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F_BETHANY CORNER_APPROVED REVISED TIR_20210429.pdf
DEVELOPMENT ENGINEERINGbbannwarth 04/29/2021 2021 D. R. STRONG Consulting Engineers Inc. Bethany Corner Technical Information Report Renton, Washington TECHNICAL INFORMATION REPORT BETHANY CORNER SHORT PLAT TABLE OF CONTENTS SECTION I ...................................................................................................................... 4 Project Overview ......................................................................................................... 4 Predeveloped Site Conditions ..................................................................................... 4 Developed Site Conditions .......................................................................................... 4 King County Area, Washington .................................................................................. 14 AgC—Alderwood gravelly sandy loam, 8 to 15 percent slopes .............................. 14 SECTION II ................................................................................................................... 16 Conditions and Requirements Summary ................................................................... 16 Conditions of Approval............................................................................................... 18 SECTION III .................................................................................................................. 20 Off-Site Analysis ........................................................................................................ 20 Task 1: Define and Map Study Area ...................................................................... 20 Task 2: Resource Review ...................................................................................... 21 Task 3: Field Inspection ......................................................................................... 30 Task 4: Drainage System Description and Problem Descriptions .......................... 31 Task 5: Mitigation of Existing or Potential Problems .............................................. 32 SECTION IV .................................................................................................................. 38 Flow Control Analysis and Water Quality Design ...................................................... 38 Existing Site Hydrology .......................................................................................... 38 Developed Site Hydrology ...................................................................................... 40 Performance Standards ............................................................................................. 43 Detention Compliance Analysis ................................................................................. 43 Flow Control System.................................................................................................. 44 Water Quality Treatment System ............................................................................... 53 SECTION V ................................................................................................................... 55 Conveyance System Analysis and Design ................................................................ 55 SECTION VI .................................................................................................................. 68 Special Reports and Studies ..................................................................................... 68 SECTION VII ................................................................................................................. 69 Other Permits, Variances and Adjustments ............................................................... 69 SECTION VIII ................................................................................................................ 70 CSWPPP Analysis and Design (Part A) .................................................................... 70 SWPPP Plan Design (Part B) .................................................................................... 70 2021 D. R. STRONG Consulting Engineers Inc. Bethany Corner Technical Information Report Renton, Washington SECTION IX .................................................................................................................. 72 Bond Quantities, Facility Summaries, and Declaration of Covenant .......................... 72 Stormwater Facility Summary Sheet.......................................................................... 73 SECTION X ................................................................................................................... 75 Operations and Maintenance Manual ........................................................................ 75 APPENDICES ............................................................................................................... 76 Appendix “A” Legal Description ................................................................................. 77 Appendix “B” CSWPPP ............................................................................................. 78 Appendix “C” Bond Quantity Worksheet .................................................................... 79 List of Figures Figure 1 TIR Worksheet .................................................................................................. 6 Figure 2 Vicinity Map ..................................................................................................... 11 Figure 3 Drainage Basins, Subbasins, and Site Characteristics ................................... 12 Figure 4 Soils ................................................................................................................ 13 Figure 5 City of Renton Topography Map ..................................................................... 22 Figure 6 City of Renton Coal Mine Hazard Areas Map.................................................. 23 Figure 7 City of Renton Flood Hazards Map ................................................................. 24 Figure 8 City of Renton Streams and Wetlands Map .................................................... 25 Figure 9 City of Renton Landslide Hazards Map ........................................................... 26 Figure 10 City of Renton Seismic Hazard Areas Map ................................................... 27 Figure 11 FEMA Map .................................................................................................... 28 Figure 12 King County iMap Drainage Complaints Map................................................ 29 Figure 13 Offsite Analysis Downstream Map ................................................................ 34 Figure 14 Offsite Analysis Downstream Table .............................................................. 35 Figure 15 Predeveloped Area Map................................................................................ 39 Figure 16 Developed Area Map .................................................................................... 42 Figure 17 Detention & Water Quality Facility Details ..................................................... 54 Figure 18 Backwater Analysis Map ............................................................................... 59 2021 D. R. STRONG Consulting Engineers Inc. Page 4 Bethany Corner Level One Downstream Analysis Renton, Washington SECTION I PROJECT OVERVIEW The Project is the proposed subdivision of two parcels into nine single-family residential lots, per the City of Renton’s (City) subdivision process. The Project is located at 16433 & 16451 111th Avenue SE, Renton, Washington (Site) also known as Tax Parcel Numbers 008800-0570 & -0560. The Project will meet the drainage requirements of the City of Renton Amendments to the 2009 King County Surface Water Design Manual (CORSWDMA). PREDEVELOPED SITE CONDITIONS The total existing Site area is approximately 79,710 s.f. (1.83 acres). The Site is currently developed with two single family homes, one trailer home, gravel driveways, one detached garage, a shed, a concrete foundation, and landscaping. The Site consists of a shallow grade to the southwest and is contains one Threshold Discharge Area (TDA). Runoff generated by the TDA gradually sheet flows east to southwest towards adjacent parcels to the west or is collected by a culvert in the southwest corner of the Site. Sheet flow over the west property line and culvert flow from the southwest corner of the Site form the two natural discharge locations for the Site. The two Natural Discharge Areas (NDAs) of the Site divide it roughly in half with the northern portion draining to the west and the southern portion draining to the cuvert. Sheet flow from the western property line is captured by Big Soos Creek on the adjacent parcels and is conveyed to the south. Runoff through the culvert in the the southwestern corner of the Site travels for approximately 55 feet in a westerly direction to a convergence point with Big Soos Creek. Flow from both NDAs converges within the ¼ mile and therefore the Site can be considered to be within one TDA. The Project frontage currently drains to a series of ditches and culverts along 111th Ave SE and converges with Big Soos Creek approximately 160 feet downstream. DEVELOPED SITE CONDITIONS The applicant is seeking approval to subdivide 1.83 acres into nine single–family residential lots (Project), with lot sizes ranging from approximately 5,617 s.f. to 7,119 s.f. All existing improvements located on the Site will be demolished or removed during plat construction. The project is required to meet the City’s Flow Control Duration Standard – Matching Forested and Basic Water Quality treatment. This standard matches the developed Site flow durations to the flow durations of pre-developed rates for forested (historical) site conditions. These standards will be met through the proposed combination detention and water quality vault. The proposed impervious surface areas are as follows: half street frontage improvements consisting of a 5’ sidewalk along 111th AVE SE, Road A, the nine new single-family residences and associated driveways, and Tract A, the storm water detention facility, will generate approximately 53,421 s.f. of impervious area (1.226 acres). Soil conditions per the Project geotech report were found to be incompatible with infiltration based BMPs and the Site layout precludes the use of disperson BMPS due to 2021 D. R. STRONG Consulting Engineers Inc. Page 5 Bethany Corner Level One Downstream Analysis Renton, Washington a lack of available flow paths. The Project will implement Reduced Impervious Surface Credit by way of the Restricted Footprint BMP and the Open grid decking over pervious surface BMP to the maximum extent feasible. A table with lot areas and BMP credits follows. Lot Lot Area (S.F.) Max Impervious Per Zoning(1) (S.F.) Proposed Impervious (S.F.) Restricted Footprint Credit(2) (S.F.) Open Grid Decking Credit (S.F.) Total Credit (S.F.) % of Lot Area 1 7,119 4,627 3,858 142 140 282 3.96% 2 5,948 3,866 3,344 522 84 606 10.19% 3 5,948 3,866 3,448 418 80 498 8.37% 4 5,948 3,866 3,576 290 72 362 6.09% 5 6,734 4,377 3,440 560 72 632 9.39% 6 6,447 4,191 3,642 358 80 438 6.79% 7 5,889 3,828 3,327 501 84 585 9.93% 8 6,148 3,996 3,391 605 72 677 11.01% 9 6,148 3,996 3,540 456 45 501 8.15% Total 8.13% (1). Max impervious allowed is 65% per Code. (2). Restricted footprint credit is measured as a reduction from either the max allowable impervious or the 4,000 s.f. “norm”, whichever is less. A section of non-target impervious surface along the north side of 111th AVE SE will be collected by the proposed detention facility. The facility has been designed with this section being proposed as an offsite flow-through area. This area will be modeled as impervious in both the predeveloped and developed scenarios. Proposed Site cover and surfaces are show in Figure 16, Developed Site Conditions. (See Section IV). The Project proposes to combine runoff from both onsite NDAs and the target frontage into one detention system and to discharge to the road-side ditch system just upstream of the confluence with Big Soos Creek. The existing natural discharge locations for the Site are not suitable for concentrated flows. No drainage easements are available for discharge to Big Soos Creek to the west. Discharge to the road-side ditch connects to a manmade public conveyance system. The proposed discharge location is well within the ¼ mile of the natural discharge locations. 2021 D. R. STRONG Consulting Engineers Inc. Page 6 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 1 TIR WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner: Dianne Dougherty, Bona Fide Properties 2, LLC Phone: (650) 888-5101 Address: 3024 90th PL SE, Mercer Island, WA 98040 Project Engineer: Jonathan S. Murray, P.E. Company: D. R. STRONG Consulting Engineers Inc. Phone: (425) 827-3063 Project Name: Bethany Corner City Permit#: PRE16-000651 Location: Township: 23 North Range: 05 East Section: 29 Site Address: 16433 & 16451 111th Avenue SE, Renton, WA Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS Landuse Services Subdivision / Short Subdivision / UPD Building Services: M/F / Commercial / SFR Clearing and Grading Right-of-Way Other: DFW HPA Shoreline Mngmt COE 404 Structural DOE Dam Safety Rockery/Vault FEMA Floodplain ESA Section 7 COE Wetlands Other: Part 5 PLAN AND REPORT INFORMATION Technical Information Report Type of Drainage Review Full / Targeted / (circle): Large Site Date (include revision dates): April 9, 2021 Date of Final: Site Improvement Plan (Engr. Plans) Type (circle one): Full / Modified / : Small Site Date (include revision dates): Date of Final: Part 6 ADJUSTMENT APPROVALS Type (circle one): Standard / Complex / Preapplication / Experimental / Blanket Description: (include conditions in TIR Section 2) _____________________________________________________________________________________ _____________________________________________________________________________________ ____________________________________________________________________________________ Date of Approval: 2021 D. R. STRONG Consulting Engineers Inc. Page 7 Bethany Corner Level One Downstream Analysis Renton, Washington Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: TBD Completion Date Describe: Monitor discharge location during construction. Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: Benson Special District Overlays: N/A Drainage Basin: Green/Duwamish River Watershed Stormwater Requirements: Flow Control Duration Standard – Matching Forested and Basic WQ treatment Part 9 ONSITE AND ADJACENT SENSITIVE AREAS River/ Stream: Big Soos Creek Lake Wetlands Closed Depression Floodplain Other Steep Slope Erosion Hazard Landslide Hazard Coal Mine Hazard Seismic Hazard Habitat Protection Part 10 SOILS Soil Type AgC Slopes 8-15% Erosion Potential Moderate to Severe High Groundwater Table Sole Source Aquifer other Seeps/Springs Additional Sheets Attached 2021 D. R. STRONG Consulting Engineers Inc. Page 8 Bethany Corner Level One Downstream Analysis Renton, Washington Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE Core Requirement #2 – Offsite Analysis SEPA Sensitive Area Buffer _______ Additional Sheet Attached LIMITATION / SITE CONSTRAINT Part 12 TIR SUMMARY SHEET Threshold Discharge Area: Site comprised of one TDA (name or description) Core Requirements (all 8 apply) Discharge of Natural Location yes Number of Natural Discharge Locations: 1 Offsite Analysis Level: 1 / 2 / 3 dated: 09/28/2016 Flow Control Level: 1 / 2 / 3 or Exemption Number (incl. facility summary sheet Small Site BMPS Restricted Footprint Conveyance System Spill containment located at: TBD Erosion and Sediment Control ESC Site Supervisor: T/B/D Contact Phone: T/B/D After Hours Phone: T/B/D Maintenance and Operation Responsibility: Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Provided: Yes / No Liability Water Quality Type: Basic / Sens Lake / Enhanced Basic / Bog (include facility summary sheet) or exemption No. Landscape Management Plan: Yes / No Special Requirements (as applicable) Area Specific Drainage Type: CDA / SDO / MDP / BP / LMP / Shared / None Requirements Name: Floodplain/Floodway Delineation Type: Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): Datum: Flood Protection Facilities Describe: N/A Source Control Describe Landuse: (comm. / industrial landuse) Describe any structural controls: Oil Control High-use Site: Yes / No Treatment BMP: Maintenance Agreement: Yes / No with whom? 2021 D. R. STRONG Consulting Engineers Inc. Page 9 Bethany Corner Level One Downstream Analysis Renton, Washington Other Drainage Structures Describe: Runoff will be collected and conveyed to the wet-vault detention facility located in Tract A. Part 13 EROSION AND SEDIMENT CONTROL REQUIREMENTS MINIMUM ESC REQUIREMENTS DURING CONSTRUCTION Clearing Limits Cover Measures Perimeter Protection Traffic Area Stabilization Sediment Retention Surface Water Collection Dewatering Control Dust control Flow Control MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION Stabilize Exposed Surfaces Remove and Restore Temporary ESC Facilities Clean and Remove All Silt and Debris, Ensure Operations of Permanent Facilities Flag Limits of SAO and open space Preservation areas Other Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch Flow Control Type/Description Water Quality Type/Description Detention Infiltration Regional Facility Shared Facility Flow Control BMPs Other Wet-Vault Restricted Footprint, Open Grid Decking Over Pervious Surface Biofiltration Wetpool Media Filtration Oil Control Spill Control Flow Control BMPs Other Wet-Vault________ 2021 D. R. STRONG Consulting Engineers Inc. Page 11 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 2 VICINITY MAP 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. 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. Site 2021 D. R. STRONG Consulting Engineers Inc. Page 12 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 3 DRAINAGE BASINS, SUBBASINS, AND SITE CHARACTERISTICS 0 GRAPHIC SCALE 604020 1 INCH = 40 FT. 2021 D. R. STRONG Consulting Engineers Inc. Page 13 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 4 SOILS 2021 D. R. STRONG Consulting Engineers Inc. Page 14 Bethany Corner Level One Downstream Analysis Renton, Washington KING COUNTY AREA, WASHINGTON AGC—ALDERWOOD GRAVELLY SANDY LOAM, 8 TO 15 PERCENT SLOPES a) Map Unit Setting • National map unit symbol: 2t626 • Elevation: 50 to 800 feet • Mean annual precipitation: 20 to 60 inches • Mean annual air temperature: 46 to 52 degrees F • Frost-free period: 160 to 240 days • Farmland classification: Prime farmland if irrigated b) Map Unit Composition • Alderwood and similar soils: 85 percent • Minor components: 15 percent • Estimates are based on observations, descriptions, and transects of the mapunit. c) Description of Alderwood (1) Setting • Landform: Ridges, hills • Landform position (two-dimensional): Shoulder • Landform position (three-dimensional): Nose slope, talf • Down-slope shape: Linear, convex • Across-slope shape: Convex • Parent material: Glacial drift and/or glacial outwash over dense glaciomarine deposits (2) Typical profile • A - 0 to 7 inches: gravelly sandy loam • Bw1 - 7 to 21 inches: very gravelly sandy loam • Bw2 - 21 to 30 inches: very gravelly sandy loam • Bg - 30 to 35 inches: very gravelly sandy loam • 2Cd1 - 35 to 43 inches: very gravelly sandy loam • 2Cd2 - 43 to 59 inches: very gravelly sandy loam (3) Properties and qualities • Slope: 8 to 15 percent • Depth to restrictive feature: 20 to 39 inches to densic material • Natural drainage class: Moderately well drained • Capacity of the most limiting layer to transmit water (Ksat): Very low to moderately low (0.00 to 0.06 in/hr) • Depth to water table: About 18 to 37 inches • Frequency of flooding: None • Frequency of ponding: None • Available water storage in profile: Very low (about 2.7 inches) (4) Interpretive groups • Land capability classification (irrigated): None specified • Land capability classification (nonirrigated): 4s • Hydrologic Soil Group: B • Other vegetative classification: Limited Depth Soils (G002XN302WA), Limited Depth Soils (G002XS301WA), Limited Depth Soils (G002XF303WA) • Hydric soil rating: No 2021 D. R. STRONG Consulting Engineers Inc. Page 15 Bethany Corner Level One Downstream Analysis Renton, Washington d) Minor Components (1) Everett • Percent of map unit: 5 percent • Landform: Eskers, kames, moraines • Landform position (two-dimensional): Shoulder, footslope • Landform position (three-dimensional): Crest, base slope • Down-slope shape: Convex • Across-slope shape: Convex • Hydric soil rating: No (2) Indianola • Percent of map unit: 5 percent • Landform: Eskers, kames, terraces • Landform position (three-dimensional): Tread • Down-slope shape: Linear • Across-slope shape: Linear • Hydric soil rating: No (3) Shalcar • Percent of map unit: 3 percent • Landform: Depressions • Landform position (three-dimensional): Dip • Down-slope shape: Concave • Across-slope shape: Concave • Hydric soil rating: Yes (4) Norma • Percent of map unit: 2 percent • Landform: Depressions, drainageways • Landform position (three-dimensional): Dip • Down-slope shape: Concave, linear • Across-slope shape: Concave • Hydric soil rating: Yes 2021 D. R. STRONG Consulting Engineers Inc. Page 16 Bethany Corner Level One Downstream Analysis Renton, Washington SECTION II CONDITIONS AND REQUIREMENTS SUMMARY The Project must comply with the following Core and Special Requirements: • C.R. #1 – Discharge at the Natural Location: Existing drainage discharges the Site at one location, maintaining one TDA. The topography indicates that all stormwater runoff leaves the Site as sheet flow across the west property line. Runoff is collected by Big Soos Creek which is located on an adjacent property to the west. Developed runoff will require discharge to a conveyance system. Discharge from the project will be directed south to the existing conveyance system along 111th Ave SE. This discharge location converges with flow from the NDA within the ¼ mile. • C.R. #2 – Offsite Analysis: Analysis is included in Section III. The Analysis describes the Site’s runoff patterns in detail. • C.R. #3 – Flow Control: The Project is required to adhere to Flow Control Duration Standard – Matching Forested site conditions. One detention/wetvault will provide flow control as required for the new and replaced impervious and pervious surfaces. The Site is required to “match the flow duration of pre-developed rates for forested (historic) site conditions over the range of flows extending from 50% of 2-year up to the full 50-year flow,” (City of Renton 2009 Surface Water Design Manual Amendment, Sec. 1.2.3.1). A detention vault will accommodate this requirement. • C.R. #4 – Conveyance System: New pipe systems are required to be designed with sufficient capacity to convey and contain (at minimum) the 25-year peak flow, assuming developed conditions for onsite tributary areas and existing conditions for any offsite tributary areas. Pipe system structures may overtop for runoff events that exceed the 25-year design capacity, provided the overflow from a 100-year runoff event does not create or aggravate a “severe flooding problem” or “severe erosion problem” as defined in C.R. #2. Any overflow occurring onsite for runoff events up to and including the 100-year event must discharge at the natural location for the project site. In residential subdivisions, such overflow must be contained within an onsite drainage easement, tract, covenant or public right-of-way. This analysis is shown in Section V. • C.R. #5 – Erosion and Sediment Control: The Project will provide the seven minimum ESC measures. A temporary erosion and sedimentation control plan is presented as part of the engineering construction plan set. • C.R. #6 – Maintenance and Operations: Maintenance of the proposed storm drainage facilities will be the responsibility of the City. An Operation and Maintenance Manual is included in Section X. • C.R. #7 – Financial Guarantees: Prior to commencing construction, the Applicant must post a drainage facilities restoration and site stabilization financial guarantee. For any constructed or modified drainage facilities to be maintained and operated by 2021 D. R. STRONG Consulting Engineers Inc. Page 17 Bethany Corner Level One Downstream Analysis Renton, Washington the City, the Applicant must: 1) Post a drainage defect and maintenance financial guarantee for a period of two years, and 2) Maintain the drainage facilities during the two-year period following posting of the drainage defect and maintenance financial guarantee. • C.R. #8 – Water Quality: The Project is required to provide basic water quality treatment. A combined detention/wetvault will accommodate this requirement. • S.R. #1 – Other Adopted Area-Specific Requirements: Not applicable for this Project. • S.R. #2 – Flood Hazard Area Delineation: Not applicable for this Project. • S.R. #3 – Flood Protection Facilities: Not applicable for this Project. • S.R. #4 – Source Control: Not applicable for this Project. • S.R. #5 – Oil Control: Not applicable for this Project. • S.R. #6 – Aquifer Protection Area: Site not located within zones 1 and 2, therefore not applicable for this Project. 2021 D. R. STRONG Consulting Engineers Inc. Page 18 Bethany Corner Level One Downstream Analysis Renton, Washington CONDITIONS OF APPROVAL Bethany Corner LUA16-000958, January 12, 2018 1. A demolition permit shall be obtained for all existing structures and all required inspections completed prior to the issuance of the Construction Permit. This condition is noted on the engineering plans. 2. The applicant shall submit a final landscape plan that provides an additional replacement tree to meet the 24 caliper inches required and revise the Replacement Tree Plant Schedule. In addition, two additional street trees shall be provided. A detailed landscape plan, as defined in RMC 4-8-120, shall be submitted at the time of Construction Permit application and shall be reviewed and approved by the Current Planning Project Manager that demonstrates compliance with both tree density and tree retention regulations. Final landscape plans show 24 caliper inches of replacement trees and two additional street trees. 3. The applicant shall submit a final landscape plan that provides the storm drain tract with the required 15-foot landscape screen consisting of trees, shrubs, and groundcover around the perimeter of the tract. A detailed landscape plan, as defined in RMC 4-8- 120, shall be submitted at the time of Construction Permit application and shall be reviewed and approved by the Current Planning Project Manager prior to construction permit issuance. Final landscape plans show a 15-foot landscape screen around the stormwater tract. 4. Landscaping within the public right-of-way and within Tract A shall be installed prior to final short plat approval. Landscaping on the individual lots shall be installed at the time of the construction of the new homes. This condition is noted on the landscape plans. 5. The applicant shall include the Stream Buffer Enhancement Plan as part of the construction plan submittal to demonstrate that the stream buffer remains forested and is planted with native landscape. The Stream Buffer Enhancement Plan shall provide for additional plant materials, tree protection, and installation of a split rail fence along the buffer’s edge to include sensitive area signage that protects the critical area buffer within a separate tract and avoids any impacts and shall be reviewed and approved by the Current Planning Project Manager prior to construction permit issuance. A stream buffer enhancement plan has been prepared by the project’s wetland biologist. 6. Any proposal to convert the proposed stormwater vault within the storm drainage tract to a stormwater detention pond shall be considered a Major Plat Amendment subject to the requirements outlined in RMC 4-7-080.M.2. Noted. No such proposal is made at this time. 2021 D. R. STRONG Consulting Engineers Inc. Page 19 Bethany Corner Level One Downstream Analysis Renton, Washington 7. A safe walking route to the schools and bus stop shall be identified with the construction permit application for review and approval by the Current Planning Project Manager prior to construction permit issuance. A safe walking route analysis has been prepared and will be provided to the City for review. 8. The following note shall be provided on the face of the final short plat: Lots 6 and 7 shall access from a joint use driveway. No additional curb cuts shall be permitted on Road A. This note is shown on the planset cover sheet. 2021 D. R. STRONG Consulting Engineers Inc. Page 20 Bethany Corner Level One Downstream Analysis Renton, Washington SECTION III OFF-SITE ANALYSIS LEVEL ONE DOWNSTREAM ANALYSIS DISCLAIMER: This report was prepared at the request of Mark Seek and Mary Nguyen for the 1.83 acre parcels known as a portion of the Northeast Quarter of Section 29, Township 23 North, Range 5 East, W.M., in King County, Tax Parcel Numbers 008800-0570, & -0560 (Site). D. R. STRONG Consulting Engineers Inc. (DRS) has prepared this report for the exclusive use of DRS, the owner, and their agents, for specific application to the development project as described herein. Use or reliance on this report, or any of its contents for any revisions of this project, or any other project, or by others not described above, is forbidden without the expressed permission by DRS. TASK 1: DEFINE AND MAP STUDY AREA This Offsite Analysis was prepared in accordance with Core Requirement #2, Section 1.2.2 of the 2009 King County Surface Water Design Manual and City Amendments as adopted by the City of Renton (Manual). The Site is located at 16433 & 16451 111th Avenue SE, Renton, Washington. The Project is the subdivision of two parcels into nine single-family lots. See Figures 5 through 12 for maps of the study area. 2021 D. R. STRONG Consulting Engineers Inc. Page 21 Bethany Corner Level One Downstream Analysis Renton, Washington TASK 2: RESOURCE REVIEW • Adopted Basin Plans: The City of Renton and King County Department of Permitting and Environmental Review (DPER) and Department of Natural Resources and Parks (DNRP) do not have a specific plan for the East Lake Washington Drainage Basin. • Finalized Drainage Studies: No available applicable drainage studies at this time. • Basin Reconnaissance Summary Reports: None available. • Comprehensive Plans: Renton’s Comprehensive Plan, adopted on June 22, 2015, effective July 1, 2015. • Floodplain/Floodway (FEMA) Map: No floodplains exist on site, See Figure 11. • Other Offsite Analysis Reports: None available within adjacent properties. • Sensitive Areas Map Folios, City of Renton GIS: See Figures 6-10. The City’s GIS system shows a wetland on Site. A Wetland Assessment dated June 2, 2016 was prepared by Mark Rigos, P.E. This assessment found that there were no areas on the Site which met the definitions of wetlands. • DNRP Drainage Complaints and Studies: Per King County Water and Land Resources Division, there is one complaint within the downstream paths, within approximately one mile from the Site within the last 10 years. See Figure 12. • USDA King County Soils Survey: See Figure 4 • King County Wetlands Inventory: Vol. 2 East (1990) – Wetland 5401 (category 2) identified within one mile of the downstream path. See Figure 8. • Migrating River Studies: The Site is not located near the channel migration zones of Cedar River, Tolt River, Raging River, Snoqualmie River, or Green River. • King County Designated Water Quality Problems: Per the Washington State Water Quality Assessment 303(d)/305(b) Integrated Report current as of 2012, there are no water quality problems within 1 mile downstream of the Site. 2021 D. R. STRONG Consulting Engineers Inc. Page 22 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 5 CITY OF RENTON TOPOGRAPHY MAP Site 2021 D. R. STRONG Consulting Engineers Inc. Page 23 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 6 CITY OF RENTON COAL MINE HAZARD AREAS MAP Site 2021 D. R. STRONG Consulting Engineers Inc. Page 24 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 7 CITY OF RENTON FLOOD HAZARDS MAP Site 2021 D. R. STRONG Consulting Engineers Inc. Page 25 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 8 CITY OF RENTON STREAMS AND WETLANDS MAP Site 2021 D. R. STRONG Consulting Engineers Inc. Page 26 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 9 CITY OF RENTON LANDSLIDE HAZARDS MAP Site 2021 D. R. STRONG Consulting Engineers Inc. Page 27 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 10 CITY OF RENTON SEISMIC HAZARD AREAS MAP Site 2021 D. R. STRONG Consulting Engineers Inc. Page 28 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 11 FEMA MAP Site (Approximate) 2021 D. R. STRONG Consulting Engineers Inc. Page 29 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 12 KING COUNTY IMAP DRAINAGE COMPLAINTS MAP Location Complaint Year Description A C 2007 Runoff from construction site Site A 2021 D. R. STRONG Consulting Engineers Inc. Page 30 Bethany Corner Level One Downstream Analysis Renton, Washington TASK 3: FIELD INSPECTION UPSTREAM TRIBUTARY AREA Upon evaluation of the upstream area through examining COR topographic map (see Figure 5) and by conducting field reconnaissance on March 21st 2016, the upstream tributary area for the Site is considered negligible. The parcels to the north and south sheet flow to the west, and a swale exists in the right of way of 111th AVE SE, conveying runoff to the south, away from the site. GENERAL ONSITE AND OFFSITE DRAINAGE DESCRIPTIONS The Site is contained within one Threshold Discharge Area (TDA). Runoff from the Site sheet flows over the west property line and is collected by Big Soos Creek, which is flowing in a southerly direction. There also exists a Natural Discharge Area (NDA) which consists of a 12 inch reinforced concrete pipe in the southeastern corner of the Site which conveys storm water approximately 55 feet before sheet flowing westerly and converging with Big Soos Creek. The convergence point for the two NDA’s is approximately 85 feet downstream from the Site. Big Soos Creek is conveyed through a series of culverts, swales, and as channel flow before discharging into an unnamed wetland approximately ½ mile downstream. 2021 D. R. STRONG Consulting Engineers Inc. Page 31 Bethany Corner Level One Downstream Analysis Renton, Washington TASK 4: DRAINAGE SYSTEM DESCRIPTION AND PROBLEM DESCRIPTIONS DRAINAGE SYSTEM DESCRIPTION The downstream analysis is further illustrated and detailed in the Downstream Map Figure 13 and Downstream Table Figure 14. The drainage area is located within the East Lake Washington - Renton Drainage Basin. The drainage area was evaluated by reviewing available resources described in task 2, and by conducting a field reconnaissance on October 28th, 2016 under overcast conditions. DOWNSTREAM PATH 1 “A1” is a Natural Discharge Area (NDA) for the Site. It is located along the western property line (±0). From Point “A1” to Point “B1”, runoff continues to flow west as sheet flow over till grass. No concentrated flow was observed (±0’-45’). Point “B1”, runoff is collected by Big Soos Creek. (±45’). From Point “B1” to Point “C1”, runoff is conveyed in a southerly direction as channel flow via Big Soos Creek. Moderate flow was observed (±45’-502’). Point “C1” is the inlet of a 12” diameter Reinforced Concrete Pipe (RCP). Did not observe. (±502’). From Point “C1” to Point “D1”, runoff is conveyed easterly as pipe flow via 12” RCP. Moderate flow observed (±502’-807’). Point “D1” is the outlet of a 12” diameter RCP. Moderate flow observed. (±807’). From Point “D1” to Point “E1”, runoff is conveyed southerly as channel flow via a 2’ tall and 3’ wide swale. Moderate flow observed (±807’-813’). Point “E1” is the inlet of a 12” diameter RCP. Moderate flow observed. (±813’). From Point “E1” to Point “F1”, runoff is conveyed in a southerly direction as pipe flow via 12” RCP culvert. Moderate flow was observed (±813’-835’). Point “F1” is the outlet of a 12” diameter RCP. Moderate flow observed. (±835’). From Point “F1” to Point “G1”, runoff is conveyed in a southerly direction as channel flow via a 2’ tall and 4’ wide swale. Moderate flow was observed. (±835’-925’). Point “G1” is the inlet of a 12” diameter RCP. Moderate flow observed. (±925’). From Point “G1” to Point “H1”, runoff is conveyed in a southerly direction as pipe flow via 12” diameter RCP culvert. Moderate flow was observed (±925’-968’). Point “H1” is the outlet of a 12” diameter RCP. Moderate flow observed. (±968’). From Point “H1” to Point “I1”, runoff is conveyed in a southerly direction as channel flow via a 2’ tall and 4’ wide swale. Moderate flow was observed (±968’-986’). Point “I1” is the inlet of a 12” diameter RCP. Inlet was partially submerged. (±986’). From Point “I1” to Point “J1”, runoff is conveyed in an easterly direction as pipe flow via 12” diameter RCP culvert. Heavy flow was observed (±986’-1,022’). Point “J1” is the outlet of a 12” RCP. Outlet was fully submerged. (±1,022’). 2021 D. R. STRONG Consulting Engineers Inc. Page 32 Bethany Corner Level One Downstream Analysis Renton, Washington From Point “J1” to Point “K1”, runoff is conveyed in a southerly direction as channel flow via a 2’ tall and 4’ wide swale. Heavy flow was observed (±1,022’-1,037’). Point “K1” is the inlet of a 24” diameter Corrugated Metal Pipe (CMP) (±1,037’). From Point “K1” to Point “L1”, runoff is conveyed in a southerly direction as pipe flow via 24” CMP. Moderate flow was observed (±1,037’-1,121’). Point “L1”, is a Type 1 CB with the outlet of a 24” diameter CMP pipe from the north and the inlet of a 12” CMP in a southeasterly direction. Facility ID No 180983. Standing water observed. (±1,121’). From Point “L1” to Point “M1”, runoff is conveyed in a southeasterly direction as pipe flow via a 12” diameter CMP. Inlet was observed to be fully submerged. (±1,121’- 1,180’). Point “M1” is the outlet of a 12” diameter CMP. Not observed. (±1,180’). From Point “M1” to Point “N1”, runoff is conveyed in a southeasterly direction as channel flow via Big Soos Creek. Moderate flow was observed. (±1,180’-1,599’). The downstream path crosses the ¼ mile point during this stretch. Point “N1” is the inlet of an 18” diameter Corrugated Plastic Pipe (CPP) with a metal debris barrier. Moderate flow observed (±1,599’). From Point “N1” to Point “O1”, runoff is conveyed in a southerly direction under SE 168th Street via an 18” CPP. Moderate flow was observed (±1,599’-1,675’). Point “O1” is the outlet of an 18” CPP discharging into Big Soos Creek. Moderate flow observed (±1,675’). The outlet could not be investigated in the field. This is the end of field investigation. DOWNSTREAM PATH 2 “A2” is a NDL for the Site. It is located in the southeastern corner of the Site. This NDL is the inlet of a 12” diameter reinforced concrete pipe conveying storm water in a southeasterly direction (±0). From Point “A2” to Point “B2”, runoff continues in a southwesterly direction as pipe flow. No concentrated flow was observed (±0’-55’). Point “B2” is the outlet of a 12” reinforced concrete. (±55’). From Point “B2” to point “C2,” runoff continues in a southwesterly direction as sheet flow. (±55’-85’). Point “C2” is Big Soos Creek which collects runoff and is the convergence point of Downstream Paths 1 and 2. (±85’). TASK 5: MITIGATION OF EXISTING OR POTENTIAL PROBLEMS A review of the King County Water and Land Resources Division – Drainage Services Section Documented Drainage Complaints within one mile of the downstream flow 2021 D. R. STRONG Consulting Engineers Inc. Page 33 Bethany Corner Level One Downstream Analysis Renton, Washington paths revealed one complaint within the last ten years and has since been closed. Several drainage complaints exist within the downstream path but are not within the last ten years and are not applicable for Level One Downstream Analysis. The project should not create any problems as specified in Section 1.2.2.1 of the Manual and therefore is not required to provide Drainage Problem Impact Mitigation subject to the requirements of Section 1.2.2.2. A wetvault will provide flow control and basic water quality requirements for the entire Site. During construction, standard sediment and erosion control methods will be utilized. This will include the use of a stabilized construction entrance, perimeter silt fencing, and other necessary measures to minimize soil erosion during construction. 2021 D. R. STRONG Consulting Engineers Inc. Page 34 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 13 OFFSITE ANALYSIS DOWNSTREAM MAP GRAPHIC SCALE 0 100 200 400 1 INCH = 200 FT. 2021 D. R. STRONG Consulting Engineers Inc. Page 35 Bethany Corner Level One Downstream Analysis Renton, Washington FIGURE 14 OFFSITE ANALYSIS DOWNSTREAM TABLE DOWNSTREAM PATH 1 Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance From site Discharge Existing Problems Potential Problems Observations of field inspector resource reviewer, or resident See map Type: sheet flow, swale, Stream, channel, pipe, Pond; Size: diameter Surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 mile = 1,320 feet Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. A1 Natural discharge area Runoff exits at the NDA along the western property line of the Site. –0’ None Observed None Anticipated No concentrated flow observed A1-B1 West sheet flow Sheet flow over till grass None Observed None Anticipated No concentrated flow observed B1 Stream Big Soos Creek –45’ None Observed None Anticipated Moderate flow observed B1-C1 Southerly channel flow Big Soos Creek None Observed None Anticipated Moderate flow observed C1 Pipe inlet 12” diameter Reinforced Concrete Pipe (RCP) ±502’ Did not observe C1-D1 Easterly pipe flow 12” diameter RCP. None Observed None Anticipated Moderate flow observed D1 Pipe outlet 12” diameter RCP ±807’ None Observed None Anticipated Moderate flow observed D1-E1 Southerly channel flow 2’ tall 3’ wide swale None Observed None Anticipated Moderate flow observed E1 Pipe inlet 12” diameter RCP ±813’ None Observed None Anticipated Moderate flow observed E1-F1 Southerly pipe flow 12” diameter RCP None Observed None Anticipated Moderate flow observed F1 Pipe outlet 12” diameter RCP ±835’ None Observed None Anticipated Moderate flow observed F1-G1 Southerly channel flow 2’ tall and 4’ wide swale None Observed None Anticipated Moderate flow observed 2021 D. R. STRONG Consulting Engineers Inc. Page 36 Bethany Corner Level One Downstream Analysis Renton, Washington G1 Pipe inlet 12” diameter RCP ±925’ None Observed None Anticipated Moderate flow observed G1-H1 Southerly pipe flow 12” diameter RCP None Observed None Anticipated Moderate flow observed H1 Pipe outlet 12” diameter RCP ±968’ None Observed None Anticipated Moderate flow observed H1-I1 Southerly channel flow 2’ tall and 4’ wide swale None Observed None Anticipated Moderate flow observed I1 Pipe inlet 12” diameter RCP ±986’ Partially submerged None Anticipated Heavy flow observed I1-J1 Easterly pipe flow 12” diameter RCP None Observed None Anticipated Heavy flow observed J1 Pipe outlet 12” diameter RCP ±1,022’ Fully submerged None Anticipated Heavy flow observed J1-K1 Southerly channel flow 2’ tall 4’ wide swale None Observed None Anticipated Heavily vegetated - moderate flow observed K1 Pipe inlet 24” diameter Corrugated Metal Pipe (CMP) ±1,037’ None Observed None Anticipated Moderate flow observed K1-L1 Southerly pipe flow 24” diameter CMP None Observed None Anticipated Moderate flow observed L1 Type 1 CB Renton Facility No. 180983 ±1,121’ None Observed None Anticipated Standing water observed L1-M1 Southeasterly pipe 12” diameter CMP Fully submerged None Anticipated Heavy flow observed M1 Pipe outlet 12” diameter CMP ±1,180’ None Observed None Anticipated Moderate flow observed M1-N1 Southeasterly channel flow Big Soos Creek None Observed None Anticipated Moderate flow observed N1 Pipe inlet 18” diameter corrugated plastic pipe (CPP) under SE 168th Street ±1,599’ None Observed None Anticipated Moderate flow observed. Metal debris barrier covering inlet N1-O1 Southerly pipe flow 18” diameter CPP None Observed None Anticipated Moderate flow observed O1 Pipe outlet 18” diameter CPP. Discharging into Big Soos Creek ±1,675’ None Observed None Anticipated Discharge point not observed 2021 D. R. STRONG Consulting Engineers Inc. Page 37 Bethany Corner Level One Downstream Analysis Renton, Washington DOWNSTREAM PATH 2 Symbol Drainage Component Type, Name, and Size Drainage Component Description Slope Distance From site Discharge Existing Problems Potential Problems Observations of field inspector resource reviewer, or resident See map Type: sheet flow, swale, Stream, channel, pipe, Pond; Size: diameter Surface area drainage basin, vegetation, cover, depth, type of sensitive area, volume % 1/4 mile = 1,320 feet Constrictions, under capacity, ponding, overtopping, flooding, habitat or organism destruction, scouring, bank sloughing, sedimentation, incision, other erosion Tributary area, likelihood of problem, overflow pathways, potential impacts. A2 Natural discharge area – Pipe inlet 12” diameter RCP. –0’ None Observed None Anticipated No concentrated flow observed A2-B2 Southwesterly pipe flow 12” diameter RCP None Observed None Anticipated No concentrated flow observed B2 Pipe outlet 12” diameter RCP –55’ None Observed None Anticipated No concentrated flow observed B2-C2 Southwesterly sheet flow Sheet flow over moderately vegetated areas None Observed None Anticipated Moderate flow observed C2 Stream Big Soos Creek. Convergence point of Downstream Paths 1 and 2 ±85’ Did not observe 2021 D. R. STRONG Consulting Engineers Inc. Page 38 Bethany Corner Technical Information Report Renton, Washington SECTION IV FLOW CONTROL ANALYSIS AND WATER QUALITY DESIGN EXISTING SITE HYDROLOGY KCRTS was used to model runoff from the Site. The Site falls within the City’s Flow Control Duration Standard – Matching Forested area. The Site was modeled as predeveloped forested condtions for target surfaces and impervious for flow-through surfaces (see Figure 15). Results of the KCRTS analysis are included in this section. Modeling Input for the Pre-developed Site Flow Frequency Analysis Time Series File:predev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.123 2 2/09/01 18:00 0.156 1 100.00 0.990 0.033 7 1/06/02 3:00 0.123 2 25.00 0.960 0.091 4 2/28/03 3:00 0.094 3 10.00 0.900 0.004 8 3/24/04 20:00 0.091 4 5.00 0.800 0.054 6 1/05/05 8:00 0.079 5 3.00 0.667 0.094 3 1/18/06 21:00 0.054 6 2.00 0.500 0.079 5 11/24/06 4:00 0.033 7 1.30 0.231 0.156 1 1/09/08 9:00 0.004 8 1.10 0.091 Computed Peaks 0.145 50.00 0.980 2021 D. R. STRONG Consulting Engineers Inc. Page 39 Bethany Corner Technical Information Report Renton, Washington FIGURE 15 PREDEVELOPED AREA MAP GRAPHIC SCALE 0 20 40 60 1 INCH = 40 FT. 2021 D. R. STRONG Consulting Engineers Inc. Page 40 Bethany Corner Technical Information Report Renton, Washington DEVELOPED SITE HYDROLOGY Soil Type The soil types are unchanged from predeveloped conditions. Land Cover KCRTS was used to model the developed peak runoff from the Site. The portions of the Site within the developable area tributary to the proposed detention facility were modeled as “Till Grass”, and Impervious as appropriate. Results of the KCRTS analysis are included in this section. Modeling Input for RDIN Site Flow Frequency Analysis Time Series File:rdin.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.327 6 2/09/01 2:00 0.661 1 100.00 0.990 0.268 8 1/05/02 16:00 0.426 2 25.00 0.960 0.393 3 2/27/03 7:00 0.393 3 10.00 0.900 0.293 7 8/26/04 2:00 0.352 4 5.00 0.800 0.352 4 10/28/04 16:00 0.348 5 3.00 0.667 0.348 5 1/18/06 16:00 0.327 6 2.00 0.500 0.426 2 10/26/06 0:00 0.293 7 1.30 0.231 0.661 1 1/09/08 6:00 0.268 8 1.10 0.091 Computed Peaks 0.583 50.00 0.980 2021 D. R. STRONG Consulting Engineers Inc. Page 41 Bethany Corner Technical Information Report Renton, Washington Modeling Input for the Bypass . Modeling Results Flow Frequency Analysis Time Series File:byp.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.025 4 2/09/01 2:00 0.055 1 100.00 0.990 0.016 7 1/05/02 16:00 0.031 2 25.00 0.960 0.031 2 2/27/03 7:00 0.026 3 10.00 0.900 0.013 8 8/26/04 2:00 0.025 4 5.00 0.800 0.017 6 10/28/04 16:00 0.024 5 3.00 0.667 0.026 3 1/18/06 16:00 0.017 6 2.00 0.500 0.024 5 11/24/06 3:00 0.016 7 1.30 0.231 0.055 1 1/09/08 6:00 0.013 8 1.10 0.091 Computed Peaks 0.047 50.00 0.980 2021 D. R. STRONG Consulting Engineers Inc. Page 42 Bethany Corner Technical Information Report Renton, Washington FIGURE 16 DEVELOPED AREA MAP GRAPHIC SCALE 0 20 40 60 1 INCH = 40 FT. 2021 D. R. STRONG Consulting Engineers Inc. Page 43 Bethany Corner Technical Information Report Renton, Washington PERFORMANCE STANDARDS The Site is required to adhere to Flow Control Duration Standard – Matching Forested site conditions of the existing site (reference 11-A of COR 2009 Surface Water Design Manual Amendment). A wet-vault will provide flow control and basic water quality treatment. The Project is required to “match the flow duration of pre-developed rates for forested (historic) site conditions over the range of flows extending from 50% of 2-year up to the full 50-year flow.” (2009 Surface Water Design Manual Amendment, Sec. 1.2.3.1). The target surfaces include areas, which, due to topography and upstream characteristics, must bypass the detention and water quality vault. Per Section 1.2.3.2 (E) Mitigation of Target Surfaces that Bypass Facility, there are certain requirements that must be met for bypassed areas. Those include: (1) The point of convergence for bypass and mitigation flows is well within a quarter- mile. (2) The total developed flow from the bypass area is 0.06 cfs, which is far less than the 0.40 cfs increase allowed. (3) No significant adverse impacts to the downstream are anticipated. (4) The bypass area includes less than 5,000 sq-ft of PGIS so water quality is not a concern. (5) The vault is designed to meet the flow control requirements at a downstream point of compliance that includes flows from the unmitigated bypass area. An area swap is proposed in which an area of non-target surface will be collected which is approximately equal to an area of target surface that is being directed to bypass. DETENTION COMPLIANCE ANALYSIS The Project is required to “match the flow duration of pre-developed rates for forested (historic) site conditions over the range of flows extending from 50% of 2-year up to the full 50-year flow.” (2009 Surface Water Design Manual Amendment, Sec. 1.2.3.1). The analysis methods were applied per the KCRTS Reference Manual for a Level 2 facility with bypass. Since a reduced time series is used, the 25-year peak is substituted for the 50-year peak. The duration analysis presented in the KCRTS output shows that the mitigated flow duration are strictly below the predeveloped for flows from ½ of the 2-year (0. 27 cfs) to the 2-year (0.54 cfs) and the maximum exceedance does not exceed 10%. The developed 2-year and 10-year peaks values of 0.35 cfs and 0.93 cfs respectively are less than or match the predeveloped 2-year and 10-year peaks values of 0.54 cfs and 0.94 cfs respectively. All values for duration and peak flow are measured at the downstream point of compliance. 2021 D. R. STRONG Consulting Engineers Inc. Page 44 Bethany Corner Technical Information Report Renton, Washington FLOW CONTROL SYSTEM The Project will utilize an detention facility designed to control site runoff. The King County Runoff Time Series (KCRTS) software was used to size the facility. The detention pond design information is included in this section. Retention/Detention Facility Type of Facility: Detention Vault Facility Length: 98.00 ft Facility Width: 46.00 ft Facility Area: 4508. sq. ft Effective Storage Depth: 5.50 ft Stage 0 Elevation: 0.00 ft Storage Volume: 24794. cu. ft Riser Head: 5.50 ft Riser Diameter: 12.00 inches Number of orifices: 2 Full Head Pipe Orifice # Height Diameter Discharge Diameter (ft) (in) (CFS) (in) 1 0.00 0.69 0.030 2 3.56 1.38 0.071 4.0 Top Notch Weir: None Outflow Rating Curve: None Stage Elevation Storage Discharge Percolation (ft) (ft) (cu. ft) (ac-ft) (cfs) (cfs) 0.00 0.00 0. 0.000 0.000 0.00 0.01 0.01 45. 0.001 0.002 0.00 0.02 0.02 90. 0.002 0.002 0.00 0.03 0.03 135. 0.003 0.002 0.00 0.04 0.04 180. 0.004 0.003 0.00 0.05 0.05 225. 0.005 0.003 0.00 0.06 0.06 271. 0.006 0.003 0.00 0.16 0.16 721. 0.017 0.005 0.00 0.26 0.26 1172. 0.027 0.007 0.00 0.36 0.36 1623. 0.037 0.008 0.00 0.46 0.46 2074. 0.048 0.009 0.00 0.56 0.56 2525. 0.058 0.010 0.00 0.66 0.66 2975. 0.068 0.010 0.00 0.76 0.76 3426. 0.079 0.011 0.00 0.86 0.86 3877. 0.089 0.012 0.00 0.96 0.96 4328. 0.099 0.013 0.00 1.06 1.06 4779. 0.110 0.013 0.00 1.16 1.16 5229. 0.120 0.014 0.00 1.26 1.26 5680. 0.130 0.014 0.00 1.36 1.36 6131. 0.141 0.015 0.00 1.46 1.46 6582. 0.151 0.016 0.00 1.56 1.56 7033. 0.161 0.016 0.00 1.66 1.66 7483. 0.172 0.017 0.00 2021 D. 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Page 45 Bethany Corner Technical Information Report Renton, Washington 1.76 1.76 7934. 0.182 0.017 0.00 1.86 1.86 8385. 0.192 0.018 0.00 1.96 1.96 8836. 0.203 0.018 0.00 2.06 2.06 9287. 0.213 0.018 0.00 2.16 2.16 9737. 0.224 0.019 0.00 2.26 2.26 10188. 0.234 0.019 0.00 2.36 2.36 10639. 0.244 0.020 0.00 2.46 2.46 11090. 0.255 0.020 0.00 2.56 2.56 11540. 0.265 0.021 0.00 2.66 2.66 11991. 0.275 0.021 0.00 2.76 2.76 12442. 0.286 0.021 0.00 2.86 2.86 12893. 0.296 0.022 0.00 2.96 2.96 13344. 0.306 0.022 0.00 3.06 3.06 13794. 0.317 0.022 0.00 3.16 3.16 14245. 0.327 0.023 0.00 3.26 3.26 14696. 0.337 0.023 0.00 3.36 3.36 15147. 0.348 0.024 0.00 3.46 3.46 15598. 0.358 0.024 0.00 3.56 3.56 16048. 0.368 0.024 0.00 3.57 3.57 16094. 0.369 0.025 0.00 3.59 3.59 16184. 0.372 0.026 0.00 3.60 3.60 16229. 0.373 0.028 0.00 3.62 3.62 16319. 0.375 0.031 0.00 3.63 3.63 16364. 0.376 0.034 0.00 3.65 3.65 16454. 0.378 0.038 0.00 3.66 3.66 16499. 0.379 0.041 0.00 3.67 3.67 16544. 0.380 0.042 0.00 3.77 3.77 16995. 0.390 0.049 0.00 3.87 3.87 17446. 0.401 0.054 0.00 3.97 3.97 17897. 0.411 0.059 0.00 4.07 4.07 18348. 0.421 0.063 0.00 4.17 4.17 18798. 0.432 0.066 0.00 4.27 4.27 19249. 0.442 0.070 0.00 4.37 4.37 19700. 0.452 0.073 0.00 4.47 4.47 20151. 0.463 0.076 0.00 4.57 4.57 20602. 0.473 0.079 0.00 4.67 4.67 21052. 0.483 0.082 0.00 4.77 4.77 21503. 0.494 0.085 0.00 4.87 4.87 21954. 0.504 0.087 0.00 4.97 4.97 22405. 0.514 0.090 0.00 5.07 5.07 22856. 0.525 0.092 0.00 5.17 5.17 23306. 0.535 0.094 0.00 5.27 5.27 23757. 0.545 0.097 0.00 5.37 5.37 24208. 0.556 0.099 0.00 5.47 5.47 24659. 0.566 0.101 0.00 5.50 5.50 24794. 0.569 0.101 0.00 5.60 5.60 25245. 0.580 0.412 0.00 5.70 5.70 25696. 0.590 0.977 0.00 5.80 5.80 26146. 0.600 1.710 0.00 5.90 5.90 26597. 0.611 2.500 0.00 6.00 6.00 27048. 0.621 2.790 0.00 6.10 6.10 27499. 0.631 3.040 0.00 6.20 6.20 27950. 0.642 3.280 0.00 6.30 6.30 28400. 0.652 3.500 0.00 2021 D. 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Page 46 Bethany Corner Technical Information Report Renton, Washington 6.40 6.40 28851. 0.662 3.710 0.00 6.50 6.50 29302. 0.673 3.900 0.00 6.60 6.60 29753. 0.683 4.090 0.00 6.70 6.70 30204. 0.693 4.270 0.00 6.80 6.80 30654. 0.704 4.440 0.00 6.90 6.90 31105. 0.714 4.600 0.00 7.00 7.00 31556. 0.724 4.760 0.00 7.10 7.10 32007. 0.735 4.910 0.00 7.20 7.20 32458. 0.745 5.060 0.00 7.30 7.30 32908. 0.755 5.210 0.00 7.40 7.40 33359. 0.766 5.350 0.00 7.50 7.50 33810. 0.776 5.490 0.00 Hyd Inflow Outflow Peak Storage Stage Elev (Cu-Ft) (Ac-Ft) 1 0.66 0.10 5.42 5.42 24437. 0.561 2 0.33 0.09 5.09 5.09 22937. 0.527 3 0.39 0.08 4.60 4.60 20738. 0.476 4 0.43 0.07 4.32 4.32 19458. 0.447 5 0.35 0.03 3.59 3.59 16166. 0.371 6 0.27 0.02 3.00 3.00 13509. 0.310 7 0.35 0.02 3.13 3.13 14104. 0.324 8 0.29 0.02 1.95 1.95 8778. 0.202 Hyd R/D Facility Tributary Reservoir POC Outflow Outflow Inflow Inflow Target Calc 1 0.10 0.06 ******** ******* 0.13 2 0.09 0.02 ******** 0.12 0.11 3 0.08 0.03 ******** ******* 0.09 4 0.07 0.02 ******** ******* 0.08 5 0.03 0.03 ******** ******* 0.05 6 0.02 0.02 ******** ******* 0.03 7 0.02 0.02 ******** ******* 0.03 8 0.02 0.01 ******** ******* 0.03 ---------------------------------- Route Time Series through Facility Inflow Time Series File:rdin.tsf Outflow Time Series File:rdout POC Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 0.661 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.100 CFS at 14:00 on Jan 9 in Year 8 Peak Reservoir Stage: 5.42 Ft Peak Reservoir Elev: 5.42 Ft Peak Reservoir Storage: 24437. Cu-Ft : 0.561 Ac-Ft Add Time Series:byp.tsf Peak Summed Discharge: 0.132 CFS at 9:00 on Jan 9 in Year 8 Point of Compliance File:dsout.tsf Flow Frequency Analysis Time Series File:rdout.tsf 2021 D. R. STRONG Consulting Engineers Inc. Page 47 Bethany Corner Technical Information Report Renton, Washington Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.092 2 2/09/01 20:00 0.100 5.42 1 100.00 0.990 0.022 7 1/07/02 4:00 0.092 5.09 2 25.00 0.960 0.080 3 3/06/03 22:00 0.080 4.60 3 10.00 0.900 0.018 8 8/26/04 8:00 0.071 4.32 4 5.00 0.800 0.023 6 1/08/05 5:00 0.026 3.59 5 3.00 0.667 0.026 5 1/19/06 9:00 0.023 3.13 6 2.00 0.500 0.071 4 11/24/06 8:00 0.022 3.00 7 1.30 0.231 0.100 1 1/09/08 14:00 0.018 1.95 8 1.10 0.091 Computed Peaks 0.097 5.29 50.00 0.980 Flow Frequency Analysis Time Series File:dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.109 2 2/09/01 18:00 0.132 1 100.00 0.990 0.035 6 1/05/02 16:00 0.109 2 25.00 0.960 0.093 3 3/06/03 19:00 0.093 3 10.00 0.900 0.029 8 8/26/04 2:00 0.084 4 5.00 0.800 0.034 7 1/05/05 8:00 0.046 5 3.00 0.667 0.046 5 1/18/06 16:00 0.035 6 2.00 0.500 0.084 4 11/24/06 6:00 0.034 7 1.30 0.231 0.132 1 1/09/08 9:00 0.029 8 1.10 0.091 Computed Peaks 0.124 50.00 0.980 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.001 27844 45.408 45.408 54.592 0.546E+00 0.004 7816 12.746 58.154 41.846 0.418E+00 0.007 4992 8.141 66.295 33.705 0.337E+00 0.009 5257 8.573 74.868 25.132 0.251E+00 0.012 5470 8.920 83.788 16.212 0.162E+00 0.014 4124 6.725 90.514 9.486 0.949E-01 0.017 1635 2.666 93.180 6.820 0.682E-01 0.019 1930 3.147 96.327 3.673 0.367E-01 0.022 1168 1.905 98.232 1.768 0.177E-01 0.025 798 1.301 99.534 0.466 0.466E-02 0.027 43 0.070 99.604 0.396 0.396E-02 0.030 15 0.024 99.628 0.372 0.372E-02 0.032 15 0.024 99.653 0.347 0.347E-02 0.035 7 0.011 99.664 0.336 0.336E-02 0.037 7 0.011 99.675 0.325 0.325E-02 0.040 6 0.010 99.685 0.315 0.315E-02 0.043 11 0.018 99.703 0.297 0.297E-02 0.045 18 0.029 99.733 0.267 0.267E-02 0.048 16 0.026 99.759 0.241 0.241E-02 0.050 17 0.028 99.786 0.214 0.214E-02 2021 D. 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Page 48 Bethany Corner Technical Information Report Renton, Washington 0.053 15 0.024 99.811 0.189 0.189E-02 0.055 6 0.010 99.821 0.179 0.179E-02 0.058 5 0.008 99.829 0.171 0.171E-02 0.061 8 0.013 99.842 0.158 0.158E-02 0.063 7 0.011 99.853 0.147 0.147E-02 0.066 17 0.028 99.881 0.119 0.119E-02 0.068 8 0.013 99.894 0.106 0.106E-02 0.071 10 0.016 99.910 0.090 0.897E-03 0.073 8 0.013 99.923 0.077 0.766E-03 0.076 7 0.011 99.935 0.065 0.652E-03 0.079 10 0.016 99.951 0.049 0.489E-03 0.081 11 0.018 99.969 0.031 0.310E-03 0.084 3 0.005 99.974 0.026 0.261E-03 0.086 4 0.007 99.980 0.020 0.196E-03 0.089 3 0.005 99.985 0.015 0.147E-03 0.091 4 0.007 99.992 0.008 0.815E-04 Flow Duration from Time Series File:dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.002 27859 45.432 45.432 54.568 0.546E+00 0.005 8687 14.167 59.599 40.401 0.404E+00 0.008 5690 9.279 68.878 31.122 0.311E+00 0.011 6356 10.365 79.243 20.757 0.208E+00 0.014 4213 6.871 86.114 13.886 0.139E+00 0.017 3348 5.460 91.574 8.426 0.843E-01 0.020 2087 3.403 94.977 5.023 0.502E-01 0.023 1416 2.309 97.286 2.714 0.271E-01 0.026 908 1.481 98.767 1.233 0.123E-01 0.029 360 0.587 99.354 0.646 0.646E-02 0.032 85 0.139 99.493 0.507 0.507E-02 0.035 58 0.095 99.587 0.413 0.413E-02 0.038 20 0.033 99.620 0.380 0.380E-02 0.041 23 0.038 99.658 0.342 0.342E-02 0.044 10 0.016 99.674 0.326 0.326E-02 0.047 16 0.026 99.700 0.300 0.300E-02 0.050 20 0.033 99.733 0.267 0.267E-02 0.053 17 0.028 99.760 0.240 0.240E-02 0.056 15 0.024 99.785 0.215 0.215E-02 0.059 10 0.016 99.801 0.199 0.199E-02 0.062 12 0.020 99.821 0.179 0.179E-02 0.065 6 0.010 99.830 0.170 0.170E-02 0.068 8 0.013 99.843 0.157 0.157E-02 0.072 11 0.018 99.861 0.139 0.139E-02 0.075 13 0.021 99.883 0.117 0.117E-02 0.078 6 0.010 99.892 0.108 0.108E-02 0.081 10 0.016 99.909 0.091 0.913E-03 0.084 11 0.018 99.927 0.073 0.734E-03 0.087 9 0.015 99.941 0.059 0.587E-03 0.090 9 0.015 99.956 0.044 0.440E-03 0.093 9 0.015 99.971 0.029 0.294E-03 0.096 3 0.005 99.976 0.024 0.245E-03 0.099 3 0.005 99.980 0.020 0.196E-03 0.102 4 0.007 99.987 0.013 0.130E-03 2021 D. 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Page 49 Bethany Corner Technical Information Report Renton, Washington 0.105 4 0.007 99.993 0.007 0.652E-04 0.108 3 0.005 99.998 0.002 0.163E-04 Duration Comparison Anaylsis Base File: predev.tsf New File: dsout.tsf Cutoff Units: Discharge in CFS -----Fraction of Time----- ---------Check of Tolerance------- Cutoff Base New %Change Probability Base New %Change 0.027 | 0.96E-02 0.92E-02 -3.7 | 0.96E-02 0.027 0.027 -0.5 0.034 | 0.64E-02 0.42E-02 -33.3 | 0.64E-02 0.034 0.029 -15.1 0.042 | 0.50E-02 0.33E-02 -32.8 | 0.50E-02 0.042 0.032 -22.7 0.049 | 0.37E-02 0.28E-02 -23.3 | 0.37E-02 0.049 0.039 -20.5 0.056 | 0.29E-02 0.22E-02 -24.6 | 0.29E-02 0.056 0.049 -13.5 0.064 | 0.22E-02 0.17E-02 -21.3 | 0.22E-02 0.064 0.055 -13.5 0.071 | 0.15E-02 0.15E-02 -1.1 | 0.15E-02 0.071 0.071 -0.6 0.078 | 0.10E-02 0.10E-02 0.0 | 0.10E-02 0.078 0.079 0.3 0.086 | 0.62E-03 0.64E-03 2.6 | 0.62E-03 0.086 0.086 0.8 0.093 | 0.34E-03 0.28E-03 -19.0 | 0.34E-03 0.093 0.091 -2.0 0.100 | 0.21E-03 0.18E-03 -15.4 | 0.21E-03 0.100 0.099 -1.6 0.108 | 0.16E-03 0.33E-04 -80.0 | 0.16E-03 0.108 0.102 -5.8 0.115 | 0.98E-04 0.00E+00 -100.0 | 0.98E-04 0.115 0.103 -10.1 0.122 | 0.16E-04 0.00E+00 -100.0 | 0.16E-04 0.122 0.109 -11.1 Maximum positive excursion = 0.002 cfs ( 2.6%) occurring at 0.080 cfs on the Base Data:predev.tsf and at 0.082 cfs on the New Data:dsout.tsf Maximum negative excursion = 0.011 cfs (-24.6%) occurring at 0.046 cfs on the Base Data:predev.tsf and at 0.034 cfs on the New Data:dsout.tsf ---------------------------------- Route Time Series through Facility Inflow Time Series File:rdin.tsf Outflow Time Series File:rdout POC Time Series File:dsout Inflow/Outflow Analysis Peak Inflow Discharge: 0.661 CFS at 6:00 on Jan 9 in Year 8 Peak Outflow Discharge: 0.100 CFS at 14:00 on Jan 9 in Year 8 Peak Reservoir Stage: 5.42 Ft Peak Reservoir Elev: 5.42 Ft Peak Reservoir Storage: 24437. Cu-Ft : 0.561 Ac-Ft Add Time Series:byp.tsf Peak Summed Discharge: 0.132 CFS at 9:00 on Jan 9 in Year 8 Point of Compliance File:dsout.tsf Flow Frequency Analysis Time Series File:rdout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- 2021 D. R. STRONG Consulting Engineers Inc. Page 50 Bethany Corner Technical Information Report Renton, Washington Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) (ft) Period 0.092 2 2/09/01 20:00 0.100 5.42 1 100.00 0.990 0.022 7 1/07/02 4:00 0.092 5.09 2 25.00 0.960 0.080 3 3/06/03 22:00 0.080 4.60 3 10.00 0.900 0.018 8 8/26/04 8:00 0.071 4.32 4 5.00 0.800 0.023 6 1/08/05 5:00 0.026 3.59 5 3.00 0.667 0.026 5 1/19/06 9:00 0.023 3.13 6 2.00 0.500 0.071 4 11/24/06 8:00 0.022 3.00 7 1.30 0.231 0.100 1 1/09/08 14:00 0.018 1.95 8 1.10 0.091 Computed Peaks 0.097 5.29 50.00 0.980 Flow Frequency Analysis Time Series File:dsout.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.109 2 2/09/01 18:00 0.132 1 100.00 0.990 0.035 6 1/05/02 16:00 0.109 2 25.00 0.960 0.093 3 3/06/03 19:00 0.093 3 10.00 0.900 0.029 8 8/26/04 2:00 0.084 4 5.00 0.800 0.034 7 1/05/05 8:00 0.046 5 3.00 0.667 0.046 5 1/18/06 16:00 0.035 6 2.00 0.500 0.084 4 11/24/06 6:00 0.034 7 1.30 0.231 0.132 1 1/09/08 9:00 0.029 8 1.10 0.091 Computed Peaks 0.124 50.00 0.980 Flow Duration from Time Series File:rdout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.001 27844 45.408 45.408 54.592 0.546E+00 0.004 7816 12.746 58.154 41.846 0.418E+00 0.007 4992 8.141 66.295 33.705 0.337E+00 0.009 5257 8.573 74.868 25.132 0.251E+00 0.012 5470 8.920 83.788 16.212 0.162E+00 0.014 4124 6.725 90.514 9.486 0.949E-01 0.017 1635 2.666 93.180 6.820 0.682E-01 0.019 1930 3.147 96.327 3.673 0.367E-01 0.022 1168 1.905 98.232 1.768 0.177E-01 0.025 798 1.301 99.534 0.466 0.466E-02 0.027 43 0.070 99.604 0.396 0.396E-02 0.030 15 0.024 99.628 0.372 0.372E-02 0.032 15 0.024 99.653 0.347 0.347E-02 0.035 7 0.011 99.664 0.336 0.336E-02 0.037 7 0.011 99.675 0.325 0.325E-02 0.040 6 0.010 99.685 0.315 0.315E-02 0.043 11 0.018 99.703 0.297 0.297E-02 0.045 18 0.029 99.733 0.267 0.267E-02 0.048 16 0.026 99.759 0.241 0.241E-02 0.050 17 0.028 99.786 0.214 0.214E-02 0.053 15 0.024 99.811 0.189 0.189E-02 0.055 6 0.010 99.821 0.179 0.179E-02 0.058 5 0.008 99.829 0.171 0.171E-02 2021 D. 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Page 51 Bethany Corner Technical Information Report Renton, Washington 0.061 8 0.013 99.842 0.158 0.158E-02 0.063 7 0.011 99.853 0.147 0.147E-02 0.066 17 0.028 99.881 0.119 0.119E-02 0.068 8 0.013 99.894 0.106 0.106E-02 0.071 10 0.016 99.910 0.090 0.897E-03 0.073 8 0.013 99.923 0.077 0.766E-03 0.076 7 0.011 99.935 0.065 0.652E-03 0.079 10 0.016 99.951 0.049 0.489E-03 0.081 11 0.018 99.969 0.031 0.310E-03 0.084 3 0.005 99.974 0.026 0.261E-03 0.086 4 0.007 99.980 0.020 0.196E-03 0.089 3 0.005 99.985 0.015 0.147E-03 0.091 4 0.007 99.992 0.008 0.815E-04 Flow Duration from Time Series File:dsout.tsf Cutoff Count Frequency CDF Exceedence_Probability CFS % % % 0.002 27859 45.432 45.432 54.568 0.546E+00 0.005 8687 14.167 59.599 40.401 0.404E+00 0.008 5690 9.279 68.878 31.122 0.311E+00 0.011 6356 10.365 79.243 20.757 0.208E+00 0.014 4213 6.871 86.114 13.886 0.139E+00 0.017 3348 5.460 91.574 8.426 0.843E-01 0.020 2087 3.403 94.977 5.023 0.502E-01 0.023 1416 2.309 97.286 2.714 0.271E-01 0.026 908 1.481 98.767 1.233 0.123E-01 0.029 360 0.587 99.354 0.646 0.646E-02 0.032 85 0.139 99.493 0.507 0.507E-02 0.035 58 0.095 99.587 0.413 0.413E-02 0.038 20 0.033 99.620 0.380 0.380E-02 0.041 23 0.038 99.658 0.342 0.342E-02 0.044 10 0.016 99.674 0.326 0.326E-02 0.047 16 0.026 99.700 0.300 0.300E-02 0.050 20 0.033 99.733 0.267 0.267E-02 0.053 17 0.028 99.760 0.240 0.240E-02 0.056 15 0.024 99.785 0.215 0.215E-02 0.059 10 0.016 99.801 0.199 0.199E-02 0.062 12 0.020 99.821 0.179 0.179E-02 0.065 6 0.010 99.830 0.170 0.170E-02 0.068 8 0.013 99.843 0.157 0.157E-02 0.072 11 0.018 99.861 0.139 0.139E-02 0.075 13 0.021 99.883 0.117 0.117E-02 0.078 6 0.010 99.892 0.108 0.108E-02 0.081 10 0.016 99.909 0.091 0.913E-03 0.084 11 0.018 99.927 0.073 0.734E-03 0.087 9 0.015 99.941 0.059 0.587E-03 0.090 9 0.015 99.956 0.044 0.440E-03 0.093 9 0.015 99.971 0.029 0.294E-03 0.096 3 0.005 99.976 0.024 0.245E-03 0.099 3 0.005 99.980 0.020 0.196E-03 0.102 4 0.007 99.987 0.013 0.130E-03 0.105 4 0.007 99.993 0.007 0.652E-04 0.108 3 0.005 99.998 0.002 0.163E-04 2021 D. R. STRONG Consulting Engineers Inc. Page 52 Bethany Corner Technical Information Report Renton, Washington Flow Frequency Duration Analysis 2021 D. R. STRONG Consulting Engineers Inc. Page 53 Bethany Corner Technical Information Report Renton, Washington WATER QUALITY TREATMENT SYSTEM The Project is required to adhere to the City of Renton’s Basic Water Quality treatment criteria. A combined detention/water quality vault located within Tract A is proposed to accommodate this requirement. Sizing for a wetvault was calculated from the formula provided by Section 6.4.1.1 Methods of Analysis of the Manual. The minimum wetpool volume required is 6,176 cubic feet. The Project will provide 11,333 cubic feet of dead storage. The wetvault will occupy the eastern half of the detention vault. The vault geometry provides a length to width ratio of 4.33 : 1 so a removable baffle will be provided as shown on the plans. BASIC WETVAULT ANALYSIS As required per Section 6.4.1.1 2009 King County Step 1: Identify required water quality facility volume factor ("f") f=3 (basic wetpond volume factor) Step 2: Determine rainfall (R) for the mean annual storm per Fig. 6.4.1.A R=0.47 in. Step 3: Calculate runoff from the mean annual storm (Vr) for the developed site. Vr =(0.9Ai + 0.25Atg + 0.10Atf + 0.01Ao) x R/12 where . . . Vr =volume of runoff from mean annual storm (c.f.) Ai=area of impervious surface (s.f.) Atg=area of till soil covered with grass (s.f.) Atf=area of till soil covered with till forest (s.f.) Ao=area of outwash soil covered with grass or forest (s.f.) R=rainfall from mean annual storm (in.) Ai=48,847 s.f. Atg=34,383 s.f. Atf=- s.f. Ao=0 s.f. R =0.47 in. Vr =2,059 c.f. Step 4: Calculate water quality volume (Vb). Vb=f x Vr where . . . Vb=water quality volume (cf) f=volume factor from Step 1 Vr =runoff volume from Step 3 Vb=6,176 c.f. (minimum wetpool volume required) 49,227 sf req. 6,215 cf < provided therefore OK 2021 D. R. STRONG Consulting Engineers Inc. Page 54 Bethany Corner Technical Information Report Renton, Washington FIGURE 17 DETENTION & WATER QUALITY FACILITY DETAILS BETHANY CORNER 16433 & 16451 111TH AVENUE SERENTON, WASHINGTON 98056 BETHANY CORNERBETHANY CORNERTED-40-4006U: 16006722DRS PROJECT NO. 16062 LUA: 16-000958IN COMPLIANCE WITH CITY OF RENTON STANDARDS PR: 16000504R-400617 2021 D. R. STRONG Consulting Engineers Inc. Page 55 Bethany Corner Technical Information Report Renton, Washington SECTION V CONVEYANCE SYSTEM ANALYSIS AND DESIGN Per Core Requirement #4 of the KCSWDM, the conveyance system must be analyzed and designed for the existing tributary and developed onsite runoff. Pipe systems shall be designed to convey the 25-year storm with a minimum of 6-inches of freeboard between the design water surface and structure grate. Any overflow from the 100-year design storm must not create or aggravate a severe flooding problem. The Rational Method will be used to calculate the Q-Ratio for each pipe node. A conveyance system consisting primarily of pipes and catch basins will be designed for the Project. Onsite runoff will be collected by the multiple catch basins. Pipes are typically six-inch to twelve-inch diameter LCPE material. Per Figures 3.2.1.C and 3.2.1.D in the 2009 Manual the 24-hour precipitation in inches is 3.4 and 3.9 for the 25-year and 100-year storms respectively. In all cases the 25-year storm was conveyed with at least 6-inches of freeboard. There were no overflows as a result of the 100-year storm. 2021 D. R. STRONG Consulting Engineers Inc. Page 56 Bethany Corner Technical Information Report Renton, Washington 2021 D. R. STRONG Consulting Engineers Inc. Page 57 Bethany Corner Technical Information Report Renton, Washington 2021 D. R. STRONG Consulting Engineers Inc. Page 58 Bethany Corner Technical Information Report Renton, Washington BACKWATER ANALYSIS Path:R:\2016\0\16062\3\Documents\Analysis\KCBW\161212\BACKWATER-16062_25.xls Storm Water Runoff Variables: A=Total of Subasin and Tributary Areas C=Runoff Coefficient (the anticipated proportion of rainfall volume that runs off the area) see '09 KCSWM Table 3.2.1A CC=Composite Runoff Coefficient CC=S(Cn*An)/ATotal Tc=Time of Concentration (Typically 6.3 minutes which is the minimum value used in calculations) R=design return frequency iR=Unit peak rainfall intensity factor iR=(aR)(Tc)^(-bR) aR,bR=coefficients from '09 KCSWM Table 3.2.1.B used to adjust the equation for the design storm IR=Peak rainfall intensity factor for a storm of return frequency 'R' IR=PR*iR PR=total precipitation (inches) for the 24-hour storm event for the given frequency. See Issopluvial Maps in '09 KCSWM Figures 3.2.1.D QR=peak flow (cfs) for a storm of return frequency 'R' QR=CC*iR*A The Q-Ratio describes the ratio of the tributary flow to the main upstream flow. R=25 -year storm aR=2.66 bR=0.65 PR=3.4 inches Conveyance System Variables: d=pipe diameter n=Manning's Number l=length of pipe Pipe Structures Subasins &A A C CC Tc iR IR QR SQR Q - d Material n l Slope invert invert over-Q V Bend CB Tributaries subasin Ratio in out flow Full Full Dia elev.Flow Flow FROM CB To CB sf Ac Ac Min.cfs cfs in ft %ft ft ft cfs fps CB-8 TO INLET 2 P-8 8 7 8 10226 0.23 0.58 6.3 0.80 2.73 0.37 0.37 0.00 12 N-12 0.012 82 7.01 425.15 419.40 428.40 10.25 13.05 90 2 FROM RUN 9-7 1957 0.04 0.90 P-7 7 INLET 2 7 794 0.02 0.90 P-7 7 INLET 2 7 2751 0.06 0.90 6.3 0.80 2.73 0.16 0.53 0.30 12 N-12 0.012 24 12.08 419.40 416.50 426.65 13.45 17.13 0 4 12977 0.30 0.64 CB-6 TO INLET 1 P-6 6 5 6 30608 0.70 0.59 6.3 0.80 2.73 1.14 1.14 0.00 12 N-12 0.012 25 1.00 421.66 421.41 424.91 3.87 4.93 90 2 P-5 5 4 5 28631 0.66 0.59 6.3 0.80 2.73 1.05 2.19 0.48 12 N-12 0.012 106 1.00 421.41 420.35 424.91 3.87 4.93 90 2 P-4 4 INLET 1 4 785 0.02 0.90 6.3 0.80 2.73 0.04 2.23 0.02 12 N-12 0.012 25 15.40 420.35 416.50 426.64 15.19 19.34 0 4 60024 1.38 0.59 CB-11 TO CB-1 P-12 12 11 12 6600 0.15 0.90 6.3 0.80 2.73 0.37 0.37 0.00 12 N-12 0.012 132 4.46 430.59 424.70 433.42 8.18 10.41 0 2 P-11 11 10 11 0 0.00 0.90 6.3 0.80 2.73 0.00 0.37 0.00 12 N-12 0.012 151 2.93 424.70 420.28 428.40 6.62 8.43 49 2 P-10 10 3 10 0 0.00 0.90 6.3 0.80 2.73 0.00 0.37 0.00 12 N-12 0.012 11 17.73 420.28 418.33 425.28 16.29 20.75 49 2 P-3 3 2 3 485 0.01 0.90 6.3 0.80 2.73 0.47 0.85 1.27 12 N-12 0.012 134 0.80 418.33 417.26 424.41 3.46 4.40 64 4 P-2 2 1 2 0 0.00 0.90 6.3 0.80 2.73 0.00 0.85 0.00 12 N-12 0.012 8 1.00 417.26 417.18 419.88 3.87 4.93 68 2 7085 0.16 0.90 CB-9 TO CB-7 P-9 9 7 9 1957 0.04 0.90 6.3 0.80 2.73 0.11 0.11 0.00 12 N-12 0.012 73 3.42 421.90 419.40 424.90 7.16 9.12 90 2 Path:R:\2016\0\16062\3\Documents\Analysis\KCBW\161212\BACKWATER-16062_100.xls Storm Water Runoff Variables: A=Total of Subasin and Tributary Areas C=Runoff Coefficient (the anticipated proportion of rainfall volume that runs off the area) see '09 KCSWM Table 3.2.1A CC=Composite Runoff Coefficient CC=S(Cn*An)/ATotal Tc=Time of Concentration (Typically 6.3 minutes which is the minimum value used in calculations) R=design return frequency iR=Unit peak rainfall intensity factor iR=(aR)(Tc)^(-bR) aR,bR=coefficients from '09 KCSWM Table 3.2.1.B used to adjust the equation for the design storm IR=Peak rainfall intensity factor for a storm of return frequency 'R' IR=PR*iR PR=total precipitation (inches) for the 24-hour storm event for the given frequency. See Issopluvial Maps in '09 KCSWM Figures 3.2.1.D QR=peak flow (cfs) for a storm of return frequency 'R' QR=CC*iR*A The Q-Ratio describes the ratio of the tributary flow to the main upstream flow. R=100 -year storm aR=2.61 bR=0.63 PR=3.9 inches Conveyance System Variables: d=pipe diameter n=Manning's Number l=length of pipe Pipe Structures Subasins &A A C CC Tc iR IR QR SQR Q - d Material n l Slope invert invert over-Q V Bend CB Tributaries subasin Ratio in out flow Full Full Dia elev.Flow Flow FROM CB To CB sf Ac Ac Min.cfs cfs in ft %ft ft ft cfs fps CB-8 TO INLET 2 P-8 8 7 8 10226 0.23 0.58 6.3 0.82 3.19 0.43 0.43 0.00 12 N-12 0.012 82 7.01 425.15 419.40 428.40 10.25 13.05 90 2 FROM RUN 9-7 1957 0.04 0.90 P-7 7 INLET 2 7 794 0.02 0.90 P-7 7 INLET 2 7 2751 0.06 0.90 6.3 0.82 3.19 0.18 0.61 0.30 12 N-12 0.012 24 12.08 419.40 416.50 426.65 13.45 17.13 0 4 12977 0.30 0.64 CB-6 TO INLET 1 P-6 6 5 6 30608 0.70 0.59 6.3 0.82 3.19 1.33 1.33 0.00 12 N-12 0.012 25 1.00 421.66 421.41 424.91 3.87 4.93 90 2 P-5 5 4 5 28631 0.66 0.59 6.3 0.82 3.19 1.23 2.56 0.48 12 N-12 0.012 106 1.00 421.41 420.35 424.91 3.87 4.93 90 2 P-4 4 INLET 1 4 785 0.02 0.90 6.3 0.82 3.19 0.05 2.61 0.02 12 N-12 0.012 25 15.40 420.35 416.50 426.64 15.19 19.34 0 4 60024 1.38 0.59 CB-11 TO CB-1 P-12 12 11 12 6600 0.15 0.90 6.3 0.82 3.19 0.44 0.44 0.00 12 N-12 0.012 132 4.46 430.59 424.70 433.42 8.18 10.41 0 2 P-11 11 10 11 0 0.00 0.90 6.3 0.82 3.19 0.00 0.44 0.00 12 N-12 0.012 151 2.93 424.70 420.28 428.40 6.62 8.43 49 2 P-10 10 3 10 0 0.00 0.90 6.3 0.82 3.19 0.00 0.44 0.00 12 N-12 0.012 11 17.73 420.28 418.33 425.28 16.29 20.75 49 2 P-3 3 2 3 485 0.01 0.90 6.3 0.82 3.19 0.48 0.91 1.10 12 N-12 0.012 134 0.80 418.33 417.26 424.41 3.46 4.40 64 4 P-2 2 1 2 0 0.00 0.90 6.3 0.82 3.19 0.00 0.91 0.00 12 N-12 0.012 8 1.00 417.26 417.18 419.88 3.87 4.93 68 2 7085 0.16 0.90 CB-9 TO CB-7 P-9 9 7 9 1957 0.04 0.90 6.3 0.82 3.19 0.13 0.13 0.00 12 N-12 0.012 73 3.42 421.90 419.40 424.90 7.16 9.12 90 2 2021 D. R. STRONG Consulting Engineers Inc. Page 59 Bethany Corner Technical Information Report Renton, Washington FIGURE 18 BACKWATER ANALYSIS MAP 0 GRAPHIC SCALE 604020 1 INCH = 40 FT. 2021 D. R. STRONG Consulting Engineers Inc. Page 60 Bethany Corner Technical Information Report Renton, Washington 25-YEAR BACKWATER ANALYSIS RESULTS BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB-6 TO INLET 1.bwp Surcharge condition at intermediate junctions Tailwater Elevation:423.5 feet Discharge Range:2.06 to 2.56 Step of 0.1 [cfs] Overflow Elevation:424.92 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 27 LF - 12"CP @ 16.56% OUTLET: 416.00 INLET: 420.47 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 426.43 BEND: 0 DEG DIA/WIDTH: 4.0 Q-RATIO: 0.23 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 2.06 3.21 423.68 * 0.012 0.62 0.25 7.50 7.50 3.11 3.21 0.80 2.16 3.23 423.70 * 0.012 0.63 0.26 7.50 7.50 3.11 3.23 0.83 2.26 3.25 423.72 * 0.012 0.65 0.26 7.50 7.50 3.12 3.25 0.85 2.36 3.27 423.74 * 0.012 0.66 0.27 7.50 7.50 3.13 3.27 0.88 2.46 3.29 423.76 * 0.012 0.68 0.27 7.50 7.50 3.14 3.29 0.90 2.56 3.31 423.78 * 0.012 0.69 0.28 7.50 7.50 3.15 3.31 0.93 2.56 3.31 423.78 * 0.012 0.69 0.28 7.50 7.50 3.15 3.31 0.93 PIPE NO. 2: 94 LF - 12"CP @ 1.00% OUTLET: 420.47 INLET: 421.41 INTYP: 5 JUNC NO. 2: OVERFLOW-EL: 424.92 BEND: 90 DEG DIA/WIDTH: 2.0 Q-RATIO: 1.01 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 1.67 2.58 423.99 * 0.012 0.55 0.47 3.21 3.21 2.46 2.58 0.83 1.75 2.62 424.03 * 0.012 0.57 0.48 3.23 3.23 2.48 2.62 0.85 1.83 2.67 424.08 * 0.012 0.58 0.49 3.25 3.25 2.52 2.67 0.88 1.92 2.72 424.13 * 0.012 0.60 0.50 3.27 3.27 2.56 2.72 0.91 2.00 2.77 424.18 * 0.012 0.61 0.52 3.29 3.29 2.60 2.77 0.94 2.08 2.83 424.24 * 0.012 0.62 0.53 3.31 3.31 2.64 2.83 0.96 2.08 2.83 424.24 * 0.012 0.62 0.53 3.31 3.31 2.64 2.83 0.96 PIPE NO. 3: 25 LF - 12"CP @ 1.00% OUTLET: 421.41 INLET: 421.66 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.83 2.38 424.04 * 0.012 0.39 0.32 2.58 2.58 2.35 2.38 0.53 0.87 2.41 424.07 * 0.012 0.40 0.33 2.62 2.62 2.38 2.41 0.54 0.91 2.46 424.12 * 0.012 0.41 0.34 2.67 2.67 2.43 2.46 0.56 0.95 2.52 424.18 * 0.012 0.41 0.34 2.72 2.72 2.48 2.52 0.57 0.99 2.58 424.24 * 0.012 0.42 0.35 2.77 2.77 2.54 2.58 0.59 1.03 2.64 424.30 * 0.012 0.43 0.36 2.83 2.83 2.60 2.64 0.60 1.03 2.64 424.30 * 0.012 0.43 0.36 2.83 2.83 2.60 2.64 0.60 BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB-11 TO CB-1.bwp Surcharge condition at intermediate junctions Tailwater Elevation:418.17 feet Discharge Range:0.58 to 0.78 Step of 0.05 [cfs] Overflow Elevation:441.79 feet Weir:NONE Upstream Velocity:0. feet/sec 2021 D. 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Page 61 Bethany Corner Technical Information Report Renton, Washington PIPE NO. 1: 8 LF - 12"CP @ 0.50% OUTLET: 417.17 INLET: 417.21 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 419.88 BEND: 63 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.00 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.58 0.98 418.19 * 0.012 0.32 0.32 1.00 1.00 0.97 0.98 0.43 0.63 0.98 418.19 * 0.012 0.34 0.33 1.00 1.00 0.97 0.98 0.45 0.68 0.98 418.19 * 0.012 0.35 0.35 1.00 1.00 0.97 0.98 0.47 0.73 0.99 418.20 * 0.012 0.36 0.36 1.00 1.00 0.97 0.99 0.49 0.78 0.99 418.20 * 0.012 0.37 0.37 1.00 1.00 0.97 0.99 0.51 PIPE NO. 2: 134 LF - 12"CP @ 0.50% OUTLET: 417.21 INLET: 417.88 INTYP: 5 JUNC NO. 2: OVERFLOW-EL: 424.41 BEND: 63 DEG DIA/WIDTH: 4.0 Q-RATIO: 0.80 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.58 0.50 418.38 * 0.012 0.32 0.32 0.98 0.98 0.41 0.50 0.43 0.63 0.51 418.39 * 0.012 0.34 0.33 0.98 0.98 0.42 0.51 0.46 0.68 0.53 418.41 * 0.012 0.35 0.35 0.98 0.98 0.43 0.53 0.48 0.73 0.55 418.43 * 0.012 0.36 0.36 0.99 0.99 0.44 0.55 0.49 0.78 0.57 418.45 * 0.012 0.37 0.37 0.99 0.99 0.45 0.57 0.51 PIPE NO. 3: 101 LF - 12"CP @ 3.26% OUTLET: 417.88 INLET: 421.17 INTYP: 5 JUNC NO. 3: OVERFLOW-EL: 426.93 BEND: 0 DEG DIA/WIDTH: 4.0 Q-RATIO: 0.11 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.32 0.30 421.47 * 0.012 0.24 0.15 0.50 0.50 0.24 ***** 0.30 0.35 0.31 421.48 * 0.012 0.25 0.16 0.51 0.51 0.25 ***** 0.31 0.38 0.33 421.50 * 0.012 0.26 0.16 0.53 0.53 0.26 ***** 0.33 0.40 0.34 421.51 * 0.012 0.27 0.17 0.55 0.55 0.27 ***** 0.34 0.43 0.35 421.52 * 0.012 0.28 0.17 0.57 0.57 0.28 ***** 0.35 PIPE NO. 4: 71 LF - 12"CP @ 3.28% OUTLET: 421.17 INLET: 423.50 INTYP: 5 JUNC NO. 4: OVERFLOW-EL: 428.38 BEND: 0 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.00 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.29 0.28 423.78 * 0.012 0.23 0.14 0.30 0.30 0.23 ***** 0.28 0.31 0.30 423.80 * 0.012 0.24 0.15 0.31 0.31 0.24 ***** 0.30 0.34 0.31 423.81 * 0.012 0.25 0.15 0.33 0.33 0.25 ***** 0.31 0.36 0.32 423.82 * 0.012 0.25 0.16 0.34 0.34 0.25 ***** 0.32 0.39 0.33 423.83 * 0.012 0.26 0.17 0.35 0.35 0.26 ***** 0.33 PIPE NO. 5: 108 LF - 12"CP @ 5.46% OUTLET: 423.50 INLET: 429.40 INTYP: 5 JUNC NO. 5: OVERFLOW-EL: 432.59 BEND: 0 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.86 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.29 0.27 429.67 * 0.012 0.23 0.13 0.28 0.28 0.23 ***** 0.27 0.31 0.29 429.69 * 0.012 0.24 0.13 0.30 0.30 0.24 ***** 0.29 0.34 0.30 429.70 * 0.012 0.25 0.14 0.31 0.31 0.25 ***** 0.30 0.36 0.31 429.71 * 0.012 0.25 0.14 0.32 0.32 0.25 ***** 0.31 0.39 0.32 429.72 * 0.012 0.26 0.15 0.33 0.33 0.26 ***** 0.32 PIPE NO. 6: 130 LF - 12"CP @ 5.27% OUTLET: 429.40 INLET: 436.25 INTYP: 5 2021 D. 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Page 62 Bethany Corner Technical Information Report Renton, Washington JUNC NO. 6: OVERFLOW-EL: 439.25 BEND: 59 DEG DIA/WIDTH: 2.0 Q-RATIO: 6.81 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.16 0.19 436.44 * 0.012 0.17 0.10 0.27 0.27 0.17 ***** 0.19 0.17 0.20 436.45 * 0.012 0.17 0.10 0.29 0.29 0.17 ***** 0.20 0.18 0.21 436.46 * 0.012 0.18 0.10 0.30 0.30 0.18 ***** 0.21 0.20 0.22 436.47 * 0.012 0.19 0.11 0.31 0.31 0.19 ***** 0.22 0.21 0.23 436.48 * 0.012 0.19 0.11 0.32 0.32 0.19 ***** 0.23 PIPE NO. 7: 130 LF - 12"CP @ 1.92% OUTLET: 436.25 INLET: 438.75 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.02 0.07 438.82 * 0.012 0.06 0.05 0.19 0.19 0.06 ***** 0.07 0.02 0.07 438.82 * 0.012 0.06 0.05 0.20 0.20 0.06 ***** 0.07 0.02 0.07 438.82 * 0.012 0.07 0.05 0.21 0.21 0.07 ***** 0.07 0.03 0.08 438.83 * 0.012 0.07 0.05 0.22 0.22 0.07 ***** 0.08 0.03 0.08 438.83 * 0.012 0.07 0.06 0.23 0.23 0.07 ***** 0.08 BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB-403 TO CB-4.bwp Surcharge condition at intermediate junctions Tailwater Elevation:423.78 feet Discharge Range:0.25 to 0.45 Step of 0.05 [cfs] Overflow Elevation:428.15 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 24 LF - 12"CP @ 4.33% OUTLET: 420.47 INLET: 421.51 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 426.41 BEND: 0 DEG DIA/WIDTH: 2.0 Q-RATIO: 1.16 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.25 2.28 423.79 * 0.012 0.21 0.13 3.31 3.31 2.28 2.28 0.26 0.30 2.27 423.78 * 0.012 0.23 0.14 3.31 3.31 2.27 2.27 0.28 0.35 2.28 423.79 * 0.012 0.25 0.15 3.31 3.31 2.27 2.28 0.31 0.40 2.28 423.79 * 0.012 0.27 0.16 3.31 3.31 2.27 2.28 0.34 0.45 2.28 423.79 * 0.012 0.28 0.17 3.31 3.31 2.27 2.28 0.36 PIPE NO. 2: 32 LF - 12"CP @ 6.62% OUTLET: 421.51 INLET: 423.63 INTYP: 5 JUNC NO. 2: OVERFLOW-EL: 427.32 BEND: 82 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.27 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.12 0.21 423.84 * 0.012 0.14 0.08 2.28 2.28 0.18 0.21 0.15 0.14 0.23 423.86 * 0.012 0.16 0.09 2.27 2.27 0.17 0.23 0.17 0.16 0.25 423.88 * 0.012 0.17 0.09 2.28 2.28 0.18 0.25 0.19 0.18 0.21 423.84 * 0.012 0.18 0.10 2.28 2.28 0.18 ***** 0.21 0.21 0.22 423.85 * 0.012 0.19 0.11 2.28 2.28 0.19 ***** 0.22 PIPE NO. 3: 21 LF - 12"CP @ 6.52% OUTLET: 423.63 INLET: 425.00 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.09 0.13 425.13 * 0.012 0.13 0.07 0.21 0.21 0.13 ***** 0.13 0.11 0.15 425.15 * 0.012 0.14 0.08 0.23 0.23 0.14 ***** 0.15 0.13 0.16 425.16 * 0.012 0.15 0.08 0.25 0.25 0.15 ***** 0.16 2021 D. 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Page 63 Bethany Corner Technical Information Report Renton, Washington 0.15 0.18 425.18 * 0.012 0.16 0.09 0.21 0.21 0.16 ***** 0.18 0.16 0.19 425.19 * 0.012 0.17 0.09 0.22 0.22 0.17 ***** 0.19 BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:OUTLET TO CB-3.bwp Surcharge condition at intermediate junctions Tailwater Elevation:418.5 feet Discharge Range:0.12 to 0.22 Step of 0.02 [cfs] Overflow Elevation:427.5 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 24 LF - 12"CP @ 0.50% OUTLET: 417.88 INLET: 418.00 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.12 0.51 418.51 * 0.012 0.15 0.15 0.62 0.62 0.51 0.51 0.19 0.14 0.51 418.51 * 0.012 0.16 0.16 0.62 0.62 0.51 0.51 0.20 0.16 0.51 418.51 * 0.012 0.17 0.17 0.62 0.62 0.51 0.51 0.22 0.18 0.51 418.51 * 0.012 0.18 0.18 0.62 0.62 0.51 0.51 0.23 0.20 0.52 418.52 * 0.012 0.19 0.19 0.62 0.62 0.51 0.52 0.25 0.22 0.52 418.52 * 0.012 0.20 0.20 0.62 0.62 0.51 0.52 0.26 0.24 0.52 418.52 * 0.012 0.21 0.21 0.62 0.62 0.51 0.52 0.27 2021 D. R. STRONG Consulting Engineers Inc. Page 64 Bethany Corner Technical Information Report Renton, Washington 100-YEAR BACKWATER ANALYSIS RESULTS BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB-6 TO INLET 1.bwp Surcharge condition at intermediate junctions Tailwater Elevation:423.5 feet Discharge Range:2.5 to 3. Step of 0.1 [cfs] Overflow Elevation:424.91 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 27 LF - 12"CP @ 16.56% OUTLET: 416.00 INLET: 420.47 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 426.43 BEND: 0 DEG DIA/WIDTH: 4.0 Q-RATIO: 0.23 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 2.50 3.30 423.77 * 0.012 0.68 0.27 7.50 7.50 3.15 3.30 0.91 2.60 3.32 423.79 * 0.012 0.70 0.28 7.50 7.50 3.15 3.32 0.94 2.70 3.34 423.81 * 0.012 0.71 0.29 7.50 7.50 3.16 3.34 0.96 2.80 3.36 423.83 * 0.012 0.72 0.29 7.50 7.50 3.17 3.36 0.99 2.90 3.39 423.86 * 0.012 0.74 0.30 7.50 7.50 3.18 3.39 1.02 3.00 3.41 423.88 * 0.012 0.75 0.30 7.50 7.50 3.19 3.41 1.04 3.00 3.41 423.88 * 0.012 0.75 0.30 7.50 7.50 3.19 3.41 1.04 PIPE NO. 2: 94 LF - 12"CP @ 1.00% OUTLET: 420.47 INLET: 421.41 INTYP: 5 JUNC NO. 2: OVERFLOW-EL: 424.92 BEND: 90 DEG DIA/WIDTH: 2.0 Q-RATIO: 1.01 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 2.03 2.81 424.22 * 0.012 0.61 0.52 3.30 3.30 2.63 2.81 0.95 2.11 2.85 424.26 * 0.012 0.63 0.53 3.32 3.32 2.66 2.85 0.98 2.19 2.91 424.32 * 0.012 0.64 0.54 3.34 3.34 2.70 2.91 1.00 2.27 2.97 424.38 * 0.012 0.65 0.56 3.36 3.36 2.75 2.97 1.03 2.35 3.04 424.45 * 0.012 0.66 0.57 3.39 3.39 2.80 3.04 1.06 2.44 3.10 424.51 * 0.012 0.67 0.58 3.41 3.41 2.85 3.10 1.09 2.44 3.10 424.51 * 0.012 0.67 0.58 3.41 3.41 2.85 3.10 1.09 PIPE NO. 3: 25 LF - 12"CP @ 1.00% OUTLET: 421.41 INLET: 421.66 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 1.01 2.62 424.28 * 0.012 0.43 0.35 2.81 2.81 2.58 2.62 0.59 1.05 2.66 424.32 * 0.012 0.44 0.36 2.85 2.85 2.62 2.66 0.61 1.09 2.73 424.39 * 0.012 0.44 0.37 2.91 2.91 2.68 2.73 0.62 1.13 2.79 424.45 * 0.012 0.45 0.38 2.97 2.97 2.74 2.79 0.63 1.17 2.86 424.52 * 0.012 0.46 0.38 3.04 3.04 2.81 2.86 0.65 1.21 2.93 424.59 * 0.012 0.47 0.39 3.10 3.10 2.88 2.93 0.66 1.21 2.93 424.59 * 0.012 0.47 0.39 3.10 3.10 2.88 2.93 0.66 BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB-11 TO CB-1.bwp Surcharge condition at intermediate junctions Tailwater Elevation:418.17 feet Discharge Range:0.58 to 0.98 Step of 0.1 [cfs] Overflow Elevation:441.79 feet Weir:NONE Upstream Velocity:0. feet/sec 2021 D. 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Page 65 Bethany Corner Technical Information Report Renton, Washington PIPE NO. 1: 8 LF - 12"CP @ 0.50% OUTLET: 417.17 INLET: 417.21 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 419.88 BEND: 63 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.00 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.58 0.98 418.19 * 0.012 0.32 0.32 1.00 1.00 0.97 0.98 0.43 0.68 0.98 418.19 * 0.012 0.35 0.35 1.00 1.00 0.97 0.98 0.47 0.78 0.99 418.20 * 0.012 0.37 0.37 1.00 1.00 0.97 0.99 0.51 0.88 0.99 418.20 * 0.012 0.40 0.40 1.00 1.00 0.97 0.99 0.54 0.98 1.00 418.21 * 0.012 0.42 0.42 1.00 1.00 0.97 1.00 0.58 PIPE NO. 2: 134 LF - 12"CP @ 0.50% OUTLET: 417.21 INLET: 417.88 INTYP: 5 JUNC NO. 2: OVERFLOW-EL: 424.41 BEND: 63 DEG DIA/WIDTH: 4.0 Q-RATIO: 0.93 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.58 0.50 418.38 * 0.012 0.32 0.32 0.98 0.98 0.41 0.50 0.43 0.68 0.53 418.41 * 0.012 0.35 0.35 0.98 0.98 0.43 0.53 0.48 0.78 0.57 418.45 * 0.012 0.37 0.37 0.99 0.99 0.45 0.57 0.51 0.88 0.61 418.49 * 0.012 0.40 0.40 0.99 0.99 0.47 0.61 0.55 0.98 0.64 418.52 * 0.012 0.42 0.42 1.00 1.00 0.49 0.64 0.59 PIPE NO. 3: 101 LF - 12"CP @ 3.26% OUTLET: 417.88 INLET: 421.17 INTYP: 5 JUNC NO. 3: OVERFLOW-EL: 426.93 BEND: 0 DEG DIA/WIDTH: 4.0 Q-RATIO: 0.11 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.30 0.29 421.46 * 0.012 0.23 0.15 0.50 0.50 0.23 ***** 0.29 0.35 0.31 421.48 * 0.012 0.25 0.16 0.53 0.53 0.25 ***** 0.31 0.40 0.34 421.51 * 0.012 0.27 0.17 0.57 0.57 0.27 ***** 0.34 0.45 0.36 421.53 * 0.012 0.28 0.18 0.61 0.61 0.28 ***** 0.36 0.51 0.38 421.55 * 0.012 0.30 0.19 0.64 0.64 0.30 ***** 0.38 PIPE NO. 4: 71 LF - 12"CP @ 3.28% OUTLET: 421.17 INLET: 423.50 INTYP: 5 JUNC NO. 4: OVERFLOW-EL: 428.38 BEND: 0 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.00 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.27 0.27 423.77 * 0.012 0.22 0.14 0.29 0.29 0.22 ***** 0.27 0.32 0.30 423.80 * 0.012 0.24 0.15 0.31 0.31 0.24 ***** 0.30 0.36 0.32 423.82 * 0.012 0.25 0.16 0.34 0.34 0.25 ***** 0.32 0.41 0.34 423.84 * 0.012 0.27 0.17 0.36 0.36 0.27 ***** 0.34 0.45 0.36 423.86 * 0.012 0.28 0.18 0.38 0.38 0.28 ***** 0.36 PIPE NO. 5: 108 LF - 12"CP @ 5.46% OUTLET: 423.50 INLET: 429.40 INTYP: 5 JUNC NO. 5: OVERFLOW-EL: 432.59 BEND: 0 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.86 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.27 0.26 429.66 * 0.012 0.22 0.12 0.27 0.27 0.22 ***** 0.26 0.32 0.29 429.69 * 0.012 0.24 0.13 0.30 0.30 0.24 ***** 0.29 0.36 0.31 429.71 * 0.012 0.25 0.14 0.32 0.32 0.25 ***** 0.31 0.41 0.33 429.73 * 0.012 0.27 0.15 0.34 0.34 0.27 ***** 0.33 0.45 0.35 429.75 * 0.012 0.28 0.16 0.36 0.36 0.28 ***** 0.35 PIPE NO. 6: 130 LF - 12"CP @ 5.27% OUTLET: 429.40 INLET: 436.25 INTYP: 5 2021 D. 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Page 66 Bethany Corner Technical Information Report Renton, Washington JUNC NO. 6: OVERFLOW-EL: 439.25 BEND: 59 DEG DIA/WIDTH: 2.0 Q-RATIO: 6.82 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.15 0.18 436.43 * 0.012 0.16 0.09 0.26 0.26 0.16 ***** 0.18 0.17 0.20 436.45 * 0.012 0.17 0.10 0.29 0.29 0.17 ***** 0.20 0.20 0.22 436.47 * 0.012 0.19 0.11 0.31 0.31 0.19 ***** 0.22 0.22 0.23 436.48 * 0.012 0.20 0.11 0.33 0.33 0.20 ***** 0.23 0.25 0.25 436.50 * 0.012 0.21 0.12 0.35 0.35 0.21 ***** 0.25 PIPE NO. 7: 130 LF - 12"CP @ 1.92% OUTLET: 436.25 INLET: 438.75 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.02 0.06 438.81 * 0.012 0.06 0.05 0.18 0.18 0.06 ***** 0.06 0.02 0.07 438.82 * 0.012 0.06 0.05 0.20 0.20 0.06 ***** 0.07 0.02 0.08 438.83 * 0.012 0.07 0.05 0.22 0.22 0.07 ***** 0.08 0.03 0.08 438.83 * 0.012 0.07 0.06 0.23 0.23 0.07 ***** 0.08 0.03 0.09 438.84 * 0.012 0.08 0.06 0.25 0.25 0.08 ***** 0.09 BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:CB-403 TO CB-4.bwp Surcharge condition at intermediate junctions Tailwater Elevation:423.88 feet Discharge Range:0.1 to 0.53 Step of 0.1 [cfs] Overflow Elevation:428.15 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 24 LF - 12"CP @ 4.33% OUTLET: 420.47 INLET: 421.51 INTYP: 5 JUNC NO. 1: OVERFLOW-EL: 426.41 BEND: 0 DEG DIA/WIDTH: 2.0 Q-RATIO: 1.16 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.10 2.38 423.89 * 0.012 0.13 0.08 3.41 3.41 2.38 2.38 0.15 0.20 2.37 423.88 * 0.012 0.19 0.11 3.41 3.41 2.37 2.37 0.23 0.30 2.37 423.88 * 0.012 0.23 0.14 3.41 3.41 2.37 2.37 0.28 0.40 2.38 423.89 * 0.012 0.27 0.16 3.41 3.41 2.37 2.38 0.34 0.50 2.38 423.89 * 0.012 0.30 0.17 3.41 3.41 2.37 2.38 0.38 0.60 2.39 423.90 * 0.012 0.33 0.19 3.41 3.41 2.38 2.39 0.42 PIPE NO. 2: 32 LF - 12"CP @ 6.62% OUTLET: 421.51 INLET: 423.63 INTYP: 5 JUNC NO. 2: OVERFLOW-EL: 427.32 BEND: 82 DEG DIA/WIDTH: 2.0 Q-RATIO: 0.27 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.05 0.27 423.90 * 0.012 0.09 0.05 2.38 2.38 0.27 0.27 0.08 0.09 0.27 423.90 * 0.012 0.13 0.07 2.37 2.37 0.26 0.27 0.13 0.14 0.28 423.91 * 0.012 0.16 0.09 2.37 2.37 0.26 0.28 0.17 0.18 0.29 423.92 * 0.012 0.18 0.10 2.38 2.38 0.26 0.29 0.21 0.23 0.31 423.94 * 0.012 0.20 0.11 2.38 2.38 0.26 0.31 0.23 0.28 0.33 423.96 * 0.012 0.22 0.12 2.39 2.39 0.27 0.33 0.26 PIPE NO. 3: 21 LF - 12"CP @ 6.52% OUTLET: 423.63 INLET: 425.00 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.04 0.08 425.08 * 0.012 0.08 0.05 0.27 0.27 0.08 ***** 0.07 2021 D. 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Page 67 Bethany Corner Technical Information Report Renton, Washington 0.07 0.11 425.11 * 0.012 0.11 0.07 0.27 0.27 0.11 ***** 0.11 0.11 0.15 425.15 * 0.012 0.14 0.08 0.28 0.28 0.14 ***** 0.15 0.15 0.18 425.18 * 0.012 0.16 0.09 0.29 0.29 0.16 ***** 0.18 0.18 0.20 425.20 * 0.012 0.18 0.10 0.31 0.31 0.18 ***** 0.20 0.22 0.23 425.23 * 0.012 0.20 0.11 0.33 0.33 0.20 ***** 0.23 BACKWATER COMPUTER PROGRAM FOR PIPES Pipe data from file:OUTLET TO CB-3.bwp Surcharge condition at intermediate junctions Tailwater Elevation:418.52 feet Discharge Range:0.12 to 0.32 Step of 0.05 [cfs] Overflow Elevation:427.5 feet Weir:NONE Upstream Velocity:0. feet/sec PIPE NO. 1: 24 LF - 12"CP @ 0.50% OUTLET: 417.88 INLET: 418.00 INTYP: 5 Q(CFS) HW(FT) HW ELEV. * N-FAC DC DN TW DO DE HWO HWI ******************************************************************************* 0.12 0.53 418.53 * 0.012 0.15 0.15 0.64 0.64 0.53 0.53 0.19 0.17 0.53 418.53 * 0.012 0.17 0.17 0.64 0.64 0.53 0.53 0.23 0.22 0.54 418.54 * 0.012 0.20 0.20 0.64 0.64 0.53 0.54 0.26 0.27 0.54 418.54 * 0.012 0.22 0.22 0.64 0.64 0.53 0.54 0.29 0.32 0.54 418.54 * 0.012 0.24 0.24 0.64 0.64 0.53 0.54 0.31 2021 D. R. STRONG Consulting Engineers Inc. Page 68 Bethany Corner Technical Information Report Renton, Washington SECTION VI SPECIAL REPORTS AND STUDIES The following report and studies are included with this submittal. Critical Areas Study: Mark Rigos, P.E. – December 10st, 2016, Revised: March 26th, 2017 Stream Buffer Mitigation Plan: Mark Rigos, P.E. – January 19th, 2019 Subsurface Exploration and Geotechnical Engineering Report: Associated Earth Sciences Incorporated – December 16, 2016 Arborist Report: Tree Harmony Arborists, LLC – December 12, 2016 Supplemental Arborist Report: Tree Harmony Arborists, LLC – March 3, 2019 Kirkland Office | 911 Fifth Avenue | Kirkland, WA 98033 P | 425.827.7701 F| 425.827.5424 Everett Office | 2911 ½ Hewitt Avenue, Suite 2 | Everett, WA 98201 P | 425.259.0522 F | 425.827.5424 Tacoma Office | 1552 Commerce Street, Suite 102 | Tacoma, WA 98402 P | 253.722.2992 F | 253.722.2993 www.aesgeo.com December 16, 2016 Project No. EE160674A Mark Seek 15233 Manion Way NE Duvall, Washington 98019 Subject: Subsurface Exploration and Geotechnical Engineering Report Bethany Corner 16451 111th Avenue SE Renton, Washington Dear Mr. Seek: As requested, this letter-report presents the results of our subsurface exploration and geotechnical engineering services for the above-referenced project. Our understanding of the project is based on our discussions with you and a review of the proposed site plan prepared by DR Strong Consulting Engineers Inc. dated November 29, 2016. Written authorization to proceed with this study was granted by Mark Seek. Our study was accomplished in general accordance with our scope of work as presented in a signed contract dated December 8, 2016. This letter-report has been prepared for the exclusive use of Mr. Mark Seek and his agents for specific application to this project. Within the limitations of scope, schedule, and budget, our services have been performed in accordance with generally accepted geotechnical engineering practices in effect, in this area at the time our letter-report was prepared. Our observations, findings, and opinions are a means to identify and reduce the inherent risks to the owner. No other warranty, express or implied, is made. SITE AND PROJECT DESCRIPTION The project site is located on two currently developed parcels with addresses of 16433 and 16451 111th Avenue Northwest in Renton, Washington. The parcels are combined for the project and create a fairly square property with a total area of about 1.8 acres. The site location is shown on the “Vicinity Map,” Figure 1. The parcel is currently developed with residential construction and is vegetated typical residential landscaping. Site topography generally slopes downward towards the west from 111th Avenue NW to the homes and is relatively level for the remainder of the lot area Bethany Corner Subsurface Exploration Renton, Washington and Geotechnical Engineering Report December 16, 2016 ASSOCIATED EARTH SCIENCES, INC. MM/pc - EE160525A4 - Projects\20160525\EE\WP Page 2 to the west. The north side of the site gradually slopes up to the adjacent lot. The total topographic difference on the site is about 6 to 8 feet We understand, the project will consist of the construction of nine single-family residential lots and a drainage tract. Access to the lots will be from the east by a single road with five lots on the north side and four on the south. Within the drainage tract at the southeast corner of the plat we understand there will be a storm water vault. Preliminary planning indicates that the bottom of the vault will be about 12 to 14 feet below the existing grade. SUBSURFACE EXPLORATION AND CONDITIONS Our subsurface exploration completed for this project included the excavation of five exploration pits dug on December 14, 2016. The conclusions and recommendations presented in this letter-report are based on the explorations completed for this study. The locations and depths of the explorations were completed within site and budget constraints. The approximate locations of explorations completed for this study are presented on the “Site and Exploration Plan,” Figure 2. Copies of the subsurface exploration logs are also attached with this letter-report in the Appendix. The exploration pits were excavated using a tracked mini excavator provided by the client. The pits permitted direct, visual observation of subsurface conditions. Materials encountered in the exploration pits were studied and classified in the field by an experienced geotechnical engineer from our firm. All exploration pits were backfilled after examination and logging. Selected samples were then transported to our laboratory for further visual classification. Our explorations generally encountered shallow, native lodgement till soils and fill placed over the lodgement till, for the full depth of the exploration to a depth of about 6 to 8 feet. The encountered lodgement till was weathered near the surface consisting of medium dense, moist, tan, silty sand with gravel and was unsorted. At depths of 2 to 3 feet below the surface the lodgement till graded to unweathered till that consisted of dense, gray, silty fine sand with gravel and was unsorted. In the vicinity of the vault we extended a pit to a depth of 14 feet. At this depth the till was underlain by a hard silt described as pre Vashon silt. On the central to west end of the site we encountered fill soils (soil not naturally placed) to a maximum depth of about 6 feet. The fill consisted of a mixture of sand silt and gravel mixed with trace amounts of debris and pockets of organics. Lodgement till was deposited at the base of an active continental glacier during the Vashon Stade of the Fraser Glaciation approximately 12,500 to 15,000 years ago. The till was compacted by the weight of about 3,000 feet of overlying ice. Lodgement till typically has high-strength and Bethany Corner Subsurface Exploration Renton, Washington and Geotechnical Engineering Report December 16, 2016 ASSOCIATED EARTH SCIENCES, INC. MM/pc - EE160525A4 - Projects\20160525\EE\WP Page 3 low-compressibility attributes that are favorable for structural support with proper preparation. Lodgement till is typically silty, moisture-sensitive, and easily disturbed under wet site or weather conditions. Excavated lodgement till is suitable for reuse in structural fill applications under dry site and weather conditions when it can be moisture-conditioned to allow compaction to a firm and unyielding condition at the specified level for the intended purpose. Lodgement till is considered suitable for foundation support but is not considered a suitable infiltration receptor. The geologic units identified on the subject property closely match those units identified within the site area on the Geologic Map of Surficial Deposits in the Seattle 30’ by 60’ Quadrangle, Washington, by J.C. Yount and others, 1993. Hydrology Minor to abundant seepage was observed in all of our explorations. We anticipate that shallow ground water will be limited to interflow. Interflow commonly occurs in areas underlain by glacially consolidated sediments and originates as surface water that percolates down through the near-surface, relatively permeable surface soils, such as weathered lodgement till, and becomes trapped or “perched” atop the underlying, relatively impermeable, glacial sediments. Interflow is often a seasonal phenomenon. It should be noted that the presence and depth of seepage at the site may vary in response to such factors as changes in season, precipitation, and site use. Infiltration Feasibility The site is underlain at shallow depths by medium dense to very dense lodgement till and fill soils. Lodgement till generally consisted of silty fine sand with gravel and has been consolidated by the weight of an overriding ice sheet during the most recent ice age. As a result, the lodgement till has a low permeability due to its relative high density and high silt content and is not a suitable receptor for infiltration. In addition, the till layer commonly creates a perched ground water layer described in the previous section that will not allow adequate separation from high winter ground water for a proposed infiltration facility, if present. Therefore, we do not recommend the use of infiltration as a method for storm water disposal. DESIGN RECOMMENDATIONS Introduction Our explorations indicate that, from a geotechnical standpoint, the proposed project is feasible provided the recommendations contained herein are properly followed. The bearing stratum is generally shallow on the east end and conventional shallow foundations should perform well with proper subgrade preparation. The west end of the site will require that the unsuitable fill be removed to a depth of about 6 feet prior to the placement of additional structural fill or Bethany Corner Subsurface Exploration Renton, Washington and Geotechnical Engineering Report December 16, 2016 ASSOCIATED EARTH SCIENCES, INC. MM/pc - EE160525A4 - Projects\20160525\EE\WP Page 4 foundations. We recommend that building foundations are founded on the dense native, glacial till soils or structural fill placed on top of the native glacial till. Site Preparation Site preparation of the construction area should include removal of all previously placed fill, grass, brush, debris, and any other deleterious materials. Erosion and surface water control should be established around the clearing limits to satisfy local requirements. We recommend existing fill, be removed from below areas of shallow foundations. When structural fill is required for restoration of the planned foundation grade, our recommendations detailed in the “Structural Fill” section should be followed. Removal of unsuitable soil should extend laterally beyond the building footprint by a distance equal to the depth of overexcavation. For example, when existing fill is removed to a depth of 2 feet below a planned footing area, the excavation should also extend laterally 2 feet beyond the building footprint in that area. Where existing fill is removed and replaced with structural fill, conventional shallow foundations may be used for structure support. The required depth of removal should be determined in the field based on actual conditions encountered during excavation. Below planned on-site paving or under building slabs-on-grade, the stripped subgrade should be proof-rolled with heavy, rubber-tired construction equipment, such as a fully loaded tandem-axle dump truck. Proof-rolling should be performed prior to structural fill placement. The proof-roll should be monitored by the geotechnical engineer so that any soft or yielding subgrade soils can be identified. Any soft or loose, yielding soils should be removed to a stable subgrade. Proof-rolling should only be attempted if soil moisture contents are at or near optimum moisture content. Proof-rolling of wet subgrades could result in further degradation. Temporary Cut Slopes In our opinion, stable construction slopes should be the responsibility of the contractor and should be determined during construction. For estimating purposes, however, temporary, unsupported cut slopes can be planned at 1.5H:1V (Horizontal:Vertical) or flatter in the existing fill and underlying weathered glacial deposits, provided they are not saturated. Temporary slopes in unsaturated, unweathered lodgement till may be planned at 1H:1V. These slope angles are for areas where ground water seepage is not encountered, and assume that surface water is not allowed to flow across the temporary slope faces. If ground or surface water is present when the temporary excavation slopes are exposed, flatter slope angles will be required. As is typical with earthwork operations, some sloughing and raveling may occur and cut slopes may have to be adjusted in the field. In addition, WISHA/OSHA regulations should be followed at all times. Bethany Corner Subsurface Exploration Renton, Washington and Geotechnical Engineering Report December 16, 2016 ASSOCIATED EARTH SCIENCES, INC. MM/pc - EE160525A4 - Projects\20160525\EE\WP Page 5 Site Disturbance The on-site soils contain a high percentage of fine-grained material, which makes them easy to disturb during wet weather. The contractor must use care during site preparation and excavation operations so that the underlying soils are not softened during wet weather conditions. Structural Fill All references to structural fill in this letter-report refer to subgrade preparation, fill type and placement, and compaction of materials, as discussed in this section. If a percentage of compaction is specified under another section of this letter-report, the value given in that section should be used. After stripping, planned excavation, and any required overexcavation have been performed to the satisfaction of the geotechnical engineer, the upper 12 inches of exposed ground in areas to receive fill should be recompacted to a firm and unyielding condition. If the subgrade contains silty soils and too much moisture, adequate recompaction may be difficult or impossible to obtain and should probably not be attempted. In lieu of recompaction, the area to receive fill should be blanketed with washed rock or quarry spalls to act as a capillary break between the new fill and the wet subgrade. Where the exposed ground remains soft and further overexcavation is impractical, placement of an engineering stabilization fabric may be necessary to prevent contamination of the free-draining layer by silt migration from below. After recompaction of the exposed ground is approved, or a free-draining rock course is laid, structural fill may be placed to attain desired grades. Structural fill is defined as non-organic soil, acceptable to the geotechnical engineer, placed in maximum 8-inch loose lifts, with each lift being compacted to 95 percent of the modified Proctor maximum density using American Society for Testing and Materials (ASTM) D-1557 as the standard. Use of soils from the site in structural fill applications is acceptable if the material meets the project specifications for the intended use, and if specifically allowed by project specifications. In the case of roadway and utility trench filling, structural fill should be placed and compacted in accordance with current City of Renton codes and standards. The top of the compacted fill should extend horizontally outward a minimum distance of 3 feet beyond the locations of the roadway edges before sloping down at an angle of 2H:1V. Structural fills with sloping faces that cannot be compacted directly by a vibratory roller should be compacted by overbuilding, then cutting back to a compacted slope core. The contractor should note that any proposed fill soils must be evaluated by Associated Earth Sciences, Inc. (AESI) prior to their use in fills. This would require that we have a sample of the material 72 hours in advance to perform a Proctor test and determine its field compaction standard. Soils in which the amount of fine-grained material (smaller than the No. 200 sieve) is greater than approximately 5 percent (measured on the minus No. 4 sieve size) should be considered moisture-sensitive. Use of moisture-sensitive soil in structural fills should be limited to Bethany Corner Subsurface Exploration Renton, Washington and Geotechnical Engineering Report December 16, 2016 ASSOCIATED EARTH SCIENCES, INC. MM/pc - EE160525A4 - Projects\20160525\EE\WP Page 6 favorable dry weather conditions, and is only permitted if specifically allowed by project plans and specifications. The native soils present onsite contained significant amounts of silt and are considered highly moisture-sensitive. If fill is placed during wet weather or if proper compaction cannot be obtained, a select import material consisting of a clean, free-draining gravel and/or sand should be used. Free-draining fill consists of non-organic soil with the amount of fine-grained material limited to 5 percent by weight when measured on the minus No. 4 sieve fraction with at least 25 percent retained on the No. 4 sieve. A representative from our firm should inspect the stripped subgrade and be present during placement of structural fill to observe the work and perform a representative number of in-place density tests. In this way, the adequacy of the earthwork may be evaluated as filling progresses, and any problem areas may be corrected at that time. It is important to understand that taking random compaction tests on a part-time basis will not assure uniformity or acceptable performance of a fill. As such, we are available to aid the owner in developing a suitable monitoring and testing program. Ground Motion Structural design of the project should be in accordance with the 2015 International Building Code (IBC) using Site Class D. Foundations Spread footings that are supported on dense native lodgement till sediments or a combination of structural fill and dense native lodgement till sediments may be designed with an allowable foundation soil bearing pressure of 2,500 pounds per square foot (psf), including both dead and live loads. For the storm water vault located at the southeast corner of the site, a higher allowable bearing capacity of 3,000 psf can be used due to the increased depth of the excavation. An increase of one-third may be used for short-term wind or seismic loading for all foundations. Perimeter footings should be buried at least 18 inches into the surrounding soil for frost protection. However, all footings must penetrate to the prescribed bearing stratum, and no footing should be founded in or above organic or loose soils. It should be noted that the area bound by lines extending downward at 1H:1V from any footing must not intersect another footing or intersect a filled area that has not been compacted to at least 95 percent of ASTM D-1557. In addition, a 1.5H:1V line extending down from any footing must not daylight because sloughing or raveling may eventually undermine the footing. Thus, footings should not be placed near the edge of steps or cuts in the bearing soils. Anticipated settlement of footings founded as described above should be on the order of ½ inch or less. However, disturbed soil not removed from footing excavations prior to footing placement Bethany Corner Subsurface Exploration Renton, Washington and Geotechnical Engineering Report December 16, 2016 ASSOCIATED EARTH SCIENCES, INC. MM/pc - EE160525A4 - Projects\20160525\EE\WP Page 7 could result in increased settlements. All footing areas should be inspected by AESI prior to placing concrete to verify that the design bearing capacity of the soils has been attained and that construction conforms to the recommendations contained in this letter-report. Such inspections may be required by the governing municipality. Perimeter footing drains should be provided, as discussed under the “Drainage Considerations” section of this letter-report. Lateral loads can be resisted by friction between the foundation and the natural glacial soils or supporting structural fill soils, and by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with structural fill and compacted to at least 95 percent of the maximum dry density to achieve the passive resistance provided below. We recommend the following allowable design parameters: • Passive equivalent fluid = 350 pounds per cubic foot (pcf) • Coefficient of friction = 0.35 Drainage Considerations Foundations should be provided with foundation drains. Drains should consist of rigid, perforated, polyvinyl chloride (PVC) pipe surrounded by washed pea gravel. The drains should be constructed with sufficient gradient to allow gravity discharge away from the proposed building. Roof and surface runoff should not discharge into the footing drain system, but should be handled by a separate, rigid, tightline drain. In planning, exterior grades adjacent to walls should be sloped downward away from the proposed building to achieve surface drainage. Lateral Wall Pressures All backfill behind foundation walls or around foundation units should be placed as per our recommendations for structural fill and as described in this section of the letter-report. Horizontally backfilled walls, which are drained and free to yield laterally at least 0.1 percent of their height, may be designed to resist active lateral earth pressure represented by an equivalent fluid equal to 35 pcf. Fully restrained, drained, horizontally backfilled, rigid walls that cannot yield such as the storm water vault should be designed for an at-rest equivalent fluid of 50 pcf. If parking areas are adjacent to walls, a surcharge equivalent to 2 feet of soil should be added to the wall height in determining lateral design forces. Walls with sloping backfill are not expected; however, if walls with sloping backfill are planned, we should be contacted to offer situation-specific surcharge recommendations. As required by the 2015 IBC, retaining wall design should include a seismic surcharge pressure in addition to the equivalent fluid pressures presented above. Considering the site soils and the recommended wall backfill materials, we recommend a seismic surcharge pressure of 8H and 11H psf, where H is the wall height in feet, for the “active” and “at-rest” loading conditions, Bethany Corner Subsurface Exploration Renton, Washington and Geotechnical Engineering Report December 16, 2016 ASSOCIATED EARTH SCIENCES, INC. MM/pc - EE160525A4 - Projects\20160525\EE\WP Page 8 respectively. The seismic surcharge should be modeled as a rectangular distribution with the resultant applied at the midpoint of the walls. The lateral pressures presented above are based on the conditions of a uniform backfill consisting of excavated on-site soils, or imported structural fill compacted to 90 percent of ASTM D-1557. A higher degree of compaction is not recommended, as this will increase the pressure acting on the walls. A lower compaction may result in settlement of slab-on-grade floors or other structures supported above the walls. Thus, the compaction level is critical and must be tested by our firm during placement. Surcharges from adjacent footings or heavy construction equipment must be added to the above values. Perimeter footing drains should be provided for all retaining walls, as discussed under the “Drainage Considerations” section of this letter-report. It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. This would involve installation of a minimum, 1-foot-wide blanket drain to within 1 foot of finish grade for the full wall height using imported, washed gravel against the walls. Pavement Recommendations Pavement areas should be prepared in accordance with the “Site Preparation” section of this letter-report. If the stripped native soil subgrade can be compacted to 95 percent of ASTM D-1557 and is firm and unyielding, no additional preparation is required. Soft or yielding areas should be overexcavated to provide a suitable subgrade and backfilled with structural fill. The pavement sections included in this letter-report section are for driveway and parking areas onsite, and are not applicable to right-of-way improvements. If any new paving of public streets is required, we should be allowed to offer situation-specific recommendations. The exposed ground should be recompacted to a firm and unyielding condition. If required, structural fill may then be placed to achieve desired subbase grades. Upon completion of the recompaction and structural fill, a pavement section consisting of 3 inches of asphaltic concrete pavement (ACP) underlain by 4 inches of 1¼-inch crushed surfacing base course is the recommended minimum in areas of planned passenger car driving and parking. In driveway areas subjected to heavier loads, such as that from school buses or fire trucks, a minimum pavement section consisting of 4 inches of ACP underlain by 2 inches of 5/8-inch crushed surfacing top course and 4 inches of 1¼-inch crushed surfacing base course is recommended. The crushed rock course must be compacted to 95 percent of the maximum density, as determined by ASTM D-1557. All paving materials should meet gradation criteria contained in the current Washington State Department of Transportation (WSDOT) Standard Specifications. Bethany Corner Subsurface Exploration Renton, Washington and Geotechnical Engineering Report December 16, 2016 ASSOCIATED EARTH SCIENCES, INC. MM/pc - EE160525A4 - Projects\20160525\EE\WP Page 9 PROJECT DESIGN AND CONSTRUCTION MONITORING We are available to provide additional geotechnical consultation as the project design develops and possibly changes from that upon which this letter-report is based. If the reviewing agency requires the Engineer of Record to review the project during final design and construction, we are available. In this way, our earthwork and foundation recommendations may be properly interpreted and implemented in the design and construction of the project. We are also available to provide geotechnical engineering and monitoring services during construction. The integrity of the building foundations depends on proper site preparation and construction procedures. In addition, engineering decisions may have to be made in the field in the event that variations in subsurface conditions become apparent. Construction monitoring services are not part of the current scope of work. If these services are desired, please let us know and we will prepare a cost proposal. We have enjoyed working with you on this study and are confident that these recommendations will aid in the successful completion of your project. If you should have any questions, or require further assistance, please do not hesitate to call. Sincerely, ASSOCIATED EARTH SCIENCES, INC. Everett, Washington Matthew A. Miller, P.E. Principal Engineer Attachments: Figure 1: Vicinity Map Figure 2: Site and Exploration Plan Appendix: Exploration Logs Copyright:© 2013 National Geographic Society, i-cubed 0 20001000 FEET ± NOTE: BLACK AND WHITEREPRODUCTION OF THIS COLORORIGINAL MAY REDUCE ITSEFFECTIVENESS AND LEAD TOINCORRECT INTERPRETATION VICINITY MAP PROJ NO. DATE: FIGURE:EE160674A 12/16 1 Document Path: G:\GIS_Projects\aTemplatesNTRP\aVM_Template\VM_MXD\160674 Fig1 ProjectVicinity_Bethany.mxdDATA SOURCES / REFERENCES:USGS: 24K SERIES TOPOGRAPHIC MAPSKING CO: STREETS, CITY LIMITS, PARCELS 2016 LOCATIONS AND DISTANCES SHOWN ARE APPROXIMATE KitsapCounty Snohomish County Pierce County King County SE 164th St 111thAveSE109thAveSE!( SITE¬«167 ¥405 ¬«515 BETHANY CORNERRENTON, WASHINGTON NOTES: 1. BASE MAP REFERENCE: D. L. STRONG CONSULTING ENGINEERS, BETHANY CORNER PRELIMINARY PLAY, PRELIMINARY PLAT PLAN, UNDATED.160674 Bethany Corner \ 160674 F2 Site-Explr.cdrBETHANY CORNER RENTON, WASHINGTON SITE AND EXPLORATION PLAN PROJ NO.DATE:FIGURE: KE160674A 12/16 2 BLACK AND WHITE REPRODUCTION OF THIS COLOR ORIGINAL MAY REDUCE ITS EFFECTIVENESS AND LEAD TO INCORRECT INTERPRETATION. a s s o c i a t e d e a r t h s c i e n c e s i n c o r p o r a t e d FEET 20 400 N CONTOUR INTERVAL = 2’ LEGEND: EXPLORATION PITEP NOTE: LOCATION AND DISTANCES SHOWN ARE APPROXIMATE. EP-3 EP-2 EP-1 EP-5 EP-4 APPENDIX Grass / Topsoil Vashon Lodgement Till Loose to medium dense, tannish gray, silty, fine SAND, some gravel; mottled (SM). Medium dense to dense, moist, tannish gray, silty, fine SAND, some gravel; unsorted (SM). Pre-Vashon Fine-Grained Stiff, moist to very moist, olive gray, fine sandy SILT, trace gravel (ML). As above. Bottom of exploration pit at depth 13.5 feet No seepage. No caving. DESCRIPTION Renton, WA Bethany Corner 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: AWR Approved by: ????12/14/16 Project No. EE160674A LOG OF EXPLORATION PIT NO. EP-1 Depth (ft)KCTP3 160674.GPJ December 15, 2016 Grass / Topsoil Fill Loose, very moist, tan and dark gray, fine to medium SAND, some silt (SP-SM). Pockets of organic soil and debris. Operator notes harder digging. Vashon Lodgement Till Medium dense, wet, gray, silty, fine SAND; mottled (SM). As above. Bottom of exploration pit at depth 8 feetModerate seepage at 3 feet. Heavy caving from 2 to 6 feet. DESCRIPTION Renton, WA Bethany Corner 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: AWR Approved by: ????12/14/16 Project No. EE160674A LOG OF EXPLORATION PIT NO. EP-2 Depth (ft)KCTP3 160674.GPJ December 15, 2016 Grass / Topsoil Fill Loose, moist, tannish brown, silty, fine SAND, some gravel; contains pockets of organics (SM). Operator notes harder digging. Vashon Lodgement Till Medium dense, wet, grayish tan, silty, fine SAND; mottled (SM). Dense, moist, tan, silty, fine SAND, some gravel; mottled (SM). Bottom of exploration pit at depth 8.5 feet Moderate seepage from 3 to 5 feet. Moderate caving from 2 to 5 feet. DESCRIPTION Renton, WA Bethany Corner 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: AWR Approved by: ????12/14/16 Project No. EE160674A LOG OF EXPLORATION PIT NO. EP-3 Depth (ft)KCTP3 160674.GPJ December 15, 2016 Grass / Topsoil Fill Loose to medium dense, very moist, tannish brown, silty, fine SAND, some gravel; contains organics soil and debris (SM). Pre-Vashon Fine-Grained Medium stiff, very moist to wet, olive gray, fine sandy SILT (ML). Tukwila Formation Weathered SAND / SILT STONE. Bottom of exploration pit at depth 10 feetMinor seepage from 2 to 3 feet. Minor caving from 1 to 5 feet. DESCRIPTION Renton, WA Bethany Corner 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: AWR Approved by: ????12/14/16 Project No. EE160674A LOG OF EXPLORATION PIT NO. EP-4 Depth (ft)KCTP3 160674.GPJ December 15, 2016 Grass / Topsoil Fill Loose, very moist, tannish brown, silty, fine SAND, some gravel, trace organic debris (SM). Vashon Lodgement Till Medium dense, wet, tan, silty, fine SAND, some gravel (SM). Dense, moist, tannish gray, silty, fine SAND, some gravel; unsorted (SM). Bottom of exploration pit at depth 7.5 feetModerate seepage at 4 feet. Minor caving from 2 to 5 feet. DESCRIPTION Renton, WA Bethany Corner 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 This log is part of the report prepared by Associated Earth Sciences, Inc. (AESI) for the named project and should be readtogether with that report for complete interpretation. This summary applies only to the location of this trench at the time ofexcavation. Subsurface conditions may change at this location with the passage of time. The data presented are a simplficationof actual conditions encountered. Logged by: AWR Approved by: ????12/14/16 Project No. EE160674A LOG OF EXPLORATION PIT NO. EP-5 Depth (ft)KCTP3 160674.GPJ December 15, 2016 December 12, 2016 Project: Pre-construction assessment for lot development at 16433 and 16451 111th Avenue SE, Renton, WA. Parcel numbers 0088000570 and -560. Contact: Jonathan Murray - D. R. Strong Consulting Engineers, Inc 620 7th Avenue, Kirkland, WA 98033 Phone – 425 827 3063 Email – jonathan.murray@drstrong.com Objectives: Evaluate health of existing trees and establish criteria for their preservation. Description: This is a pair of midsized parcels, each close to 40,000 square feet, tucked in the middle of a row larger lots in the Renton Higlands (Figures 1-3). Each property has an existing home on the east end, the 16433 home was built in 1952, and the 16451 home in 1966. The 16433 parcel is lightly treed and no significant changes have occurred on it over the last twenty years. The 16451 parcel was fairly well covered with trees until 2009 when it was partially cleared. It was totally cleared by 2012. There is a wire fence running between the 16433 property and the 16411 property to the north. Another wire fence runs along the west end of 16433 and ties into a wood fence at the west end of the 16451 property. The wood fence runs nearly the entire width of the property, stopping about 5’ short of what appeared to be the SW corner of the 16451 parcel. Another wire fence runs east from that corner to about even with the back of the house. Both existing homes will be razed. According to the proposed development plans each parcel will be subdivided into five lots. A new home will be built on each save the east end of the 16451 parcel which will have a water retention area (Figures 4 and 5). The following itemized list begins at the SE corner of the 16433 property and runs roughly counter clockwise through the two parcels. Each tree was tagged and their numerical designations are reflected in Figures 3-5. Diameters were measured at the standard height of 54” above grade (DSH) during the December 2016 site visit. Heights were estimated. The majority of the trees described are shown on the November 2016 Short Plat. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner 1) Weeping Willow (Salix babylonica) 26.5” DSH, 22’ tall, 14’ spread standing just to the right side of the south entrance to the 16433 property. The tree is in weak condition. It has been topped repeatedly and has multiple atrophied and decayed areas. 2) Scots Pine (Pinus sylvestris) 18” DSH, 30’ tall in fair condition with average new growth and color. Standing at east end of line at south end of the house. 3) Scots Pine 16” DSH, 32’ tall in fair condition with average new growth and color. Next tree west of #2. 4) Scots Pine 16” DSH, 35’ tall in fair condition with average new growth and color. Next tree west of #3. 5) Scots Pine 10.5” DSH, 25’ tall in weak condition with below average new growth, poor color, and signs of needle blight. Next tree west of #4. 6) Douglas Fir (Pseudotsuga menziesii) 10.5” DSH, 20’ tall standing just north of the end of the line of pines. Tree is dead. 7) Douglas Fir 12.5” DSH, 22’ tall standing at the SW corner of the 16433 house. Tree is dead. 8) Ash (Fraxinus sp) 19” DSH, 30’ tall, 14’ spread standing in line with and north of the #7 tree. It is in poor condition with a significant decay column running from the base to where it was topped near the 12’ level. 9) Douglas Fir 15” DSH, 26’ tall standing north of #8. It is in fair health but bifurcates at the 9’ mark and has an active fracture plane. May have been topped. 10) Douglas Fir 14” DSH, 28’ tall standing north of #9. It bifurcates at the 6’ mark and has an active fracture plane. May have been topped. Upper canopy is stunted and discolored. 11) Douglas Fir 12.5” DSH, 26’ tall standing at the NW corner of the 16433 house. It is in fair health but bifurcates at the 10’ mark and the codominant stems twine. May have been topped. 12) Big Leaf Maple (Acer macrophyllum) clump standing 15’ north of #11 and on the north fenceline. There are 10 stem in the stand varying from 3-6” DSH and they average 20’ tall. Most likely stump sprouts. 13) White Ash (Fraxinus Americana) 10” DSH, 26’ tall 9’ spread standing 20’ west of the #12 tree and in the fence line area. Fair condition. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner 14) Excelsa Cedar (Thuja plicata ‘Excelsa’) 20” DSH, 25’ tall standing 10’ west of #11. Tree is in good condition. 15) Redwood (Sequoia sempervirens) 26” and 24” DSH, 50’ tall standing 17 west of #14 and 8’north of the fence. Separates at base. Good condition. 16) White Ash 5.5” and 8.5” DSH, 37’ tall, 16’ one sided spread standing 10’ SSW of #15. Fair condition. Tree separates at 3’ level. 17) Redwood 28” DSH, 48’ tall standing 20’ west of the #15 tree and 8’ north of the fence. Good condition. 18) White Ash 5” and 10” DSH, 39’ tall, 10’ spread standing 15’ SW of #15. Fair condition. Tree separates at 40” level. 19) Redwood 27” DSH, 46’ tall standing 20’ west of the #17 tree and 8’ north of the fence. Good condition. 20) White Ash 13” DSH, 26’ tall, 8’ spread standing 22’ W of #18. Fair condition. Tree bifurcates at 5’ mark. 21) White Ash 6.5” and 10.5” DSH, 25’ tall, 8’ spread standing 21’ east of the NW corner of the property. Fair condition. Tree separates at 13” level. 22) Weeping Willow 17.5” DSH, 20’ tall, standing 17’ south of the north line and 14’ east of the west line. The tree leans east near 20 degrees and extends 24’ and about 14’ wide. 23) Cottonwood (Populus trichocarpa) 25” DSH, 65’ tall, 18’ spread standing 6’ west of the west fence line and 20’ south of the north line. Tree has a significant structural fault near the 30’ level. Decay may be present. 24) Red Alder (Alnus rubra) 13” and 15” DSH, 45’ tall, 8’ spreads standing 5’ west of the west line and 15’ south of #23. Both stems have less than 15% viable canopies and both lean lightly to the southeast. 25) Western Red Cedar (Thuja plicata) 13.5” DSH, 35’ tall standing 5’ east of the west line and 8’ south of the #24 tree. There is a tree fort fastened between this tree and the #26 tree which has been in place at least 8 years based on how much the tree has grown around the boards and bolts. Tree is in poor condition with little to no new growth and weak color. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner 26) Western Red Cedar 11.5” DSH and 14” DSH, 35’ tall standing 10’ south of #25 and holding the other end of the fort. Stems separate from the base. Tree is in poor condition. 27) Western Red Cedar 12” and 14” DSH, 31’ tall standing 9’ south of #26. The stems separate from the base and the larger is on the east side. Tree is in weak condition. 28) Western Red Cedar 15” DSH, 30’ tall standing 42’ north of the SE corner of the 16433 property and 6’ east of the west line. It is in weak condition. 29) Western Red Cedar 18” DSH, 26’ tall standing 6’ south of the #28 tree. It is in weak condition. 30) Cottonwood 16” DSH, 52’ tall, 16’ spread standing 5’ west of the four way corner at the NW corner of the 16451 parcel and in the property due west of it. Tree is in fair condition. 31) Cottonwood tree 12” DSH, 65’ tall, 9’ spread standing as part of a clump 15’ south and 15’ east of the NW corner of the 16451 property. It is in fair condition. 32) Cottonwood tree 12.5” DSH, 42’ tall, 9’ spread standing just south of the #31 tree. It is in fair condition. 33) Cottonwood tree 22.5” DSH, 75’ tall, 18’ spread standing in between and just west of the #31 and #32 trees. It is in fair condition. There are two subordinate saplings, 4” and 6” caliper, standing below this tree and closer to the west fence. 34) Cottonwood tree 10” DSH, 35’ tall and 14” DSH, 45’ tall, 9’ overall spread standing 28’ south of the #31-33 clump. It is in the west fence line and in weak condition. 35) Cottonwood tree 13” DSH, 32’ tall, 8’ spread standing 35’ south of the #34 tree and against the fence. It is in fair condition. 36) Big Leaf Maple 10” DSH, 33’ tall, 10’ spread standing 5’ north of the SW corner of the 16451 property. It is in fair condition. 37) Grove of at least twelve cottonwood saplings, all less than 6” DSH, standing at about the center point of the south side of the property and on the southern neighbor’s side of the line. Fair conditions. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Methods: Tree assessment is both an art and a science. To properly perform, an arborist must have an extensive background in biology, tree mechanics, and tree structure that is equal parts academic and field knowledge. It takes years of study to recognize and correctly diagnose the subtle signs trees exhibit before their failure, whether it be partial or total. The process begins with a visual inspection (visual tree assessment, VTA) which is followed up as necessary with soundings, core testing, and/or other detection means. Each tree is examined and evaluated according to several factors including species type, size, vigor, injuries present, root and grade disturbance, deadwood, location and extent of decay, stem taper, exposure, and targets that are at risk. Discussion: There are two levels of concern at this site, primary and secondary. The primary construction impact zone includes the environs immediately within the boundaries of the new home base areas (see Figures 4 and 5), those in the area of the new road improvements, the areas expected for the driveway access to each home site, and the regions within ten feet of those boundaries. Trees #1-11, #28, and #31-33 clearly stand in the primary impact zones. They will be removed at the time of clearing and grading The secondary impact area includes the trees which have root systems extending within the construction area. This region, the Critical Root Zone (CRZ), is defined as a circle with a radius of one foot per inch of tree diameter. For example the #13 White Ash, with a 10” DSH, has a 10’ radial CRZ. Typically intrusion within the CRZ is strongly discouraged by the tree care industry. However trenching type incursion, that is excavation that will occur along only one sector of a tree’s CRZ, can reach significantly into the root growth area without having a detrimental long term effect. What does have to be absolutely protected is a tree’s Structural Root Plate (SRP). This radial area is again related to the diameter inches of the tree in question but not quite in a direct proportion as in the CRZ. Figure 6 below illustrates the relationship. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Figure 6. Size of the Structural Root Plate in relation to tree stem diameter. Note that the SRP levels off at 10’ for any tree over 24” in diameter. In the case of the #10 White Ash mentioned above, the #2 house base area will be 20’ back from the north property line so will not interfere with tree. But if other grading is required along the edges of the parcel then the #10 tree, as seen in Figure 6, has a 5’ Structural Root Plate, and excavating will have to stay outside of that area. Looking at the entire row of trees along the north fence line the redwoods have the largest diameters and will require the full 10’ set back. They are already 8’ north of the line so only 2’ of their SRP extends into the parcel. The Ash standing on the property line have diameters which indicate no greater than 6’ SRPs. The #22 willow has a 17.5” DSH and means it has somewhere around an 8’ SRP. The area shown on the short plat as set aside for the #5 house will be just at 8’ from the base of the tree. The largest of the cedars standing on the west end of the 16433 parcel has an 18” DSH which indicates an 8’ SRP. The cottonwoods and maple standing on the west end of the 16451 parcel range between 10” DSH and 13” DSH which indicate SRPs between 6’ and 7’ radial spread. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner The chart shown in Figure 7 below is used to determine what percentage of a tree’s Critical Root Zone will be affected by trenching type incursion. In general trees can sustain losses of up to 30% of the overall area within their CRZ without having long term detrimental results. Figure 7. Chart giving the loss in critical root area as a function of the radial distance to the CRZ disturbance. For the trees along the north border, the CRZs of the redwoods (26-28’ radial spread) overlap those of the ash (10-12’ radial spreads) in the fence line. From the chart in Figure 7 the redwoods require a 19’ setback to prevent detrimental impact. As they are 8’ north of the fence line an 11’ non-intrusion zone along the length of the north line should be adequate for all the trees. The #22 willow requires a 13’ set back which appears to overlap with the graded area at the NW corner of the #5 home site. The cedars #25-27 are in an region set aside as a sensitive area. But there appears to be step down grading which will occur in their vicinity. Their CRZ should not be disturbed within 10’ of the base of the trees. If fill is being brought in it can be no deeper than 4” within 10’ of the trees. The #29 cedar is close to the SW corner of the graded site for the #5 home. It requires a 13’ set back. The cottonwoods and maple on the west end of 16451 all have 10’ maximum setbacks. They also appear to be in regions of stepped down grading. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Recommendations: Nearly all the trees present on site in this case will have to be removed. The majority stand in the primary impact zone for the development. Of these only the #2-4 Scots pines are in at least average condition. The others are dead, in weak to poor condition, and/or have structural issues making them undesirable to retain. Removal and replacement with young, healthy trees is the most viable option for these spaces. The #22 willow and # 29 cedar stand in the center of grade transition zones. Neither is in good condition and both require CRZ protection at 18’ out from their bases. If it is not possible, or practical, to maintain these protection circles then the trees should be removed. Note that burying the CRZs of trees with more than 4” of soil interferes with their biological functions and for all intents and purposes is no different from cutting the roots. Raising grade within the CRZ of a retained tree is not allowed. Typically protection fencing such as 6’ chain link is set at the CRZ limits for retained trees. For the north side border stand the simplest thing is to just run the fence 11’ south of the property line for the length of the row. If the #22 willow is to be kept than it will require a circular enclosure at 17.5’ radial distance. Obviously the tree itself will extend beyond the fence line and may require clearance pruning. The protection fence for the #25-27 cedars can be set at their 10’ one-sided encroachment limit on the east and then tapered around both ends at 14’ distance. The #29 cedar, if it is to be kept, will have to be circled at 18’ radial distance. The two cottonwoods and maple at the west end of 16451 should be fenced at their CRZ extent and the fence tied back to the existing wood one. All the retained trees should be covered with 6-8” of arbormulch within the region of their CRZs. Excelsior cedars, Deodar cedar, Alaska Weeping Cedar, and even Sequoia are great options for evergreen replacements. Columnar maples, hornbeams, beech, Katsura, Crimson King maple, and certain oak varieties are options for larger deciduous. Japanese Snowbell, Stewartia, redbuds, vine maples, and columnar magnolias can work for color and more mid-sized options. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Waiver of Liability Because the science of tree risk assessment is constantly broadening its understanding, it cannot be said to be an exact science. Every tree is different and performing tree risk assessment is a continual learning process. Many variables beyond the control, or immediate knowledge, of the arborist involved may adversely affect a tree and cause its premature failure. Internal cracks and faults, undetectable root rot, unexposed construction damage, interior decay, and even nutrient deficiencies can be debilitating factors. Changes in circumstance and condition can also lead to a tree’s rapid deterioration and resulting instability. All trees have a risk of failure. As they increase in stature and mass their risk of breakdown also increases, eventual failure is inevitable. While every effort has been taken to provide the most thorough and accurate snapshot of the trees’ health, it is just that, a snapshot, a frozen moment in time. These findings do not guarantee future safety nor are they predictions of imminent events. It is the responsibility of the property owner to adequately care for the tree(s) in question by utilizing the proper professionals and to schedule future assessments in a timely fashion. This report and all attachments, enclosures, and references, are confidential and are for the use of D.R. Strong Consulting Engineers and their representatives only. They may not be reproduced, used in any way, or disseminated in any form without the prior consent of the client concerned. Anthony Moran Certified Arborist Qualified Tree Risk Assessor ISA #PN-5847A ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Figure 1. Aerial overview of the two property. The subject trees are labeled in red. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Figure 2. Close up aerial view of the 16433 property. Not that the faint red lines designating the boundaries appear to be shifted to the south. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Figure 3. Close up aerial view of the 16451 property. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Figure 4. Excerpt from plot plan showing location of proposed new lots and road improvements for the 16433 parcel. Note the step down grading notation at the west (left) side of the image. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Figure 5. Excerpt from plot plan showing location of proposed new lots and road improvements for the 16451 parcel. Note the stepped grading at the west end of the property. March 3, 2019 Project: Identify trees along 111th Avenue SE from the 16433 address north to the corner of 164th Street Contact: Jonathan Murray - D. R. Strong Consulting Engineers, Inc 620 7th Avenue, Kirkland, WA 98033 Phone – 425 827 3063 Email – jonathan.murray@drstrong.com Mark Seek Phone – 206 619 4062 Email – MarkSeek1@yahoo.com Objectives: Identify row of trees on west side of 111th as to species, size and condition. Description: There is a row of trees which start on the 16411 111th Avenue SE property and run all the way to the corner of 164th Street. Starting at the south end they are as follows: 1) Western Red Cedar (Thuja plicata) 32”” DSH, 60’ tall, dual stem from 28’ mark in fair condition. It is standing at the south end of the line and just to the north side of the driveway to the 16411 property. 2) Grand Fir (Abies grandis) 21” DSH, 45’ tall in fair condition with average new growth and color. Tree bifurcates at the 8’ level. Standing 25’ north of the #1 tree and on the north side of the entrance walk. 3) Douglas Fir (Pseudotsuga menziesii) 15” DSH, 45’ tall, dual stem from the 9’ level. It is standing just north of #2 tree and is in fair condition. 4) Spruce (Picea glauca)12” DSH, 45’ tall standing just north of #3. It is in fair condition. 5) Incense Cedar (Calocedrus decurrens) multistem form the 5’ level all rising off of a20” caliper base. It reaches over 30’ tall and the stems spread widely. The larger ones are weighted toward the road. It is in poor structural condition but in average health. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner 6) Spruce 25” DSH, 50’ tall standing just north of #5 and mostly likely at the NE corner of the lot. It is in fair health but appears to have had its top broken as it has multiple new spars rising from around the 35’ level. 7) Row of eleven birch, most likely Himalayans (Betula utilis), ranging in size from 5” to 10” DSH and 18’ to 45’ tall. They start on or near the SE corner of the 10955 Se 164th Street property and run for roughly 50’ to the north. The trees are in poor condition with nearly every one having a broken top. Appear to being suffering from Bronze Birch Bore and they are covered in ivy. Their canopies spread as much as 12’ over the road in places. 8) Weeping Flowering Cherry (Prunus sp) 10” DSH, topped near the 10’ level, and regrown to 16’ tall. It is standing at the north end of the birch row and at the south side of the driveway entrance. It is in poor condition. 9) Douglas fir 14” DSH, 50’ tall standing on the north side of the driveway entrance. Tree is in good condition. 10) Sitka Spruce (Picea sitchensis) 18” DSH, 50’ tall standing at the NE corner of the 10955 property which is the corner of 111th and 164th. Tree is in good condition. 11) Sitka spruce 11” DSH, 40’ tall standing 6’ west of the #10 tree and leaning west away from it. Tree is in fair condition. ______________________________________________________________________________ ______ PO Box 1261, Mercer Island, WA 98040 • 206-275-0991 • paulscottsinclair@gmail.com Scott Sinclair - Owner Rough location of the trees identified in the report. 2021 D. R. STRONG Consulting Engineers Inc. Page 69 Bethany Corner Technical Information Report Renton, Washington SECTION VII OTHER PERMITS, VARIANCES AND ADJUSTMENTS NPDES Permit from DOE. 2021 D. R. STRONG Consulting Engineers Inc. Page 70 Bethany Corner Technical Information Report Renton, Washington SECTION VIII CSWPPP ANALYSIS AND DESIGN (PART A) The Erosion and Sedimentation Control Design will meet the seven minimum King County requirements: 1. Areas to remain undisturbed shall be delineated with a high visibility plastic fence prior to any site clearing or grading. 2. Site disturbed areas shall be covered with mulch and seeded, as appropriate, for temporary or permanent measures. 3. Perimeter protection shall consist of a silt fence down slope of any disturbed areas or stockpiles. 4. A stabilized construction entrance will be located at the point of ingress/egress (i.e. onsite access road). 5. The detention pond will act as a sediment pond for sediment retention. Perimeter silt fences will provide sediment retention within the bypass areas. 6. Surface water from disturbed areas will sheet flow to the sediment pond for treatment. 7. Dust control shall be provided by spraying exposed soils with water until wet. This is required when exposed soils are dry to the point that wind transport is possible which would impact roadways, drainage ways, surface waters, or neighboring residences. SWPPP PLAN DESIGN (PART B) Construction activities that could contribute pollutants to surface and storm water include the following, with applicable BMP’s listed for each item: 1. Storage and use of chemicals: Utilize source control, and soil erosion and sedimentation control practices, such as using only recommended amounts of chemical materials applied in the proper manner; neutralizing concrete wash water, and disposing of excess concrete material only in areas prepared for concrete placement, or return to batch plant; disposing of wash-up waters from water-based paints in sanitary sewer; disposing of wastes from oil-based paints, solvents, thinners, and mineral spirits only through a licensed waste management firm, or treatment, storage, and disposal (TSD) facility. 2. Material delivery and storage: Locate temporary storage areas away from vehicular traffic, near the construction entrance, and away from storm drains. Material Safety Data Sheets (MSDS) should be supplied for all materials stored, and chemicals kept in their original labeled containers. Maintenance, fueling, and repair of heavy equipment and vehicles shall be conducted using spill prevention and control measures. Contaminated surfaces shall be cleaned immediately following any spill incident. Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other potentially hazardous materials. 2021 D. R. STRONG Consulting Engineers Inc. Page 71 Bethany Corner Technical Information Report Renton, Washington 3. Building demolition: Protect stormwater drainage system from sediment-laden runoff and loose particles. To the extent possible, use dikes, berms, or other methods to protect overland discharge paths from runoff. Street gutter, sidewalks, driveways, and other paved surfaces in the immediate area of demolition must be swept daily to collect and properly dispose of loose debris and garbage. Spray the minimum amount of water to help control windblown fine particles such as concrete, dust, and paint chips. Avoid excessive spraying so that runoff from the site does not occur, yet dust control is achieved. Oils must never be used for dust control. 4. Sawcutting: Slurry and cuttings shall be vacuumed during the activity to prevent migration offsite and must not remain on permanent concrete or asphalt paving overnight. Collected slurry and cuttings shall be disposed of in a manner that does not violate ground water or surface water quality standards. The complete CSWPPP can be found in Appendix B. 2021 D. R. STRONG Consulting Engineers Inc. Page 72 Bethany Corner Technical Information Report Renton, Washington SECTION IX BOND QUANTITIES, FACILITY SUMMARIES, AND DECLARATION OF COVENANT 1. Bond Quantity Worksheet – is located in Appendix C 2. The Stormwater Facility Summary Sheet is included in this section 2021 D. R. STRONG Consulting Engineers Inc. Page 73 Bethany Corner Technical Information Report Renton, Washington STORMWATER FACILITY SUMMARY SHEET Development Bethany Corner Date April 9, 2021 Location: 16433 & 16451 111th Avenue SE, Renton, Washington ENGINEER DEVELOPER Name Jonathan S. Murray, P.E. Name Dianne Dougherty Firm D.R. STRONG Consulting Engineers, Inc. Firm Bona Fide Properties 2, LLC Address 620 7th Avenue Address… 3024 90th PL SE Kirkland, WA 98033 Mercer Island, WA 98040 Phone (425) 827-3063 Phone (650) 888-5101 Developed Site: 1.953 acres Number of lots: 9 Number of detention facilities on site: Number of infiltration facilities on site: ___1__ vaults ______ vaults ______ pond ______ ponds ______ tanks ______ tanks Flow control provided in regional facility (give location)___________________________ No flow control required_____ Exemption number ______________________________ Downstream Drainage Basins Immediate Major Basin Basin Benson Green/Duwamish River Watershed Number & type of water quality facilities on site: biofiltration swale (regular/wet/ or continuous inflow?) ______ sand filter (basic or large?) ______ sand filter, linear (basic or large?) ______ CONTECH Stormfilter __1___ combined detention/WQ vault ______ sand filter vault (basic or large?) ______ combined detention/wetpond ______ stormwater wetland ______ compost filter ______ wetvault (basic or large?) ______ filter strip ______ Wetvault ______ flow dispersion ______ pre-settling pond ______ farm management plan ______ flow-splitter catchbasin ______ landscape management plan ______ oil/water separator (baffle or coalescing plate?) ______ catch basin inserts: Manufacturer_____________________________________ ______ pre-settling structure: Manufacturer___________________________________ 2021 D. R. STRONG Consulting Engineers Inc. Page 74 Bethany Corner Technical Information Report Renton, Washington DESIGN INFORMATION INDIVIDUAL BASIN Water Quality design flow Water Quality treated volume Drainage basin(s) 1 Onsite area (includes frontage) 1.911 Offsite area 0.0 Type of Storage Facility Detention Vault Live Storage Volume (required) 24,794 Predev Runoff Rate 2-year 0.054 10-year 0.094 100-year 0.156 Developed Runoff Rate 2-year 0.035 (includes bypass) 10-year 0.094 100-year 0.132 Type of Restrictor FROP Tee Size of orifice/restriction No. 1 0.6875” Ø 0.00’ No. 2 1.375” Ø 3.56’ No. 3 2021 D. R. STRONG Consulting Engineers Inc. Page 75 Bethany Corner Technical Information Report Renton, Washington SECTION X OPERATIONS AND MAINTENANCE MANUAL The Home Owners Association will be responsible for maintenance of several private catch basins on various lots as depicted on the plans. Maintenance guidelines set forth in the 2009 KCSWDM are included in this section. All other drainage elements are to be publicly maintained. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-5 NO. 3 – DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Trash and debris Any trash and debris which exceed 1 cubic foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard 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 may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or 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 if appropriate. No contaminants present other than a surface oil film. Site Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non-floatables). No trash or debris in vault. Tank or Vault Storage Area Sediment accumulation Accumulated sediment depth exceeds 10% of the diameter of the storage area for ½ length of storage vault or any point depth exceeds 15% of diameter. Example: 72-inch storage tank would require cleaning when sediment reaches depth of 7 inches for more than ½ length of tank. All sediment removed from storage area. Plugged air vent Any blockage of the vent. Tank or vault freely vents. Tank bent out of shape Any part of tank/pipe is bent out of shape more than 10% of its design shape. Tank repaired or replaced to design. Tank Structure Gaps between sections, damaged joints or cracks or tears in wall A gap wider than ½-inch at the joint of any tank sections or any evidence of soil particles entering the tank at a joint or through a wall. No water or soil entering tank through joints or walls. Vault Structure Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Sediment accumulation 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 Pipes Damaged Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering at 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 A A-6 NO. 3 – DETENTION TANKS AND VAULTS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. 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 maintenance person. Access Manhole Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Damaged or difficult to open Large access doors or plates cannot be opened/removed using normal equipment. Replace or repair access door so it can opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat and covers access opening completely. Large access doors/plate Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-7 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Trash or debris of more than ½ cubic foot which is located immediately in front of the structure opening or is blocking capacity of the structure by more than 10%. No Trash or debris blocking or potentially blocking entrance to structure. Trash or debris in the structure that exceeds 1/3the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Trash and debris Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment Sediment exceeds 60% of the depth from the bottom of the structure to the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section or is within 6 inches of the invert of the lowest pipe into or out of the structure or the bottom of the FROP-T section. Sump of structure contains no sediment. Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Damage to frame and/or top slab Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the 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 structure through cracks, or maintenance person judges that structure is unsound. Structure is sealed and structurally sound. Cracks in walls or bottom Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering structure through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Structure has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of inlet/outlet pipes. 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 if appropriate. No contaminants present other than a surface oil film. Structure Ladder rungs missing or unsafe Ladder is unsafe due to missing rungs, misalignment, rust, cracks, or sharp edges. Ladder meets design standards and allows maintenance person safe access. T section is not securely attached to structure wall and outlet pipe structure should support at least 1,000 lbs of up or down pressure. T section securely attached to wall and outlet pipe. Structure is not in upright position (allow up to 10% from plumb). Structure in correct position. Connections to outlet pipe are not watertight or show signs of deteriorated grout. Connections to outlet pipe are water tight; structure repaired or replaced and works as designed. FROP-T Section Damage Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing Cleanout gate is missing. Replace cleanout gate. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix A A-8 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Cleanout gate is not watertight. Gate is watertight and works as designed. Gate cannot be moved up and down by one maintenance person. Gate moves up and down easily and is watertight. Chain/rod leading to gate is missing or damaged. Chain is in place and works as designed. Damaged or missing Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Orifice Plate Obstructions Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Obstructions Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Overflow Pipe Deformed or damaged lip Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Sediment accumulation 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 entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Unsafe grate opening Grate with opening wider than 7/8 inch. Grate opening meets design standards. 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 (If Applicable) Damaged or missing Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. 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 maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-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 the bottom of the catch basin to the invert of the lowest pipe into or out of the catch basin or is within 6 inches of the invert of the lowest pipe into or out of the catch basin. Sump of catch basin contains no sediment. Trash or debris of more than ½ cubic foot which is located immediately in front of the catch basin opening or is blocking capacity of the catch basin by more than 10%. No Trash or debris blocking or potentially blocking entrance to catch basin. Trash or debris in the catch basin that exceeds 1/3 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 generate odors that could cause complaints or dangerous gases (e.g., methane). No dead animals or vegetation present within catch basin. Trash and debris Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Corner of frame extends more than ¾ inch past curb face into the street (If applicable). Frame is even with curb. Top slab has holes larger than 2 square inches or cracks wider than ¼ inch. Top slab is free of holes and cracks. Damage to frame and/or top slab Frame not sitting flush on top slab, i.e., separation of more than ¾ inch of the frame from the 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 catch basin through cracks, or maintenance person judges that catch basin is unsound. Catch basin is sealed and structurally sound. Cracks in walls or bottom Cracks wider than ½ inch and longer than 1 foot at the joint of any inlet/outlet pipe or any evidence of soil particles entering catch basin through cracks. No cracks more than 1/4 inch wide at the joint of inlet/outlet pipe. Settlement/ misalignment Catch basin has settled more than 1 inch or has rotated more than 2 inches out of alignment. Basin replaced or repaired to design standards. Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the catch basin at the joint of the inlet/outlet pipes. No cracks more than ¼-inch wide at the 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 if appropriate. No contaminants present other than a surface oil film. Sediment accumulation 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 entering at 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 A A-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 design standards. 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 design standards. Cover/lid not in place Cover/lid is missing or only partially in place. Any open structure requires urgent maintenance. Cover/lid protects opening to structure. Locking mechanism Not Working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. 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 maintenance person. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-11 NO. 6 – CONVEYANCE PIPES AND DITCHES Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% 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 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 if appropriate. No contaminants present other than a surface oil film. Damage to protective coating or corrosion Protective coating is damaged; rust or corrosion is weakening the structural integrity of any part of pipe. Pipe repaired or replaced. Pipes Damaged Any dent that decreases the cross section area of pipe by more than 20% or is determined to have weakened structural integrity of the pipe. Pipe repaired or replaced. Trash and debris Trash and debris exceeds 1 cubic foot per 1,000 square feet of ditch and slopes. Trash and debris cleared from ditches. 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 the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or 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 if appropriate. No contaminants present other than a surface oil film. Vegetation Vegetation that reduces free movement of water through ditches. Water flows freely through ditches. Erosion damage to slopes Any erosion observed on a ditch slope. Slopes are not eroding. Ditches Rock lining out of place or missing (If Applicable) One layer or less of rock exists above native soil area 5 square feet or more, any exposed native soil. Replace rocks to design standards. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix A A-12 NO. 7 – DEBRIS BARRIERS (E.G., TRASH RACKS) Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed. Trash and debris Trash or debris plugging more than 20% of the area of the barrier. Barrier clear to receive capacity flow. Site Sediment accumulation Sediment accumulation of greater than 20% of the area of the barrier Barrier clear to receive capacity flow. Structure Cracked broken or loose Structure which bars attached to is damaged - pipe is loose or cracked or concrete structure is cracked, broken of loose. Structure barrier attached to is sound. Bar spacing Bar spacing exceeds 6 inches. Bars have at most 6 inche spacing. Bars are bent out of shape more than 3 inches. Bars in place with no bends more than ¾ inch. Bars are missing or entire barrier missing. Bars in place according to design. Bars Damaged or missing bars Bars are loose and rust is causing 50% deterioration to any part of barrier. Repair or replace barrier to design standards. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-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/or debris. 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 if appropriate. No contaminants present other than a surface oil film. Rock Pad Missing or moved Rock Only one layer of rock exists above native soil in area five square feet or larger or any exposure of native soil. Rock pad prevents erosion. Pipe plugged with sediment Accumulated sediment that exceeds 20% of the design depth. Pipe cleaned/flushed so that it matches design. Not discharging water properly Visual evidence of water discharging at concentrated points along trench (normal condition is a “sheet flow” of water along trench). Water discharges from feature by sheet flow. Perforations plugged. Over 1/4 of perforations in pipe are plugged with debris or sediment. Perforations freely discharge flow. Water flows out top of “distributor” catch basin. 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 has potential 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 than ¼ of its gage. All gabion mesh capable of containing rock and retaining designed form. Collapsed or deformed baskets Gabion basket shape deformed due to any cause. All gabion baskets intact, structure stands as designed. Gabions Missing rock Any rock missing that could cause gabion to loose structural integrity. No rock missing. Worn or damaged post, baffles or side of chamber Structure dissipating flow deteriorates to ½ or original size or any concentrated worn spot exceeding one square foot which would make structure unsound. Structure is in no danger of failing. Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch or any evidence of soil entering the structure through cracks, or maintenance inspection personnel determines that the structure is not structurally sound. Manhole/chamber is sealed and structurally sound. Manhole/Chamber Damaged pipe joints Cracks wider than ½-inch at the joint of the inlet/outlet pipes or any evidence of soil entering the structure at the joint of the inlet/outlet pipes. No soil or water enters and no water discharges at the joint of inlet/outlet pipes. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix A A-14 NO. 9 – FENCING Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Site Erosion or holes under fence Erosion or holes more than 4 inches high and 12- 18 inches wide permitting access through an opening under a fence. No access under the fence. Missing or damaged parts Missing or broken boards, post out of plumb by more than 6 inches or cross members broken No gaps on fence due to missing or broken boards, post plumb to within 1½ inches, cross members sound. Weakened by rotting or insects Any part showing structural deterioration due to rotting or insect damage All parts of fence are structurally sound. Wood Posts, Boards and Cross Members Damaged or failed post foundation Concrete or metal attachments deteriorated or unable to support posts. Post foundation capable of supporting posts even in strong wind. Post out of plumb more than 6 inches. Post plumb to within 1½ inches. Top rails bent more than 6 inches. Top rail free of bends greater than 1 inch. Any part of fence (including post, top rails, and fabric) more than 1 foot out of design alignment. Fence is aligned and meets design standards. Damaged parts Missing or loose tension wire. Tension wire in place and holding fabric. Deteriorated paint or protective coating Part or parts that have a rusting or scaling condition that has affected structural adequacy. Structurally adequate posts or parts with a uniform protective coating. Metal Posts, Rails and Fabric Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-15 NO. 10 – GATES/BOLLARDS/ACCESS BARRIERS Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Missing gate. Gates in place. Broken or missing hinges such that gate cannot be easily opened and closed by a maintenance person. Hinges intact and lubed. Gate is working freely. Gate is out of plumb more than 6 inches and more than 1 foot out of design alignment. Gate is aligned and vertical. Damaged or missing members Missing stretcher bar, stretcher bands, and ties. Stretcher bar, bands, and ties in place. Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate. Chain Link Fencing Gate Openings in fabric Openings in fabric are such that an 8-inch diameter ball could fit through. Fabric mesh openings within 50% of grid size. Damaged or missing cross bar Cross bar does not swing open or closed, is missing or is bent to where it does not prevent vehicle access. Cross bar swings fully open and closed and prevents vehicle access. Locking mechanism does not lock gate Locking device missing, no-functioning or does not link to all parts. Locking mechanism prevents opening of gate. Bar Gate Support post damaged Support post does not hold cross bar up. Cross bar held up preventing vehicle access into facility. Damaged or missing Bollard broken, missing, does not fit into support hole or hinge broken or missing. No access for motorized vehicles to get into facility. Bollards Does not lock Locking assembly or lock missing or cannot be attached to lock bollard in place. No access for motorized vehicles to get into facility. Dislodged Boulders not located to prevent motorized vehicle access. No access for motorized vehicles to get into facility. Boulders Circumvented Motorized vehicles going around or between boulders. No access for motorized vehicles to get into facility. APPENDIX A MAINTENANCE REQUIREMENTS FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 1/9/2009 2009 Surface Water Design Manual – Appendix A A-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 foot per 1,000 square feet (this is about equal to the amount of trash it would take to fill up one standard 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 may constitute a hazard to County personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where County personnel or 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 if appropriate. No contaminants present other than a surface oil film. Site Grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Hazard Any tree or limb of a tree identified as having a potential to fall and cause property damage or threaten 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 or broken which affect more than 25% of the total foliage of the tree or shrub. Trees and shrubs with less than 5% of total foliage with split or broken limbs. Trees or shrubs that have been blown down or knocked over. No blown down vegetation or knocked over vegetation. Trees or shrubs free of injury. Trees and Shrubs Damaged Trees or shrubs which are not adequately supported or are leaning over, causing exposure of the roots. Tree or shrub in place and adequately supported; dead or diseased trees removed. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-17 NO. 12 – ACCESS ROADS Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Trash and debris exceeds 1 cubic foot per 1,000 square feet (i.e., trash and debris would fill up one standards size garbage can). Roadway drivable by maintenance vehicles. Trash and debris Debris which could damage vehicle tires or prohibit use of road. Roadway drivable by maintenance vehicles. 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 if appropriate. No contaminants present other than a surface oil film. Any obstruction which reduces clearance above road surface to less than 14 feet. Roadway overhead clear to 14 feet high. Site Blocked roadway Any obstruction restricting the access to a 10- to 12 foot width for a distance of more than 12 feet or any point restricting access to less than a 10 foot width. At least 12-foot of width on access road. Erosion, settlement, potholes, soft spots, ruts Any surface defect which hinders or prevents maintenance access. Road drivable by maintenance vehicles. Road Surface Vegetation on road surface Trees or other vegetation prevent access to facility by maintenance vehicles. Maintenance vehicles can access facility. Erosion Erosion within 1 foot of the roadway more than 8 inches wide and 6 inches deep. Shoulder free of erosion and matching the surrounding road. Shoulders and Ditches Weeds and brush Weeds and brush exceed 18 inches in height or hinder maintenance access. Weeds and brush cut to 2 inches in height or cleared in such a way as to allow maintenance access. 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 if appropriate. No contaminants present other than a surface oil film. Modular Grid Pavement Damaged or missing Access surface compacted because of broken on missing modular block. Access road surface restored so road infiltrates. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-23 NO. 17 – WETVAULT Maintenance Component Defect or Problem Condition When Maintenance is Needed Results Expected When Maintenance is Performed Site Trash and debris Trash and debris accumulated on facility site. Trash and debris removed from facility site. Trash and debris Any trash and debris accumulated in vault (includes floatables and non-floatables). No trash or debris in vault. Sediment accumulation Sediment accumulation in vault bottom exceeds the depth of the sediment zone plus 6 inches. No sediment in vault. Treatment Area 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 if appropriate. No contaminants present other than a surface oil film. Damage to wall, frame, bottom, and/or top slab Cracks wider than ½-inch, any evidence of soil entering the structure through cracks, vault does not retain water or qualified inspection personnel determines that the vault is not structurally sound. Vault is sealed and structurally sound. Baffles damaged Baffles corroding, cracking, warping and/or showing signs of failure or baffle cannot be removed. Repair or replace baffles or walls to specifications. Vault Structure Ventilation Ventilation area blocked or plugged. No reduction of ventilation area exists. Sediment accumulation 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 entering at the joints of the inlet/outlet pipes. No cracks more than ¼-inch wide at the joint of the inlet/outlet pipe. Inoperable valve Valve will not open and close. Valve opens and closes normally. Gravity Drain Valve won’t seal Valve does not seal completely. Valve completely seals closed. Access cover/lid damaged or difficult to open Access cover/lid cannot be easily opened by one person. Corrosion/deformation of cover/lid. Access cover/lid can be opened by one person. Locking mechanism not working Mechanism cannot be opened by one maintenance person with proper tools. Bolts cannot be seated. Self-locking cover/lid does not work. Mechanism opens with proper tools. 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 maintenance person. Access doors/plate has gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat and covers access opening completely. Lifting Rings missing, rusted Lifting rings not capable of lifting weight of door or plate. Lifting rings sufficient to lift or remove door or plate. Access Manhole Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. APPENDIX A MAINTENANCE REQUIREMENTS FOR FLOW CONTROL, CONVEYANCE, AND WQ FACILITIES 2009 Surface Water Design Manual – Appendix A 1/9/2009 A-35 NO. 24 – CATCH BASIN INSERT Maintenance Component Defect or Problem Conditions When Maintenance is Needed Results Expected When Maintenance is Performed Visible Oil Visible oil sheen passing through media Media inset replaced. Insert does not fit catch basin properly Flow gets into catch basin without going through media. All flow goes through media. Filter media plugged Filter media plugged. Flow through filter media is normal. Oil absorbent media saturated Media oil saturated. Oil absorbent media replaced. Water saturated Catch basin insert is saturated with water, which no longer has the capacity to absorb. Insert replaced. Service life exceeded Regular interval replacement due to typical average life of media insert product, typically one month. Media replaced at manufacturer’s recommended interval. Media Insert Seasonal maintenance When storms occur and during the wet season. Remove, clean and replace or install new insert after major storms, monthly during the wet season or at manufacturer’s recommended interval. 2021 D. R. STRONG Consulting Engineers Inc. Page 76 Bethany Corner Technical Information Report Renton, Washington APPENDICES 2021 D. R. STRONG Consulting Engineers Inc. Page 77 Bethany Corner Technical Information Report Renton, Washington APPENDIX “A” LEGAL DESCRIPTION LOT 11, BLOCK 7, AKER'S FARMS NO. 6, ACCORDING TO THE PLAT THEREOF RECORDED IN VOLUME 42 OF PLATS, PAGE 15, RECORDS OF KING COUNTY, WASHINGTON; SITUATE IN THE COUNTY OF KING, STATE OF WASHINGTON. LOT 12, BLOCK 7, AKER'S FARMS NO. 6 ACCORDING TO PLAT RECORDED IN VOLUME 42 OF PLATS, PAGE 15, RECORDS OF KING COUNTY WASHINGTON. SITUATE IN THE COUNTY OF KING, STATE OF WASHINGTON. 2021 D. R. STRONG Consulting Engineers Inc. Page 78 Bethany Corner Technical Information Report Renton, Washington APPENDIX “B” CSWPPP 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Construction Stormwater General Permit Stormwater Pollution Prevention Plan (SWPPP) for Bethany Corner Prepared for: The Washington State Department of Ecology Northwest Regional Office 3190 16th Avenue SE Bellevue, WA 98008-5452 Permittee / Owner Developer Operator / Contractor Mark Seek 15233 Manion Way NE Duvall, WA 98019 TBD TBD 16433 & 16451 111th Avenue SE, Renton, Washington Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number TBD Associated Earth Sciences, Inc 425.827.7701 SWPPP Prepared By Name Organization Contact Phone Number Jonathan S. Murray, PE DR Strong Consulting Engineers, Inc. (425) 827-3063 SWPPP Preparation Date August 28, 2018 Project Construction Dates Activity / Phase Start Date End Date Site Development 4/2019 10/2019 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page i Table of Contents 1 Project Information ...............................................................................................................2 1.1 Existing Conditions .......................................................................................................2 1.2 Proposed Construction Activities ...................................................................................2 2 Construction Stormwater Best Management Practices (BMPs) ............................................4 2.1 The 12 Elements ...........................................................................................................4 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits .........................................4 2.1.2 Element 2: Establish Construction Access .............................................................5 2.1.3 Element 3: Control Flow Rates...............................................................................6 2.1.4 Element 4: Install Sediment Controls .....................................................................7 2.1.5 Element 5: Stabilize Soils.......................................................................................9 2.1.6 Element 6: Protect Slopes....................................................................................10 2.1.7 Element 7: Protect Drain Inlets.............................................................................11 2.1.8 Element 8: Stabilize Channels and Outlets ..........................................................12 2.1.9 Element 9: Control Pollutants ...............................................................................13 2.1.10 Element 10: Control Dewatering ..........................................................................16 2.1.11 Element 11: Maintain BMPs .................................................................................17 2.1.12 Element 12: Manage the Project ..........................................................................18 3 Pollution Prevention Team .................................................................................................20 4 Monitoring and Sampling Requirements ............................................................................21 4.1 Site Inspection ............................................................................................................21 4.2 Stormwater Quality Sampling ......................................................................................21 4.2.1 Turbidity Sampling ...............................................................................................22 4.2.2 pH Sampling ........................................................................................................23 5 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies .........................24 5.1 303(d) Listed Waterbodies ..........................................................................................24 5.2 TMDL Waterbodies .....................................................................................................24 6 Reporting and Record Keeping ..........................................................................................25 6.1 Record Keeping ..........................................................................................................25 6.1.1 Site Log Book ......................................................................................................25 6.1.2 Records Retention ...............................................................................................25 6.1.3 Updating the SWPPP ...........................................................................................25 6.2 Reporting ....................................................................................................................25 6.2.1 Discharge Monitoring Reports ..............................................................................25 6.2.2 Notification of Noncompliance ..............................................................................26 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page ii List of Tables Table 1 – Summary of Site Pollutant Constituents .................................................................2 Table 3 – pH-Modifying Sources ............................................................................................15 Table 5 – Management ............................................................................................................18 Table 7 – Team Information ....................................................................................................20 Table 8 – Turbidity Sampling Method ....................................................................................22 Table 9 – pH Sampling Method ..............................................................................................23 List of Appendices A. Site Map B. BMP Detail C. Correspondence D. Site Inspection Form E. Construction Stormwater General Permit (CSWGP) F. Engineering Calculations 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 1 List of Acronyms and Abbreviations Acronym / Abbreviation Explanation 303(d) Section of the Clean Water Act pertaining to Impaired Waterbodies BFO Bellingham Field Office of the Department of Ecology BMP(s) Best Management Practice(s) CESCL Certified Erosion and Sediment Control Lead CO2 Carbon Dioxide CRO Central Regional Office of the Department of Ecology CSWGP Construction Stormwater General Permit CWA Clean Water Act DMR Discharge Monitoring Report DO Dissolved Oxygen Ecology Washington State Department of Ecology EPA United States Environmental Protection Agency ERO Eastern Regional Office of the Department of Ecology ERTS Environmental Report Tracking System ESC Erosion and Sediment Control GULD General Use Level Designation NPDES National Pollutant Discharge Elimination System NTU Nephelometric Turbidity Units NWRO Northwest Regional Office of the Department of Ecology pH Power of Hydrogen RCW Revised Code of Washington SPCC Spill Prevention, Control, and Countermeasure su Standard Units SWMMEW Stormwater Management Manual for Eastern Washington SWMMWW Stormwater Management Manual for Western Washington SWPPP Stormwater Pollution Prevention Plan TESC Temporary Erosion and Sediment Control SWRO Southwest Regional Office of the Department of Ecology TMDL Total Maximum Daily Load VFO Vancouver Field Office of the Department of Ecology WAC Washington Administrative Code WSDOT Washington Department of Transportation WWHM Western Washington Hydrology Model 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 2 1 Project Information Project/Site Name: Bethany Corner Street/Location: 16433 & 16451 111th Avenue SE City: Renton State: WA Zip code: 98055 Subdivision: N/A Receiving waterbody: Green/Duwamish River watershed 1.1 Existing Conditions Total acreage (including support activities such as off-site equipment staging yards, material storage areas, borrow areas). Total acreage: 1.96 Disturbed acreage: 1.96 Existing structures: 0.15 Landscape topography: 1.68 (estimate) Drainage patterns: 0.00 Existing Vegetation: 0.00 (estimate) Critical Areas (wetlands, streams, high erosion risk, steep or difficult to stabilize slopes): 0.01 Stream and adjacent wetland List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: Green River – Dissolved Oxygen, Temperature, Bioassessment, pH Table 1 includes a list of suspected and/or known contaminants associated with the construction activity. Table 1 – Summary of Site Pollutant Constituents Constituent (Pollutant) Location Depth Concentration No known contaminants exist on the Site 1.2 Proposed Construction Activities The applicant is seeking approval to subdivide 1.83 acres into nine single–family residential lots (Project), with lot sizes ranging from approximately 5,948 s.f. to 7,118 s.f. All existing improvements located on the Site will be demolished or removed during plat construction. The proposed impervious surface includes an internal plat road, Road A, which will have a proposed 53-foot right of way and will be improved with 26 feet of pavement ,vertical curbs, 8’ planter strip and 5’ sidewalks. Frontage improvements will be made to 111th AVE SE, including catch basins, vertical gutter, and 5 foot sidewalk. Lot improvements will include single family residential houses and associated driveways. The total proposed impervious area for the Site is 50,896 s.f. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 3 Construction work will be completed under the Site Development permit. Activities will include installation of sewer, water and dry utilities; installation of storm sewer; construction of stormwater detention vault; road and sidewalks; and landscaping. Runoff will be collected and conveyed to the proposed detention vault. Appendix A shows the Site Plan with T.E.S.C. measures. Final stabilization of the disturbed land will include: • Asphalt roadway • Concrete sidewalks • Formal landscape planting Contaminated Site Information: No known contamination exists on Site. Proposed activities regarding contaminated soils or groundwater (example: on-site treatment system, authorized sanitary sewer discharge): Not applicable as no known contamination. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 4 2 Construction Stormwater Best Management Practices (BMPs) The SWPPP is a living document reflecting current conditions and changes throughout the life of the project. These changes may be informal (i.e., hand-written notes and deletions). Update the SWPPP when the CESCL has noted a deficiency in BMPs or deviation from original design. 2.1 The 12 Elements 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits To protect adjacent properties and reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land-disturbing activities begin. Trees that are to be preserved, as well as all sensitive areas and their buffers, shall be clearly delineated, both in the field and on the plans. In general, natural vegetation and native topsoil shall be retained in an undisturbed state to the maximum extent possible. The BMPs relevant to marking the clearing limits that will be applied for this project include: The plastic or metal fence will be placed around the perimeter of the developable area of the Site. BMP will be implemented at the start of construction. Alternate BMPs for marking clearing limits are included in Appendix B as a quick reference tool for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the NPDES Construction Stormwater permit (as provided in Appendix D), the CESCL will promptly initiate the implementation of one or more of the alternative BMPs listed in Appendix B after the first sign that existing BMPs are ineffective or failing. List and describe BMPs: High Visibility Plastic or Metal Fence (BMP C103) Silt Fence (BMP C223) Installation Schedules: Installation will occur before all other activity. Inspection and Maintenance plan: Weekly Responsible Staff: CESCL 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 5 2.1.2 Element 2: Establish Construction Access Construction access or activities occurring on unpaved areas will be minimized, yet where necessary, access points shall be stabilized to minimize the tracking of sediment onto public roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent sediment from entering state waters. All wash wastewater shall be controlled on site. Construction entrances will be installed in the location of the proposed access entrance, located on 111th Avenue SE. Construction road and parking area stabilization will occur along this entrance. List and describe BMPs: Stabilized Construction Entrance (BMP C105) Construction Road/Parking Area Stabilization (BMP C107) Installation Schedules: Installation will occur after the clearing limits are marked. Inspection and Maintenance plan: Weekly Responsible Staff: CESCL 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 6 2.1.3 Element 3: Control Flow Rates In order to protect the properties and waterways downstream of the project site, stormwater discharges from the site will be controlled. Once the detention vault is constructed, it will be utilized during construction as a flow control and sedimentation device. Discharge from the vault will be conveyed south to the existing storm conveyance system located in 111th Avenue SE. Alternate flow control BMPs are included in Appendix B as a quick reference tool for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the NPDES Construction Stormwater permit (as provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs listed in Appendix B after the first sign that existing BMPs are ineffective or failing. The project site is located west of the Cascade Mountain Crest. As such, the project must comply with Minimum Requirement 7 (Ecology 2005). In general, discharge rates of stormwater from the site will be controlled where increases in impervious area or soil compaction during construction could lead to downstream erosion, or where necessary to meet local agency stormwater discharge requirements (e.g. discharge to combined sewer systems). Will you construct stormwater retention and/or detention facilities? Yes No Will you use permanent infiltration ponds or other low impact development (example: rain gardens, bio-retention, porous pavement) to control flow during construction? Yes No List and describe BMPs: Sediment Trap (BMP C240) Installation Schedules: Installation will occur before any grading occurs. Inspection and Maintenance plan: Weekly Responsible Staff: CESCL 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 7 2.1.4 Element 4: Install Sediment Controls Silt fence will be installed around the perimeter of the Site in areas where runoff could sheet- flow offsite. This BMP will be installed at the start of construction. Alternate sediment control BMPs are included in Appendix B as a quick reference tool for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the NPDES Construction Stormwater permit (as provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs listed in Appendix B after the first sign that existing BMPs are ineffective or failing. In addition, sediment will be removed from paved areas in and adjacent to construction work areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on vehicle tires away from the site and to minimize washoff of sediments from adjacent streets in runoff. Whenever possible, sediment laden water shall be discharged into onsite, relatively level, vegetated areas (BMP C240 paragraph 5, page 4-102). In some cases, sediment discharge in concentrated runoff can be controlled using permanent stormwater BMPs (e.g., infiltration swales, ponds, trenches). Sediment loads can limit the effectiveness of some permanent stormwater BMPs, such as those used for infiltration or biofiltration; however, those BMPs designed to remove solids by settling (wet ponds or detention ponds) can be used during the construction phase. When permanent stormwater BMPs will be used to control sediment discharge during construction, the structure will be protected from excessive sedimentation with adequate erosion and sediment control BMPs. Any accumulated sediment shall be removed after construction is complete and the permanent stormwater BMP will be restabilized with vegetation per applicable design requirements once the remainder of the site has been stabilized. The following BMPs will be implemented as end-of-pipe sediment controls as required to meet permitted turbidity limits in the site discharge(s). Prior to the implementation of these technologies, sediment sources and erosion control and soil stabilization BMP efforts will be maximized to reduce the need for end-of-pipe sedimentation controls. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 8 List and describe BMPs: Silt Fence (BMP C233) Interceptor Swale (BMP C200) Storm Drain Inlet Protection (BMP C220) Sediment Trap (BMP C240) Installation Schedules: These will all be installed before any grading occurs. Inspection and Maintenance plan: Weekly Responsible Staff: CESCL 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 9 2.1.5 Element 5: Stabilize Soils Temporary seeding and cover measures may be required for interim grading activity and at soil stockpiles. Permanent Seeding will occur as grading is completed. All stabilized sections will be seeded and vegetated. Nets and Blankets along with Plastic Covering will be used on all slopes of 2:1 as shown on the plan. Dust Control will occur throughout the site as deemed necessary by the contractor and CESCL. Alternate soil stabilization BMPs are included in Appendix B as a quick reference tool for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the NPDES Construction Stormwater permit (as provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs listed in Appendix B after the first sign that existing BMPs are ineffective or failing. In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be temporarily covered with plastic sheeting. All stockpiled soils shall be stabilized from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. West of the Cascade Mountains Crest Season Dates Number of Days Soils Can be Left Exposed During the Dry Season May 1 – September 30 7 days During the Wet Season October 1 – April 30 2 days Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. Anticipated project dates: Start date: TBD End date: TBD Will you construct during the wet season? Yes No List and describe BMPs: Temporary and Permanent Seeding (BMP C120) Nets and Blankets (BMP C122) Plastic Covering (BMP C123) Dust Control (BMP C140) Installation Schedules: These will all be installed before any grading occurs. Inspection and Maintenance plan: Weekly Responsible Staff: CESCL 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 10 2.1.6 Element 6: Protect Slopes Temporary slope protection measures may be required for interim grading activity and at soil stockpiles. Permanent Seeding will occur throughout the site as slopes are stabilized. Nets and Blankets along with Plastic Covering will be used on all slopes of 2:1 Checks Dams will be installed every 50’ as shown on the plan. Alternate slope protection BMPs are included in Appendix B as a quick reference tool for the onsite inspector in the event the BMP(s) listed above are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix D). To avoid potential erosion and sediment control issues that may cause a violation(s) of the NPDES Construction Stormwater permit (as provided in Appendix D), the Certified Erosion and Sediment Control Lead will promptly initiate the implementation of one or more of the alternative BMPs listed in Appendix B after the first sign that existing BMPs are ineffective or failing. Will steep slopes be present at the site during construction? Yes No List and describe BMPs: Temporary and Permanent Seeding (BMP C120) Nets and Blankets (BMP C122) Plastic Covering (BMP C123) Check Dams (BMP C207) Installation Schedules: In general, cut and fill slopes will be stabilized as soon as possible and soil stockpiles will be temporarily covered with plastic sheeting. Inspection and Maintenance plan: Weekly Responsible Staff: CESCL 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 11 2.1.7 Element 7: Protect Drain Inlets All storm drain inlets and culverts made operable during construction shall be protected to prevent unfiltered or untreated water from entering the drainage conveyance system. However, the first priority is to keep all access roads clean of sediment and keep street wash water separate from entering storm drains until treatment can be provided. Storm Drain Inlet Protection (BMP C220) will be implemented for all drainage inlets and culverts that could potentially be impacted by sediment-laden runoff on and near the project site. The following inlet protection measures will be applied on this project: • Storm Drain Inlet Protection (BMP C220) There are several existing catch basins which will require filters. If the BMP options listed above are deemed ineffective or inappropriate during construction to satisfy the requirements set forth in the General NPDES Permit (Appendix D), or if no BMPs are listed above but deemed necessary during construction, the Certified Erosion and Sediment Control Lead shall implement one or more of the alternative BMP inlet protection options listed in Appendix B. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 12 2.1.8 Element 8: Stabilize Channels and Outlets Rip Rap (BMP C209) will be provided at all outlets. Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches, will be installed at the outlets of all conveyance systems. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 13 2.1.9 Element 9: Control Pollutants All pollutants, including waste materials and demolition debris, that occur onsite shall be handled and disposed of in a manner that does not cause contamination of stormwater. Good housekeeping and preventative measures will be taken to ensure that the site will be kept clean, well-organized, and free of debris. If required, BMPs to be implemented to control specific sources of pollutants are discussed below. Vehicles, construction equipment, and/or petroleum product storage/dispensing: • All vehicles, equipment, and petroleum product storage/dispensing areas will be inspected regularly to detect any leaks or spills, and to identify maintenance needs to prevent leaks or spills. • On-site fueling tanks and petroleum product storage containers shall include secondary containment. • Spill prevention measures, such as drip pans, will be used when conducting maintenance and repair of vehicles or equipment. • In order to perform emergency repairs on site, temporary plastic will be placed beneath and, if raining, over the vehicle. • Contaminated surfaces shall be cleaned immediately following any discharge or spill incident. Demolition: • Dust released from demolished sidewalks, buildings, or structures will be controlled using Dust Control measures (BMP C140). • Storm drain inlets vulnerable to stormwater discharge carrying dust, soil, or debris will be protected using Storm Drain Inlet Protection (BMP C220 as described above for Element 7). • Process water and slurry resulting from sawcutting and surfacing operations will be prevented from entering the waters of the State by implementing Sawcutting and Surfacing Pollution Prevention measures (BMP C152). Concrete and grout: • Process water and slurry resulting from concrete work will be prevented from entering the waters of the State by implementing Concrete Handling measures (BMP C151). Sanitary wastewater: • Portable sanitation facilities will be firmly secured, regularly maintained, and emptied when necessary. Solid Waste: • Solid waste will be stored in secure, clearly marked containers. Other: • Other BMPs will be administered as necessary to address any additional pollutant sources on site. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 14 The project is not expected to exceed the 1,320 gallon stored-fuel threshold that requires developing a Spill Prevention, Control, and Countermeasure (SPCC) Plan under the Federal regulations of the Clean Water Act (CWA). List and describe BMPs: Dust Control measures (BMP C140) Concrete Handling measures (BMP C151) Sawcutting and Surfacing Pollution Prevention measures (BMP C152) Storm Drain Inlet Protection (BMP C220) Installation Schedules: Immediately following or in conjunction with activities. Inspection and Maintenance plan: Weekly Responsible Staff: CESCL Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site? Yes No List and describe BMPs: N/A Installation Schedules: N/A Inspection and Maintenance plan: Weekly Responsible Staff: CESCL Will wheel wash or tire bath system BMPs be used during construction? Yes No List and describe BMPs: Presently not anticipated . SWPPP to be amended if wheel wash proves necessary. Installation Schedules: TBD Inspection and Maintenance plan: Weekly Responsible Staff: CESCL Will pH-modifying sources be present on-site? 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 15 Yes No Table 3 – pH-Modifying Sources None Bulk cement Cement kiln dust Fly ash Other cementitious materials New concrete washing or curing waters Waste streams generated from concrete grinding and sawing Exposed aggregate processes Dewatering concrete vaults Concrete pumping and mixer washout waters Recycled concrete Other (i.e., calcium lignosulfate) [please describe: ] List and describe BMPs: Specific pH treatment measures to be determined by contractor and CECSL. Presently, CO2 sparging or dry ice anticipated approach if pH must be altered. Installation Schedules: prior to placement of concrete Inspection and Maintenance plan: Monitoring will occur at the time of concrete wash operations. Responsible Staff: CESCL Concrete trucks must not be washed out onto the ground, or into storm drains, open ditches, streets, or streams. Excess concrete must not be dumped on-site, except in designated concrete washout areas with appropriate BMPs installed. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 16 2.1.10 Element 10: Control Dewatering There will be no dewatering as part of this construction project. If excavation results in the requirement of dewatering, this SWPPP can be modified to include dewatering measures including control of discharge waters. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 17 2.1.11 Element 11: Maintain BMPs All temporary and permanent Erosion and Sediment Control (ESC) BMPs shall be maintained and repaired as needed to ensure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with each particular BMP specification (see Volume II of the SWMMWW or Chapter 7 of the SWMMEW). Visual monitoring of all BMPs installed at the site will be conducted at least once every calendar week and within 24 hours of any stormwater or non-stormwater discharge from the site. If the site becomes inactive and is temporarily stabilized, the inspection frequency may be reduced to once every calendar month. All temporary ESC BMPs shall be removed within 30 days after final site stabilization is achieved or after the temporary BMPs are no longer needed. Trapped sediment shall be stabilized on-site or removed. Disturbed soil resulting from removal of either BMPs or vegetation shall be permanently stabilized. Additionally, protection must be provided for all BMPs installed for the permanent control of stormwater from sediment and compaction. BMPs that are to remain in place following completion of construction shall be examined and restored to full operating condition. If sediment enters these BMPs during construction, the sediment shall be removed and the facility shall be returned to conditions specified in the construction documents. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 18 2.1.12 Element 12: Manage the Project Project management will incorporate the key components listed below: Table 5 – Management Design the project to fit the existing topography, soils, and drainage patterns Emphasize erosion control rather than sediment control Minimize the extent and duration of the area exposed Keep runoff velocities low Retain sediment on-site Thoroughly monitor site and maintain all ESC measures Schedule major earthwork during the dry season Other (please describe) As this project site is located west of the Cascade Mountain Crest, the project will be managed according to the following key project components: Phasing of Construction • The construction project is being phased to the extent practicable in order to prevent soil erosion, and, to the maximum extent possible, the transport of sediment from the site during construction. • Revegetation of exposed areas and maintenance of that vegetation shall be an integral part of the clearing activities during each phase of construction, per the Scheduling BMP (C 162). Seasonal Work Limitations • From October 1 through April 30, clearing, grading, and other soil disturbing activities shall only be permitted if shown to the satisfaction of the local permitting authority that silt-laden runoff will be prevented from leaving the site through a combination of the following: o Site conditions including existing vegetative coverage, slope, soil type, and proximity to receiving waters; and o Limitations on activities and the extent of disturbed areas; and o Proposed erosion and sediment control measures. • Based on the information provided and/or local weather conditions, the local permitting authority may expand or restrict the seasonal limitation on site disturbance. • The following activities are exempt from the seasonal clearing and grading limitations: o Routine maintenance and necessary repair of erosion and sediment control BMPs; o Routine maintenance of public facilities or existing utility structures that do not expose the soil or result in the removal of the vegetative cover to soil; and o Activities where there is 100 percent infiltration of surface water runoff within the site in approved and installed erosion and sediment control facilities. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 19 Coordination with Utilities and Other Jurisdictions • Care has been taken to coordinate with utilities, other construction projects, and the local jurisdiction in preparing this SWPPP and scheduling the construction work. Inspection and Monitoring • All BMPs shall be inspected, maintained, and repaired as needed to assure continued performance of their intended function. Site inspections shall be conducted by a person who is knowledgeable in the principles and practices of erosion and sediment control. This person has the necessary skills to: o Assess the site conditions and construction activities that could impact the quality of stormwater, and o Assess the effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. • A Certified Erosion and Sediment Control Lead shall be on-site or on-call at all times. • Whenever inspection and/or monitoring reveals that the BMPs identified in this SWPPP are inadequate, due to the actual discharge of or potential to discharge a significant amount of any pollutant, appropriate BMPs or design changes shall be implemented as soon as possible. Maintaining an Updated Construction SWPPP • This SWPPP shall be retained on-site or within reasonable access to the site. • The SWPPP shall be modified whenever there is a change in the design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the state. • The SWPPP shall be modified if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The SWPPP shall be modified as necessary to include additional or modified BMPs designed to correct problems identified. Revisions to the SWPPP shall be completed within seven (7) days following the inspection. • If BMP(s) are deemed do not satisfy the requirements set forth in the General NPDES Permit (Appendix D), the CESCL will promptly implement one or more of the alternative BMPs listed in Appendix B after the first sign that existing BMPs are ineffective or failing. • Site inspections and monitoring will be conducted in accordance with Special Condition S4 of the CSWGP. Sampling will occur at the baker tank discharge piping. • The SWPPP will be updated, maintained, and implemented in accordance with Special Conditions S3, S4, and S9 of the CSWGP. • As site work progresses the SWPPP will be modified routinely to reflect changing site conditions. The SWPPP will be reviewed monthly to ensure the content is current. • Upon request, contractor shall provide the DOE and City of Sammamish with current SWPPP. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 20 3 Pollution Prevention Team Table 7 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) Associated Earth Sciences, Inc. 425.827.7701 Resident Engineer Jonathan S. Murray, PE 425-827-3063 Emergency Ecology Contact Howard Zorzi 425-649-7130 Emergency Permittee/ Owner Contact Mark Seek 206-315-8130 Non-Emergency Owner Contact Mark Seek 206-315-8130 Monitoring Personnel Associated Earth Sciences, Inc. 425.827.7701 Ecology Regional Office Northwest Regional Office 425-649-7000 City Spill Hotline (8:00 am to 5:00 pm) 425-295-0500 King County Spill Hotline (After Hours) 206-296-8100 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 21 4 Monitoring and Sampling Requirements Monitoring includes visual inspection, sampling for water quality parameters of concern, and documentation of the inspection and sampling findings in a site log book. A site log book will be maintained for all on-site construction activities and will include: • A record of the implementation of the SWPPP and other permit requirements • Site inspections • Stormwater sampling data File a blank form under Appendix D. The site log book must be maintained on-site within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. Numeric effluent limits may be required for certain discharges to 303(d) listed waterbodies. See CSWGP Special Condition S8 and Section 5 of this template. 4.1 Site Inspection All BMPs will be inspected, maintained, and repaired as needed to assure continued performance of their intended function. The inspector will be a Certified Erosion and Sediment Control Lead (CESCL) per BMP C160. The name and contact information for the CESCL is provided in Section 3 of this SWPPP. Site inspection will occur in all areas disturbed by construction activities and at all stormwater discharge points. Stormwater will be examined for the presence of suspended sediment, turbidity, discoloration, and oily sheen. The site inspector will evaluate and document the effectiveness of the installed BMPs and determine if it is necessary to repair or replace any of the BMPs to improve the quality of stormwater discharges. All maintenance and repairs will be documented in the site log book or forms provided in this document. All new BMPs or design changes will be documented in the SWPPP as soon as possible. Site inspections will be conducted at least once every calendar week and within 24 hours following any discharge from the site. For sites that are temporarily stabilized and inactive, the required frequency is reduced to once per calendar month. The site inspector will record each site inspection using the site log inspection forms provided in Appendix E. The site inspection log forms may be separated from this SWPPP document, but will be maintained on-site or within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. 4.2 Stormwater Quality Sampling Runoff will be collected and conveyed to the proposed vault, followed by a StormFilter media filtration system to meet Enhanced Water Quality requirements. Testing will occur as deemed necessary by the CESCL. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 22 4.2.1 Turbidity Sampling Requirements include calibrated turbidity meter or transparency tube to sample site discharges for compliance with the CSWGP. Sampling will be conducted at all discharge points at least once per calendar week. Method for sampling turbidity: Table 8 – Turbidity Sampling Method Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size) Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size) The benchmark for turbidity value is 25 nephelometric turbidity units (NTU) and a transparency less than 33 centimeters. If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to or greater than 6 cm, the following steps will be conducted: 1. Review the SWPPP for compliance with Special Condition S9. Make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. 3. Document BMP implementation and maintenance in the site log book. If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following steps will be conducted: 1. Telephone the applicable Ecology Region’s Environmental Report Tracking System (ERTS) number within 24 hours. • Central Region (Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, Yakima): (509) 575-2490 • Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman): (509) 329-3400 • Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish, Whatcom): (425) 649-7000 • Southwest Region (Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, Wahkiakum,): (360) 407-6300 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period 3. Document BMP implementation and maintenance in the site log book. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 23 4. Continue to sample discharges daily until one of the following is true: • Turbidity is 25 NTU (or lower). • Transparency is 33 cm (or greater). • Compliance with the water quality limit for turbidity is achieved. o 1 - 5 NTU over background turbidity, if background is less than 50 NTU o 1% - 10% over background turbidity, if background is 50 NTU or greater • The discharge stops or is eliminated. 4.2.2 pH Sampling pH monitoring is required for “Significant concrete work” (i.e., greater than 1000 cubic yards poured or recycled concrete over the life of the project). The use of engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD] or fly ash) also requires pH monitoring. For significant concrete work, pH sampling will start the first day concrete is poured and continue until it is cured, typically three (3) weeks after the last pour. For engineered soils, pH sampling begins when engineered soils are first exposed to precipitation and continues until the area is fully stabilized. If the measured pH is 8.5 or greater, the following measures will be taken: 1. Prevent high pH water from entering storm sewer systems or surface water. 2. Adjust or neutralize the high pH water to the range of 6.5 to 8.5 su using appropriate technology such as carbon dioxide (CO2) sparging (liquid or dry ice). 3. Written approval will be obtained from Ecology prior to the use of chemical treatment other than CO2 sparging or dry ice. Method for sampling pH: Table 9 – pH Sampling Method pH meter pH test kit Wide range pH indicator paper Not: pH monitoring equipment unknown at this time; to be determined by CESCL 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 24 5 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies 5.1 303(d) Listed Waterbodies Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH? Yes No List the impairment(s): Green River - pH 5.2 TMDL Waterbodies Waste Load Allocation for CWSGP discharges: List and describe BMPs: Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point of discharge. The Construction Stormwater General Permit Proposed New Discharge to an Impaired Water Body form is included in Appendix F. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 25 6 Reporting and Record Keeping 6.1 Record Keeping 6.1.1 Site Log Book A site log book will be maintained for all on-site construction activities and will include: • A record of the implementation of the SWPPP and other permit requirements • Site inspections • Sample logs 6.1.2 Records Retention Records will be retained during the life of the project and for a minimum of three (3) years following the termination of permit coverage in accordance with Special Condition S5.C of the CSWGP. Permit documentation to be retained on-site: • CSWGP • Permit Coverage Letter • SWPPP • Site Log Book Permit documentation will be provided within 14 days of receipt of a written request from Ecology. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with Special Condition S5.G.2.b of the CSWGP. 6.1.3 Updating the SWPPP The SWPPP will be modified if: • Found ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. • There is a change in design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the State. The SWPPP will be modified within seven (7) days if inspection(s) or investigation(s) determine additional or modified BMPs are necessary for compliance. An updated timeline for BMP implementation will be prepared. 6.2 Reporting 6.2.1 Discharge Monitoring Reports Cumulative soil disturbance is one (1) acre or larger; therefore, Discharge Monitoring Reports (DMRs) will be submitted to Ecology monthly. If there was no discharge during a given 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page 26 monitoring period the DMR will be submitted as required, reporting “No Discharge”. The DMR due date is fifteen (15) days following the end of each calendar month. DMRs will be reported online through Ecology’s WQWebDMR System. 6.2.2 Notification of Noncompliance If any of the terms and conditions of the permit is not met, and the resulting noncompliance may cause a threat to human health or the environment, the following actions will be taken: 1. Ecology will be immediately notified of the failure to comply by calling the applicable Regional office ERTS phone number (Regional office numbers listed below). 2. Immediate action will be taken to prevent the discharge/pollution or otherwise stop or correct the noncompliance. If applicable, sampling and analysis of any noncompliance will be repeated immediately and the results submitted to Ecology within five (5) days of becoming aware of the violation. 3. A detailed written report describing the noncompliance will be submitted to Ecology within five (5) days, unless requested earlier by Ecology. Anytime turbidity sampling indicates turbidity is 250 NTUs or greater, or water transparency is 6 cm or less, the Ecology Regional office will be notified by phone within 24 hours of analysis as required by Special Condition S5.A of the CSWGP. • Central Region at (509) 575-2490 for Benton, Chelan, Douglas, Kittitas, Klickitat, Okanogan, or Yakima County • Eastern Region at (509) 329-3400 for Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, or Whitman County • Northwest Region at (425) 649-7000 for Island, King, Kitsap, San Juan, Skagit, Snohomish, or Whatcom County • Southwest Region at (360) 407-6300 for Clallam, Clark, Cowlitz, Grays Harbor, Jefferson, Lewis, Mason, Pacific, Pierce, Skamania, Thurston, or Wahkiakum Include the following information: 1. Your name and / Phone number 2. Permit number 3. City / County of project 4. Sample results 5. Date / Time of call 6. Date / Time of sample 7. Project name In accordance with Special Condition S4.D.5.b of the CSWGP, the Ecology Regional office will be notified if chemical treatment other than CO2 sparging is planned for adjustment of high pH water. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page A-1 Appendix A Site Map IN COMPLIANCE WITH CITY OF RENTON STANDARDS GRAPHIC SCALE01530 60 1 INCH = 30 FT. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page B-1 Appendix B BMP Details 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page C-1 Appendix C Correspondence None at this time. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page D-1 Appendix D Site Inspection Form The results of each inspection shall be summarized in an inspection report or checklist that is entered into or attached to the site log book. It is suggested that the inspection report or checklist be included in this appendix to keep monitoring and inspection information in one document, but this is optional. However, it is mandatory that this SWPPP and the site inspection forms be kept onsite at all times during construction, and that inspections be performed and documented as outlined below. At a minimum, each inspection report or checklist shall include: Inspection date/times Weather information: general conditions during inspection, approximate amount of precipitation since the last inspection, and approximate amount of precipitation within the last 24 hours. A summary or list of all BMPs that have been implemented, including observations of all erosion/sediment control structures or practices. The following shall be noted: locations of BMPs inspected, locations of BMPs that need maintenance, the reason maintenance is needed, locations of BMPs that failed to operate as designed or intended, and locations where additional or different BMPs are needed, and the reason(s) why A description of stormwater discharged from the site. The presence of suspended sediment, turbid water, discoloration, and/or oil sheen shall be noted, as applicable. A description of any water quality monitoring performed during inspection, and the results of that monitoring. General comments and notes, including a brief description of any BMP repairs, maintenance or installations made as a result of the inspection. A statement that, in the judgment of the person conducting the site inspection, the site is either in compliance or out of compliance with the terms and conditions of the SWPPP and the NPDES permit. If the site inspection indicates that the site is out of compliance, the inspection report shall include a summary of the remedial actions required to bring the site back into compliance, as well as a schedule of implementation. Name, title, and signature of person conducting the site inspection; and the following statement: “I certify under penalty of law that this report is true, accurate, and complete, to the best of my knowledge and belief”. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page D-2 When the site inspection indicates that the site is not in compliance with any terms and conditions of the NPDES permit, the Permittee shall take immediate action(s) to: stop, contain, and clean up the unauthorized discharges, or otherwise stop the noncompliance; correct the problem(s); implement appropriate Best Management Practices (BMPs), and/or conduct maintenance of existing BMPs; and achieve compliance with all applicable standards and permit conditions. In addition, if the noncompliance causes a threat to human health or the environment, the Permittee shall comply with the Noncompliance Notification requirements in Special Condition S5.F of the permit. Construction Stormwater Site Inspection Form 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page D-3 Project Name Permit #: Date: Time: Name of Certified Erosion Sediment Control Lead (CESCL) or qualified inspector if less than one acre Print Name: Approximate rainfall amount since the last inspection (in inches): Approximate rainfall amount in the last 24 hours (in inches): Current Weather Clear Cloudy Mist Rain Wind Fog A. Type of inspection: Weekly Post Storm Event Other B. Phase of Active Construction (check all that apply): Pre Construction/installation of erosion/sediment controls Clearing/Demo/Grading Infrastructure/storm/roads Concrete pours Vertical Construction/buildings Utilities Offsite improvements Site temporary stabilized Final stabilization C. Questions: 1. Were all areas of construction and discharge points inspected? Yes No 2. Did you observe the presence of suspended sediment, turbidity, discoloration, or oil sheen Yes No 3. Was a water quality sample taken during inspection? (refer to permit conditions S4 & S5) Yes No 4. Was there a turbid discharge 250 NTU or greater, or Transparency 6 cm or less?* Yes No 5. If yes to #4 was it reported to Ecology? Yes No 6. Is pH sampling required? pH range required is 6.5 to 8.5. Yes No If answering yes to a discharge, describe the event. Include when, where, and why it happened; what action was taken, and when. *If answering yes to # 4 record NTU/Transparency with continual sampling daily until turbidity is 25 NTU or less/ transparency is 33 cm or greater. Sampling Results: Date: Parameter Method (circle one) Result Other/Note NTU cm pH Turbidity tube, meter, laboratory pH Paper, kit, meter Construction Stormwater Site Inspection Form 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page D-4 D. Check the observed status of all items. Provide “Action Required “details and dates. Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 1 Clearing Limits Before beginning land disturbing activities are all clearing limits, natural resource areas (streams, wetlands, buffers, trees) protected with barriers or similar BMPs? (high visibility recommended) 2 Construction Access Construction access is stabilized with quarry spalls or equivalent BMP to prevent sediment from being tracked onto roads? Sediment tracked onto the road way was cleaned thoroughly at the end of the day or more frequent as necessary. 3 Control Flow Rates Are flow control measures installed to control stormwater volumes and velocity during construction and do they protect downstream properties and waterways from erosion? If permanent infiltration ponds are used for flow control during construction, are they protected from siltation? 4 Sediment Controls All perimeter sediment controls (e.g. silt fence, wattles, compost socks, berms, etc.) installed, and maintained in accordance with the Stormwater Pollution Prevention Plan (SWPPP). Sediment control BMPs (sediment ponds, traps, filters etc.) have been constructed and functional as the first step of grading. Stormwater runoff from disturbed areas is directed to sediment removal BMP. 5 Stabilize Soils Have exposed un-worked soils been stabilized with effective BMP to prevent erosion and sediment deposition? Are stockpiles stabilized from erosion, protected with sediment trapping measures and located away from drain inlet, waterways, and drainage channels? Have soils been stabilized at the end of the shift, before a holiday or weekend if needed based on the weather forecast? Construction Stormwater Site Inspection Form 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page D-5 Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 6 Protect Slopes Has stormwater and ground water been diverted away from slopes and disturbed areas with interceptor dikes, pipes and or swales? Is off-site storm water managed separately from stormwater generated on the site? Is excavated material placed on uphill side of trenches consistent with safety and space considerations? Have check dams been placed at regular intervals within constructed channels that are cut down a slope? 7 Drain Inlets Storm drain inlets made operable during construction are protected. Are existing storm drains within the influence of the project protected? 8 Stabilize Channel and Outlets Have all on-site conveyance channels been designed, constructed and stabilized to prevent erosion from expected peak flows? Is stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes and downstream conveyance systems? 9 Control Pollutants Are waste materials and demolition debris handled and disposed of to prevent contamination of stormwater? Has cover been provided for all chemicals, liquid products, petroleum products, and other material? Has secondary containment been provided capable of containing 110% of the volume? Were contaminated surfaces cleaned immediately after a spill incident? Were BMPs used to prevent contamination of stormwater by a pH modifying sources? Wheel wash wastewater is handled and disposed of properly. 10 Control Dewatering Concrete washout in designated areas. No washout or excess concrete on the ground. Dewatering has been done to an approved source and in compliance with the SWPPP. Were there any clean non turbid dewatering discharges? Construction Stormwater Site Inspection Form 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page D-6 Element # Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 11 Maintain BMP Are all temporary and permanent erosion and sediment control BMPs maintained to perform as intended? 12 Manage the Project Has the project been phased to the maximum degree practicable? Has regular inspection, monitoring and maintenance been performed as required by the permit? Has the SWPPP been updated, implemented and records maintained? E. Check all areas that have been inspected. All in place BMPs All discharge locations All concrete wash out areas All construction entrances/exits All disturbed soils All material storage areas All equipment storage areas F. Elements checked “Action Required” (section D) describe corrective action to be taken. List the element number; be specific on location and work needed. Document, initial, and date when the corrective action has been completed and inspected. Element # Description and Location Action Required Completion Date Initials Attach additional page if needed Sign the following certification: “I certify that this report is true, accurate, and complete, to the best of my knowledge and belief” Inspected by: Print Signature Title/Qualification of Inspector Date 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page F-2 Appendix E Construction Stormwater General Permit (CSWGP) Issuance Date: Effective Date: Expiration Date: November 18, 2015 January I, 2016 December 31, 2020 Modification Issuance Date: March 22, 2017 Modification Effective Date: May 5, 2017 CONSTRUCTION STORMW ATER GENERAL PERMIT National Pollutant Discharge Elimination System (NPDES) and State Waste Discharge General Permit for Stormwater Discharges Associated with Construction Activity State of Washington Department of Ecology Olympia, Washington 98504 In compliance with the provisions of Chapter 90.48 Revised Code of Washington (State of Washington Water Pollution Control Act) and Title 33 United States Code, Section 1251 et seq. The Federal Water Pollution Control Act (The Clean Water Act) Until this permit expires, is modified, or revoked, Permittees that have properly obtained coverage under this general permit are authorized to discharge in accordance with the special and general conditions that follow. her R. Bartlett Wa r Quality Program Manager Washington State Department of Ecology Construction Stormwater General Permit Page 2 TABLE OF CONTENTS LIST OF TABLES ...........................................................................................................................3 SUMMARY OF PERMIT REPORT SUBMITTALS .....................................................................4 SPECIAL CONDITIONS ................................................................................................................5 S1. PERMIT COVERAGE ........................................................................................................5 S2. APPLICATION REQUIREMENTS ...................................................................................8 S3. COMPLIANCE WITH STANDARDS .............................................................................12 S4. MONITORING REQUIREMENTS, BENCHMARKS, AND REPORTING TRIGGERS ................................................................................................13 S5. REPORTING AND RECORDKEEPING REQUIREMENTS .........................................20 S6. PERMIT FEES...................................................................................................................23 S7. SOLID AND LIQUID WASTE DISPOSAL ....................................................................23 S8. DISCHARGES TO 303(d) OR TMDL WATERBODIES ................................................23 S9. STORMWATER POLLUTION PREVENTION PLAN...................................................27 S10. NOTICE OF TERMINATION .........................................................................................37 GENERAL CONDITIONS ...........................................................................................................38 G1. DISCHARGE VIOLATIONS ...........................................................................................38 G2. SIGNATORY REQUIREMENTS.....................................................................................38 G3. RIGHT OF INSPECTION AND ENTRY .........................................................................39 G4. GENERAL PERMIT MODIFICATION AND REVOCATION ......................................39 G5. REVOCATION OF COVERAGE UNDER THE PERMIT .............................................39 G6. REPORTING A CAUSE FOR MODIFICATION ............................................................40 G7. COMPLIANCE WITH OTHER LAWS AND STATUTES .............................................40 G8. DUTY TO REAPPLY .......................................................................................................40 G9. TRANSFER OF GENERAL PERMIT COVERAGE .......................................................41 G10. REMOVED SUBSTANCES .............................................................................................41 G11. DUTY TO PROVIDE INFORMATION ...........................................................................41 G12. OTHER REQUIREMENTS OF 40 CFR ...........................................................................41 G13. ADDITIONAL MONITORING ........................................................................................41 G14. PENALTIES FOR VIOLATING PERMIT CONDITIONS .............................................41 G15. UPSET ...............................................................................................................................42 G16. PROPERTY RIGHTS ........................................................................................................42 Construction Stormwater General Permit Page 3 G17. DUTY TO COMPLY ........................................................................................................42 G18. TOXIC POLLUTANTS.....................................................................................................42 G19. PENALTIES FOR TAMPERING .....................................................................................43 G20. REPORTING PLANNED CHANGES .............................................................................43 G21. REPORTING OTHER INFORMATION ..........................................................................43 G22. REPORTING ANTICIPATED NON-COMPLIANCE .....................................................43 G23. REQUESTS TO BE EXCLUDED FROM COVERAGE UNDER THE PERMIT ..........44 G24. APPEALS ..........................................................................................................................44 G25. SEVERABILITY ...............................................................................................................44 G26. BYPASS PROHIBITED ....................................................................................................44 APPENDIX A – DEFINITIONS ...................................................................................................47 APPENDIX B – ACRONYMS .....................................................................................................55 LIST OF TABLES Table 1: Summary of Required Submittals ................................................................................... 4 Table 2: Summary of Required On-site Documentation............................................................... 4 Table 3: Summary of Primary Monitoring Requirements .......................................................... 15 Table 4: Monitoring and Reporting Requirements ..................................................................... 17 Table 5: Turbidity, Fine Sediment & Phosphorus Sampling and Limits for 303(d)-Listed Waters .................................................................................................... 25 Table 6: pH Sampling and Limits for 303(d)-Listed Waters ...................................................... 26 Construction Stormwater General Permit Page 4 SUMMARY OF PERMIT REPORT SUBMITTALS Refer to the Special and General Conditions within this permit for additional submittal requirements. Appendix A provides a list of definitions. Appendix B provides a list of acronyms. Table 1: Summary of Required Submittals Permit Section Submittal Frequency First Submittal Date S5.A and S8 High Turbidity/Transparency Phone Reporting As Necessary Within 24 hours S5.B Discharge Monitoring Report Monthly* Within 15 days following the end of each month S5.F and S8 Noncompliance Notification – Telephone Notification As necessary Within 24-hours S5.F Noncompliance Notification – Written Report As necessary Within 5 Days of non- compliance S9.C Request for Chemical Treatment Form As necessary Written approval from Ecology is required prior to using chemical treatment (with the exception of dry ice or CO2 to adjust pH) G2 Notice of Change in Authorization As necessary G6 Permit Application for Substantive Changes to the Discharge As necessary G8 Application for Permit Renewal 1/permit cycle No later than 180 days before expiration G9 Notice of Permit Transfer As necessary G20 Notice of Planned Changes As necessary G22 Reporting Anticipated Non- compliance As necessary SPECIAL NOTE: *Permittees must submit electronic Discharge Monitoring Reports (DMRs) to the Washington State Department of Ecology monthly, regardless of site discharge, for the full duration of permit coverage. Refer to Section S5.B of this General Permit for more specific information regarding DMRs. Table 2: Summary of Required On-site Documentation Document Title Permit Conditions Permit Coverage Letter See Conditions S2, S5 Construction Stormwater General Permit See Conditions S2, S5 Site Log Book See Conditions S4, S5 Stormwater Pollution Prevention Plan (SWPPP) See Conditions S9, S5 Construction Stormwater General Permit Page 5 SPECIAL CONDITIONS S1. PERMIT COVERAGE A. Permit Area This Construction Stormwater General Permit (CSWGP) covers all areas of Washington State, except for federal operators and Indian Country as specified in Special Condition S1.E.3. B. Operators Required to Seek Coverage Under this General Permit: 1. Operators of the following construction activities are required to seek coverage under this CSWGP: a. Clearing, grading and/or excavation that results in the disturbance of one or more acres (including off-site disturbance acreage authorized in S1.C.2) and discharges stormwater to surface waters of the State; and clearing, grading and/or excavation on sites smaller than one acre that are part of a larger common plan of development or sale, if the common plan of development or sale will ultimately disturb one acre or more and discharge stormwater to surface waters of the State. i. This includes forest practices (including, but not limited to, class IV conversions) that are part of a construction activity that will result in the disturbance of one or more acres, and discharge to surface waters of the State (that is, forest practices that prepare a site for construction activities); and b. Any size construction activity discharging stormwater to waters of the State that the Washington State Department of Ecology (Ecology): i. Determines to be a significant contributor of pollutants to waters of the State of Washington. ii. Reasonably expects to cause a violation of any water quality standard. 2. Operators of the following activities are not required to seek coverage under this CSWGP (unless specifically required under Special Condition S1.B.1.b. above): a. Construction activities that discharge all stormwater and non-stormwater to ground water, sanitary sewer, or combined sewer, and have no point source discharge to either surface water or a storm sewer system that drains to surface waters of the State. b. Construction activities covered under an Erosivity Waiver (Special Condition S2.C). c. Routine maintenance that is performed to maintain the original line and grade, hydraulic capacity, or original purpose of a facility. Construction Stormwater General Permit Page 6 C. Authorized Discharges: 1. Stormwater Associated with Construction Activity. Subject to compliance with the terms and conditions of this permit, Permittees are authorized to discharge stormwater associated with construction activity to surface waters of the State or to a storm sewer system that drains to surface waters of the State. (Note that “surface waters of the State” may exist on a construction site as well as off site; for example, a creek running through a site.) 2. Stormwater Associated with Construction Support Activity. This permit also authorizes stormwater discharge from support activities related to the permitted construction site (for example, an on-site portable rock crusher, off-site equipment staging yards, material storage areas, borrow areas, etc.) provided: a. The support activity relates directly to the permitted construction site that is required to have an NPDES permit; and b. The support activity is not a commercial operation serving multiple unrelated construction projects, and does not operate beyond the completion of the construction activity; and c. Appropriate controls and measures are identified in the Stormwater Pollution Prevention Plan (SWPPP) for the discharges from the support activity areas. 3. Non-Stormwater Discharges. The categories and sources of non-stormwater discharges identified below are authorized conditionally, provided the discharge is consistent with the terms and conditions of this permit: a. Discharges from fire-fighting activities. b. Fire hydrant system flushing. c. Potable water, including uncontaminated water line flushing. d. Hydrostatic test water. e. Uncontaminated air conditioning or compressor condensate. f. Uncontaminated ground water or spring water. g. Uncontaminated excavation dewatering water (in accordance with S9.D.10). h. Uncontaminated discharges from foundation or footing drains. i. Uncontaminated or potable water used to control dust. Permittees must minimize the amount of dust control water used. j. Routine external building wash down that does not use detergents. k. Landscape irrigation water. The SWPPP must adequately address all authorized non-stormwater discharges, except for discharges from fire-fighting activities, and must comply with Special Condition S3. Construction Stormwater General Permit Page 7 At a minimum, discharges from potable water (including water line flushing), fire hydrant system flushing, and pipeline hydrostatic test water must undergo the following: dechlorination to a concentration of 0.1 parts per million (ppm) or less, and pH adjustment to within 6.5 – 8.5 standard units (su), if necessary. D. Prohibited Discharges: The following discharges to waters of the State, including ground water, are prohibited. 1. Concrete wastewater. 2. Wastewater from washout and clean-up of stucco, paint, form release oils, curing compounds and other construction materials. 3. Process wastewater as defined by 40 Code of Federal Regulations (CFR) 122.2 (see Appendix A of this permit). 4. Slurry materials and waste from shaft drilling, including process wastewater from shaft drilling for construction of building, road, and bridge foundations unless managed according to Special Condition S9.D.9.j. 5. Fuels, oils, or other pollutants used in vehicle and equipment operation and maintenance. 6. Soaps or solvents used in vehicle and equipment washing. 7. Wheel wash wastewater, unless managed according to Special Condition S9.D.9. 8. Discharges from dewatering activities, including discharges from dewatering of trenches and excavations, unless managed according to Special Condition S9.D.10. E. Limits on Coverage Ecology may require any discharger to apply for and obtain coverage under an individual permit or another more specific general permit. Such alternative coverage will be required when Ecology determines that this CSWGP does not provide adequate assurance that water quality will be protected, or there is a reasonable potential for the project to cause or contribute to a violation of water quality standards. The following stormwater discharges are not covered by this permit: 1. Post-construction stormwater discharges that originate from the site after completion of construction activities and the site has undergone final stabilization. 2. Non-point source silvicultural activities such as nursery operations, site preparation, reforestation and subsequent cultural treatment, thinning, prescribed burning, pest and fire control, harvesting operations, surface drainage, or road construction and maintenance, from which there is natural runoff as excluded in 40 CFR Subpart 122. 3. Stormwater from any federal operator. Construction Stormwater General Permit Page 8 4. Stormwater from facilities located on “Indian Country” as defined in 18 U.S.C.§1151, except portions of the Puyallup Reservation as noted below. Indian Country includes: a. All land within any Indian Reservation notwithstanding the issuance of any patent, and, including rights-of-way running through the reservation. This includes all federal, tribal, and Indian and non-Indian privately owned land within the reservation. b. All off-reservation Indian allotments, the Indian titles to which have not been extinguished, including rights-of-way running through the same. c. All off-reservation federal trust lands held for Native American Tribes. Puyallup Exception: Following the Puyallup Tribes of Indians Land Settlement Act of 1989, 25 U.S.C. §1773; the permit does apply to land within the Puyallup Reservation except for discharges to surface water on land held in trust by the federal government. 5. Stormwater from any site covered under an existing NPDES individual permit in which stormwater management and/or treatment requirements are included for all stormwater discharges associated with construction activity. 6. Stormwater from a site where an applicable Total Maximum Daily Load (TMDL) requirement specifically precludes or prohibits discharges from construction activity. S2. APPLICATION REQUIREMENTS A. Permit Application Forms 1. Notice of Intent Form/Timeline a. Operators of new or previously unpermitted construction activities must submit a complete and accurate permit application (Notice of Intent, or NOI) to Ecology. b. Operators must apply using the electronic application form (NOI) available on Ecology’s website http://www.ecy.wa.gov/programs/wq/stormwater/ construction/index.html. Permittees unable to submit electronically (for example, those who do not have an internet connection) must contact Ecology to request a waiver and obtain instructions on how to obtain a paper NOI. Department of Ecology Water Quality Program - Construction Stormwater PO Box 47696 Olympia, Washington 98504-7696 Construction Stormwater General Permit Page 9 c. The operator must submit the NOI at least 60 days before discharging stormwater from construction activities and must submit it on or before the date of the first public notice (see Special Condition S2.B below for details). The 30- day public comment period begins on the publication date of the second public notice. Unless Ecology responds to the complete application in writing, based on public comments, or any other relevant factors, coverage under the general permit will automatically commence on the thirty-first day following receipt by Ecology of a completed NOI, or the issuance date of this permit, whichever is later; unless Ecology specifies a later date in writing as required by WAC173- 226-200(2). d. If an applicant intends to use a Best Management Practice (BMP) selected on the basis of Special Condition S9.C.4 (“demonstrably equivalent” BMPs), the applicant must notify Ecology of its selection as part of the NOI. In the event the applicant selects BMPs after submission of the NOI, it must provide notice of the selection of an equivalent BMP to Ecology at least 60 days before intended use of the equivalent BMP. e. Permittees must notify Ecology regarding any changes to the information provided on the NOI by submitting an updated NOI. Examples of such changes include, but are not limited to: i. Changes to the Permittee’s mailing address, ii. Changes to the on-site contact person information, and iii. Changes to the area/acreage affected by construction activity. f. Applicants must notify Ecology if they are aware of contaminated soils and/or groundwater associated with the construction activity. Provide detailed information with the NOI (as known and readily available) on the nature and extent of the contamination (concentrations, locations, and depth), as well as pollution prevention and/or treatment BMPs proposed to control the discharge of soil and/or groundwater contaminants in stormwater. Examples of such detail may include, but are not limited to: i. List or table of all known contaminants with laboratory test results showing concentration and depth, ii. Map with sample locations, iii. Temporary Erosion and Sediment Control (TESC) plans, iv. Related portions of the Stormwater Pollution Prevention Plan (SWPPP) that address the management of contaminated and potentially contaminated construction stormwater and dewatering water, v. Dewatering plan and/or dewatering contingency plan. Construction Stormwater General Permit Page 10 2. Transfer of Coverage Form The Permittee can transfer current coverage under this permit to one or more new operators, including operators of sites within a Common Plan of Development, provided the Permittee submits a Transfer of Coverage Form in accordance with General Condition G9. Transfers do not require public notice. B. Public Notice For new or previously unpermitted construction activities, the applicant must publish a public notice at least one time each week for two consecutive weeks, at least 7 days apart, in a newspaper with general circulation in the county where the construction is to take place. The notice must contain: 1. A statement that “The applicant is seeking coverage under the Washington State Department of Ecology’s Construction Stormwater NPDES and State Waste Discharge General Permit”. 2. The name, address and location of the construction site. 3. The name and address of the applicant. 4. The type of construction activity that will result in a discharge (for example, residential construction, commercial construction, etc.), and the number of acres to be disturbed. 5. The name of the receiving water(s) (that is, the surface water(s) to which the site will discharge), or, if the discharge is through a storm sewer system, the name of the operator of the system. 6. The statement: “Any persons desiring to present their views to the Washington State Department of Ecology regarding this application, or interested in Ecology’s action on this application, may notify Ecology in writing no later than 30 days of the last date of publication of this notice. Ecology reviews public comments and considers whether discharges from this project would cause a measurable change in receiving water quality, and, if so, whether the project is necessary and in the overriding public interest according to Tier II antidegradation requirements under WAC 173-201A-320. Comments can be submitted to: Department of Ecology, PO Box 47696, Olympia, Washington 98504-7696 Attn: Water Quality Program, Construction Stormwater.” Construction Stormwater General Permit Page 11 C. Erosivity Waiver Construction site operators may qualify for an erosivity waiver from the CSWGP if the following conditions are met: 1. The site will result in the disturbance of fewer than 5 acres and the site is not a portion of a common plan of development or sale that will disturb 5 acres or greater. 2. Calculation of Erosivity “R” Factor and Regional Timeframe: a. The project’s rainfall erosivity factor (“R” Factor) must be less than 5 during the period of construction activity, as calculated (see the CSWGP homepage http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html for a link to the EPA’s calculator and step by step instructions on computing the “R” Factor in the EPA Erosivity Waiver Fact Sheet). The period of construction activity starts when the land is first disturbed and ends with final stabilization. In addition: b. The entire period of construction activity must fall within the following timeframes: i. For sites west of the Cascades Crest: June 15 – September 15. ii. For sites east of the Cascades Crest, excluding the Central Basin: June 15 – October 15. iii. For sites east of the Cascades Crest, within the Central Basin: no additional timeframe restrictions apply. The Central Basin is defined as the portions of Eastern Washington with mean annual precipitation of less than 12 inches. For a map of the Central Basin (Average Annual Precipitation Region 2), refer to http://www.ecy.wa.gov/programs/wq/stormwater/ construction/resourcesguidance.html. 3. Construction site operators must submit a complete Erosivity Waiver certification form at least one week before disturbing the land. Certification must include statements that the operator will: a. Comply with applicable local stormwater requirements; and b. Implement appropriate erosion and sediment control BMPs to prevent violations of water quality standards. 4. This waiver is not available for facilities declared significant contributors of pollutants as defined in Special Condition S1.B.1.b. or for any size construction activity that could reasonably expect to cause a violation of any water quality standard as defined in Special Condition S1.B.1.b.ii. 5. This waiver does not apply to construction activities which include non- stormwater discharges listed in Special Condition S1.C.3. Construction Stormwater General Permit Page 12 6. If construction activity extends beyond the certified waiver period for any reason, the operator must either: a. Recalculate the rainfall erosivity “R” factor using the original start date and a new projected ending date and, if the “R” factor is still under 5 and the entire project falls within the applicable regional timeframe in Special Condition S2.C.2.b, complete and submit an amended waiver certification form before the original waiver expires; or b. Submit a complete permit application to Ecology in accordance with Special Condition S2.A and B before the end of the certified waiver period. S3. COMPLIANCE WITH STANDARDS A. Discharges must not cause or contribute to a violation of surface water quality standards (Chapter 173-201A WAC), ground water quality standards (Chapter 173-200 WAC), sediment management standards (Chapter 173-204 WAC), and human health-based criteria in the National Toxics Rule (40 CFR Part 131.36). Discharges not in compliance with these standards are not authorized. B. Prior to the discharge of stormwater and non-stormwater to waters of the State, the Permittee must apply all known, available, and reasonable methods of prevention, control, and treatment (AKART). This includes the preparation and implementation of an adequate SWPPP, with all appropriate BMPs installed and maintained in accordance with the SWPPP and the terms and conditions of this permit. C. Ecology presumes that a Permittee complies with water quality standards unless discharge monitoring data or other site-specific information demonstrates that a discharge causes or contributes to a violation of water quality standards, when the Permittee complies with the following conditions. The Permittee must fully: 1. Comply with all permit conditions, including planning, sampling, monitoring, reporting, and recordkeeping conditions. 2. Implement stormwater BMPs contained in stormwater management manuals published or approved by Ecology, or BMPs that are demonstrably equivalent to BMPs contained in stormwater technical manuals published or approved by Ecology, including the proper selection, implementation, and maintenance of all applicable and appropriate BMPs for on-site pollution control. (For purposes of this section, the stormwater manuals listed in Appendix 10 of the Phase I Municipal Stormwater Permit are approved by Ecology.) D. Where construction sites also discharge to ground water, the ground water discharges must also meet the terms and conditions of this CSWGP. Permittees who discharge to ground water through an injection well must also comply with any applicable requirements of the Underground Injection Control (UIC) regulations, Chapter 173-218 WAC. Construction Stormwater General Permit Page 13 S4. MONITORING REQUIREMENTS, BENCHMARKS AND REPORTING TRIGGERS A. Site Log Book The Permittee must maintain a site log book that contains a record of the implementation of the SWPPP and other permit requirements, including the installation and maintenance of BMPs, site inspections, and stormwater monitoring. B. Site Inspections The Permittee’s site inspections must include all areas disturbed by construction activities, all BMPs, and all stormwater discharge points under the Permittee’s operational control. (See Special Conditions S4.B.3 and B.4 below for detailed requirements of the Permittee’s Certified Erosion and Sediment Control Lead [CESCL].) Construction sites one acre or larger that discharge stormwater to surface waters of the State must have site inspections conducted by a certified CESCL. Sites less than one acre may have a person without CESCL certification conduct inspections. 1. The Permittee must examine stormwater visually for the presence of suspended sediment, turbidity, discoloration, and oil sheen. The Permittee must evaluate the effectiveness of BMPs and determine if it is necessary to install, maintain, or repair BMPs to improve the quality of stormwater discharges. Based on the results of the inspection, the Permittee must correct the problems identified by: a. Reviewing the SWPPP for compliance with Special Condition S9 and making appropriate revisions within 7 days of the inspection. b. Immediately beginning the process of fully implementing and maintaining appropriate source control and/or treatment BMPs as soon as possible, addressing the problems no later than within 10 days of the inspection. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when an extension is requested by a Permittee within the initial 10-day response period. c. Documenting BMP implementation and maintenance in the site log book. 2. The Permittee must inspect all areas disturbed by construction activities, all BMPs, and all stormwater discharge points at least once every calendar week and within 24 hours of any discharge from the site. (For purposes of this condition, individual discharge events that last more than one day do not require daily inspections. For example, if a stormwater pond discharges continuously over the course of a week, only one inspection is required that week.) The Permittee may reduce the inspection frequency for temporarily stabilized, inactive sites to once every calendar month. Construction Stormwater General Permit Page 14 3. The Permittee must have staff knowledgeable in the principles and practices of erosion and sediment control. The CESCL (sites one acre or more) or inspector (sites less than one acre) must have the skills to assess the: a. Site conditions and construction activities that could impact the quality of stormwater, and b. Effectiveness of erosion and sediment control measures used to control the quality of stormwater discharges. 4. The SWPPP must identify the CESCL or inspector, who must be present on site or on-call at all times. The CESCL must obtain this certification through an approved erosion and sediment control training program that meets the minimum training standards established by Ecology (see BMP C160 in the manual referred to in Special Condition S9.C.1 and 2). 5. The Permittee must summarize the results of each inspection in an inspection report or checklist and enter the report/checklist into, or attach it to, the site log book. At a minimum, each inspection report or checklist must include: a. Inspection date and time. b. Weather information, the general conditions during inspection and the approximate amount of precipitation since the last inspection, and precipitation within the last 24 hours. c. A summary or list of all implemented BMPs, including observations of all erosion/sediment control structures or practices. d. A description of the locations: i. Of BMPs inspected; ii. Of BMPs that need maintenance and why; iii. Of BMPs that failed to operate as designed or intended; and iv. Where additional or different BMPs are needed, and why. e. A description of stormwater discharged from the site. The Permittee must note the presence of suspended sediment, turbidity, discoloration, and oil sheen, as applicable. f. Any water quality monitoring performed during inspection. g. General comments and notes, including a brief description of any BMP repairs, maintenance or installations made following the inspection. h. A summary report and a schedule of implementation of the remedial actions that the Permittee plans to take if the site inspection indicates that the site is out of compliance. The remedial actions taken must meet the requirements of the SWPPP and the permit. Construction Stormwater General Permit Page 15 i. The name, title, and signature of the person conducting the site inspection, a phone number or other reliable method to reach this person, and the following statement: “I certify that this report is true, accurate, and complete to the best of my knowledge and belief.” Table 3: Summary of Primary Monitoring Requirements Size of Soil Disturbance1 Weekly Site Inspections Weekly Sampling w/ Turbidity Meter Weekly Sampling w/ Transparency Tube Weekly pH Sampling2 CESCL Required for Inspections? Sites that disturb less than 1 acre, but are part of a larger Common Plan of Development Required Not Required Not Required Not Required No Sites that disturb 1 acre or more, but fewer than 5 acres Required Sampling Required – either method3 Required Yes Sites that disturb 5 acres or more Required Required Not Required4 Required Yes 1 Soil disturbance is calculated by adding together all areas that will be affected by construction activity. Construction activity means clearing, grading, excavation, and any other activity that disturbs the surface of the land, including ingress/egress from the site. 2 If construction activity results in the disturbance of 1 acre or more, and involves significant concrete work (1,000 cubic yards of poured concrete or recycled concrete over the life of a project) or the use of engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD], or fly ash), and stormwater from the affected area drains to surface waters of the State or to a storm sewer stormwater collection system that drains to other surface waters of the State, the Permittee must conduct pH sampling in accordance with Special Condition S4.D. 3 Sites with one or more acres, but fewer than 5 acres of soil disturbance, must conduct turbidity or transparency sampling in accordance with Special Condition S4.C. 4 Sites equal to or greater than 5 acres of soil disturbance must conduct turbidity sampling using a turbidity meter in accordance with Special Condition S4.C. Construction Stormwater General Permit Page 16 C. Turbidity/Transparency Sampling Requirements 1. Sampling Methods a. If construction activity involves the disturbance of 5 acres or more, the Permittee must conduct turbidity sampling per Special Condition S4.C. b. If construction activity involves 1 acre or more but fewer than 5 acres of soil disturbance, the Permittee must conduct either transparency sampling or turbidity sampling per Special Condition S4.C. 2. Sampling Frequency a. The Permittee must sample all discharge points at least once every calendar week when stormwater (or authorized non-stormwater) discharges from the site or enters any on-site surface waters of the state (for example, a creek running through a site); sampling is not required on sites that disturb less than an acre. b. Samples must be representative of the flow and characteristics of the discharge. c. Sampling is not required when there is no discharge during a calendar week. d. Sampling is not required outside of normal working hours or during unsafe conditions. e. If the Permittee is unable to sample during a monitoring period, the Permittee must include a brief explanation in the monthly Discharge Monitoring Report (DMR). f. Sampling is not required before construction activity begins. g. The Permittee may reduce the sampling frequency for temporarily stabilized, inactive sites to once every calendar month. 3. Sampling Locations a. Sampling is required at all points where stormwater associated with construction activity (or authorized non-stormwater) is discharged off site, including where it enters any on-site surface waters of the state (for example, a creek running through a site). b. The Permittee may discontinue sampling at discharge points that drain areas of the project that are fully stabilized to prevent erosion. c. The Permittee must identify all sampling point(s) on the SWPPP site map and clearly mark these points in the field with a flag, tape, stake or other visible marker. d. Sampling is not required for discharge that is sent directly to sanitary or combined sewer systems. Construction Stormwater General Permit Page 17 e. The Permittee may discontinue sampling at discharge points in areas of the project where the Permittee no longer has operational control of the construction activity. 4. Sampling and Analysis Methods a. The Permittee performs turbidity analysis with a calibrated turbidity meter (turbidimeter) either on site or at an accredited lab. The Permittee must record the results in the site log book in nephelometric turbidity units (NTUs). b. The Permittee performs transparency analysis on site with a 1¾-inch-diameter, 60-centimeter (cm)-long transparency tube. The Permittee will record the results in the site log book in centimeters (cm). Table 4: Monitoring and Reporting Requirements Parameter Unit Analytical Method Sampling Frequency Benchmark Value Phone Reporting Trigger Value Turbidity NTU SM2130 Weekly, if discharging 25 NTUs 250 NTUs Transparency cm Manufacturer instructions, or Ecology guidance Weekly, if discharging 33 cm 6 cm 5. Turbidity/Transparency Benchmark Values and Reporting Triggers The benchmark value for turbidity is 25 NTUs or less. The benchmark value for transparency is 33 centimeters (cm). Note: Benchmark values do not apply to discharges to segments of water bodies on Washington State’s 303(d) list (Category 5) for turbidity, fine sediment, or phosphorus; these discharges are subject to a numeric effluent limit for turbidity. Refer to Special Condition S8 for more information. a. Turbidity 26 – 249 NTUs, or Transparency 32 – 7 cm: If the discharge turbidity is 26 to 249 NTUs; or if discharge transparency is less than 33 cm, but equal to or greater than 6 cm, the Permittee must: i. Review the SWPPP for compliance with Special Condition S9 and make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. ii. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible, addressing the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. Construction Stormwater General Permit Page 18 iii. Document BMP implementation and maintenance in the site log book. b. Turbidity 250 NTUs or greater, or Transparency 6 cm or less: If a discharge point’s turbidity is 250 NTUs or greater, or if discharge transparency is less than or equal to 6 cm, the Permittee must complete the reporting and adaptive management process described below. i. Telephone or submit an electronic report to the applicable Ecology Region’s Environmental Report Tracking System (ERTS) number (or through Ecology’s Water Quality Permitting Portal [WQWebPortal] – Permit Submittals when the form is available) within 24 hours, in accordance with Special Condition S5.A. Central Region (Okanogan, Chelan, Douglas, Kittitas, Yakima, Klickitat, Benton): (509) 575-2490 Eastern Region (Adams, Asotin, Columbia, Ferry, Franklin, Garfield, Grant, Lincoln, Pend Oreille, Spokane, Stevens, Walla Walla, Whitman): (509) 329-3400 Northwest Region (Kitsap, Snohomish, Island, King, San Juan, Skagit, Whatcom): (425) 649-7000 Southwest Region (Grays Harbor, Lewis, Mason, Thurston, Pierce, Clark, Cowlitz, Skamania, Wahkiakum, Clallam, Jefferson, Pacific): (360) 407-6300 Links to these numbers and the ERTS reporting page are located on the following web site: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html. ii. Review the SWPPP for compliance with Special Condition S9 and make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. iii. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible, addressing the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. iv. Document BMP implementation and maintenance in the site log book. v. Sample discharges daily until: a) Turbidity is 25 NTUs (or lower); or b) Transparency is 33 cm (or greater); or Construction Stormwater General Permit Page 19 c) The Permittee has demonstrated compliance with the water quality limit for turbidity: 1) No more than 5 NTUs over background turbidity, if background is less than 50 NTUs, or 2) No more than 10% over background turbidity, if background is 50 NTUs or greater; or d) The discharge stops or is eliminated. D. pH Sampling Requirements – Significant Concrete Work or Engineered Soils If construction activity results in the disturbance of 1 acre or more, and involves significant concrete work (significant concrete work means greater than 1000 cubic yards poured concrete or recycled concrete used over the life of a project) or the use of engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD], or fly ash), and stormwater from the affected area drains to surface waters of the State or to a storm sewer system that drains to surface waters of the State, the Permittee must conduct pH sampling as set forth below. Note: In addition, discharges to segments of water bodies on Washington State’s 303(d) list (Category 5) for high pH are subject to a numeric effluent limit for pH; refer to Special Condition S8. 1. For sites with significant concrete work, the Permittee must begin the pH sampling period when the concrete is first poured and exposed to precipitation, and continue weekly throughout and after the concrete pour and curing period, until stormwater pH is in the range of 6.5 to 8.5 (su). 2. For sites with recycled concrete where monitoring is required, the Permittee must begin the weekly pH sampling period when the recycled concrete is first exposed to precipitation and must continue until the recycled concrete is fully stabilized with the stormwater pH in the range of 6.5 to 8.5 (su). 3. For sites with engineered soils, the Permittee must begin the pH sampling period when the soil amendments are first exposed to precipitation and must continue until the area of engineered soils is fully stabilized. 4. During the applicable pH monitoring period defined above, the Permittee must obtain a representative sample of stormwater and conduct pH analysis at least once per week. 5. The Permittee must sample pH in the sediment trap/pond(s) or other locations that receive stormwater runoff from the area of significant concrete work or engineered soils before the stormwater discharges to surface waters. 6. The benchmark value for pH is 8.5 standard units. Anytime sampling indicates that pH is 8.5 or greater, the Permittee must either: Construction Stormwater General Permit Page 20 a. Prevent the high pH water (8.5 or above) from entering storm sewer systems or surface waters; or b. If necessary, adjust or neutralize the high pH water until it is in the range of pH 6.5 to 8.5 (su) using an appropriate treatment BMP such as carbon dioxide (CO2) sparging or dry ice. The Permittee must obtain written approval from Ecology before using any form of chemical treatment other than CO2 sparging or dry ice. 7. The Permittee must perform pH analysis on site with a calibrated pH meter, pH test kit, or wide range pH indicator paper. The Permittee must record pH sampling results in the site log book. S5. REPORTING AND RECORDKEEPING REQUIREMENTS A. High Turbidity Reporting Anytime sampling performed in accordance with Special Condition S4.C indicates turbidity has reached the 250 NTUs or more (or transparency less than or equal to 6 cm) high turbidity reporting level, the Permittee must either call the applicable Ecology Region’s Environmental Report Tracking System (ERTS) number by phone within 24 hours of analysis or submit an electronic ERTS report (or submit an electronic report through Ecology’s Water Quality Permitting Portal (WQWebPortal) – Permit Submittals when the form is available). See the CSWGP web site for links to ERTS and the WQWebPortal: http://www.ecy.wa.gov/programs/wq/stormwater/construction/ index.html. Also, see phone numbers in Special Condition S4.C.5.b.i. B. Discharge Monitoring Reports (DMRs) Permittees required to conduct water quality sampling in accordance with Special Conditions S4.C (Turbidity/Transparency), S4.D (pH), S8 (303[d]/TMDL sampling), and/or G13 (Additional Sampling) must submit the results to Ecology. Permittees must submit monitoring data using Ecology's WQWebDMR web application accessed through Ecology’s Water Quality Permitting Portal. To find out more information and to sign up for WQWebDMR go to: http://www.ecy.wa.gov/programs/ wq/permits/paris/portal.html. Permittees unable to submit electronically (for example, those who do not have an internet connection) must contact Ecology to request a waiver and obtain instructions on how to obtain a paper copy DMR at: Department of Ecology Water Quality Program - Construction Stormwater PO Box 47696 Olympia, Washington 98504-7696 Permittees who obtain a waiver not to use WQWebDMR must use the forms provided to them by Ecology; submittals must be mailed to the address above. Permittees shall Construction Stormwater General Permit Page 21 submit DMR forms to be received by Ecology within 15 days following the end of each month. If there was no discharge during a given monitoring period, all Permittees must submit a DMR as required with “no discharge" entered in place of the monitoring results. DMRs are required for the full duration of permit coverage (from issuance date to termination). For more information, contact Ecology staff using information provided at the following web site: www.ecy.wa.gov/programs/wq/permits/paris/contacts.html. C. Records Retention The Permittee must retain records of all monitoring information (site log book, sampling results, inspection reports/checklists, etc.), Stormwater Pollution Prevention Plan, copy of the permit coverage letter (including Transfer of Coverage documentation), and any other documentation of compliance with permit requirements for the entire life of the construction project and for a minimum of three years following the termination of permit coverage. Such information must include all calibration and maintenance records, and records of all data used to complete the application for this permit. This period of retention must be extended during the course of any unresolved litigation regarding the discharge of pollutants by the Permittee or when requested by Ecology. D. Recording Results For each measurement or sample taken, the Permittee must record the following information: 1. Date, place, method, and time of sampling or measurement. 2. The first and last name of the individual who performed the sampling or measurement. 3. The date(s) the analyses were performed. 4. The first and last name of the individual who performed the analyses. 5. The analytical techniques or methods used. 6. The results of all analyses. E. Additional Monitoring by the Permittee If the Permittee monitors any pollutant more frequently than required by this permit using test procedures specified by Special Condition S4 of this permit, the results of this monitoring must be included in the calculation and reporting of the data submitted in the Permittee’s DMR. F. Noncompliance Notification In the event the Permittee is unable to comply with any part of the terms and conditions of this permit, and the resulting noncompliance may cause a threat to human health or the environment (such as but not limited to spills of fuels or other materials, catastrophic pond or slope failure, and discharges that violate water quality standards), or exceed Construction Stormwater General Permit Page 22 numeric effluent limitations (see S8. Discharges to 303(d) or TMDL Waterbodies), the Permittee must, upon becoming aware of the circumstance: 1. Notify Ecology within 24-hours of the failure to comply by calling the applicable Regional office ERTS phone number (refer to Special Condition S4.C.5.b.i. or www.ecy.wa.gov/programs/wq/stormwater/construction/turbidity.html for Regional ERTS phone numbers). 2. Immediately take action to prevent the discharge/pollution, or otherwise stop or correct the noncompliance, and, if applicable, repeat sampling and analysis of any noncompliance immediately and submit the results to Ecology within five (5) days of becoming aware of the violation. 3. Submit a detailed written report to Ecology within five (5) days, of the time the Permittee becomes aware of the circumstances, unless requested earlier by Ecology. The report must be submitted using Ecology’s Water Quality Permitting Portal (WQWebPortal) - Permit Submittals, unless a waiver from electronic reporting has been granted according to S5.B. The report must contain a description of the noncompliance, including exact dates and times, and if the noncompliance has not been corrected, the anticipated time it is expected to continue; and the steps taken or planned to reduce, eliminate, and prevent reoccurrence of the noncompliance. The Permittee must report any unanticipated bypass and/or upset that exceeds any effluent limit in the permit in accordance with the 24-hour reporting requirement contained in 40 C.F.R. 122.41(l)(6). Compliance with these requirements does not relieve the Permittee from responsibility to maintain continuous compliance with the terms and conditions of this permit or the resulting liability for failure to comply. Upon request of the Permittee, Ecology may waive the requirement for a written report on a case-by- case basis, if the immediate notification is received by Ecology within 24 hours. G. Access to Plans and Records 1. The Permittee must retain the following permit documentation (plans and records) on site, or within reasonable access to the site, for use by the operator or for on-site review by Ecology or the local jurisdiction: a. General Permit b. Permit Coverage Letter c. Stormwater Pollution Prevention Plan (SWPPP) d. Site Log Book 2. The Permittee must address written requests for plans and records listed above (Special Condition S5.G.1) as follows: Construction Stormwater General Permit Page 23 a. The Permittee must provide a copy of plans and records to Ecology within 14 days of receipt of a written request from Ecology. b. The Permittee must provide a copy of plans and records to the public when requested in writing. Upon receiving a written request from the public for the Permittee’s plans and records, the Permittee must either: i. Provide a copy of the plans and records to the requester within 14 days of a receipt of the written request; or ii. Notify the requester within 10 days of receipt of the written request of the location and times within normal business hours when the plans and records may be viewed; and provide access to the plans and records within 14 days of receipt of the written request; or iii. Within 14 days of receipt of the written request, the Permittee may submit a copy of the plans and records to Ecology for viewing and/or copying by the requester at an Ecology office, or a mutually agreed location. If plans and records are viewed and/or copied at a location other than at an Ecology office, the Permittee will provide reasonable access to copying services for which a reasonable fee may be charged. The Permittee must notify the requester within 10 days of receipt of the request where the plans and records may be viewed and/or copied. S6. PERMIT FEES The Permittee must pay permit fees assessed by Ecology. Fees for stormwater discharges covered under this permit are established by Chapter 173-224 WAC. Ecology continues to assess permit fees until the permit is terminated in accordance with Special Condition S10 or revoked in accordance with General Condition G5. S7. SOLID AND LIQUID WASTE DISPOSAL The Permittee must handle and dispose of solid and liquid wastes generated by construction activity, such as demolition debris, construction materials, contaminated materials, and waste materials from maintenance activities, including liquids and solids from cleaning catch basins and other stormwater facilities, in accordance with: A. Special Condition S3, Compliance with Standards B. WAC 173-216-110 C. Other applicable regulations S8. DISCHARGES TO 303(d) OR TMDL WATERBODIES A. Sampling and Numeric Effluent Limits For Certain Discharges to 303(d)-listed Waterbodies Construction Stormwater General Permit Page 24 1. Permittees who discharge to segments of waterbodies listed as impaired by the State of Washington under Section 303(d) of the Clean Water Act for turbidity, fine sediment, high pH, or phosphorus, must conduct water quality sampling according to the requirements of this section, and Special Conditions S4.C.2.b-f and S4.C.3.b-d, and must comply with the applicable numeric effluent limitations in S8.C and S8.D. 2. All references and requirements associated with Section 303(d) of the Clean Water Act mean the most current listing by Ecology of impaired waters (Category 5) that exists on January 1, 2016, or the date when the operator’s complete permit application is received by Ecology, whichever is later. B. Limits on Coverage for New Discharges to TMDL or 303(d)-listed Waters Operators of construction sites that discharge to a TMDL or 303(d)-listed waterbody are not eligible for coverage under this permit unless the operator: 1. Prevents exposing stormwater to pollutants for which the waterbody is impaired, and retains documentation in the SWPPP that details procedures taken to prevent exposure on site; or 2. Documents that the pollutants for which the waterbody is impaired are not present at the site, and retains documentation of this finding within the SWPPP; or 3. Provides Ecology with data indicating the discharge is not expected to cause or contribute to an exceedance of a water quality standard, and retains such data on site with the SWPPP. The operator must provide data and other technical information to Ecology that sufficiently demonstrate: a. For discharges to waters without an EPA-approved or -established TMDL, that the discharge of the pollutant for which the water is impaired will meet in- stream water quality criteria at the point of discharge to the waterbody; or b. For discharges to waters with an EPA-approved or -established TMDL, that there is sufficient remaining wasteload allocation in the TMDL to allow construction stormwater discharge and that existing dischargers to the waterbody are subject to compliance schedules designed to bring the waterbody into attainment with water quality standards. Operators of construction sites are eligible for coverage under this permit if Ecology issues permit coverage based upon an affirmative determination that the discharge will not cause or contribute to the existing impairment. C. Sampling and Numeric Effluent Limits for Discharges to Water Bodies on the 303(d) List for Turbidity, Fine Sediment, or Phosphorus 1. Permittees who discharge to segments of water bodies on the 303(d) list (Category 5) for turbidity, fine sediment, or phosphorus must conduct turbidity sampling in accordance with Special Condition S4.C.2 and comply with either of the numeric effluent limits noted in Table 5 below. Construction Stormwater General Permit Page 25 2. As an alternative to the 25 NTUs effluent limit noted in Table 5 below (applied at the point where stormwater [or authorized non-stormwater] is discharged off-site), Permittees may choose to comply with the surface water quality standard for turbidity. The standard is: no more than 5 NTUs over background turbidity when the background turbidity is 50 NTUs or less, or no more than a 10% increase in turbidity when the background turbidity is more than 50 NTUs. In order to use the water quality standard requirement, the sampling must take place at the following locations: a. Background turbidity in the 303(d)-listed receiving water immediately upstream (upgradient) or outside the area of influence of the discharge. b. Turbidity at the point of discharge into the 303(d)-listed receiving water, inside the area of influence of the discharge. 3. Discharges that exceed the numeric effluent limit for turbidity constitute a violation of this permit. 4. Permittees whose discharges exceed the numeric effluent limit shall sample discharges daily until the violation is corrected and comply with the non- compliance notification requirements in Special Condition S5.F. Table 5: Turbidity, Fine Sediment & Phosphorus Sampling and Limits for 303(d)-Listed Waters Parameter identified in 303(d) listing Parameter Sampled Unit Analytical Method Sampling Frequency Numeric Effluent Limit1 Turbidity Fine Sediment Phosphorus Turbidity NTU SM2130 Weekly, if discharging 25 NTUs, at the point where stormwater is discharged from the site; OR In compliance with the surface water quality standard for turbidity (S8.C.2.a) 1Permittees subject to a numeric effluent limit for turbidity may, at their discretion, choose either numeric effluent limitation based on site-specific considerations including, but not limited to, safety, access and convenience. D. Discharges to Water Bodies on the 303(d) List for High pH 1. Permittees who discharge to segments of water bodies on the 303(d) list (Category 5) for high pH must conduct pH sampling in accordance with the table below, and comply with the numeric effluent limit of pH 6.5 to 8.5 su (Table 6). Construction Stormwater General Permit Page 26 Table 6: pH Sampling and Limits for 303(d)-Listed Waters Parameter identified in 303(d) listing Parameter Sampled/Units Analytical Method Sampling Frequency Numeric Effluent Limit High pH pH /Standard Units pH meter Weekly, if discharging In the range of 6.5 – 8.5 2. At the Permittee’s discretion, compliance with the limit shall be assessed at one of the following locations: a. Directly in the 303(d)-listed waterbody segment, inside the immediate area of influence of the discharge; or b. Alternatively, the Permittee may measure pH at the point where the discharge leaves the construction site, rather than in the receiving water. 3. Discharges that exceed the numeric effluent limit for pH (outside the range of 6.5 – 8.5 su) constitute a violation of this permit. 4. Permittees whose discharges exceed the numeric effluent limit shall sample discharges daily until the violation is corrected and comply with the non- compliance notification requirements in Special Condition S5.F. E. Sampling and Limits for Sites Discharging to Waters Covered by a TMDL or Another Pollution Control Plan 1. Discharges to a waterbody that is subject to a Total Maximum Daily Load (TMDL) for turbidity, fine sediment, high pH, or phosphorus must be consistent with the TMDL. Refer to http://www.ecy.wa.gov/programs/wq/tmdl/ TMDLsbyWria/TMDLbyWria.html for more information on TMDLs. a. Where an applicable TMDL sets specific waste load allocations or requirements for discharges covered by this permit, discharges must be consistent with any specific waste load allocations or requirements established by the applicable TMDL. i. The Permittee must sample discharges weekly or as otherwise specified by the TMDL to evaluate compliance with the specific waste load allocations or requirements. ii. Analytical methods used to meet the monitoring requirements must conform to the latest revision of the Guidelines Establishing Test Procedures for the Analysis of Pollutants contained in 40 CFR Part 136. Turbidity and pH methods need not be accredited or registered unless conducted at a laboratory which must otherwise be accredited or registered. b. Where an applicable TMDL has established a general waste load allocation for construction stormwater discharges, but has not identified specific requirements, Construction Stormwater General Permit Page 27 compliance with Special Conditions S4 (Monitoring) and S9 (SWPPPs) will constitute compliance with the approved TMDL. c. Where an applicable TMDL has not specified a waste load allocation for construction stormwater discharges, but has not excluded these discharges, compliance with Special Conditions S4 (Monitoring) and S9 (SWPPPs) will constitute compliance with the approved TMDL. d. Where an applicable TMDL specifically precludes or prohibits discharges from construction activity, the operator is not eligible for coverage under this permit. 2. Applicable TMDL means a TMDL for turbidity, fine sediment, high pH, or phosphorus that is completed and approved by EPA before January 1, 2016, or before the date the operator’s complete permit application is received by Ecology, whichever is later. TMDLs completed after the operator’s complete permit application is received by Ecology become applicable to the Permittee only if they are imposed through an administrative order by Ecology, or through a modification of permit coverage. S9. STORMWATER POLLUTION PREVENTION PLAN The Permittee must prepare and properly implement an adequate Stormwater Pollution Prevention Plan (SWPPP) for construction activity in accordance with the requirements of this permit beginning with initial soil disturbance and until final stabilization. A. The Permittee’s SWPPP must meet the following objectives: 1. To implement best management practices (BMPs) to prevent erosion and sedimentation, and to identify, reduce, eliminate or prevent stormwater contamination and water pollution from construction activity. 2. To prevent violations of surface water quality, ground water quality, or sediment management standards. 3. To control peak volumetric flow rates and velocities of stormwater discharges. B. General Requirements 1. The SWPPP must include a narrative and drawings. All BMPs must be clearly referenced in the narrative and marked on the drawings. The SWPPP narrative must include documentation to explain and justify the pollution prevention decisions made for the project. Documentation must include: a. Information about existing site conditions (topography, drainage, soils, vegetation, etc.). b. Potential erosion problem areas. c. The 13 elements of a SWPPP in Special Condition S9.D.1-13, including BMPs used to address each element. Construction Stormwater General Permit Page 28 d. Construction phasing/sequence and general BMP implementation schedule. e. The actions to be taken if BMP performance goals are not achieved—for example, a contingency plan for additional treatment and/or storage of stormwater that would violate the water quality standards if discharged. f. Engineering calculations for ponds, treatment systems, and any other designed structures. When a treatment system requires engineering calculations, these calculations must be included in the SWPPP. Engineering calculations do not need to be included in the SWPPP for treatment systems that do not require such calculations. 2. The Permittee must modify the SWPPP if, during inspections or investigations conducted by the owner/operator, or the applicable local or state regulatory authority, it is determined that the SWPPP is, or would be, ineffective in eliminating or significantly minimizing pollutants in stormwater discharges from the site. The Permittee must then: a. Review the SWPPP for compliance with Special Condition S9 and make appropriate revisions within 7 days of the inspection or investigation. b. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible, addressing the problems no later than 10 days from the inspection or investigation. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when an extension is requested by a Permittee within the initial 10-day response period. c. Document BMP implementation and maintenance in the site log book. The Permittee must modify the SWPPP whenever there is a change in design, construction, operation, or maintenance at the construction site that has, or could have, a significant effect on the discharge of pollutants to waters of the State. C. Stormwater Best Management Practices (BMPs) BMPs must be consistent with: 1. Stormwater Management Manual for Western Washington (most current approved edition at the time this permit was issued), for sites west of the crest of the Cascade Mountains; or 2. Stormwater Management Manual for Eastern Washington (most current approved edition at the time this permit was issued), for sites east of the crest of the Cascade Mountains; or 3. Revisions to the manuals listed in Special Condition S9.C.1. & 2., or other stormwater management guidance documents or manuals which provide an equivalent level of pollution prevention, that are approved by Ecology and incorporated into this permit in accordance with the permit modification requirements of WAC 173-226-230; or Construction Stormwater General Permit Page 29 4. Documentation in the SWPPP that the BMPs selected provide an equivalent level of pollution prevention, compared to the applicable Stormwater Management Manuals, including: a. The technical basis for the selection of all stormwater BMPs (scientific, technical studies, and/or modeling) that support the performance claims for the BMPs being selected. b. An assessment of how the selected BMP will satisfy AKART requirements and the applicable federal technology-based treatment requirements under 40 CFR part 125.3. D. SWPPP – Narrative Contents and Requirements The Permittee must include each of the 13 elements below in Special Condition S9.D.1-13 in the narrative of the SWPPP and implement them unless site conditions render the element unnecessary and the exemption from that element is clearly justified in the SWPPP. 1. Preserve Vegetation/Mark Clearing Limits a. Before beginning land-disturbing activities, including clearing and grading, clearly mark all clearing limits, sensitive areas and their buffers, and trees that are to be preserved within the construction area. b. Retain the duff layer, native topsoil, and natural vegetation in an undisturbed state to the maximum degree practicable. 2. Establish Construction Access a. Limit construction vehicle access and exit to one route, if possible. b. Stabilize access points with a pad of quarry spalls, crushed rock, or other equivalent BMPs, to minimize tracking sediment onto roads. c. Locate wheel wash or tire baths on site, if the stabilized construction entrance is not effective in preventing tracking sediment onto roads. d. If sediment is tracked off site, clean the affected roadway thoroughly at the end of each day, or more frequently as necessary (for example, during wet weather). Remove sediment from roads by shoveling, sweeping, or pickup and transport of the sediment to a controlled sediment disposal area. e. Conduct street washing only after sediment removal in accordance with Special Condition S9.D.2.d. Control street wash wastewater by pumping back on site or otherwise preventing it from discharging into systems tributary to waters of the State. 3. Control Flow Rates a. Protect properties and waterways downstream of development sites from erosion and the associated discharge of turbid waters due to increases in the Construction Stormwater General Permit Page 30 velocity and peak volumetric flow rate of stormwater runoff from the project site, as required by local plan approval authority. b. Where necessary to comply with Special Condition S9.D.3.a, construct stormwater retention or detention facilities as one of the first steps in grading. Assure that detention facilities function properly before constructing site improvements (for example, impervious surfaces). c. If permanent infiltration ponds are used for flow control during construction, protect these facilities from siltation during the construction phase. 4. Install Sediment Controls The Permittee must design, install and maintain effective erosion controls and sediment controls to minimize the discharge of pollutants. At a minimum, the Permittee must design, install and maintain such controls to: a. Construct sediment control BMPs (sediment ponds, traps, filters, infiltration facilities, etc.) as one of the first steps in grading. These BMPs must be functional before other land disturbing activities take place. b. Minimize sediment discharges from the site. The design, installation and maintenance of erosion and sediment controls must address factors such as the amount, frequency, intensity and duration of precipitation, the nature of resulting stormwater runoff, and soil characteristics, including the range of soil particle sizes expected to be present on the site. c. Direct stormwater runoff from disturbed areas through a sediment pond or other appropriate sediment removal BMP, before the runoff leaves a construction site or before discharge to an infiltration facility. Runoff from fully stabilized areas may be discharged without a sediment removal BMP, but must meet the flow control performance standard of Special Condition S9.D.3.a. d. Locate BMPs intended to trap sediment on site in a manner to avoid interference with the movement of juvenile salmonids attempting to enter off-channel areas or drainages. e. Provide and maintain natural buffers around surface waters, direct stormwater to vegetated areas to increase sediment removal and maximize stormwater infiltration, unless infeasible. f. Where feasible, design outlet structures that withdraw impounded stormwater from the surface to avoid discharging sediment that is still suspended lower in the water column. 5. Stabilize Soils a. The Permittee must stabilize exposed and unworked soils by application of effective BMPs that prevent erosion. Applicable BMPs include, but are not limited to: temporary and permanent seeding, sodding, mulching, plastic covering, erosion control fabrics and matting, soil application of polyacrylamide Construction Stormwater General Permit Page 31 (PAM), the early application of gravel base on areas to be paved, and dust control. b. The Permittee must control stormwater volume and velocity within the site to minimize soil erosion. c. The Permittee must control stormwater discharges, including both peak flow rates and total stormwater volume, to minimize erosion at outlets and to minimize downstream channel and stream bank erosion. d. Depending on the geographic location of the project, the Permittee must not allow soils to remain exposed and unworked for more than the time periods set forth below to prevent erosion: West of the Cascade Mountains Crest During the dry season (May 1 - September 30): 7 days During the wet season (October 1 - April 30): 2 days East of the Cascade Mountains Crest, except for Central Basin* During the dry season (July 1 - September 30): 10 days During the wet season (October 1 - June 30): 5 days The Central Basin*, East of the Cascade Mountains Crest During the dry season (July 1 - September 30): 30 days During the wet season (October 1 - June 30): 15 days *Note: The Central Basin is defined as the portions of Eastern Washington with mean annual precipitation of less than 12 inches. e. The Permittee must stabilize soils at the end of the shift before a holiday or weekend if needed based on the weather forecast. f. The Permittee must stabilize soil stockpiles from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. g. The Permittee must minimize the amount of soil exposed during construction activity. h. The Permittee must minimize the disturbance of steep slopes. i. The Permittee must minimize soil compaction and, unless infeasible, preserve topsoil. 6. Protect Slopes a. The Permittee must design and construct cut-and-fill slopes in a manner to minimize erosion. Applicable practices include, but are not limited to, reducing continuous length of slope with terracing and diversions, reducing slope steepness, and roughening slope surfaces (for example, track walking). Construction Stormwater General Permit Page 32 b. The Permittee must divert off-site stormwater (run-on) or ground water away from slopes and disturbed areas with interceptor dikes, pipes, and/or swales. Off-site stormwater should be managed separately from stormwater generated on the site. c. At the top of slopes, collect drainage in pipe slope drains or protected channels to prevent erosion. i. West of the Cascade Mountains Crest: Temporary pipe slope drains must handle the peak 10-minute flow rate from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year, 1-hour flow rate predicted by an approved continuous runoff model, increased by a factor of 1.6, may be used. The hydrologic analysis must use the existing land cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis must use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the Western Washington Hydrology Model (WWHM) to predict flows, bare soil areas should be modeled as "landscaped area.” ii. East of the Cascade Mountains Crest: Temporary pipe slope drains must handle the expected peak flow rate from a 6-month, 3-hour storm for the developed condition, referred to as the short duration storm. d. Place excavated material on the uphill side of trenches, consistent with safety and space considerations. e. Place check dams at regular intervals within constructed channels that are cut down a slope. 7. Protect Drain Inlets a. Protect all storm drain inlets made operable during construction so that stormwater runoff does not enter the conveyance system without first being filtered or treated to remove sediment. b. Clean or remove and replace inlet protection devices when sediment has filled one-third of the available storage (unless a different standard is specified by the product manufacturer). 8. Stabilize Channels and Outlets a. Design, construct and stabilize all on-site conveyance channels to prevent erosion from the following expected peak flows: i. West of the Cascade Mountains Crest: Channels must handle the peak 10-minute flow rate from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Alternatively, the 10-year, 1-hour flow rate indicated by an approved continuous runoff model, increased by a factor of 1.6, may be used. The hydrologic analysis must use the existing land Construction Stormwater General Permit Page 33 cover condition for predicting flow rates from tributary areas outside the project limits. For tributary areas on the project site, the analysis must use the temporary or permanent project land cover condition, whichever will produce the highest flow rates. If using the WWHM to predict flows, bare soil areas should be modeled as "landscaped area.” ii. East of the Cascade Mountains Crest: Channels must handle the expected peak flow rate from a 6-month, 3-hour storm for the developed condition, referred to as the short duration storm. b. Provide stabilization, including armoring material, adequate to prevent erosion of outlets, adjacent stream banks, slopes, and downstream reaches at the outlets of all conveyance systems. 9. Control Pollutants Design, install, implement and maintain effective pollution prevention measures to minimize the discharge of pollutants. The Permittee must: a. Handle and dispose of all pollutants, including waste materials and demolition debris that occur on site in a manner that does not cause contamination of stormwater. b. Provide cover, containment, and protection from vandalism for all chemicals, liquid products, petroleum products, and other materials that have the potential to pose a threat to human health or the environment. On-site fueling tanks must include secondary containment. Secondary containment means placing tanks or containers within an impervious structure capable of containing 110% of the volume contained in the largest tank within the containment structure. Double- walled tanks do not require additional secondary containment. c. Conduct maintenance, fueling, and repair of heavy equipment and vehicles using spill prevention and control measures. Clean contaminated surfaces immediately following any spill incident. d. Discharge wheel wash or tire bath wastewater to a separate on-site treatment system that prevents discharge to surface water, such as closed-loop recirculation or upland land application, or to the sanitary sewer with local sewer district approval. e. Apply fertilizers and pesticides in a manner and at application rates that will not result in loss of chemical to stormwater runoff. Follow manufacturers’ label requirements for application rates and procedures. f. Use BMPs to prevent contamination of stormwater runoff by pH-modifying sources. The sources for this contamination include, but are not limited to: bulk cement, cement kiln dust, fly ash, new concrete washing and curing waters, recycled concrete stockpiles, waste streams generated from concrete grinding and sawing, exposed aggregate processes, dewatering concrete vaults, concrete Construction Stormwater General Permit Page 34 pumping and mixer washout waters. (Also refer to the definition for "concrete wastewater" in Appendix A--Definitions.) g. Adjust the pH of stormwater or authorized non-stormwater if necessary to prevent an exceedance of groundwater and/or surface water quality standards. h. Assure that washout of concrete trucks is performed off-site or in designated concrete washout areas only. Do not wash out concrete truck drums or concrete handling equipment onto the ground, or into storm drains, open ditches, streets, or streams. Washout of concrete handling equipment may be disposed of in a designated concrete washout area or in a formed area awating concrete where it will not contaminate surface or ground water. Do not dump excess concrete on site, except in designated concrete washout areas. Concrete spillage or concrete discharge directly to groundwater or surface waters of the State is prohibited. Do not wash out to formed areas awaiting LID facilities. i. Obtain written approval from Ecology before using any chemical treatment, with the exception of CO2 or dry ice used to adjust pH. j. Uncontaminated water from water-only based shaft drilling for construction of building, road, and bridge foundations may be infiltrated provided the wastewater is managed in a way that prohibits discharge to surface waters. Prior to infiltration, water from water-only based shaft drilling that comes into contact with curing concrete must be neutralized until pH is in the range of 6.5 to 8.5 (su). 10. Control Dewatering a. Permittees must discharge foundation, vault, and trench dewatering water, which have characteristics similar to stormwater runoff at the site, into a controlled conveyance system before discharge to a sediment trap or sediment pond. b. Permittees may discharge clean, non-turbid dewatering water, such as well- point ground water, to systems tributary to, or directly into surface waters of the State, as specified in Special Condition S9.D.8, provided the dewatering flow does not cause erosion or flooding of receiving waters. Do not route clean dewatering water through stormwater sediment ponds. Note that “surface waters of the State” may exist on a construction site as well as off site; for example, a creek running through a site. c. Other dewatering treatment or disposal options may include: i. Infiltration. ii. Transport off site in a vehicle, such as a vacuum flush truck, for legal disposal in a manner that does not pollute state waters. Construction Stormwater General Permit Page 35 iii. Ecology-approved on-site chemical treatment or other suitable treatment technologies (see S9.D.9.i. regarding chemical treatment written approval). iv. Sanitary or combined sewer discharge with local sewer district approval, if there is no other option. v. Use of a sedimentation bag with discharge to a ditch or swale for small volumes of localized dewatering. d. Permittees must handle highly turbid or contaminated dewatering water separately from stormwater. 11. Maintain BMPs a. Permittees must maintain and repair all temporary and permanent erosion and sediment control BMPs as needed to assure continued performance of their intended function in accordance with BMP specifications. b. Permittees must remove all temporary erosion and sediment control BMPs within 30 days after achieving final site stabilization or after the temporary BMPs are no longer needed. 12. Manage the Project a. Phase development projects to the maximum degree practicable and take into account seasonal work limitations. b. Inspection and monitoring – Inspect, maintain and repair all BMPs as needed to assure continued performance of their intended function. Conduct site inspections and monitoring in accordance with Special Condition S4. c. Maintaining an updated construction SWPPP – Maintain, update, and implement the SWPPP in accordance with Special Conditions S3, S4 and S9. 13. Protect Low Impact Development (LID) BMPs The primary purpose of LID BMPs/On-site LID Stormwater Management BMPs is to reduce the disruption of the natural site hydrology. LID BMPs are permanent facilities. a. Permittees must protect all Bioretention and Rain Garden facilities from sedimentation through installation and maintenance of erosion and sediment control BMPs on portions of the site that drain into the Bioretention and/or Rain Garden facilities. Restore the facilities to their fully functioning condition if they accumulate sediment during construction. Restoring the facility must include removal of sediment and any sediment-laden Bioretention/Rain Garden soils, and replacing the removed soils with soils meeting the design specification. Construction Stormwater General Permit Page 36 b. Permittees must maintain the infiltration capabilities of Bioretention and Rain Garden facilities by protecting against compaction by construction equipment and foot traffic. Protect completed lawn and landscaped areas from compaction due to construction equipment. c. Permittees must control erosion and avoid introducing sediment from surrounding land uses onto permeable pavements. Do not allow muddy construction equipment on the base material or pavement. Do not allow sediment-laden runoff onto permeable pavements. d. Permittees must clean permeable pavements fouled with sediments or no longer passing an initial infiltration test using local stormwater manual methodology or the manufacturer’s procedures. e. Permittees must keep all heavy equipment off existing soils under LID facilities that have been excavated to final grade to retain the infiltration rate of the soils. E. SWPPP – Map Contents and Requirements The Permittee’s SWPPP must also include a vicinity map or general location map (for example, a USGS quadrangle map, a portion of a county or city map, or other appropriate map) with enough detail to identify the location of the construction site and receiving waters within one mile of the site. The SWPPP must also include a legible site map (or maps) showing the entire construction site. The following features must be identified, unless not applicable due to site conditions: 1. The direction of north, property lines, and existing structures and roads. 2. Cut and fill slopes indicating the top and bottom of slope catch lines. 3. Approximate slopes, contours, and direction of stormwater flow before and after major grading activities. 4. Areas of soil disturbance and areas that will not be disturbed. 5. Locations of structural and nonstructural controls (BMPs) identified in the SWPPP. 6. Locations of off-site material, stockpiles, waste storage, borrow areas, and vehicle/equipment storage areas. 7. Locations of all surface water bodies, including wetlands. 8. Locations where stormwater or non-stormwater discharges off-site and/or to a surface waterbody, including wetlands. 9. Location of water quality sampling station(s), if sampling is required by state or local permitting authority. Construction Stormwater General Permit Page 37 10. Areas where final stabilization has been accomplished and no further construction- phase permit requirements apply. 11. Location or proposed location of LID facilities. S10. NOTICE OF TERMINATION A. The site is eligible for termination of coverage when it has met any of the following conditions: 1. The site has undergone final stabilization, the Permittee has removed all temporary BMPs (except biodegradable BMPs clearly manufactured with the intention for the material to be left in place and not interfere with maintenance or land use), and all stormwater discharges associated with construction activity have been eliminated; or 2. All portions of the site that have not undergone final stabilization per Special Condition S10.A.1 have been sold and/or transferred (per General Condition G9), and the Permittee no longer has operational control of the construction activity; or 3. For residential construction only, the Permittee has completed temporary stabilization and the homeowners have taken possession of the residences. B. When the site is eligible for termination, the Permittee must submit a complete and accurate Notice of Termination (NOT) form, signed in accordance with General Condition G2, to: Department of Ecology Water Quality Program – Construction Stormwater PO Box 47696 Olympia, Washington 98504-7696 When an electronic termination form is available, the Permittee may choose to submit a complete and accurate Notice of Termination (NOT) form through the Water Quality Permitting Portal rather than mailing a hardcopy as noted above. The termination is effective on the thirty-first calendar day following the date Ecology receives a complete NOT form, unless Ecology notifies the Permittee that the termination request is denied because the Permittee has not met the eligibility requirements in Special Condition S10.A. Permittees are required to comply with all conditions and effluent limitations in the permit until the permit has been terminated. Permittees transferring the property to a new property owner or operator/Permittee are required to complete and submit the Notice of Transfer form to Ecology, but are not required to submit a Notice of Termination form for this type of transaction. Construction Stormwater General Permit Page 38 GENERAL CONDITIONS G1. DISCHARGE VIOLATIONS All discharges and activities authorized by this general permit must be consistent with the terms and conditions of this general permit. Any discharge of any pollutant more frequent than or at a level in excess of that identified and authorized by the general permit must constitute a violation of the terms and conditions of this permit. G2. SIGNATORY REQUIREMENTS A. All permit applications must bear a certification of correctness to be signed: 1. In the case of corporations, by a responsible corporate officer; 2. In the case of a partnership, by a general partner of a partnership; 3. In the case of sole proprietorship, by the proprietor; or 4. In the case of a municipal, state, or other public facility, by either a principal executive officer or ranking elected official. B. All reports required by this permit and other information requested by Ecology (including NOIs, NOTs, and Transfer of Coverage forms) must be signed by a person described above or by a duly authorized representative of that person. A person is a duly authorized representative only if: 1. The authorization is made in writing by a person described above and submitted to Ecology. 2. The authorization specifies either an individual or a position having responsibility for the overall operation of the regulated facility, such as the position of plant manager, superintendent, position of equivalent responsibility, or an individual or position having overall responsibility for environmental matters. C. Changes to authorization. If an authorization under paragraph G2.B.2 above is no longer accurate because a different individual or position has responsibility for the overall operation of the facility, a new authorization satisfying the requirements of paragraph G2.B.2 above must be submitted to Ecology prior to or together with any reports, information, or applications to be signed by an authorized representative. D. Certification. Any person signing a document under this section must make the following certification: “I certify under penalty of law, that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gathered and evaluated the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering information, the information submitted is, to the best of my Construction Stormwater General Permit Page 39 knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations.” G3. RIGHT OF INSPECTION AND ENTRY The Permittee must allow an authorized representative of Ecology, upon the presentation of credentials and such other documents as may be required by law: A. To enter upon the premises where a discharge is located or where any records are kept under the terms and conditions of this permit. B. To have access to and copy – at reasonable times and at reasonable cost – any records required to be kept under the terms and conditions of this permit. C. To inspect – at reasonable times – any facilities, equipment (including monitoring and control equipment), practices, methods, or operations regulated or required under this permit. D. To sample or monitor – at reasonable times – any substances or parameters at any location for purposes of assuring permit compliance or as otherwise authorized by the Clean Water Act. G4. GENERAL PERMIT MODIFICATION AND REVOCATION This permit may be modified, revoked and reissued, or terminated in accordance with the provisions of Chapter 173-226 WAC. Grounds for modification, revocation and reissuance, or termination include, but are not limited to, the following: A. When a change occurs in the technology or practices for control or abatement of pollutants applicable to the category of dischargers covered under this permit. B. When effluent limitation guidelines or standards are promulgated pursuant to the CWA or Chapter 90.48 RCW, for the category of dischargers covered under this permit. C. When a water quality management plan containing requirements applicable to the category of dischargers covered under this permit is approved, or D. When information is obtained that indicates cumulative effects on the environment from dischargers covered under this permit are unacceptable. G5. REVOCATION OF COVERAGE UNDER THE PERMIT Pursuant to Chapter 43.21B RCW and Chapter 173-226 WAC, the Director may terminate coverage for any discharger under this permit for cause. Cases where coverage may be terminated include, but are not limited to, the following: A. Violation of any term or condition of this permit. B. Obtaining coverage under this permit by misrepresentation or failure to disclose fully all relevant facts. Construction Stormwater General Permit Page 40 C. A change in any condition that requires either a temporary or permanent reduction or elimination of the permitted discharge. D. Failure or refusal of the Permittee to allow entry as required in RCW 90.48.090. E. A determination that the permitted activity endangers human health or the environment, or contributes to water quality standards violations. F. Nonpayment of permit fees or penalties assessed pursuant to RCW 90.48.465 and Chapter 173-224 WAC. G. Failure of the Permittee to satisfy the public notice requirements of WAC 173-226- 130(5), when applicable. The Director may require any discharger under this permit to apply for and obtain coverage under an individual permit or another more specific general permit. Permittees who have their coverage revoked for cause according to WAC 173-226-240 may request temporary coverage under this permit during the time an individual permit is being developed, provided the request is made within ninety (90) days from the time of revocation and is submitted along with a complete individual permit application form. G6. REPORTING A CAUSE FOR MODIFICATION The Permittee must submit a new application, or a supplement to the previous application, whenever a material change to the construction activity or in the quantity or type of discharge is anticipated which is not specifically authorized by this permit. This application must be submitted at least sixty (60) days prior to any proposed changes. Filing a request for a permit modification, revocation and reissuance, or termination, or a notification of planned changes or anticipated noncompliance does not relieve the Permittee of the duty to comply with the existing permit until it is modified or reissued. G7. COMPLIANCE WITH OTHER LAWS AND STATUTES Nothing in this permit will be construed as excusing the Permittee from compliance with any applicable federal, state, or local statutes, ordinances, or regulations. G8. DUTY TO REAPPLY The Permittee must apply for permit renewal at least 180 days prior to the specified expiration date of this permit. The Permittee must reapply using the electronic application form (NOI) available on Ecology’s website. Permittees unable to submit electronically (for example, those who do not have an internet connection) must contact Ecology to request a waiver and obtain instructions on how to obtain a paper NOI. Department of Ecology Water Quality Program - Construction Stormwater PO Box 47696 Olympia, Washington 98504-7696 Construction Stormwater General Permit Page 41 G9. TRANSFER OF GENERAL PERMIT COVERAGE Coverage under this general permit is automatically transferred to a new discharger, including operators of lots/parcels within a common plan of development or sale, if: A. A written agreement (Transfer of Coverage Form) between the current discharger (Permittee) and new discharger, signed by both parties and containing a specific date for transfer of permit responsibility, coverage, and liability (including any Administrative Orders associated with the Permit) is submitted to the Director; and B. The Director does not notify the current discharger and new discharger of the Director’s intent to revoke coverage under the general permit. If this notice is not given, the transfer is effective on the date specified in the written agreement. When a current discharger (Permittee) transfers a portion of a permitted site, the current discharger must also submit an updated application form (NOI) to the Director indicating the remaining permitted acreage after the transfer. G10. REMOVED SUBSTANCES The Permittee must not re-suspend or reintroduce collected screenings, grit, solids, sludges, filter backwash, or other pollutants removed in the course of treatment or control of stormwater to the final effluent stream for discharge to state waters. G11. DUTY TO PROVIDE INFORMATION The Permittee must submit to Ecology, within a reasonable time, all information that Ecology may request to determine whether cause exists for modifying, revoking and reissuing, or terminating this permit or to determine compliance with this permit. The Permittee must also submit to Ecology, upon request, copies of records required to be kept by this permit [40 CFR 122.41(h)]. G12. OTHER REQUIREMENTS OF 40 CFR All other requirements of 40 CFR 122.41 and 122.42 are incorporated in this permit by reference. G13. ADDITIONAL MONITORING Ecology may establish specific monitoring requirements in addition to those contained in this permit by administrative order or permit modification. G14. PENALTIES FOR VIOLATING PERMIT CONDITIONS Any person who is found guilty of willfully violating the terms and conditions of this permit shall be deemed guilty of a crime, and upon conviction thereof shall be punished by a fine of up to ten thousand dollars ($10,000) and costs of prosecution, or by imprisonment at the discretion of the court. Each day upon which a willful violation occurs may be deemed a separate and additional violation. Construction Stormwater General Permit Page 42 Any person who violates the terms and conditions of a waste discharge permit shall incur, in addition to any other penalty as provided by law, a civil penalty in the amount of up to ten thousand dollars ($10,000) for every such violation. Each and every such violation shall be a separate and distinct offense, and in case of a continuing violation, every day’s continuance shall be deemed to be a separate and distinct violation. G15. UPSET Definition – “Upset” means an exceptional incident in which there is unintentional and temporary noncompliance with technology-based permit effluent limitations because of factors beyond the reasonable control of the Permittee. An upset does not include noncompliance to the extent caused by operational error, improperly designed treatment facilities, inadequate treatment facilities, lack of preventive maintenance, or careless or improper operation. An upset constitutes an affirmative defense to an action brought for noncompliance with such technology-based permit effluent limitations if the requirements of the following paragraph are met. A Permittee who wishes to establish the affirmative defense of upset must demonstrate, through properly signed, contemporaneous operating logs or other relevant evidence that: 1) an upset occurred and that the Permittee can identify the cause(s) of the upset; 2) the permitted facility was being properly operated at the time of the upset; 3) the Permittee submitted notice of the upset as required in Special Condition S5.F, and; 4) the Permittee complied with any remedial measures required under this permit. In any enforcement proceeding, the Permittee seeking to establish the occurrence of an upset has the burden of proof. G16. PROPERTY RIGHTS This permit does not convey any property rights of any sort, or any exclusive privilege. G17. DUTY TO COMPLY The Permittee must comply with all conditions of this permit. Any permit noncompliance constitutes a violation of the Clean Water Act and is grounds for enforcement action; for permit termination, revocation and reissuance, or modification; or denial of a permit renewal application. G18. TOXIC POLLUTANTS The Permittee must comply with effluent standards or prohibitions established under Section 307(a) of the Clean Water Act for toxic pollutants within the time provided in the regulations that establish those standards or prohibitions, even if this permit has not yet been modified to incorporate the requirement. Construction Stormwater General Permit Page 43 G19. PENALTIES FOR TAMPERING The Clean Water Act provides that any person who falsifies, tampers with, or knowingly renders inaccurate any monitoring device or method required to be maintained under this permit shall, upon conviction, be punished by a fine of not more than $10,000 per violation, or by imprisonment for not more than two years per violation, or by both. If a conviction of a person is for a violation committed after a first conviction of such person under this condition, punishment shall be a fine of not more than $20,000 per day of violation, or imprisonment of not more than four (4) years, or both. G20. REPORTING PLANNED CHANGES The Permittee must, as soon as possible, give notice to Ecology of planned physical alterations, modifications or additions to the permitted construction activity. The Permittee should be aware that, depending on the nature and size of the changes to the original permit, a new public notice and other permit process requirements may be required. Changes in activities that require reporting to Ecology include those that will result in: A. The permitted facility being determined to be a new source pursuant to 40 CFR 122.29(b). B. A significant change in the nature or an increase in quantity of pollutants discharged, including but not limited to: for sites 5 acres or larger, a 20% or greater increase in acreage disturbed by construction activity. C. A change in or addition of surface water(s) receiving stormwater or non-stormwater from the construction activity. D. A change in the construction plans and/or activity that affects the Permittee’s monitoring requirements in Special Condition S4. Following such notice, permit coverage may be modified, or revoked and reissued pursuant to 40 CFR 122.62(a) to specify and limit any pollutants not previously limited. Until such modification is effective, any new or increased discharge in excess of permit limits or not specifically authorized by this permit constitutes a violation. G21. REPORTING OTHER INFORMATION Where the Permittee becomes aware that it failed to submit any relevant facts in a permit application, or submitted incorrect information in a permit application or in any report to Ecology, it must promptly submit such facts or information. G22. REPORTING ANTICIPATED NON-COMPLIANCE The Permittee must give advance notice to Ecology by submission of a new application or supplement thereto at least forty-five (45) days prior to commencement of such discharges, of any facility expansions, production increases, or other planned changes, such as process modifications, in the permitted facility or activity which may result in noncompliance with permit limits or conditions. Any maintenance of facilities, which might necessitate Construction Stormwater General Permit Page 44 unavoidable interruption of operation and degradation of effluent quality, must be scheduled during non-critical water quality periods and carried out in a manner approved by Ecology. G23. REQUESTS TO BE EXCLUDED FROM COVERAGE UNDER THE PERMIT Any discharger authorized by this permit may request to be excluded from coverage under the general permit by applying for an individual permit. The discharger must submit to the Director an application as described in WAC 173-220-040 or WAC 173-216-070, whichever is applicable, with reasons supporting the request. These reasons will fully document how an individual permit will apply to the applicant in a way that the general permit cannot. Ecology may make specific requests for information to support the request. The Director will either issue an individual permit or deny the request with a statement explaining the reason for the denial. When an individual permit is issued to a discharger otherwise subject to the construction stormwater general permit, the applicability of the construction stormwater general permit to that Permittee is automatically terminated on the effective date of the individual permit. G24. APPEALS A. The terms and conditions of this general permit, as they apply to the appropriate class of dischargers, are subject to appeal by any person within 30 days of issuance of this general permit, in accordance with Chapter 43.21B RCW, and Chapter 173-226 WAC. B. The terms and conditions of this general permit, as they apply to an individual discharger, are appealable in accordance with Chapter 43.21B RCW within 30 days of the effective date of coverage of that discharger. Consideration of an appeal of general permit coverage of an individual discharger is limited to the general permit’s applicability or nonapplicability to that individual discharger. C. The appeal of general permit coverage of an individual discharger does not affect any other dischargers covered under this general permit. If the terms and conditions of this general permit are found to be inapplicable to any individual discharger(s), the matter shall be remanded to Ecology for consideration of issuance of an individual permit or permits. G25. SEVERABILITY The provisions of this permit are severable, and if any provision of this permit, or application of any provision of this permit to any circumstance, is held invalid, the application of such provision to other circumstances, and the remainder of this permit shall not be affected thereby. G26. BYPASS PROHIBITED A. Bypass Procedures Bypass, which is the intentional diversion of waste streams from any portion of a treatment facility, is prohibited for stormwater events below the design criteria for Construction Stormwater General Permit Page 45 stormwater management. Ecology may take enforcement action against a Permittee for bypass unless one of the following circumstances (1, 2, 3 or 4) is applicable. 1. Bypass of stormwater is consistent with the design criteria and part of an approved management practice in the applicable stormwater management manual. 2. Bypass for essential maintenance without the potential to cause violation of permit limits or conditions. Bypass is authorized if it is for essential maintenance and does not have the potential to cause violations of limitations or other conditions of this permit, or adversely impact public health. 3. Bypass of stormwater is unavoidable, unanticipated, and results in noncompliance of this permit. This bypass is permitted only if: a. Bypass is unavoidable to prevent loss of life, personal injury, or severe property damage. “Severe property damage” means substantial physical damage to property, damage to the treatment facilities which would cause them to become inoperable, or substantial and permanent loss of natural resources which can reasonably be expected to occur in the absence of a bypass. b. There are no feasible alternatives to the bypass, such as the use of auxiliary treatment facilities, retention of untreated wastes, maintenance during normal periods of equipment downtime (but not if adequate backup equipment should have been installed in the exercise of reasonable engineering judgment to prevent a bypass which occurred during normal periods of equipment downtime or preventative maintenance), or transport of untreated wastes to another treatment facility. c. Ecology is properly notified of the bypass as required in Special Condition S5.F of this permit. 4. A planned action that would cause bypass of stormwater and has the potential to result in noncompliance of this permit during a storm event. The Permittee must notify Ecology at least thirty (30) days before the planned date of bypass. The notice must contain: a. A description of the bypass and its cause. b. An analysis of all known alternatives which would eliminate, reduce, or mitigate the need for bypassing. c. A cost-effectiveness analysis of alternatives including comparative resource damage assessment. d. The minimum and maximum duration of bypass under each alternative. e. A recommendation as to the preferred alternative for conducting the bypass. Construction Stormwater General Permit Page 46 f. The projected date of bypass initiation. g. A statement of compliance with SEPA. h. A request for modification of water quality standards as provided for in WAC 173-201A-110, if an exceedance of any water quality standard is anticipated. i. Steps taken or planned to reduce, eliminate, and prevent reoccurrence of the bypass. 5. For probable construction bypasses, the need to bypass is to be identified as early in the planning process as possible. The analysis required above must be considered during preparation of the Stormwater Pollution Prevention Plan (SWPPP) and must be included to the extent practical. In cases where the probable need to bypass is determined early, continued analysis is necessary up to and including the construction period in an effort to minimize or eliminate the bypass. Ecology will consider the following before issuing an administrative order for this type bypass: a. If the bypass is necessary to perform construction or maintenance-related activities essential to meet the requirements of this permit. b. If there are feasible alternatives to bypass, such as the use of auxiliary treatment facilities, retention of untreated wastes, stopping production, maintenance during normal periods of equipment down time, or transport of untreated wastes to another treatment facility. c. If the bypass is planned and scheduled to minimize adverse effects on the public and the environment. After consideration of the above and the adverse effects of the proposed bypass and any other relevant factors, Ecology will approve, conditionally approve, or deny the request. The public must be notified and given an opportunity to comment on bypass incidents of significant duration, to the extent feasible. Approval of a request to bypass will be by administrative order issued by Ecology under RCW 90.48.120. B. Duty to Mitigate The Permittee is required to take all reasonable steps to minimize or prevent any discharge or sludge use or disposal in violation of this permit that has a reasonable likelihood of adversely affecting human health or the environment. Construction Stormwater General Permit Page 47 APPENDIX A – DEFINITIONS AKART is an acronym for “all known, available, and reasonable methods of prevention, control, and treatment.” AKART represents the most current methodology that can be reasonably required for preventing, controlling, or abating the pollutants and controlling pollution associated with a discharge. Applicable TMDL means a TMDL for turbidity, fine sediment, high pH, or phosphorus, which was completed and approved by EPA before January 1, 2016, or before the date the operator’s complete permit application is received by Ecology, whichever is later. Applicant means an operator seeking coverage under this permit. Benchmark means a pollutant concentration used as a permit threshold, below which a pollutant is considered unlikely to cause a water quality violation, and above which it may. When pollutant concentrations exceed benchmarks, corrective action requirements take effect. Benchmark values are not water quality standards and are not numeric effluent limitations; they are indicator values. Best Management Practices (BMPs) means schedules of activities, prohibitions of practices, maintenance procedures, and other physical, structural and/or managerial practices to prevent or reduce the pollution of waters of the State. BMPs include treatment systems, operating procedures, and practices to control: stormwater associated with construction activity, spillage or leaks, sludge or waste disposal, or drainage from raw material storage. Buffer means an area designated by a local jurisdiction that is contiguous to and intended to protect a sensitive area. Bypass means the intentional diversion of waste streams from any portion of a treatment facility. Calendar Day A period of 24 consecutive hours starting at 12:00 midnight and ending the following 12:00 midnight. Calendar Week (same as Week) means a period of seven consecutive days starting at 12:01 a.m. (0:01 hours) on Sunday. Certified Erosion and Sediment Control Lead (CESCL) means a person who has current certification through an approved erosion and sediment control training program that meets the minimum training standards established by Ecology (see BMP C160 in the SWMM). Chemical Treatment means the addition of chemicals to stormwater and/or authorized non- stormwater prior to filtration and discharge to surface waters. Clean Water Act (CWA) means the Federal Water Pollution Control Act enacted by Public Law 92-500, as amended by Public Laws 95-217, 95-576, 96-483, and 97-117; USC 1251 et seq. Combined Sewer means a sewer which has been designed to serve as a sanitary sewer and a storm sewer, and into which inflow is allowed by local ordinance. Construction Stormwater General Permit Page 48 Common Plan of Development or Sale means a site where multiple separate and distinct construction activities may be taking place at different times on different schedules and/or by different contractors, but still under a single plan. Examples include: 1) phased projects and projects with multiple filings or lots, even if the separate phases or filings/lots will be constructed under separate contract or by separate owners (e.g., a development where lots are sold to separate builders); 2) a development plan that may be phased over multiple years, but is still under a consistent plan for long-term development; 3) projects in a contiguous area that may be unrelated but still under the same contract, such as construction of a building extension and a new parking lot at the same facility; and 4) linear projects such as roads, pipelines, or utilities. If the project is part of a common plan of development or sale, the disturbed area of the entire plan must be used in determining permit requirements. Composite Sample means a mixture of grab samples collected at the same sampling point at different times, formed either by continuous sampling or by mixing discrete samples. May be "time-composite" (collected at constant time intervals) or "flow-proportional" (collected either as a constant sample volume at time intervals proportional to stream flow, or collected by increasing the volume of each aliquot as the flow increases while maintaining a constant time interval between the aliquots. Concrete Wastewater means any water used in the production, pouring and/or clean-up of concrete or concrete products, and any water used to cut, grind, wash, or otherwise modify concrete or concrete products. Examples include water used for or resulting from concrete truck/mixer/pumper/tool/chute rinsing or washing, concrete saw cutting and surfacing (sawing, coring, grinding, roughening, hydro-demolition, bridge and road surfacing). When stormwater comingles with concrete wastewater, the resulting water is considered concrete wastewater and must be managed to prevent discharge to waters of the State, including ground water. Construction Activity means land disturbing operations including clearing, grading or excavation which disturbs the surface of the land. Such activities may include road construction, construction of residential houses, office buildings, or industrial buildings, site preparation, soil compaction, movement and stockpiling of topsoils, and demolition activity. Contaminant means any hazardous substance that does not occur naturally or occurs at greater than natural background levels. See definition of “hazardous substance” and WAC 173-340-200. Contaminated Groundwater means groundwater which contains contaminants, pollutants, or hazardous substances that do not occur naturally or occur at levels greater than natural background. Contaminated Soil means soil which contains contaminants, pollutants, or hazardous substances that do not occur naturally or occur at levels greater than natural background. Demonstrably Equivalent means that the technical basis for the selection of all stormwater BMPs is documented within a SWPPP, including: 1. The method and reasons for choosing the stormwater BMPs selected. Construction Stormwater General Permit Page 49 2. The pollutant removal performance expected from the BMPs selected. 3. The technical basis supporting the performance claims for the BMPs selected, including any available data concerning field performance of the BMPs selected. 4. An assessment of how the selected BMPs will comply with state water quality standards. 5. An assessment of how the selected BMPs will satisfy both applicable federal technology- based treatment requirements and state requirements to use all known, available, and reasonable methods of prevention, control, and treatment (AKART). Department means the Washington State Department of Ecology. Detention means the temporary storage of stormwater to improve quality and/or to reduce the mass flow rate of discharge. Dewatering means the act of pumping ground water or stormwater away from an active construction site. Director means the Director of the Washington State Department of Ecology or his/her authorized representative. Discharger means an owner or operator of any facility or activity subject to regulation under Chapter 90.48 RCW or the Federal Clean Water Act. Domestic Wastewater means water carrying human wastes, including kitchen, bath, and laundry wastes from residences, buildings, industrial establishments, or other places, together with such ground water infiltration or surface waters as may be present. Ecology means the Washington State Department of Ecology. Engineered Soils means the use of soil amendments including, but not limited, to Portland cement treated base (CTB), cement kiln dust (CKD), or fly ash to achieve certain desirable soil characteristics. Equivalent BMPs means operational, source control, treatment, or innovative BMPs which result in equal or better quality of stormwater discharge to surface water or to ground water than BMPs selected from the SWMM. Erosion means the wearing away of the land surface by running water, wind, ice, or other geological agents, including such processes as gravitational creep. Erosion and Sediment Control BMPs means BMPs intended to prevent erosion and sedimentation, such as preserving natural vegetation, seeding, mulching and matting, plastic covering, filter fences, sediment traps, and ponds. Erosion and sediment control BMPs are synonymous with stabilization and structural BMPs. Federal Operator is an entity that meets the definition of “Operator” in this permit and is either any department, agency or instrumentality of the executive, legislative, and judicial branches of Construction Stormwater General Permit Page 50 the Federal government of the United States, or another entity, such as a private contractor, performing construction activity for any such department, agency, or instrumentality. Final Stabilization (same as fully stabilized or full stabilization) means the establishment of a permanent vegetative cover, or equivalent permanent stabilization measures (examples of permanent non-vegetative stabilization methods include, but are not limited to riprap, gabions or geotextiles) which prevents erosion. Ground Water means water in a saturated zone or stratum beneath the land surface or a surface waterbody. Hazardous Substance means any dangerous or extremely hazardous waste as defined in RCW 70.105.010 (5) and (6), or any dangerous or extremely dangerous waste as designated by rule under chapter 70.105 RCW; any hazardous substance as defined in RCW 70.105.010(10) or any hazardous substance as defined by rule under chapter 70.105 RCW; any substance that, on the effective date of this section, is a hazardous substance under section 101(14) of the federal cleanup law, 42 U.S.C., Sec. 9601(14); petroleum or petroleum products; and any substance or category of substances, including solid waste decomposition products, determined by the director by rule to present a threat to human health or the environment if released into the environment. The term hazardous substance does not include any of the following when contained in an underground storage tank from which there is not a release: crude oil or any fraction thereof or petroleum, if the tank is in compliance with all applicable federal, state, and local law. Injection Well means a well that is used for the subsurface emplacement of fluids. (See Well.) Jurisdiction means a political unit such as a city, town or county; incorporated for local self- government. National Pollutant Discharge Elimination System (NPDES) means the national program for issuing, modifying, revoking and reissuing, terminating, monitoring, and enforcing permits, and imposing and enforcing pretreatment requirements, under sections 307, 402, 318, and 405 of the Federal Clean Water Act, for the discharge of pollutants to surface waters of the State from point sources. These permits are referred to as NPDES permits and, in Washington State, are administered by the Washington State Department of Ecology. Notice of Intent (NOI) means the application for, or a request for coverage under this general permit pursuant to WAC 173-226-200. Notice of Termination (NOT) means a request for termination of coverage under this general permit as specified by Special Condition S10 of this permit. Operator means any party associated with a construction project that meets either of the following two criteria: The party has operational control over construction plans and specifications, including the ability to make modifications to those plans and specifications; or Construction Stormwater General Permit Page 51 The party has day-to-day operational control of those activities at a project that are necessary to ensure compliance with a SWPPP for the site or other permit conditions (e.g., they are authorized to direct workers at a site to carry out activities required by the SWPPP or comply with other permit conditions). Permittee means individual or entity that receives notice of coverage under this general permit. pH means a liquid’s measure of acidity or alkalinity. A pH of 7 is defined as neutral. Large variations above or below this value are considered harmful to most aquatic life. pH Monitoring Period means the time period in which the pH of stormwater runoff from a site must be tested a minimum of once every seven days to determine if stormwater pH is between 6.5 and 8.5. Point Source means any discernible, confined, and discrete conveyance, including but not limited to, any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, and container from which pollutants are or may be discharged to surface waters of the State. This term does not include return flows from irrigated agriculture. (See Fact Sheet for further explanation.) Pollutant means dredged spoil, solid waste, incinerator residue, filter backwash, sewage, garbage, domestic sewage sludge (biosolids), munitions, chemical wastes, biological materials, radioactive materials, heat, wrecked or discarded equipment, rock, sand, cellar dirt, and industrial, municipal, and agricultural waste. This term does not include sewage from vessels within the meaning of section 312 of the CWA, nor does it include dredged or fill material discharged in accordance with a permit issued under section 404 of the CWA. Pollution means contamination or other alteration of the physical, chemical, or biological properties of waters of the State; including change in temperature, taste, color, turbidity, or odor of the waters; or such discharge of any liquid, gaseous, solid, radioactive or other substance into any waters of the State as will or is likely to create a nuisance or render such waters harmful, detrimental or injurious to the public health, safety or welfare; or to domestic, commercial, industrial, agricultural, recreational, or other legitimate beneficial uses; or to livestock, wild animals, birds, fish or other aquatic life. Process Wastewater means any water which, during manufacturing or processing, comes into direct contact with or results from the production or use of any raw material, intermediate product, finished product, byproduct, or waste product. If stormwater commingles with process wastewater, the commingled water is considered process wastewater. Receiving Water means the waterbody at the point of discharge. If the discharge is to a storm sewer system, either surface or subsurface, the receiving water is the waterbody to which the storm system discharges. Systems designed primarily for other purposes such as for ground water drainage, redirecting stream natural flows, or for conveyance of irrigation water/return flows that coincidentally convey stormwater are considered the receiving water. Construction Stormwater General Permit Page 52 Representative means a stormwater or wastewater sample which represents the flow and characteristics of the discharge. Representative samples may be a grab sample, a time- proportionate composite sample, or a flow proportionate sample. Ecology’s Construction Stormwater Monitoring Manual provides guidance on representative sampling. Responsible Corporate Officer for the purpose of signatory authority means: (i) a president, secretary, treasurer, or vice-president of the corporation in charge of a principal business function, or any other person who performs similar policy- or decision-making functions for the corporation, or (ii) the manager of one or more manufacturing, production, or operating facilities, provided, the manager is authorized to make management decisions which govern the operation of the regulated facility including having the explicit or implicit duty of making major capital investment recommendations, and initiating and directing other comprehensive measures to assure long term environmental compliance with environmental laws and regulations; the manager can ensure that the necessary systems are established or actions taken to gather complete and accurate information for permit application requirements; and where authority to sign documents has been assigned or delegated to the manager in accordance with corporate procedures (40 CFR 122.22). Sanitary Sewer means a sewer which is designed to convey domestic wastewater. Sediment means the fragmented material that originates from the weathering and erosion of rocks or unconsolidated deposits, and is transported by, suspended in, or deposited by water. Sedimentation means the depositing or formation of sediment. Sensitive Area means a waterbody, wetland, stream, aquifer recharge area, or channel migration zone. SEPA (State Environmental Policy Act) means the Washington State Law, RCW 43.21C.020, intended to prevent or eliminate damage to the environment. Significant Amount means an amount of a pollutant in a discharge that is amenable to available and reasonable methods of prevention or treatment; or an amount of a pollutant that has a reasonable potential to cause a violation of surface or ground water quality or sediment management standards. Significant Concrete Work means greater than 1000 cubic yards poured concrete or recycled concrete used over the life of a project. Significant Contributor of Pollutants means a facility determined by Ecology to be a contributor of a significant amount(s) of a pollutant(s) to waters of the State of Washington. Site means the land or water area where any "facility or activity" is physically located or conducted. Source Control BMPs means physical, structural or mechanical devices or facilities that are intended to prevent pollutants from entering stormwater. A few examples of source control Construction Stormwater General Permit Page 53 BMPs are erosion control practices, maintenance of stormwater facilities, constructing roofs over storage and working areas, and directing wash water and similar discharges to the sanitary sewer or a dead end sump. Stabilization means the application of appropriate BMPs to prevent the erosion of soils, such as, temporary and permanent seeding, vegetative covers, mulching and matting, plastic covering and sodding. See also the definition of Erosion and Sediment Control BMPs. Storm Drain means any drain which drains directly into a storm sewer system, usually found along roadways or in parking lots. Storm Sewer System means a means a conveyance, or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, or storm drains designed or used for collecting or conveying stormwater. This does not include systems which are part of a combined sewer or Publicly Owned Treatment Works (POTW) as defined at 40 CFR 122.2. Stormwater means that portion of precipitation that does not naturally percolate into the ground or evaporate, but flows via overland flow, interflow, pipes, and other features of a stormwater drainage system into a defined surface waterbody, or a constructed infiltration facility. Stormwater Management Manual (SWMM) or Manual means the technical Manual published by Ecology for use by local governments that contain descriptions of and design criteria for BMPs to prevent, control, or treat pollutants in stormwater. Stormwater Pollution Prevention Plan (SWPPP) means a documented plan to implement measures to identify, prevent, and control the contamination of point source discharges of stormwater. Surface Waters of the State includes lakes, rivers, ponds, streams, inland waters, salt waters, and all other surface waters and water courses within the jurisdiction of the State of Washington. Temporary Stabilization means the exposed ground surface has been covered with appropriate materials to provide temporary stabilization of the surface from water or wind erosion. Materials include, but are not limited to, mulch, riprap, erosion control mats or blankets and temporary cover crops. Seeding alone is not considered stabilization. Temporary stabilization is not a substitute for the more permanent “final stabilization.” Total Maximum Daily Load (TMDL) means a calculation of the maximum amount of a pollutant that a waterbody can receive and still meet state water quality standards. Percentages of the total maximum daily load are allocated to the various pollutant sources. A TMDL is the sum of the allowable loads of a single pollutant from all contributing point and nonpoint sources. The TMDL calculations must include a "margin of safety" to ensure that the waterbody can be protected in case there are unforeseen events or unknown sources of the pollutant. The calculation must also account for seasonable variation in water quality. Construction Stormwater General Permit Page 54 Transfer of Coverage (TOC) means a request for transfer of coverage under this general permit as specified by General Condition G9 of this permit. Treatment BMPs means BMPs that are intended to remove pollutants from stormwater. A few examples of treatment BMPs are detention ponds, oil/water separators, biofiltration, and constructed wetlands. Transparency means a measurement of water clarity in centimeters (cm), using a 60 cm transparency tube. The transparency tube is used to estimate the relative clarity or transparency of water by noting the depth at which a black and white Secchi disc becomes visible when water is released from a value in the bottom of the tube. A transparency tube is sometimes referred to as a “turbidity tube.” Turbidity means the clarity of water expressed as nephelometric turbidity units (NTUs) and measured with a calibrated turbidimeter. Uncontaminated means free from any contaminant. See definition of “contaminant” and WAC 173-340-200. Waste Load Allocation (WLA) means the portion of a receiving water’s loading capacity that is allocated to one of its existing or future point sources of pollution. WLAs constitute a type of water quality based effluent limitation (40 CFR 130.2[h]). Water-only Based Shaft Drilling is a shaft drilling process that uses water only and no additives are involved in the drilling of shafts for construction of building, road, or bridge foundations. Water quality means the chemical, physical, and biological characteristics of water, usually with respect to its suitability for a particular purpose. Waters of the State includes those waters as defined as "waters of the United States" in 40 CFR Subpart 122.2 within the geographic boundaries of Washington State and "waters of the State" as defined in Chapter 90.48 RCW, which include lakes, rivers, ponds, streams, inland waters, underground waters, salt waters, and all other surface waters and water courses within the jurisdiction of the state of Washington. Well means a bored, drilled or driven shaft, or dug hole whose depth is greater than the largest surface dimension. (See Injection well.) Wheel Wash Wastewater means any water used in, or resulting from the operation of, a tire bath or wheel wash (BMP C106: Wheel Wash), or other structure or practice that uses water to physically remove mud and debris from vehicles leaving a construction site and prevent track- out onto roads. When stormwater comingles with wheel wash wastewater, the resulting water is considered wheel wash wastewater and must be managed according to Special Condition S9.D.9. Construction Stormwater General Permit Page 55 APPENDIX B – ACRONYMS AKART All Known, Available, and Reasonable Methods of Prevention, Control, and Treatment BMP Best Management Practice CESCL Certified Erosion and Sediment Control Lead CFR Code of Federal Regulations CKD Cement Kiln Dust cm Centimeters CTB Cement-Treated Base CWA Clean Water Act DMR Discharge Monitoring Report EPA Environmental Protection Agency ERTS Environmental Report Tracking System ESC Erosion and Sediment Control FR Federal Register LID Low Impact Development NOI Notice of Intent NOT Notice of Termination NPDES National Pollutant Discharge Elimination System NTU Nephelometric Turbidity Unit RCW Revised Code of Washington SEPA State Environmental Policy Act SWMM Stormwater Management Manual SWPPP Stormwater Pollution Prevention Plan TMDL Total Maximum Daily Load UIC Underground Injection Control USC United States Code USEPA United States Environmental Protection Agency WAC Washington Administrative Code WQ Water Quality WWHM Western Washington Hydrology Model 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page F-2 Appendix F Engineering Calculations Existing Site Hydrology KCRTS was used to model the peak runoff from the Site. Per Table 3.2.2.b of the Manual the soil type is modeled as “Till” for the Alderwood gravelly sandy loam SCS classification. The entire Site is modeled as “Forest.” Results of the KCRTS analysis are included in this section. Flow Frequency Analysis Time Series File:predev.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.131 2 2/09/01 18:00 0.176 1 100.00 0.990 0.042 7 1/05/02 16:00 0.131 2 25.00 0.960 0.103 3 2/28/03 3:00 0.103 3 10.00 0.900 0.012 8 8/26/04 2:00 0.103 4 5.00 0.800 0.061 6 1/05/05 8:00 0.091 5 3.00 0.667 0.103 4 1/18/06 20:00 0.061 6 2.00 0.500 0.091 5 11/24/06 4:00 0.042 7 1.30 0.231 0.176 1 1/09/08 9:00 0.012 8 1.10 0.091 Computed Peaks 0.161 50.00 0.980 The maximum discharge of the construction stormwater will not exceed 50% of the 2-year predeveloped peak flow rate of 0.061 cfs. Therefore the max discharge from the Site during construction will not exceed 0.0305 cfs. 2018 D.R. STRONG Consulting Engineers, Inc. Bethany Corner Stormwater Pollution Prevention Plan Page F-2 Flow Frequency Analysis Time Series File:rdin_15.tsf Project Location:Sea-Tac ---Annual Peak Flow Rates--- -----Flow Frequency Analysis------- Flow Rate Rank Time of Peak - - Peaks - - Rank Return Prob (CFS) (CFS) Period 0.557 6 8/27/01 18:00 1.72 1 100.00 0.990 0.396 8 1/05/02 15:00 1.20 2 25.00 0.960 1.20 2 12/08/02 17:15 0.778 3 10.00 0.900 0.449 7 8/23/04 14:30 0.690 4 5.00 0.800 0.690 4 11/17/04 5:00 0.668 5 3.00 0.667 0.668 5 10/27/05 10:45 0.557 6 2.00 0.500 0.778 3 10/25/06 22:45 0.449 7 1.30 0.231 1.72 1 1/09/08 6:30 0.396 8 1.10 0.091 Computed Peaks 1.55 50.00 0.980 Sediment Trap Facility Sizing The Site will utilize one sediment trap for sediment control. The maximum discharge rate for the site is 0.031 cfs (50% of the 2-year predeveloped peak). The sediment traps will discharge to the collection system on 111th AVE SE. Below is sizing summary: Sediment Trap basin: 1.85 acres 2-year peak flow rate: 0.557 cfs Required Surface Area: 1,159 s.f. Provided Surface Area: 1,700 s.f. 2021 D. R. STRONG Consulting Engineers Inc. Page 79 Bethany Corner Technical Information Report Renton, Washington APPENDIX “C” BOND QUANTITY WORKSHEET CED Permit #:U16006722 Unit Reference #Price Unit Quantity Cost Backfill & compaction-embankment ESC-1 6.50$ CY Check dams, 4" minus rock ESC-2 SWDM 5.4.6.3 80.00$ Each 19 1,520.00 Catch Basin Protection ESC-3 35.50$ Each 16 568.00 Crushed surfacing 1 1/4" minus ESC-4 WSDOT 9-03.9(3)95.00$ CY Ditching ESC-5 9.00$ CY Excavation-bulk ESC-6 2.00$ CY 12 24.00 Fence, silt ESC-7 SWDM 5.4.3.1 1.50$ LF 965 1,447.50 Fence, Temporary (NGPE)ESC-8 1.50$ LF 65 97.50 Geotextile Fabric ESC-9 2.50$ SY Hay Bale Silt Trap ESC-10 0.50$ Each Hydroseeding ESC-11 SWDM 5.4.2.4 0.80$ SY 6500 5,200.00 Interceptor Swale / Dike ESC-12 1.00$ LF 1000 1,000.00 Jute Mesh ESC-13 SWDM 5.4.2.2 3.50$ SY Level Spreader ESC-14 1.75$ LF Mulch, by hand, straw, 3" deep ESC-15 SWDM 5.4.2.1 2.50$ SY Mulch, by machine, straw, 2" deep ESC-16 SWDM 5.4.2.1 2.00$ SY 650 1,300.00 Piping, temporary, CPP, 6"ESC-17 12.00$ LF Piping, temporary, CPP, 8"ESC-18 14.00$ LF Piping, temporary, CPP, 12"ESC-19 18.00$ LF 54 972.00 Plastic covering, 6mm thick, sandbagged ESC-20 SWDM 5.4.2.3 4.00$ SY Rip Rap, machine placed; slopes ESC-21 WSDOT 9-13.1(2)45.00$ CY 10 450.00 Rock Construction Entrance, 50'x15'x1'ESC-22 SWDM 5.4.4.1 1,800.00$ Each Rock Construction Entrance, 100'x15'x1'ESC-23 SWDM 5.4.4.1 3,200.00$ Each 1 3,200.00 Sediment pond riser assembly ESC-24 SWDM 5.4.5.2 2,200.00$ Each 1 2,200.00 Sediment trap, 5' high berm ESC-25 SWDM 5.4.5.1 19.00$ LF 180 3,420.00 Sed. trap, 5' high, riprapped spillway berm section ESC-26 SWDM 5.4.5.1 70.00$ LF Seeding, by hand ESC-27 SWDM 5.4.2.4 1.00$ SY Sodding, 1" deep, level ground ESC-28 SWDM 5.4.2.5 8.00$ SY Sodding, 1" deep, sloped ground ESC-29 SWDM 5.4.2.5 10.00$ SY TESC Supervisor ESC-30 110.00$ HR 16 1,760.00 Water truck, dust control ESC-31 SWDM 5.4.7 140.00$ HR 16 2,240.00 Unit Reference #Price Unit Quantity Cost 250.00$ Each 1 250.00 EROSION/SEDIMENT SUBTOTAL:25,649.00 SALES TAX @ 10%2,564.90 EROSION/SEDIMENT TOTAL:28,213.90 (A) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR EROSION & SEDIMENT CONTROL Description No. (A) WRITE-IN-ITEMS Sump Pump Page 1 of 1 Ref 8-H Bond Quantity Worksheet SECTION II.a EROSION_CONTROL Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019 CED Permit #:U16006722 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost GENERAL ITEMS Backfill & Compaction- embankment GI-1 6.00$ CY 2368 14,208.00 7224 43,344.00 Backfill & Compaction- trench GI-2 9.00$ CY 115 1,035.00 470 4,230.00 Clear/Remove Brush, by hand (SY)GI-3 1.00$ SY Bollards - fixed GI-4 240.74$ Each Bollards - removable GI-5 452.34$ Each Clearing/Grubbing/Tree Removal GI-6 10,000.00$ Acre 0.3 3,000.00 1.5 15,000.00 Excavation - bulk GI-7 2.00$ CY 12 24.00 Excavation - Trench GI-8 5.00$ CY 115 575.00 470 2,350.00 Fencing, cedar, 6' high GI-9 20.00$ LF Fencing, chain link, 4'GI-10 38.31$ LF Fencing, chain link, vinyl coated, 6' high GI-11 20.00$ LF Fencing, chain link, gate, vinyl coated, 20' GI-12 1,400.00$ Each Fill & compact - common barrow GI-13 25.00$ CY Fill & compact - gravel base GI-14 27.00$ CY Fill & compact - screened topsoil GI-15 39.00$ CY Gabion, 12" deep, stone filled mesh GI-16 65.00$ SY Gabion, 18" deep, stone filled mesh GI-17 90.00$ SY Gabion, 36" deep, stone filled mesh GI-18 150.00$ SY Grading, fine, by hand GI-19 2.50$ SY Grading, fine, with grader GI-20 2.00$ SY Monuments, 3' Long GI-21 250.00$ Each 1 250.00 Sensitive Areas Sign GI-22 7.00$ Each 1 7.00 Sodding, 1" deep, sloped ground GI-23 8.00$ SY Surveying, line & grade GI-24 850.00$ Day 2 1,700.00 2 1,700.00 Surveying, lot location/lines GI-25 1,800.00$ Acre 0.3 540.00 1.5 2,700.00 Topsoil Type A (imported)GI-26 28.50$ CY Traffic control crew ( 2 flaggers )GI-27 120.00$ HR 40 4,800.00 Trail, 4" chipped wood GI-28 8.00$ SY Trail, 4" crushed cinder GI-29 9.00$ SY Trail, 4" top course GI-30 12.00$ SY Conduit, 2"GI-31 5.00$ LF Wall, retaining, concrete GI-32 55.00$ SF Wall, rockery GI-33 15.00$ SF SUBTOTAL THIS PAGE:5,050.00 21,058.00 69,355.00 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) Page 1 of 3 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019 CED Permit #:U16006722 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) ROAD IMPROVEMENT/PAVEMENT/SURFACING AC Grinding, 4' wide machine < 1000sy RI-1 30.00$ SY AC Grinding, 4' wide machine 1000-2000sy RI-2 16.00$ SY AC Grinding, 4' wide machine > 2000sy RI-3 10.00$ SY AC Removal/Disposal RI-4 35.00$ SY Barricade, Type III ( Permanent )RI-5 56.00$ LF Guard Rail RI-6 30.00$ LF Curb & Gutter, rolled RI-7 17.00$ LF Curb & Gutter, vertical RI-8 12.50$ LF 275 3,437.50 516 6,450.00 Curb and Gutter, demolition and disposal RI-9 18.00$ LF Curb, extruded asphalt RI-10 5.50$ LF Curb, extruded concrete RI-11 7.00$ LF Sawcut, asphalt, 3" depth RI-12 1.85$ LF 425 786.25 Sawcut, concrete, per 1" depth RI-13 3.00$ LF Sealant, asphalt RI-14 2.00$ LF 425 850.00 Shoulder, gravel, 4" thick RI-15 15.00$ SY Sidewalk, 4" thick RI-16 38.00$ SY 152 5,776.00 287 10,906.00 Sidewalk, 4" thick, demolition and disposal RI-17 32.00$ SY Sidewalk, 5" thick RI-18 41.00$ SY Sidewalk, 5" thick, demolition and disposal RI-19 40.00$ SY Sign, Handicap RI-20 85.00$ Each Striping, per stall RI-21 7.00$ Each Striping, thermoplastic, ( for crosswalk )RI-22 3.00$ SF Striping, 4" reflectorized line RI-23 0.50$ LF Additional 2.5" Crushed Surfacing RI-24 3.60$ SY HMA 1/2" Overlay 1.5" RI-25 14.00$ SY HMA 1/2" Overlay 2"RI-26 18.00$ SY 375 6,750.00 HMA Road, 2", 4" rock, First 2500 SY RI-27 28.00$ SY HMA Road, 2", 4" rock, Qty. over 2500SY RI-28 21.00$ SY HMA Road, 4", 6" rock, First 2500 SY RI-29 45.00$ SY 120 5,400.00 685 30,825.00 HMA Road, 4", 6" rock, Qty. over 2500 SY RI-30 37.00$ SY HMA Road, 4", 4.5" ATB RI-31 38.00$ SY Gravel Road, 4" rock, First 2500 SY RI-32 15.00$ SY Gravel Road, 4" rock, Qty. over 2500 SY RI-33 10.00$ SY Thickened Edge RI-34 8.60$ LF SUBTOTAL THIS PAGE:22,999.75 48,181.00 (B)(C)(D)(E) Page 2 of 3 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019 CED Permit #:U16006722 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR STREET AND SITE IMPROVEMENTS Quantity Remaining (Bond Reduction) (B)(C) PARKING LOT SURFACING No. 2" AC, 2" top course rock & 4" borrow PL-1 21.00$ SY 2" AC, 1.5" top course & 2.5" base course PL-2 28.00$ SY 4" select borrow PL-3 5.00$ SY 1.5" top course rock & 2.5" base course PL-4 14.00$ SY SUBTOTAL PARKING LOT SURFACING: (B)(C)(D)(E) LANDSCAPING & VEGETATION No. Street Trees LA-1 150.00$ EACH 5 750.00 6 900.00 Median Landscaping LA-2 Right-of-Way Landscaping LA-3 Wetland Landscaping LA-4 2,500.00$ LS 1 2,500.00 SUBTOTAL LANDSCAPING & VEGETATION:750.00 900.00 2,500.00 (B)(C)(D)(E) TRAFFIC & LIGHTING No. Signs TR-1 150.00$ 6 900.00 Street Light System ( # of Poles)TR-2 6,000.00$ EACH 4 24,000.00 5 30,000.00 Traffic Signal TR-3 Traffic Signal Modification TR-4 SUBTOTAL TRAFFIC & LIGHTING:24,000.00 30,900.00 (B)(C)(D)(E) WRITE-IN-ITEMS SUBTOTAL WRITE-IN ITEMS: STREET AND SITE IMPROVEMENTS SUBTOTAL:52,799.75 101,039.00 71,855.00 SALES TAX @ 10%5,279.98 10,103.90 7,185.50 STREET AND SITE IMPROVEMENTS TOTAL:58,079.73 111,142.90 79,040.50 (B)(C)(D)(E) Page 3 of 3 Ref 8-H Bond Quantity Worksheet SECTION II.b TRANSPORTATION Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019 CED Permit #:U16006722 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost DRAINAGE (CPE = Corrugated Polyethylene Pipe, N12 or Equivalent) For Culvert prices, Average of 4' cover was assumed. Assume perforated PVC is same price as solid pipe.) Access Road, R/D D-1 26.00$ SY 10 260.00 * (CBs include frame and lid) Beehive D-2 90.00$ Each Through-curb Inlet Framework D-3 400.00$ Each 2 800.00 CB Type I D-4 1,500.00$ Each 8 12,000.00 3 4,500.00 2 3,000.00 CB Type IL D-5 1,750.00$ Each CB Type II, 48" diameter D-6 2,300.00$ Each 2 4,600.00 1 2,300.00 for additional depth over 4' D-7 480.00$ FT 5 2,400.00 2 960.00 CB Type II, 54" diameter D-8 2,500.00$ Each for additional depth over 4'D-9 495.00$ FT CB Type II, 60" diameter D-10 2,800.00$ Each for additional depth over 4'D-11 600.00$ FT CB Type II, 72" diameter D-12 6,000.00$ Each for additional depth over 4'D-13 850.00$ FT CB Type II, 96" diameter D-14 14,000.00$ Each for additional depth over 4'D-15 925.00$ FT Trash Rack, 12"D-16 350.00$ Each Trash Rack, 15"D-17 410.00$ Each Trash Rack, 18"D-18 480.00$ Each Trash Rack, 21"D-19 550.00$ Each Cleanout, PVC, 4"D-20 150.00$ Each Cleanout, PVC, 6"D-21 170.00$ Each 7 1,190.00 Cleanout, PVC, 8"D-22 200.00$ Each Culvert, PVC, 4" D-23 10.00$ LF Culvert, PVC, 6" D-24 13.00$ LF 300 3,900.00 Culvert, PVC, 8" D-25 15.00$ LF Culvert, PVC, 12" D-26 23.00$ LF Culvert, PVC, 15" D-27 35.00$ LF Culvert, PVC, 18" D-28 41.00$ LF Culvert, PVC, 24"D-29 56.00$ LF Culvert, PVC, 30" D-30 78.00$ LF Culvert, PVC, 36" D-31 130.00$ LF Culvert, CMP, 8"D-32 19.00$ LF Culvert, CMP, 12"D-33 29.00$ LF SUBTOTAL THIS PAGE:19,000.00 8,560.00 8,350.00 (B)(C)(D)(E) SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) Page 1 of 5 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019 CED Permit #:U16006722 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) DRAINAGE (Continued) Culvert, CMP, 15"D-34 35.00$ LF Culvert, CMP, 18"D-35 41.00$ LF Culvert, CMP, 24"D-36 56.00$ LF Culvert, CMP, 30"D-37 78.00$ LF Culvert, CMP, 36"D-38 130.00$ LF Culvert, CMP, 48"D-39 190.00$ LF Culvert, CMP, 60"D-40 270.00$ LF Culvert, CMP, 72"D-41 350.00$ LF Culvert, Concrete, 8"D-42 42.00$ LF Culvert, Concrete, 12"D-43 48.00$ LF Culvert, Concrete, 15"D-44 78.00$ LF Culvert, Concrete, 18"D-45 48.00$ LF Culvert, Concrete, 24"D-46 78.00$ LF Culvert, Concrete, 30"D-47 125.00$ LF Culvert, Concrete, 36"D-48 150.00$ LF Culvert, Concrete, 42"D-49 175.00$ LF Culvert, Concrete, 48"D-50 205.00$ LF Culvert, CPE Triple Wall, 6" D-51 14.00$ LF Culvert, CPE Triple Wall, 8" D-52 16.00$ LF Culvert, CPE Triple Wall, 12" D-53 24.00$ LF Culvert, CPE Triple Wall, 15" D-54 35.00$ LF Culvert, CPE Triple Wall, 18" D-55 41.00$ LF Culvert, CPE Triple Wall, 24" D-56 56.00$ LF Culvert, CPE Triple Wall, 30" D-57 78.00$ LF Culvert, CPE Triple Wall, 36" D-58 130.00$ LF Culvert, LCPE, 6"D-59 60.00$ LF Culvert, LCPE, 8"D-60 72.00$ LF Culvert, LCPE, 12"D-61 84.00$ LF 727 61,068.00 202 16,968.00 Culvert, LCPE, 15"D-62 96.00$ LF Culvert, LCPE, 18"D-63 108.00$ LF Culvert, LCPE, 24"D-64 120.00$ LF Culvert, LCPE, 30"D-65 132.00$ LF Culvert, LCPE, 36"D-66 144.00$ LF Culvert, LCPE, 48"D-67 156.00$ LF Culvert, LCPE, 54"D-68 168.00$ LF SUBTOTAL THIS PAGE:61,068.00 16,968.00 (B)(C)(D)(E) Page 2 of 5 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019 CED Permit #:U16006722 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) DRAINAGE (Continued) Culvert, LCPE, 60"D-69 180.00$ LF Culvert, LCPE, 72"D-70 192.00$ LF Culvert, HDPE, 6"D-71 42.00$ LF Culvert, HDPE, 8"D-72 42.00$ LF Culvert, HDPE, 12"D-73 74.00$ LF Culvert, HDPE, 15"D-74 106.00$ LF Culvert, HDPE, 18"D-75 138.00$ LF Culvert, HDPE, 24"D-76 221.00$ LF Culvert, HDPE, 30"D-77 276.00$ LF Culvert, HDPE, 36"D-78 331.00$ LF Culvert, HDPE, 48"D-79 386.00$ LF Culvert, HDPE, 54"D-80 441.00$ LF Culvert, HDPE, 60"D-81 496.00$ LF Culvert, HDPE, 72"D-82 551.00$ LF Pipe, Polypropylene, 6"D-83 84.00$ LF Pipe, Polypropylene, 8"D-84 89.00$ LF Pipe, Polypropylene, 12"D-85 95.00$ LF Pipe, Polypropylene, 15"D-86 100.00$ LF Pipe, Polypropylene, 18"D-87 106.00$ LF Pipe, Polypropylene, 24"D-88 111.00$ LF Pipe, Polypropylene, 30"D-89 119.00$ LF Pipe, Polypropylene, 36"D-90 154.00$ LF Pipe, Polypropylene, 48"D-91 226.00$ LF Pipe, Polypropylene, 54"D-92 332.00$ LF Pipe, Polypropylene, 60"D-93 439.00$ LF Pipe, Polypropylene, 72"D-94 545.00$ LF Culvert, DI, 6"D-95 61.00$ LF Culvert, DI, 8"D-96 84.00$ LF Culvert, DI, 12"D-97 106.00$ LF Culvert, DI, 15"D-98 129.00$ LF Culvert, DI, 18"D-99 152.00$ LF Culvert, DI, 24"D-100 175.00$ LF Culvert, DI, 30"D-101 198.00$ LF Culvert, DI, 36"D-102 220.00$ LF Culvert, DI, 48"D-103 243.00$ LF Culvert, DI, 54"D-104 266.00$ LF Culvert, DI, 60"D-105 289.00$ LF Culvert, DI, 72"D-106 311.00$ LF SUBTOTAL THIS PAGE: (B)(C)(D)(E) Page 3 of 5 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019 CED Permit #:U16006722 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) Specialty Drainage Items Ditching SD-1 9.50$ CY Flow Dispersal Trench (1,436 base+)SD-3 28.00$ LF French Drain (3' depth)SD-4 26.00$ LF 255 6,630.00 Geotextile, laid in trench, polypropylene SD-5 3.00$ SY Mid-tank Access Riser, 48" dia, 6' deep SD-6 2,000.00$ Each Pond Overflow Spillway SD-7 16.00$ SY Restrictor/Oil Separator, 12"SD-8 1,150.00$ Each 1 1,150.00 Restrictor/Oil Separator, 15"SD-9 1,350.00$ Each Restrictor/Oil Separator, 18"SD-10 1,700.00$ Each Riprap, placed SD-11 42.00$ CY 2 84.00 Tank End Reducer (36" diameter)SD-12 1,200.00$ Each Infiltration pond testing SD-13 125.00$ HR Permeable Pavement SD-14 Permeable Concrete Sidewalk SD-15 Culvert, Box __ ft x __ ft SD-16 SUBTOTAL SPECIALTY DRAINAGE ITEMS:7,864.00 (B)(C)(D)(E) STORMWATER FACILITIES (Include Flow Control and Water Quality Facility Summary Sheet and Sketch) Detention Pond SF-1 Each Detention Tank SF-2 Each Detention Vault SF-3 Each Infiltration Pond SF-4 Each Infiltration Tank SF-5 Each Infiltration Vault SF-6 Each Infiltration Trenches SF-7 Each Basic Biofiltration Swale SF-8 Each Wet Biofiltration Swale SF-9 Each Wetpond SF-10 Each Wetvault SF-11 160,500.00$ Each 1 160,500.00 Sand Filter SF-12 Each Sand Filter Vault SF-13 Each Linear Sand Filter SF-14 Each Proprietary Facility SF-15 Each Bioretention Facility SF-16 Each SUBTOTAL STORMWATER FACILITIES:160,500.00 (B)(C)(D)(E) Page 4 of 5 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019 CED Permit #:U16006722 Existing Future Public Private Right-of-Way Improvements Improvements (D) (E) Description No. Unit Price Unit Quant.Cost Quant.Cost Quant.Cost Quant.Cost SITE IMPROVEMENT BOND QUANTITY WORKSHEET FOR DRAINAGE AND STORMWATER FACILITIES Quantity Remaining (Bond Reduction) (B)(C) WRITE-IN-ITEMS (INCLUDE ON-SITE BMPs) WI-1 WI-2 WI-3 WI-4 WI-5 WI-6 WI-7 WI-8 WI-9 WI-10 WI-11 WI-12 WI-13 WI-14 WI-15 SUBTOTAL WRITE-IN ITEMS: DRAINAGE AND STORMWATER FACILITIES SUBTOTAL:80,068.00 25,528.00 176,714.00 SALES TAX @ 10%8,006.80 2,552.80 17,671.40 DRAINAGE AND STORMWATER FACILITIES TOTAL:88,074.80 28,080.80 194,385.40 (B)(C)(D)(E) Page 5 of 5 Ref 8-H Bond Quantity Worksheet SECTION II.c DRAINAGE Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019 Planning Division |1055 South Grady Way – 6th Floor | Renton, WA 98057 (425) 430-7200 Date: Name:Project Name: PE Registration No:CED Plan # (LUA): Firm Name:CED Permit # (U): Firm Address:Site Address: Phone No.Parcel #(s): Email Address:Project Phase: Site Restoration/Erosion Sediment Control Subtotal (a) Existing Right-of-Way Improvements Subtotal (b)(b)58,079.73$ Future Public Improvements Subtotal (c)111,142.90$ Stormwater & Drainage Facilities (Public & Private) Subtotal (d)(d)310,541.00$ (e) (f) Site Restoration Civil Construction Permit Maintenance Bond 95,952.73$ Bond Reduction 2 Construction Permit Bond Amount 3 Minimum Bond Amount is $10,000.00 1 Estimate Only - May involve multiple and variable components, which will be established on an individual basis by Development Engineering. 2 The City of Renton allows one request only for bond reduction prior to the maintenance period. Reduction of not more than 70% of the original bond amount, provided that the remaining 30% will cover all remaining items to be constructed. 3 Required Bond Amounts are subject to review and modification by Development Engineering. * Note: The word BOND as used in this document means any financial guarantee acceptable to the City of Renton. ** Note: All prices include labor, equipment, materials, overhead and profit. (425) 827-3063 jonathan.murray@drstrong.com Bethany Corner LUA16-000958 16433 & 16451 111th Ave SE 008800-0560, -0570 FOR APPROVAL U16006722 620 7th Avenue, Kirkland, WA 98033 425,874.49$ P (a) x 100% SITE IMPROVEMENT BOND QUANTITY WORKSHEET BOND CALCULATIONS 2/13/2019 Jonathan S. Murray, P.E. 50096 D.R. STRONG Consulting Engineers, Inc. R ((b x 150%) + (d x 100%)) S (e) x 150% + (f) x 100% Bond Reduction: Existing Right-of-Way Improvements (Quantity Remaining)2 Bond Reduction: Stormwater & Drainage Facilities (Quantity Remaining)2 T (P +R - S) Prepared by:Project Information CONSTRUCTION BOND AMOUNT */** (prior to permit issuance) EST1 ((b) + (c) + (d)) x 20% -$ MAINTENANCE BOND */** (after final acceptance of construction) 28,213.90$ 58,079.73$ 397,660.59$ 28,213.90$ -$ 310,541.00$ -$ Page 1 of 1 Ref 8-H Bond Quantity Worksheet SECTION III. BOND WORKSHEET Unit Prices Updated: 06/14/2016 Version: 04/26/2017 Printed 2/13/2019