards (Tukwila Addendum, Tukwila 2010). All three manuals identified above apply requirements based on the size of a project. The Segment A project will result in greater than 2,000 square feet (approximately 0.05 acre) of new and replaced impervious surface (Table 1‐1); therefore, the project requires a full drainage review. According to Table 1.1.2.A in the KCSWDM, projects subject to a full drainage review must meet eight core requirements and five special requirements. In addition, the 2010 Renton Addendum lists a sixth special requirement that must be reviewed. The core and special requirements were evaluated for each TDA and summarized in Table 2‐1. The details of the analysis, including the basis of hydrologic and hydraulic design, are discussed in subsequent sections of this TIR. Table 2‐1. Summary of Core and Special Requirements Core and Special Requirements Proposed Stormwater Management Approach TIR Section CR1: Discharge Location Preserve existing discharge locations to Black River and riparian wetlands. 4 CR2: Offsite Analysis Offsite analysis complete. 3 CR3: Flow Control TDA 1a is subject to Tukwila Level 2 Conservation Flow Control Standard (match flow durations from one‐half of 2‐year through 50‐year frequencies). TDAs 1b to 5 are subject to the Renton Peak Rate Flow Control Standard (Level 1/Basic Flow Control) matching existing conditions, (match the 2‐, 10‐, and 100‐year peak rate flows). The Segment A project is subject to a flow control exemption because it will result in no more than 0.1 cubic feet per second (cfs) increase in the 100‐year peak flow rate in each TDA. 4 CR4: Conveyance System Typically, runoff will sheet flow from the paved trail to the adjacent gravel shoulder and then to existing drainage pathways. At Monster Road, the project will install connections to the existing roadway conveyance systems to maintain existing drainage patterns. A new pedestrian bridge will be constructed to cross over the Black River east of the Monster Road Bridge. The bridge is designed to have 3 feet of freeboard from 100 year floodplain to bottom of superstructure elevation. A new box culvert at B‐Line Station 126+00 will be designed to convey discharge from offsite areas at the 25‐year peak flow with 6 inches of freeboard. Near B‐Line 105+00, one new catch basin will be installed to extend an existing pipe. 5 Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County 2‐2 April 2015 │ 554‐1521‐084 (A/3T200B) Table 2‐1. Summary of Core and Special Requirements Core and Special Requirements Proposed Stormwater Management Approach TIR Section CR5: Erosion and Sediment Control The construction stormwater pollution prevention plan (CSWPPP) will be prepared and submitted to the Cities of Tukwila and Renton prior to construction as a separate document. 8 CR6: Maintenance and Operations (M&O) King County will provide maintenance and operations for the trail. 10 CR7: Financial Guarantees and Liability King County will provide financial information at the time of permit application. 9 CR8: Water Quality Non‐motorized trails are considered non‐pollution generating impervious surfaces and water quality treatment is not required. Therefore, a water quality analysis is not required for the Segment A trail. 4 SR1: Other Adopted Requirements No area‐specific requirements apply to this project. n/a2 SR2: Flood Hazard Area Delineation The trail is located within the 100‐year floodplain in TDA 1. 6 SR3: Flood Protection Facilities The trail design provides onsite compensatory storage for trail grading within the 100‐ year floodplain in TDA 1. 6 SR4: Source Control This special requirement is not applicable to this project because it does not meet the commercial development permit threshold. n/a SR5: Oil Control This special requirement is not applicable to this project because the trail is not a pollution‐generating surface and does not meet the high‐use site threshold. n/a SR6: Aquifer Protection Area1 This special requirement is not applicable to this project because the trail is not in an Aquifer Protection Area. n/a 1 Special Requirement 6 is specific to the 2010 Renton Addendum. 2 n/a = not applicable Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 3‐1 3. OFFSITE ANALYSIS This section presents the Level 1 downstream analysis performed for the site in compliance with KCSWDM Core Requirement Number 2. The intent of the downstream analysis is to identify potential offsite flooding, erosion, water quality, and/or other hydrology‐related issues that may be created or aggravated by the proposed project; evaluate issues identified; and take appropriate measures to prevent creating or aggravating potential problems. The elements of the downstream analysis are described in the sections below. 3.1 Study Area Definition and Maps The study area includes the proposed Segment A project site, Wetlands 1 through 5, and the overland flow path to the Black River. As shown on Figure 1‐3, the study area lies within the Black River Basin in the Springbrook 17 and 18 Subbasins. The study area extends through the cities of Tukwila and Renton, within Section 13, Township 23N, Range 04E. 3.2 Resource Review The King County geographic information system (GIS) was accessed through the web‐based iMAP tool (King County 2013) to identify past studies, known drainage problems, sensitive areas, wetlands, migrating river studies, King County‐designated water quality problems, and floodplain/floodway studies within the study area. Map sets were reviewed for information on land use, zoning, surface water features, stormwater services, groundwater, critical areas, and shorelines (Appendix C). Based on the review of the King County GIS information, the following water resource‐related elements exist within the study area:  Black River and Green River  Black River Riparian Forest  Floodway and 100‐year floodplain  High susceptibility to groundwater contamination within TDA 1  Shoreline designation along the Green River in TDA 1  National Pollutant Discharge Elimination System (NPDES) discharge point in TDA 1 In addition, the Green River is classified as having a Shoreline of Statewide Significance, and the Black River and Springbrook Creek are city‐designated Shorelines [Renton Shoreline Master Program 4‐3‐090‐B]. 3.3 Field Inspection Parametrix performed a Level 1 field inspection of the trail corridor on February 12, 2013. The weather was overcast and cool. The purpose of the field inspection was to identify any drainage or erosion problems downstream of the project corridor. The field inspection was also used to verify TDA boundaries and their connections 0.25 mile downstream of their trail discharge location. Photographs from the field inspection are provided in Appendix C. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County 3‐2 April 2015 │ 554‐1521‐084 (A/3T200B) 3.3.1 TDA 1 (A‐Line Stations 1+00 to 14+20) TDA 1 begins within the city of Tukwila from Station 1+00 to Station 7+65 between the Green River and the soccer fields at Fort Dent. Land cover consists of well‐established grass and planted trees with an access road composed of a compacted tire track. Soils are classified as Newberg silt loam, hydrologic soil group A/B (NRCS 2013). The ground surface is relatively flat with small undulations. Runoff in this area infiltrates into the soil on the south side of the proposed trail. Any runoff on the north side of the proposed trail that does not infiltrate will flow into the Black River. Two railroad trestles and one overhead water line are located between Station 6+95 and Station 8+00. The trestles form a cover over this area and intercept the rainfall. The portion of TDA 1 from Station 7+65 to Station 14+82 lies within the city of Renton. Land cover in this area is established grass, shrubs, and trees surrounding a compacted dirt path/access road. Runoff between Stations 7+65 and 10+50 tends to sheet flow to the north towards the Black River. From Stations 10+50 to 14+20, runoff sheet flows along the path/access road and then discharges at approximately Station 10+50 to the north and the Black River. 3.3.2 TDA 2 (C‐Line Stations 201+11to206+50) TDA 2 is located along Monster Road and includes areas south and north of the road. The south approach consists of the KP Corporation driveway and roadway, sidewalk, and wide shoulder associated with Monster Road. The north approach consists of the vegetated area between Monster Road and the south embankment of the Black River, where the proposed pedestrian bridge approach and abutment will be installed and the pedestrian bridge will cross over the Black River. Monster Road consists of a 60‐foot to 90 foot‐wide paved area (roadway, sidewalk, and existing bridge) that will not change from the existing impervious land cover. Runoff from the portion of the proposed trail that approaches and crosses the existing Monster Road (TDA 2) is collected into the storm drain systems on the north and south sides of the roadway. The north Monster Road storm drain system drains to an existing ditch that discharges to the Black River on the southeast side of the bridge. The south Monster Road storm drain system is conveyed southwest of Monster Road and continues onto private property adjacent the Black River. Runoff from TDA 2 sheet flows southeast on top of the bridge and is collected in a piped conveyance system that discharges to a roadside ditch north of Monster Road, adjacent to C‐Line Station 203+70. The ditch flows northwest adjacent to the bridge and discharges to the Black River. Land cover and related runoff quantities will not change for TDA 2; therefore, the piped conveyance system and roadside ditch are expected to have adequate capacity for the proposed project. 3.3.3 TDA 3 (B‐Line Stations 101+77 to 110+00) TDA 3 follows along the existing gravel access roadway from Station 101+77 to Station 110+00. Soils in TDA 3 are classified as Woodinville silt loam, hydrologic soil group D (NRCS 2013). Drainage along the roadway in TDA 3 tends to sheet flow to the southwest along the gravel road and then discharges to the south into the Black River. An ecology block barrier exists between the existing 12‐foot‐wide gravel road and the Black River to the south from Station 101+00 to the point at which the access road splits near Station 105+00. Beyond the split at Station 105+00, the proposed project follows the alignment to the north, where the existing access road narrows to approximately 10 feet. Wetland 5 is located on the northwest side of the gravel roadway between Stations 102+25 and 106+00. Drainage from this area enters a catch basin, is conveyed beneath the access road through a 12‐inch culvert near Station Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 3‐3 105+18, and discharges into the Black River. Wetland 6 is located on the southeast side of the trail between Stations 105+90 and 107+10. Drainage in this area sheet flows diagonally across the gravel roadway from the northwest to the southwest towards Wetland 6. A slight ridge exists at Station 110+00 where TDA 2 ends and TDA 3 begins. 3.3.4 TDA 4 (B‐Line Stations 110+00 to 132+50) Topography in TDA 4 gently slopes from the northwest to the southeast and runoff sheet flows to nearby wetlands. Soils are classified as Woodinville silt loam, hydrologic soil group D (NRCS 2013). Beginning at Station 110+00, the gravel roadway narrows to approximately 6 feet in width and then narrows to 4 feet around Station 124+00. A low point is located near Station 126+00 where a small drainage ditch (approximately 12 inches wide) crosses from the north to the south and discharges into Wetlands 3 and 4. The main contribution of flow in this ditch is from a 12‐inch culvert located on the north side of the road that directs drainage under the railway. The gravel road gently slopes uphill towards Station 132+50 where there is a slight high point. Water from the nearby wetlands slowly flows through the Black River Riparian Forest to the Black River, which is approximately 300 to 1,000 feet south of the gravel roadway. The water then flows towards the Black River Pump Station dam to the west, then to the convergence point with the Green River. 3.3.5 TDA 5 (B‐Line Stations 132+50 to 143+17) The ground surface in TDA 5 is relatively flat, with a slight downward slope to the south towards the Black River. Soils are classified as Woodinville silt loam, hydrologic soil group D (NRCS 2013). Runoff from the existing access road/path discharges to the west/southwest to the Wetland 1/2 Complex, which is a series of interconnected wetlands located on either side of the existing road. The width of the access road/path is approximately 4 feet wide throughout TDA 5. The elevation along the project alignment is very flat between Stations 132+50 and 138+00, holding at approximately 28 feet. Runoff in this area slowly sheet flows to the southwest. A catch basin with a solid lid is located near Station 133+00 on the north side of the gravel road. This catch basin is connected on the north to an 18‐inch ADS (Advanced Drainage Systems high‐density polyethylene) pipe and on the south to a 24‐inch ADS pipe. This system appears to convey drainage from the north side of the railway to the Wetland 1/2 Complex located approximately 90 feet to the south of the gravel road. Near Station 139+50, a 12‐inch culvert connects the Wetland 1/2 Complex across the access road. Drainage from the wetlands reaches the Black River approximately 600 feet to the southwest. Water flows to the west in the Black River where it joins with drainage from TDAs 2 and 3 more than 0.25 mile downstream. 3.4 Drainage System and Problem Descriptions The existing drainage systems consists of the cross culverts, and Monster Road conveyance systems described in Section 3.3. There appears to be adequate capacity and no apparent drainage problems. 3.5 Mitigation of Existing or Potential Problems No existing problems were identified and no potential problems are anticipated. Therefore, no mitigation is proposed. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 4‐1 4. FLOW CONTROL AND WATER QUALITY FACILITY ANALYSIS AND DESIGN The flow control analysis and water quality evaluation for the project is presented in the following sections. 4.1 Existing Site Hydrology (Part A) Existing soil types, land cover, and runoff patterns are described for each TDA in Section 3.2. This section describes runoff modeling assumptions and site parameters used in analyzing the existing site hydrology. Drainage Area Delineations TDA boundaries for the project vicinity were delineated based on existing site topography. Within each identified TDA, the site boundaries were delineated based on the proposed cut‐and‐fill line. Some clearing may take place beyond the cut‐and‐fill line; however, these areas will be restored to vegetated cover. The vegetated areas beyond the cut‐and‐fill line were not included in the runoff modeling analysis. Land Cover Existing land cover within the site boundary for each TDA was identified based on field investigation and review of aerial photography. The existing cover in TDA 1 was generally modeled as forest, with the exception of the existing railroad crossings, which were modeled as impervious surface. The existing compacted dirt path/road in TDA 1 was not differentiated from the forested area in the model. TDA 2 consists of the impervious surface of Monster Road and the vegetated Black River embankment where the bridge approach and abutment will be installed. The existing land cover was modeled as impervious surface area and till forest. In TDAs 3, 4, and 5, the existing gravel maintenance road was considered impervious surface with an effective impervious fraction of 0.50 based on Table 3.2.2.E of the KCSWDM. The ineffective impervious portion of the maintenance road was modeled as grass and the remaining area in TDAs 3, 4, and 5 was modeled as forest. Soils Soil types were sorted into hydrologic soil groups based on Natural Resources Conservation Service classifications (NRCS 2013) and model soil types based on Table 3.2.2.B of the KCSWDM. Newberg silt loam (TDAs 1, 2, and 3) is considered hydrologic soil group A/B and was modeled as till. Woodinville silt loam (TDAs 4 and 5) is considered hydrologic soil group D and was modeled as till. 4.2 Developed Site Hydrology (Part B) The proposed condition is shown on the design drawings provided in Appendix A. Modeling assumptions and site parameters used in analyzing the proposed site hydrology are discussed in this section. Drainage Area Delineations The proposed trail will maintain the existing drainage patterns along the trail corridor. Therefore, proposed drainage areas will match existing drainage areas. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County 4‐2 April 2015 │ 554‐1521‐084 (A/3T200B) Land Cover Within each TDA, proposed land cover was determined by separating the total site area into (1) the portion that will be the proposed trail, and (2) everything else, which will be shrub/forest. The area of the proposed trail was calculated as 16‐foot width (the 12‐foot‐wide paved trail and two 2‐foot‐wide gravel shoulders) multiplied by the length of the TDA segment. The trail and gravel shoulders are considered new impervious area based on the KCSWDM definition. The total impervious area proposed for each TDA was assigned an effective impervious percentage based on the flow dispersion BMP planned for that portion of the trail. In TDA 2, remaining areas outside of the proposed trail and the impervious surface of Monster Road were modeled as grass. For all other TDAs, remaining areas within the proposed site boundary will be shrub/forest and were modeled as forest. BMP Adjustments Following the guidelines in Table 1.2.3.C of the KCSWDM, impervious portions of the trail that will be fully dispersed were modeled as forest, while portions of the trail that will receive basic dispersion were modeled as 50 percent impervious and 50 percent grass. 4.3 Performance Standards (Part C) This section discusses applicable design standards from the KCSWDM and the Renton and Tukwila Addenda. 4.3.1 Flow Control Standards The Cities of Renton and Tukwila have designated area‐specific flow control standards for each of their jurisdictions. The portion of the project within the city of Tukwila (TDA 1a) is subject to a Level 2 Conservation Flow Control Standard matching existing conditions, which requires proposed target surfaces to match existing runoff flow durations for one‐half of the 2‐year frequency through the 50‐ year frequency (Tukwila 2010). The remainder of the project area is located within the City of Renton and is subject to a Peak Rate Flow Control Standard (Level 1/Basic Flow Control) matching existing conditions, which requires runoff from proposed target surfaces to match the 2‐, 10‐, and 100‐year peak rate runoff flows for existing conditions (Renton 2010). Target Surfaces Flow control requirements apply to areas identified as target surfaces. Target surfaces for Basic (Peak) Flow Control Areas include new impervious and new pervious surfaces that are not fully dispersed. Target surfaces for Conservation Flow Control Areas include areas not fully dispersed that are new impervious surface; new pervious surface; existing impervious surface added since January 8, 2001; and certain types of replaced impervious surface. Flow Control Exemption In both jurisdictions, projects are exempt from constructing flow control facilities for a given TDA if the 100‐year peak runoff flow from the proposed target surfaces will be within 0.1 cfs of the existing 100‐ year peak runoff flow. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 4‐3 4.3.2 Conveyance System The Segment A project will maintain the existing drainage patterns of dispersed sheet flows from the trail surface within TDAs 1, 3, 4, and 5. For off‐site runoff that passes through the project site, existing culverts and storm pipes will either remain undisturbed or be extended to account for the trail alignment and width. TDA 2 is located on Monster Road, and the proposed trail and sidewalk improvements will require additions to the existing conveyance systems to maintain existing drainage patterns. Also, one new box culvert will be constructed in TDA 4 in Renton at the existing ditch location near B‐Line Station 126+00 to convey the off‐site drainage to the opposite side of the trail and discharge in the same location as the existing ditch. The proposed pedestrian bridge and abutments are designed to be above the 100‐year floodplain elevation. Construction activities will occur outside of the Black River ordinary high water mark (OHWM) and project improvements will not change the shape of the Black River channel. Therefore, no conveyance or hydraulic analyses were performed for the pedestrian bridge crossing over the Black River. Further discussion of the pedestrian bridge is provided in Section 5.2. The existing onsite conveyance systems will not experience a change in contributing flow characteristics as a result of the proposed project, therefore, the proposed modifications to the Monster Road conveyance systems and trail culverts do not require conveyance capacity analysis. Similarly, the proposed box culvert will replace an existing ditch that flows across the current access road near station. The contributing runoff will not change as a result of the trail project, therefore, culvert will be sized to convey at least as much capacity as the existing ditch. 4.3.3 Water Quality Treatment Water quality treatment is required by the Cities of Renton and Tukwila for runoff from pollution‐ generating surfaces. The Segment A project will not include any pollution‐generating surfaces; therefore, no water quality treatment is proposed. 4.4 Flow Control System (Part D) Flow Control Facility Exemption The proposed Segment A project will maintain 100‐year peak flows for each TDA within the 0.1 cfs threshold and will therefore be exempt from requirements to construct flow control facilities. The King County Runoff Time Series (KCRTS, King County 2009b) software was used to simulate runoff flows from existing and proposed conditions (including dispersion BMPs) for the Segment A project. Table 4‐1 summarizes the modeling results. Detailed results of flow modeling for each TDA are provided in Appendix D. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County 4‐4 April 2015 │ 554‐1521‐084 (A/3T200B) Table 4‐1. Comparison of Peak Runoff Rates TDA Total Area (acre) Existing Cover (acre) Proposed Cover (acre) 100‐Year Peak Runoff (cfs) EIA1 Grass Shrub/ Forest EIA1 Grass Shrub/ Forest Existing Proposed Change 1 0.78 0.04 ‐ 0.73 0.31 0.18 0.29 0.1 0.2 0.1 2 1.05 0.85 ‐ 0.21 0.87 0.18 ‐ 0.4 0.4 0 3 0.52 0.12 ‐ 0.40 0.14 0.07 0.31 0.1 0.1 0 4 1.36 0.14 ‐ 1.22 0.07 0.02 1.27 0.1 0.1 0 5 0.64 0.05 ‐ 0.60 0.15 0.12 0.37 0.1 0.1 0 1 EIA = effective impervious area Flow Dispersion BMPs The Segment A project will employ basic and full dispersion BMPs wherever possible. The following design requirements apply: Basic Dispersion:  The dispersion device is sheet flow provided by the 12‐foot‐wide paved trail and 2‐foot‐wide gravel shoulders.  A 10‐foot‐wide vegetated flow path is provided to meet the requirements of the sheet flow dispersion method.  The dispersion flow path is less than 15 percent in grade, covered in native vegetation, and located between the trail and the downstream drainage feature (wetlands and/or Black River).  There are no landslide hazard areas or septic systems downstream and the dispersion will not create flooding or erosion impacts downstream. Full Dispersion:  The dispersion device is sheet flow provided by the 12‐foot‐wide paved trail and 2‐foot‐wide gravel shoulders.  A 100‐foot‐wide vegetated flow path is provided to meet the requirements of the sheet flow dispersion method.  The dispersion flow path is less than 15 percent in grade, covered in native vegetation, and located between the trail and a downstream drainage feature (wetlands and/or Black River).  There are no landslide hazard areas or septic systems downstream and the dispersion will not create flooding or erosion impacts downstream. The locations of dispersion techniques within each TDA are listed in Appendix B. The Segment A trail, along with the proposed sheet flow dispersion components, will be located within wetland buffers in TDAs 3, 4, and 5. As discussed in the critical area report (Parametrix 2015b), the proposed trail alignment will result in some impacts to adjacent wetland buffers; therefore, a wetland mitigation site will be developed. The critical area report details the impacts study, the selection of the mitigation site, and the size of the mitigation site. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 4‐5 4.5 Water Quality (Part E) The Segment A project will not include any pollution‐generating surfaces; therefore, no water quality treatment is proposed. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 5‐1 5. CONVEYANCE SYSTEM ANALYSIS AND DESIGN The Segment A project will maintain the existing dispersed sheet flow drainage patterns within each TDA and leave all existing cross‐culverts in place. The project will include the new conveyance system components discussed below. 5.1 Monster Road Storm Drain Systems Two existing conveyance systems are located on Monster Road: one on the north side of the road, and another along the gutter line of the south sidewalk, in front of the KP Corporation property (TDA 2). As shown on the design drawings presented in Appendix A, the project will install a new ramp and pedestrian‐actuated signal crossing at the southeast end of the Monster Road bridge (C‐Line Station 202+50). To accommodate the new flow line that will be created by the pedestrian safety improvements, a lateral connection with the 12‐inch storm drain pipe will be established by installing one new catch basin in the gutter and a second catch basin in the existing conveyance system on the north side of Monster Road. The south trail approach to Monster Road will follow the existing Monster Road sidewalk and a new sidewalk will be installed further north. The new sidewalk will create a new gutter flow line and a depressed area southwest of the trail ramp. To accommodate for the modified runoff patterns, one new catch basin will be installed in the depression between the sidewalk and the trail southwest of the trail ramp (C‐Line Station 202+37), and a second catch basin will be installed in the gutter near the driveway entrance to the KP Corporation property (C‐Line Station 203+34). Collected runoff will be conveyed via 12‐inch storm drain pipe from the catch basin near the trail ramp (C‐Line Station 202+37) to the catch basin in the new gutterline (C‐Line Station 203+34), and re‐connect to the existing storm conveyance system in the existing catch basin located south side of the trail near C‐Line Station 203+33. Drainage problems have not been documented in this area and the contributing area will be less than or equal to the existing area; therefore, 12‐inch storm drain pipes similar to the existing pipe systems will have adequate capacity to convey runoff. As a result, no calculations were performed. 5.2 Pedestrian Bridge As previously discussed, the proposed pedestrian bridge and abutments will be constructed above the Black River 100‐year floodplain elevation. The Black River 100‐year floodplain elevation at the proposed pedestrian bridge is calculated at 22.57 feet (NAVD 88) using the 1995 Flood Insurance Rate Map (FIRM). The trail surface across the bridge is 6‐ feet above the floodplain elevation, which allows up to 3‐feet in bridge depth from top of trail to the bottom of any bridge element, plus 3‐feet of clearance from the bottom of any bridge element to the 100‐year floodplain elevation. Additionally, the north and south pedestrian bridge abutments will be installed outside of the 100 year floodplain elevation. The 3‐ foot clearance to base of bridge meets the bridge clearance design requirements for rivers where the 100‐year peak flow exceeds 100 cfs (Section 6.03.F of the King County Road Standards, Section 6.02.F). The project does not propose changes to the Black River channel and all work will be done outside of the ordinary high water mark (OHWM). As a result, the project does not anticipate the trail bridge improvements to have conveyance impacts to the Black River, and no calculations were performed. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County 5‐2 April 2015 │ 554‐1521‐084 (A/3T200B) Floodplain elevations are further discussed in Section 6.1, and the bridge design drawings are found in Appendix A. 5.3 TDA 3 Catch Basin The project will install a new catch basin in TDA 3 near B‐Line Station 105+05 with a 12‐inch storm drain pipe to tie into the existing catch basin. The existing catch basin collects offsite runoff and overflow from Wetland 5. The proposed trail cannot avoid covering this catch basin; therefore, it will be raised to grade and a solid locking lid will be installed. To maintain existing flow patterns, the new catch basin will be installed west of the trail perpendicular to the existing catch basin. This area does not have documentation of drainage problems and the contributing area will be less than or equal to the existing area. Therefore, a 12‐inch storm drain pipe extending the existing pipe will have adequate capacity to convey runoff. As a result, no calculations were performed. 5.4 TDA 4 Box Culvert The project will construct one new box culvert in Renton at the existing ditch location near B‐Line Station 126+00 to convey the upstream drainage to the opposite side of the trail and discharge in the same location as the existing ditch. The existing ditch is 1 foot wide and 1 foot deep with 2:1 side slopes and a longitudinal slope of 5.26 percent. The maximum capacity of this ditch is 13.29 cfs. No signs of erosion or drainage problems were evident during the downstream analysis. Because there will be no change in the area contributing runoff to the culvert, the project did not perform a separate drainage basin analysis for contributing flow, and will instead design a culvert that will convey at least 13.29 cfs when half full. Based on stakeholder negotiations, a concrete box culvert with a 48‐inch rise and 40‐inch width will be installed. The culvert will be set flat and countersunk with streambed gravel with a depth of approximately 2 feet at the upstream end and approximately 1 foot at the outfall. The culvert will convey 29.6 cfs at 1 foot deep (1 foot of freeboard) and 59.2 cfs at full flow capacity. Culvert analysis and design documentation is provided in Appendix E. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 6‐1 6. SPECIAL REPORTS AND STUDIES 6.1 Floodplain Analysis Floodplain impacts include any site activity that will place material at or below the 100‐year floodplain elevation within a floodplain boundary. The Green and Black River floodplain boundaries and elevations within the vicinity of the Segment A project were identified based on 1995 Federal Emergency Management Agency (FEMA) Federal Insurance Rate Map 53033C, Panels 0975F and 0976F (FEMA 1995). The project team depicted the floodplain boundary in the design drawings and floodplain figures using City of Renton GIS Data (Renton 2015), which is a digital interpretation of the 1995 FEMA FIRM. The floodplain boundary is shown on Figure 1‐3 and in detail in Appendix F. Approximately 1,050 feet of the Segment A trail alignment is located within the Green River and Black River floodplains in TDA 1, from the connection to the Green River Trail at A‐Line Station 1+00 to Station 11+50. In TDA 3, approximately 350 feet of the proposed trail alignment is located in the Black River floodplain from B‐Line Station 101+77 to approximately Station 105+50. The remainder of the trail in TDA 3 and the entire length in TDA 4 is located adjacent to the floodplain. The trail in TDA 5 is located in the floodplain from B‐Line Station 132+50 to the end of the project at Naches Avenue (B‐Line Station 143+17). The FEMA floodplain elevation west of the Black River Pump Station (A‐Line Station 1+00 through 17+76, and B‐Line Station 101+78 through 105+50 is 19 feet NGVD 29, which translates to 22.57 feet NAVD 88 in the project datum. East of the Black River Pump Station, the FEMA floodplain elevation is 15 feet NGVD 29, which translates to 18.57 feet NAVD 88. Based on floodplain elevations, the proposed trail is beneath the 100‐year floodplain elevations in TDA 1 from A‐Line Station 1+00 to Station 11+50. The remainder of the trail will be constructed above the floodplain elevations. The proposed vertical alignment of the trail will approximate existing grade as close as possible while providing smooth transitions for ADA compliance and positive drainage towards the river. Between A‐ Line Stations 1+00 and 12+25, approximately 217 cubic yards of fill will be placed and approximately 242 cubic yards of excavation will be conducted. The net result of the project will remove approximately 25 cubic yards of material below the floodplain elevation. Detailed calculations are provided in Appendix F. 6.2 Stream Discipline Report In support of the WSDOT Environmental Classification Summary form for the NEPA Documented Categorical Exclusion process, this report describes streams and aquatic resources in the project vicinity, including two fish‐bearing streams. This report also evaluates potential impacts to streams and stream buffers from the proposed project, presents avoidance and minimization measures included in the project design, and discusses conceptual mitigation for unavoidable impacts (Parametrix 2015a). 6.3 Critical Area Study A critical area report (Parametrix 2015) has been prepared to evaluate the proposed trail impacts to the wetlands and associated buffers along the trail corridor in Renton. Because of the amount of wetland buffer impacts created by the new trail alignment, there will be a wetland mitigation site. The critical area report details the impacts study, the selection of the mitigation site, and the size of the mitigation site. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County 6‐2 April 2015 │ 554‐1521‐084 (A/3T200B) 6.4 Vegetation and Wildlife Discipline Report This report provides information in support of the WSDOT Environmental Classification Summary form for the National Environmental Policy Act (NEPA) Documented Categorical Exclusion process by describing vegetation and wildlife resources in the project vicinity, evaluating potential impacts to critical areas from the proposed project, and presenting mitigation for potential impacts (Parametrix 2015c). Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 7‐1 7. OTHER PERMITS Other permits required for this project include:  City of Tukwila Shoreline Master Program  City of Renton Shoreline Conditional Use Permit  NPDES Construction Stormwater General Permit Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 8‐1 8. CSWPPP ANALYSIS AND DESIGN The construction stormwater pollution prevention plan (CSWPPP) will be prepared and submitted to the Cities of Tukwila and Renton prior to construction as a separate document. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 9‐1 9. BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT The Segment A project is a public improvement project led by King County within the public county right‐of‐way. Quantities will be prepared for the work elements pertaining to the project, and an engineer’s estimate will be provided to establish an opinion of cost for the project. However, bonding worksheets usually prepared for private developer projects have not been developed for this public county project. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 10‐1 10. OPERATIONS AND MAINTENANCE MANUAL Operation and maintenance of the Segment A trail will be provided by King County staff after completion of the project. Applicable operation and maintenance guidelines from the KCSWDM are provided in Appendix G. Lake to Sound Trail ‐ Segment A Final Technical Information Report Drainage and Floodplain King County April 2015 │ 554‐1521‐084 (A/3T200B) 11‐1 11. REFERENCES FEMA (Federal Emergency Management Agency). 1995. Flood Insurance Rate Map for King County, Washington, and Incorporated Areas. Map 53033C, Panels 0957F and 0976F. Effective September 29, 1989; Revised May 16, 1995. King County. 2009a. King County Surface Water Design Manual. King County Department of Natural Resources and Parks. January 2009. King County. 2009b. King County Runoff Time Series (KCRTS) Hydrologic Simulation Model for Implementing the Runoff‐Files Methodology, Version 6.0. King County Department of Natural Resources and Parks Water and Land Resources Division. March 2009. King County. 2012. King County Geographic Information System Floodway and Floodplain data layers. Available at: http://www5.kingcounty.gov/gisdataportal/. Data generated 2012. King County. 2013. King County iMap Interactive Mapping Tool. Accessed at: http://www.kingcounty.gov/operations/gis/Maps/iMAP.aspx. May 2013. NRCS (Natural Resources Conservation Service). 2013. Web Soil Survey Application. Accessed at: http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm. April 2013. Parametrix. 2015a. Lake to Sound Trail – Segment A: Stream Discipline Report. Prepared for King County, Seattle, Washington. April 2015. Parametrix. 2015b. Lake to Sound Trail – Segment A, Final Critical Area Study. Prepared for King County Parks Division. Seattle, Washington. April 2015. Parametrix. 2015c. Lake to Sound Trail – Segment A: Vegetation and Wildlife Discipline Report. Prepared for King County, Seattle, Washington. April 2015. Renton, City of. 2010. Amendments to the King County Surface Water Design Manual. City of Renton Public Works Department, Surface Water Utility. February 2010. Renton, City of. 2015. GIS Data. FEMA Floodplain Boundary. http://rentonwa.gov/government/default.aspx?id=29887. Data Downloaded May 30, 2015. Tukwila, City of. 2010. Infrastructure Design and Construction Standards. City of Tukwila Public Works Department. Fourth Edition, revised April 2010. NRCS (Natural Resources Conservation Service). 2013. Web Soil Survey. Accessed at: http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm. April 2013. Appendix A Project Design Drawings 1 G1COVER SHEETENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 2 G2 ABBREVIATIONS AND SHEET LIST ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 3 G3LEGENDENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL LEGEND LEGEND ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 9 DM1 DEMOLITION AND TESC PLAN ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 10 DM2 DEMOLITION AND TESC PLAN ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 11 DM3 DEMOLITION AND TESC PLAN ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 12 DM4 DEMOLITION AND TESC PLAN ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 13 DM5 DEMOLITION AND TESC PLAN ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 14 DM6 DEMOLITION AND TESC PLAN ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 15 DM7 DEMOLITION AND TESC PLAN WETLAND 1 / 2 COMPLEX WETLAND 1 / 2 COMPLEX WETLAND 1 / 2 COMPLEX ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 16 DM8 DEMOLITION AND TESC PLAN WETLAND 2A WETLAND 1 / 2 COMPLEX WETLAND 1 / 2 COMPLEX WETLAND 1 / 2 COMPLEX ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 17 DM9 DEMOLITION AND TESC PLAN 18 CS1TYPICAL CROSS SECTIONSENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL19C1PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL20C2PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL21C3PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL22C4PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL23C5INTERSECTION PLAN ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL24C6PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL25C7PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL26C8PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL27C9PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL28C10PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL29C11PLAN AND PROFILE ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL30C12PLAN AND PROFILEWETLAND 1 / 2COMPLEX ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL31C13PLAN AND PROFILEWETLAND 1 / 2COMPLEXWETLAND 1 / 2COMPLEX ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCESOFLAKE TO SOUND TRAIL SEGMENT AGREEN RIVER TRAIL TO NACHES AVE SW47DRAFT411 108TH AVENUE N.E., SUITE 1800BELLEVUE, WASHINGTON 98004T. 425.458.6200 F. 425.458.6363www.parametrix.com60% REVIEW SUBMITTAL32C14PLAN AND PROFILEWETLAND 2AWETLAND 1 / 2COMPLEXWETLAND 1 / 2COMPLEXWETLAND 1 / 2COMPLEX ENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL 33 C15 SIGN SCHEDULE AND GRADING DETAIL 34 SD1CULVERT DETAILSENGINEERING . PLANNING . ENVIRONMENTAL SCIENCES OFLAKE TO SOUND TRAIL SEGMENT A GREEN RIVER TRAIL TO NACHES AVE SW 47 DRAFT 411 108TH AVENUE N.E., SUITE 1800 BELLEVUE, WASHINGTON 98004 T. 425.458.6200 F. 425.458.6363 www.parametrix.com 60% REVIEW SUBMITTAL Appendix B Land Cover Area Calculations Appendix B - Land Cover Area CalculationsTDA 1ExistingProposedImpervious Pervious Impervious PerviousWidth [ft] Area [sf] Area [sf] Width [ft] Area [sf] Width Area [sf]Sta Start Sta EndTotal Length [ft]Gravel Trail(50% EIA)Crossing Imperv FeatureTotal Effective WidthTotal Exist Imperv Shrub/ ForestAsphaltTrailGravel Shoulders (Both)Crossing Imperv FeatureTotal WidthPost-BMP Dispersed WidthTotal New ImpervGrass GrassReplanted Shrub/ ForestCity of TukwilaNewberg soils = TillTDA 1A - 1+00 6+95 595 0 0 0 0 - 12 4 0 16 8 4760 8 4760 - Basic dispersion6+95 7+26 31 0 18 18 558 - 0 0 18 18 18 558 0 0 - BNSF Overpass7+26 7+65 39 0 0 0 0 - 12 4 0 16 8 312 8 312 - Basic dispersionSubtotal [sf] 15473 - - - - - - 558 14915 - - - - - 5630 - 5072 4771Subtotal [ac] 0.355 - - - - - - 0.013 0.342 - - - - - 0.129 - 0.116 0.110City of RentonNewberg soils = TillTDA 1B - 7+65 7+86 21 0 0 0 0 - 12 4 0 16 8 168 8 168 - Basic dispersion- 7+86 7+99 13 0 18 18 234 - 0 0 18 18 18 234 0 0 - Union Pacific Overpass7+99 11+00 301 0 0 0 0 - 12 4 0 16 8 2408 8 2408 - Basic dispersion- 11+00 13+56 256 0 0 0 0 - 12 4 0 16 16 4096 0 0 - No dispersion- 13+56 14+20 64 0 18 18 1152 - 0 0 18 18 18 1152 0 0 - KP Corp driveway, no LU changeSubtotal [sf] 18428 - - - - - - 1386 17042 - - - - - 8058 - 2576 7794Subtotal [ac] 0.423 - - - - - - 0.032 0.391 - - - - - 0.185 - 0.059 0.179TDA 1KCRTS Hourly, HistoricTotal [sf] 33901--- - - -1944 31957-----13688-7648 12565 Q100 = 0.08 cfsTotal [ac] 0.778--- - - -0.045 0.734-----0.314-0.176 0.288 Q100 = 0.19 cfs (increase of 0.11 cfs)TDA 2ProposedImpervious Pervious Impervious PerviousArea [sf] Area [sf] Width [ft] Area [sf] Area [sf]Sta Start Sta EndTotal Length [ft]Total Exist Imperv Shrub/ ForestExist Imperv to RemainNew ImperviousTotal New ImpervGrassReplanted Shrub/ ForestCity of RentonC-Line - 201+11 206+50 539 36828 9071 36828 1073 37901 7998 -TDA 2Subtotal [sf] 45899 - - - 36828 9071 - - 37901 7998 0Subtotal [ac] 1.054 - - - 0.845 0.208 - - 0.870 0.184 0.000Total Area[sf]JurisdictionStations(A-Line)CommentsJurisdictionTotal Area[sf]Stations(C-Line)ExistingCommentsNewberg soils = TillQ100 = 0.44 cfs (increase < 0.1 cfs)Q100 = 0.40 cfsKCRTS Hourly, HistoricMonster Rd and Ped Bridge1 of 3 Appendix B - Land Cover Area CalculationsTDA 3ExistingProposedImpervious Pervious Impervious PerviousWidth [ft] Area [sf] Area [sf] Width [ft] Area [sf] Width Area [sf]Sta Start Sta EndTotal Length [ft]Gravel Trail(50% EIA)Crossing Imperv FeatureTotal Effective WidthTotal Exist Imperv Shrub/ ForestAsphaltTrailGravel Shoulders (Both)Crossing Imperv FeatureTotal WidthPost-BMP Dispersed WidthTotal New ImpervGrass GrassReplanted Shrub/ ForestCity of RentonNewberg/ Woodinville soils = Till17+11 17+76 65 0 0 14 910 - 0 0 14 14 14 910 0 0 - Bridge over Black River- 101+77 103+00 123 12 0 6 738 - 12 4 0 16 16 1968 0 0 - No dispersion103+00 105+00 200 12 0 6 1200 - 12 4 0 16 8 1600 8 1600 -Basic Dispersion105+00 107+00 200 10 0 5 1000 - 12 4 0 16 8 1600 8 1600 -Basic Dispersion107+00 110+00 300 10 0 5 1500 - 12 4 0 16 0 0 0 0 -Full DispersionTDA 3KCRTS Hourly, HistoricTotal [sf] 22724 - - - - - - 5348 17376 - - - - - 6078 - 3200 13446Q100 = 0.08 cfsTotal [ac] 0.522 - - - - - - 0.123 0.399 - - - - - 0.140 - 0.073 0.309Q100 = 0.09 cfs(increase < 0.1 cfs)TDA 4Existing ProposedImpervious PerviousImpervious PerviousWidth [ft] Area [sf] Area [sf] Width [ft] Area [sf] Width Area [sf]Sta Start Sta EndTotal Length [ft]Gravel Trail(50% EIA)Crossing Imperv FeatureTotal Effective WidthTotal Exist Imperv Shrub/ ForestAsphaltTrailGravel Shoulders (Both)Crossing Imperv FeatureTotal WidthPost-BMP Dispersed WidthTotal New ImpervGrass GrassReplanted Shrub/ ForestCity of RentonWoodinville soils = Till- 110+00 124+00 1400 6 0 3 4200 - 12 4 0 16 0 0 0 0 - Full Dispersion124+00 124+33 33 4 0 2 66 - 12 4 0 16 0 0 0 0 -Full Dispersion124+33 125+50 117 4 0 2 234 - 12 4 0 16 8 936 8 936 -Basic Dispersion125+50 126+75 125 4 0 2 250 - 12 4 0 16 16 2000 0 0 -Walls: No Dispersion126+75 132+50 575 4 0 2 1150 - 12 4 0 16 0 0 0 0 -Full DispersionTDA 4KCRTS Hourly, HistoricTotal [sf] 59104 - - - - - - 5900 53204 - - - - - 2936 - 936 55232Q100 = 0.15 cfsTotal [ac] 1.357 - - - - - - 0.135 1.221 - - - - - 0.067 - 0.021 1.268Q100 = 0.13 cfs(increase < 0.1 cfs)JurisdictionTotal Area[sf]Stations(B-Line)CommentsJurisdictionTotal Area[sf]Stations(B-Line)Comments2 of 3 Appendix B - Land Cover Area CalculationsTDA 5ExistingProposedImpervious Pervious Impervious PerviousWidth [ft] Area [sf] Area [sf] Width [ft] Area [sf] Width Area [sf]Sta Start Sta EndTotal Length [ft]Gravel Trail(50% EIA)Crossing Imperv FeatureTotal Effective WidthTotal Exist Imperv Shrub/ ForestAsphaltTrailGravel Shoulders (Both)Crossing Imperv FeatureTotal WidthPost-BMP Dispersed WidthTotal New ImpervGrass GrassReplanted Shrub/ ForestCity of RentonWoodinville soils = Till- 132+50 132+59 9 4 0 2 18 - 12 4 0 16 0 0 0 0 - Full Dispersion132+59 135+85 326 4 0 2 652 - 12 4 0 16 8 2608 8 2608 -Basic Dispersion135+85 138+27 242 4 0 2 484 - 12 4 0 16 0 0 0 0 - Full Dispersion138+27 141+75 348 4 0 2 696 - 12 4 0 16 8 2784 8 2784 -Basic Dispersion141+75 142+50 75 4 0 2 150 - 12 4 0 16 0 0 0 0 - Full Dispersion142+50 143+17 67 4 0 2 135 - 12 4 0 16 16 1078 0 0 -No DispersionTDA 5KCRTS Hourly, HistoricTotal [sf] 28083 - - - - - - 2135 25948 - - - - - 6470 - 5392 16221Q100 = 0.07 cfsTotal [ac] 0.645 - - - - - - 0.049 0.596 - - - - - 0.149 - 0.124 0.372Q100 = 0.12 cfs(increase < 0.1 cfs)JurisdictionTotal Area[sf]Stations(B-Line)Comments3 of 3 Appendix C Offsite Analysis – Resource Review and Site Visit Photos Land Use & Zoning (Property Information) The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Property Information (http://www.metrokc.gov/GIS/iMAP) COMMENTS: Lake to Sound Trail Segment A Land Use & Zoning (Property Information) The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Property Information (http://www.metrokc.gov/GIS/iMAP) Hydrographic (Water Resources) The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Hydrographic Information (http://www.metrokc.gov/GIS/iMAP) COMMENTS: Lake to Sound Trail Segment A Hydrographic (Water Resources) The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Hydrographic Information (http://www.metrokc.gov/GIS/iMAP) Stormwater The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Stormwater (http://www.metrokc.gov/GIS/iMAP) COMMENTS: Lake to Sound Trail Segment A Stormwater The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Stormwater (http://www.metrokc.gov/GIS/iMAP) Groundwater The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Groundwater Program (http://www.metrokc.gov/GIS/iMAP) COMMENTS: Lake to Sound Trail Segment A Groundwater The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Groundwater Program (http://www.metrokc.gov/GIS/iMAP) Sensitive Areas The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Sensitive Areas (http://www.metrokc.gov/GIS/iMAP) COMMENTS: Lake to Sound Trail Segment A Sensitive Areas The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Sensitive Areas (http://www.metrokc.gov/GIS/iMAP) Shoreline Master Program The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Shoreline Master Program (http://www.metrokc.gov/GIS/iMAP) COMMENTS: Lake to Sound Trail Segment A Shoreline Master Program The information included on this map has been compiled by King County staff from a variety of sources and is subject to change without notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liable for any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map is prohibited except by written permission of King County. Date: 5/7/2013 Source: King County iMAP - Shoreline Master Program (http://www.metrokc.gov/GIS/iMAP) Project start, looking west at Green River Trail (near A‐Line Station 1+00) Looking west (near A‐Line Station 3+00) Looking west (near A‐Line Station 5+50) Looking west (near A‐Line Station 6+00) Looking east at railroad crossings (near A‐Line Station 6+25) Looking west at railroad crossings (near A‐Line Station 8+25) Looking west (near A‐Line Station 11+00) Looking east at Monster Road driveway (near A‐Line Station 13+50) Looking north at Monster Road (near A‐Line Station 14+00) Looking northwest at Monster Road (near A‐Line Station 14+50/C‐Line Station 201+75) Looking north at Monster Road (near A‐Line 15+00/C‐Line Station 202+20) Looking northwest at Monster Road (near A‐Line Station 16+20/C‐Line Station 202+50) Looking north at pedestrian crossing location over the Black River (near A‐Line 16+00/ C‐Line Station 202+50) Looking south at pedestrian crossing location over the Black River (near A‐Line 17+50/B‐Line 102+50) Looking east at Monster Road (near B‐Line Station 102+50) Looking west (near B‐Line Station 105+00) Looking east (near B‐Line Station 105+00) Looking west (near B‐Line Station 121+00) Location of proposed box culvert, looking west (near B‐Line Station 126+00) Project End, looking north (B‐Line Station 143+17) Appendix D KCRTS Runoff Modeling Documentation Appendix D ‐ KCRTS Runoff Modeling Documentation 1 TDA 1 Project Location : Sea-Tac Computing Series : L2SA1pre.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Forest 0.73 acres Impervious 0.05 acres -------------- Total Area : 0.76 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa1pre.tsf Mean= -1.572 StdDev= 0.187 Project Location:Sea-Tac Skew= -0.062 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob Computed Peaks 0.075 100.00 0.990 Computed Peaks 0.066 50.00 0.980 Computed Peaks 0.058 25.00 0.960 Computed Peaks 0.047 10.00 0.900 Computed Peaks 0.045 8.00 0.875 Computed Peaks 0.038 5.00 0.800 Computed Peaks 0.027 2.00 0.500 Computed Peaks 0.019 1.30 0.231 Project Location : Sea-Tac Computing Series : L2SA1dev.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Forest 0.27 acres Till Grass 0.18 acres Impervious 0.31 acres -------------- Total Area : 0.76 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa1dev.tsf Mean= -1.024 StdDev= 0.115 Project Location:Sea-Tac Skew= 0.390 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period Computed Peaks 0.188 100.00 0.990 Computed Peaks 0.171 50.00 0.980 Computed Peaks 0.155 25.00 0.960 Computed Peaks 0.134 10.00 0.900 Computed Peaks 0.129 8.00 0.875 Computed Peaks 0.117 5.00 0.800 Computed Peaks 0.093 2.00 0.500 Computed Peaks 0.077 1.30 0.231 Appendix D ‐ KCRTS Runoff Modeling Documentation 2 TDA 2 Project Location : Sea-Tac Computing Series : L2SA2pre.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Forest 0.21 acres Impervious 0.84 acres -------------- Total Area : 1.05 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa2pre.tsf Mean= -1.661 StdDev= 0.096 Project Location:Sea-Tac Skew= 0.528 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob Computed Peaks 0.398 100.00 0.990 Computed Peaks 0.365 50.00 0.980 Computed Peaks 0.334 25.00 0.960 Computed Peaks 0.293 10.00 0.900 Computed Peaks 0.284 8.00 0.875 Computed Peaks 0.261 5.00 0.800 Computed Peaks 0.214 2.00 0.500 Computed Peaks 0.184 1.30 0.231 Project Location : Sea-Tac Computing Series : L2SA2dev.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Grass 0.18 acres Impervious 0.87 acres -------------- Total Area : 1.05 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa2dev.tsf Mean= -0.631 StdDev= 0.100 Project Location:Sea-Tac Skew= 0.505 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period Computed Peaks 0.435 100.00 0.990 Computed Peaks 0.399 50.00 0.980 Computed Peaks 0.363 25.00 0.960 Computed Peaks 0.317 10.00 0.900 Computed Peaks 0.308 8.00 0.875 Computed Peaks 0.282 5.00 0.800 Computed Peaks 0.229 2.00 0.500 Computed Peaks 0.196 1.30 0.231 Appendix D ‐ KCRTS Runoff Modeling Documentation 3 TDA 3 Project Location : Sea-Tac Computing Series : L2SA3pre.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Forest 0.40 acres Impervious 0.12 acres -------------- Total Area : 0.52 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa3pre.tsf Mean= -1.431 StdDev= 0.118 Project Location:Sea-Tac Skew= 0.498 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period Computed Peaks 0.077 100.00 0.990 Computed Peaks 0.069 50.00 0.980 Computed Peaks 0.062 25.00 0.960 Computed Peaks 0.053 10.00 0.900 Computed Peaks 0.051 8.00 0.875 Computed Peaks 0.046 5.00 0.800 Computed Peaks 0.036 2.00 0.500 Computed Peaks 0.030 1.30 0.231 Project Location : Sea-Tac Computing Series : L2SA3dev.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Forest 0.31 acres Till Grass 0.07 acres Impervious 0.14 acres -------------- Total Area : 0.52 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa3dev.tsf Mean= -1.348 StdDev= 0.120 Project Location:Sea-Tac Skew= 0.466 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period Computed Peaks 0.094 100.00 0.990 Computed Peaks 0.085 50.00 0.980 Computed Peaks 0.076 25.00 0.960 Computed Peaks 0.065 10.00 0.900 Computed Peaks 0.062 8.00 0.875 Computed Peaks 0.056 5.00 0.800 Computed Peaks 0.044 2.00 0.500 Computed Peaks 0.036 1.30 0.231 Appendix D ‐ KCRTS Runoff Modeling Documentation 4 TDA 4 Project Location : Sea-Tac Computing Series : L2SA4pre.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Forest 1.22 acres Impervious 0.14 acres -------------- Total Area : 1.36 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa4pre.tsf Mean= -1.239 StdDev= 0.158 Project Location:Sea-Tac Skew= 0.370 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period Computed Peaks 0.148 100.00 0.990 Computed Peaks 0.131 50.00 0.980 Computed Peaks 0.114 25.00 0.960 Computed Peaks 0.093 10.00 0.900 Computed Peaks 0.089 8.00 0.875 Computed Peaks 0.078 5.00 0.800 Computed Peaks 0.056 2.00 0.500 Computed Peaks 0.044 1.30 0.231 Project Location : Sea-Tac Computing Series : L2SA4dev.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Forest 1.27 acres Till Grass 0.02 acres Impervious 0.07 acres -------------- Total Area : 1.36 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa4dev.tsf Mean= -1.356 StdDev= 0.199 Project Location:Sea-Tac Skew= -0.023 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period Computed Peaks 0.127 100.00 0.990 Computed Peaks 0.112 50.00 0.980 Computed Peaks 0.098 25.00 0.960 Computed Peaks 0.078 10.00 0.900 Computed Peaks 0.075 8.00 0.875 Computed Peaks 0.065 5.00 0.800 Computed Peaks 0.044 2.00 0.500 Computed Peaks 0.031 1.30 0.231 Appendix D ‐ KCRTS Runoff Modeling Documentation 5 TDA 5 Project Location : Sea-Tac Computing Series : L2SA5pre.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Forest 0.60 acres Impervious 0.05 acres -------------- Total Area : 0.65 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa5pre.tsf Mean= -1.618 StdDev= 0.176 Project Location:Sea-Tac Skew= 0.175 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period Computed Peaks 0.065 100.00 0.990 Computed Peaks 0.058 50.00 0.980 Computed Peaks 0.050 25.00 0.960 Computed Peaks 0.041 10.00 0.900 Computed Peaks 0.039 8.00 0.875 Computed Peaks 0.034 5.00 0.800 Computed Peaks 0.024 2.00 0.500 Computed Peaks 0.018 1.30 0.231 Project Location : Sea-Tac Computing Series : L2SA5dev.tsf Regional Scale Factor : 1.00 Data Type : Historic Creating Hourly Time Series File Till Forest 0.37 acres Till Grass 0.13 acres Impervious 0.15 acres -------------- Total Area : 0.65 acres Flow Frequency Analysis LogPearson III Coefficients Time Series File:l2sa5dev.tsf Mean= -1.282 StdDev= 0.127 Project Location:Sea-Tac Skew= 0.544 ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period Computed Peaks 0.116 100.00 0.990 Computed Peaks 0.103 50.00 0.980 Computed Peaks 0.092 25.00 0.960 Computed Peaks 0.077 10.00 0.900 Computed Peaks 0.074 8.00 0.875 Computed Peaks 0.066 5.00 0.800 Computed Peaks 0.051 2.00 0.500 Computed Peaks 0.042 1.30 0.231 Appendix E Box Culvert Design Calculations Project Description Friction Method Manning Formula Solve For Discharge Input Data Roughness Coefficient 0.030 Channel Slope 0.05260 ft/ft Normal Depth 1.00 ft Left Side Slope 2.00 ft/ft (H:V) Right Side Slope 2.00 ft/ft (H:V) Results Discharge 13.29 ft³/s Flow Area 2.00 ft² Wetted Perimeter 4.47 ft Hydraulic Radius 0.45 ft Top Width 4.00 ft Critical Depth 1.22 ft Critical Slope 0.01793 ft/ft Velocity 6.64 ft/s Velocity Head 0.69 ft Specific Energy 1.69 ft Froude Number 1.66 Flow Type Supercritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Downstream Velocity Infinity ft/s Upstream Velocity Infinity ft/s Normal Depth 1.00 ft Critical Depth 1.22 ft Channel Slope 0.05260 ft/ft Critical Slope 0.01793 ft/ft Worksheet for Existing Ditch 125+95 6/25/2013 8:46:27 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 1of1Page Project Description Friction Method Manning Formula Solve For Discharge Input Data Roughness Coefficient 0.028 Channel Slope 0.05260 ft/ft Normal Depth 1.00 ft Height 2.00 ft Bottom Width 3.33 ft Results Discharge 29.62 ft³/s Flow Area 3.33 ft² Wetted Perimeter 5.33 ft Hydraulic Radius 0.62 ft Top Width 3.33 ft Critical Depth 1.35 ft Percent Full 50.0 % Critical Slope 0.02281 ft/ft Velocity 8.89 ft/s Velocity Head 1.23 ft Specific Energy 2.23 ft Froude Number 1.57 Discharge Full 59.24 ft³/s Slope Full 0.21040 ft/ft Flow Type Supercritical GVF Input Data Downstream Depth 0.00 ft Length 0.00 ft Number Of Steps 0 GVF Output Data Upstream Depth 0.00 ft Profile Description Profile Headloss 0.00 ft Average End Depth Over Rise 0.00 % Normal Depth Over Rise 50.00 % Downstream Velocity Infinity ft/s Worksheet for BOX 125+95 - 1 ft depth 6/25/2013 8:49:54 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of1Page GVF Output Data Upstream Velocity Infinity ft/s Normal Depth 1.00 ft Critical Depth 1.35 ft Channel Slope 0.05260 ft/ft Critical Slope 0.02281 ft/ft Worksheet for BOX 125+95 - 1 ft depth 6/25/2013 8:49:54 AM Bentley Systems, Inc. Haestad Methods Solution CenterBentley FlowMaster V8i (SELECTseries 1) [08.11.01.03] 27 Siemons Company Drive Suite 200 W Watertown, CT 06795 USA +1-203-755-1666 2of2Page Appendix F Grading Within the Floodplain Cut and Fill Calculations Prepared By:MD 4/2/2015 Checked By: CAB 4/6/2015 Station Fill (sf) Exc (sf) Fill (cf) Exc (cf) floodplain Elevation = 19.00 ft NGVD 29 FEMA 1995 1+00 floodplain Elevation = 22.57 ft Coverted to NAVD 88 1.36 0.00 NAVD 88 is project datum 1+25 0.11 0.00 FIRM Panels 957 and 976 1.36 0.00 1+50 0.00 0.00 0.00 0.001+75 0.00 0.00 0.32 0.00 2+00 0.03 0.00 1.94 0.00 2+25 0.13 0.00 3.98 0.00 2+50 0.19 0.00 3.61 0.00 2+75 0.10 0.00 9.81 0.00 3+00 0.69 0.00 8.56 0.00 3+25 0.00 0.00 2.67 0.003+50 0.21 0.00 12.47 0.00 City of Tukwila 3+75 0.78 0.00 City Floodplain Fill City Floodplain Exc 20.90 0.00 3122.29 147.76 CF4+00 0.89 0.00 115.64 5.47 CY 20.64 0.00 110.17 Total Impact (CY) 4+25 0.76 0.00 9.53 21.87 4+50 0.00 1.75 0.00 73.88 4+75 0.00 4.16 120.01 52.01 5+00 9.60 0.00 264.89 0.00 5+25 11.59 0.00 259.38 0.00 5+50 9.16 0.00 205.25 0.00 5+75 7.26 0.00 182.88 0.00 6+00 7.37 0.00 198.38 0.00 6+25 8.50 0.00 208.63 0.00 6+50 8.19 0.00 252.75 0.006+75 12.03 0.00 322.63 0.00 7+00 13.78 0.00 320.63 0.00 7+25 11.87 0.00 285.00 0.00 7+50 10.93 0.00 228.75 0.00 7+75 7.37 0.00 176.00 0.00 City of Tukwila Lake to Sound Trail April 2015 - Black and Green Rivers Floodplain Fill Impacts Page 1 of 2 Prepared By:MD 4/2/2015 Checked By: CAB 4/6/2015 Station Fill (sf) Exc (sf) Fill (cf) Exc (cf) floodplain Elevation = 19.00 ft NGVD 29 FEMA 1995 Lake to Sound Trail April 2015 - Black and Green Rivers Floodplain Fill Impacts 8+00 6.71 0.00 City of Renton 156.00 0.008+25 5.77 0.00 264.00 0.00 8+50 15.35 0.00 456.13 0.00 8+75 21.14 0.00 473.50 0.00 9+00 16.74 0.00 311.13 0.00 9+25 8.15 0.00 61.43 0.00 9+31.48 10.81 0.00 5.90 0.09 9+32.01 11.45 0.34 26.34 0.729+34.34 11.16 0.28 3.21 0.08 9+34.63 10.98 0.28 114.89 2.15 9+50 3.97 0.00 83.75 0.00 9+75 2.73 0.00 108.38 0.00 City of Renton 10+00 5.94 0.00 City Floodplain Fill City Floodplain Exc 173.25 584.13 2723.90 6382.55 CF 10+25 7.92 46.73 100.89 236.39 CY 161.25 1600.00 -135.51 Total Impact (CY) 10+50 4.98 81.27 180.38 1800.13 10+75 9.45 62.74 131.25 1248.50 11+00 1.05 37.14 13.13 805.50 Floodway Boundary11+25 0.00 27.30 0.00 341.25 11+50 0.00 0.00 0.00 0.00 11+75 0.00 0.00 0.00 0.00 12+00 0.00 0.00 0.00 0.00 12+25 0.00 0.00 0.00 0.00 12+50 0.00 0.00 0.00 0.00 12+75 0.00 0.00 0.00 0.00 13+00 0.00 0.00 0.00 0.00 13+25 0.00 0.00 0.00 0.00 13+50 0.00 0.00 0.00 0.00 13+75 0.00 0.00 0.00 0.0014+00 0.00 0.00 0.00 0.00 14+25 0.00 0.00 0.00 0.00 14+50 0.00 0.00 0.00 0.00 14+75 0.00 0.00 Total Fill Total Exc 5846.19 6530.30 CF 216.53 241.86 CY Total Impact (CF) -684.11 Total Impact (CY)-25.34 Page 2 of 2 Appendix G King County Surface Water Design Manual Operation and Maintenance Excerpts APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009A-9 NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Sediment Sediment exceeds 60% of the depth from thebottom of the catch basin to the invert of thelowest pipe into or out of the catch basin or iswithin 6 inches of the invert of the lowest pipeinto or out of the catch basin. Sump of catch basin contains nosediment. Trash or debris of more than ½ cubic foot whichis located immediately in front of the catch basinopening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking orpotentially blocking entrance tocatch basin. Trash or debris in the catch basin that exceeds1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the catch basin. Dead animals or vegetation that could generateodors that could cause complaints or dangerousgases (e.g., methane). No dead animals or vegetationpresent within catch basin. Trash and debris Deposits of garbage exceeding 1 cubic foot involume.No condition present which wouldattract or support the breeding of insects or rodents. Corner of frame extends more than ¾ inch pastcurb face into the street (If applicable).Frame is even with curb. Top slab has holes larger than 2 square inches orcracks wider than ¼ inch.Top slab is free of holes and cracks. Damage to frameand/or top slab Frame not sitting flush on top slab, i.e.,separation of more than ¾ inch of the frame fromthe top slab. Frame is sitting flush on top slab. Cracks wider than ½ inch and longer than 3 feet,any evidence of soil particles entering catchbasin through cracks, or maintenance personjudges that catch basin is unsound. Catch basin is sealed andstructurally sound.Cracks in walls orbottom Cracks wider than ½ inch and longer than 1 footat the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin throughcracks. No cracks more than 1/4 inch wide atthe joint of inlet/outlet pipe. Settlement/misalignment Catch basin has settled more than 1 inch or hasrotated more than 2 inches out of alignment.Basin replaced or repaired to designstandards. Damaged pipe joints Cracks wider than ½-inch at the joint of theinlet/outlet pipes or any evidence of soil enteringthe catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide atthe joint of inlet/outlet pipes. Structure Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations.Source control BMPs implemented ifappropriate. No contaminantspresent other than a surface oil film. Sedimentaccumulation Sediment filling 20% or more of the pipe. Inlet/outlet pipes clear of sediment. Trash and debris Trash and debris accumulated in inlet/outlet pipes (includes floatables and non-floatables). No trash or debris in pipes. Inlet/Outlet Pipe Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil enteringat the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix AA-10 NO. 5 – CATCH BASINS AND MANHOLES Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets designstandards. Trash and debris Trash and debris that is blocking more than 20% of grate surface. Grate free of trash and debris. footnote to guidelines for disposal Metal Grates(Catch Basins) Damaged or missing Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets designstandards. Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening tostructure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Boltscannot be seated. Self-locking cover/lid does notwork. Mechanism opens with proper tools. Manhole Cover/Lid Cover/lid difficult to Remove One maintenance person cannot remove cover/lid after applying 80 lbs. of lift. Cover/lid can be removed and reinstalled by one maintenanceperson. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009A-11 NO. 6 – CONVEYANCE PIPES AND DITCHES Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Sediment & debrisaccumulation Accumulated sediment or debris that exceeds20% of the diameter of the pipe.Water flows freely through pipes. Vegetation/roots Vegetation/roots that reduce free movement of water through pipes. Water flows freely through pipes. Contaminants andpollution Any evidence of contaminants or pollution suchas oil, gasoline, concrete slurries or paint.Materials removed and disposed ofaccording to applicable regulations. Source control BMPs implemented ifappropriate. No contaminantspresent other than a surface oil film. Damage to protectivecoating or corrosion Protective coating is damaged; rust or corrosionis weakening the structural integrity of any part ofpipe. Pipe repaired or replaced. Pipes Damaged Any dent that decreases the cross section area ofpipe by more than 20% or is determined to haveweakened structural integrity of the pipe. Pipe repaired or replaced. Trash and debris Trash and debris exceeds 1 cubic foot per 1,000square feet of ditch and slopes.Trash and debris cleared fromditches. Sediment accumulation Accumulated sediment that exceeds 20% of the design depth. Ditch cleaned/flushed of all sediment and debris so that it matches design. Noxious weeds Any noxious or nuisance vegetation which may constitute a hazard to County personnel or thepublic. Noxious and nuisance vegetation removed according to applicableregulations. No danger of noxiousvegetation where County personnelor the public might normally be. Contaminants andpollution Any evidence of contaminants or pollution suchas oil, gasoline, concrete slurries or paint.Materials removed and disposed ofaccording to applicable regulations.Source control BMPs implemented ifappropriate. No contaminantspresent other than a surface oil film. Vegetation Vegetation that reduces free movement of waterthrough ditches.Water flows freely through ditches. Erosion damage toslopes Any erosion observed on a ditch slope. Slopes are not eroding. Ditches Rock lining out ofplace or missing (IfApplicable) One layer or less of rock exists above native soilarea 5 square feet or more, any exposed nativesoil. Replace rocks to design standards. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009A-13 NO. 8 – ENERGY DISSIPATERS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed. Trash and debris Trash and/or debris accumulation. Dissipater clear of trash and/ordebris.Site Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations.Source control BMPs implemented ifappropriate. No contaminantspresent other than a surface oil film. Rock Pad Missing or movedRock Only one layer of rock exists above native soil inarea five square feet or larger or any exposure ofnative soil. Rock pad prevents erosion. Pipe plugged withsediment Accumulated sediment that exceeds 20% of thedesign depth.Pipe cleaned/flushed so that itmatches design. Not discharging waterproperly Visual evidence of water discharging atconcentrated points along trench (normalcondition is a “sheet flow” of water along trench). Water discharges from feature bysheet flow. Perforations plugged. Over 1/4 of perforations in pipe are plugged withdebris or sediment. Perforations freely discharge flow. Water flows out top of “distributor” catchbasin. Water flows out of distributor catch basin during any storm less than the design storm. No flow discharges from distributor catch basin. Dispersion Trench Receiving area over-saturated Water in receiving area is causing or haspotential of causing landslide problems.No danger of landslides. Damaged mesh Mesh of gabion broken, twisted or deformed so structure is weakened or rock may fall out. Mesh is intact, no rock missing. Corrosion Gabion mesh shows corrosion through more than¼ of its gage.All gabion mesh capable ofcontaining rock and retainingdesigned form. Collapsed ordeformed baskets Gabion basket shape deformed due to anycause.All gabion baskets intact, structurestands as designed. Gabions Missing rock Any rock missing that could cause gabion toloose structural integrity.No rock missing. Worn or damagedpost, baffles or side ofchamber Structure dissipating flow deteriorates to ½ ororiginal size or any concentrated worn spotexceeding one square foot which would makestructure unsound. Structure is in no danger of failing. Damage to wall,frame, bottom, and/ortop slab Cracks wider than ½-inch or any evidence of soilentering the structure through cracks, ormaintenance inspection personnel determinesthat the structure is not structurally sound. Manhole/chamber is sealed andstructurally sound. Manhole/Chamber Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil enteringthe structure at the joint of the inlet/outlet pipes. No soil or water enters and no waterdischarges at the joint of inlet/outletpipes. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix AA-16 NO. 11 – GROUNDS (LANDSCAPING) Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Trash or litter Any trash and debris which exceed 1 cubic footper 1,000 square feet (this is about equal to theamount of trash it would take to fill up onestandard size office garbage can). In general,there should be no visual evidence of dumping. Trash and debris cleared from site. Noxious weeds Any noxious or nuisance vegetation which mayconstitute a hazard to County personnel or thepublic. Noxious and nuisance vegetationremoved according to applicableregulations. No danger of noxious vegetation where County personnelor the public might normally be. Contaminants and pollution Any evidence of contaminants or pollution such as oil, gasoline, concrete slurries or paint. Materials removed and disposed of according to applicable regulations.Source control BMPs implemented ifappropriate. No contaminantspresent other than a surface oil film. Site Grass/groundcover Grass or groundcover exceeds 18 inches inheight.Grass or groundcover mowed to aheight no greater than 6 inches. Hazard Any tree or limb of a tree identified as having apotential to fall and cause property damage orthreaten human life.A hazard tree identified by a qualified arborist must be removed as soon as possible. No hazard trees in facility. Limbs or parts of trees or shrubs that are split orbroken which affect more than 25% of the totalfoliage of the tree or shrub. Trees and shrubs with less than 5%of total foliage with split or brokenlimbs. Trees or shrubs that have been blown down orknocked over.No blown down vegetation orknocked over vegetation. Trees orshrubs free of injury. Trees and Shrubs Damaged Trees or shrubs which are not adequatelysupported or are leaning over, causing exposureof the roots. Tree or shrub in place andadequately supported; dead ordiseased trees removed.