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Home My WebLink AboutTIR-4315 Sophie Jo Short Plat TIR & Level 1 Downstream Analysis June 6, 2024 PR24-000024 LUA24-000081 Prepared for Schneider Homes, Inc. 6510 Southcenter Blvd, Suite100 Tukwila, WA 98188 Submitted by ESM Consulting Engineers, LLC 33400 8th Avenue S, Suite 205 Federal Way, WA 98003 253.838.6113 tel 253.838.7104 fax www.esmcivil.com June 6, 2024 Revised: February 20, 2025 02-20-2025 DEVELOPMENT ENGINEERING HHuynh 04/30/2025 Table of Contents Section 1. Project Overview Section 2. Conditions and Requirements Summary Section 3. Level 1 Off-Site Analysis Section 4. Flow Control & Water Quality Facility Analysis and Design Section 5. Conveyance System Analysis and Design Section 6. Special Reports and Studies Section 7. Other Permits Section 8. ESC Analysis and Design Section 9. Bond Quantities, Facility Summaries, & Declaration of Covenant Section 10. Operations and Maintenance Manual List of Figures 1.1 TIR Worksheet 1.2 Vicinity Map 1.3A Predeveloped Basin Map – Before Mitigation Trade 1.3B Predeveloped Basin Map – After Mitigation Trade 1.3C Developed Basin Map – After Mitigation Trade 1.4 Soils Map 3.1 Water Quality Assessment Map (DOE) 3.2 Downstream Study Area 3.3 Field Study Area 5.1A Onsite Conveyance Basin Map 5.1B Offsite Conveyance Basin Map Appendix Appendix A Hydrology Model Output (WHMM) Appendix B Geotechnical Study Appendix C CSWPPP Appendix D Operations and Maintenance Manual \\esm8\engr\esm-jobs\441\004\023\stormreport\rprt - stormreport.docx Sophie Jo Short Plat Page 3 January 7, 2025 Technical Information Report PR24-000024, LUA24-000081 1. Project Overview The proposed Sophie Jo Short Plat project is a 3-lot plat with associated utilities, street improvements, sidewalk, and stormwater infrastructure. The purpose of this report is to encapsulate the documents and analysis in accordance with the 2022 City of Renton Surface Water Design Manual (RSWDM), the King County Stormwater Pollution Prevention Manual (KCSPPM), and the latest edition of the LID Technical Guidance Manual for the Puget Sound (LID Manual), for the proposed short plat. Stormwater Review: The project is subject to a Full Drainage Review according to Section 1.1.2.4 of the RSWDM. The proposed development will result in greater than 2,000 sf of new plus replaced impervious surfaces but less than 50 acres of new impervious surface. A Full Drainage Review consists of reviewing Core Requirements #1-9 and Special Requirements #1-6 as outlined in Figure 1.1.2.A of the RSWDM. A discussion of these requirements can be found in Section 2 of this report. Existing Site: The proposed Sophie Jo Short Plat project site is located in the Southeast Quarter of Section 19, Township 23 N, Range 05 E, W.M., situated on one parcel, The site is located at the southeast corner of the intersection between S 21st Street and Smithers Ave S in the City of Renton, within the urban growth area, Zoned R-8. Parcel (722200-0110): 20,010 sf (0.46 ac) is currently undeveloped and does not have an address assigned to the property. The property is rectangular in shape, approximately 290’ x 74’. Adjacent to the Parcel is 21st St (Neighborhood Collector Arterial) to the north, 2114 Smithers Ave S (a single-family home) to the south, the Zetterberg Project (Medium Density, Single-Family development) to the East, and Smithers Ave S (Residential Access) to the west. The property has remained undeveloped and vegetated with trees and underbrush. The grades across the property slope down towards the west central area of the site at grades approximately 5%. Overall, the site is flat to moderately sloped with approximately 6 feet of vertical relief. There are no known critical areas on or adjacent to the project site. Proposed improvements: The plat infrastructure improvements include 3 single family lots, and a joint use driveway tract used for a shared access between lots 2 and 3, and a stormwater detention facility. Additional site improvements include public right-of-way, road and sidewalk, improvements, associated utilities, including new sewer and water services, and landscaping. The improvements are currently slated to be built in one phase. Stormwater will be collected and conveyed by a series of pipes and catch basins. A flow control facility, and an underground detention facility, are proposed to meet the flow control standards associated with this project. The design of the stormwater management/flow control facility mitigation includes implementation of a mitigation trade to meet the required flow control standard for the area. This treatment trade had been mapped and included with the basin maps at the end of this Section. Refer to Section 4 for further discussion of the existing and proposed hydrology, performance criteria, and design details. Sophie Jo Short Plat Page 4 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Geotechnical: A geotechnical study has been completed by Development Engineering, PLLC., dated September 7, 2017. Three exploration pits were dug across the project site. See Figure 1.4 for the Soils Map provided by Development Engineering for test pit locations. In summary, the three test pits had uniform subsurface conditions that confirmed the general geological mapping stratigraphy. The soils generally consisted of a minimum of 24 to 36 inches of weathered silty sand and gravel over a dense sandstone layer. No groundwater seepage was observed in any of the test pits. Although based on soil observations, it is anticipated that the upper soils would become saturated during periods of heavy rainfall. Based on the soil findings, the subsurface conditions observed in the test pits are not favorable for infiltration of significant volumes of project stormwater This is due primarily to the site soil’s relatively high fines content, and shallow groundwater observed in the test pits. A copy of Development Engineering’s report has been included In Appendix B. A geologic assessment for mine hazard areas in the vicinity of the site has been completed by DE-Civil, PLLC., dated December 28, 2023. Based on their findings, a mine hazard area does not exist on or within 300 feet of the site. A copy of DE-Civil, PLLC’s geologic assessment report has been included In Appendix B. CITY OF RENTON SURFACE WATER DESIGN MANUAL 2022 City of Renton Surface Water Design Manual 6/22/2022 8-A-1 REFERENCE 8-A TECHNICAL INFORMATION REPORT (TIR) WORKSHEET Part 1 PROJECT OWNER AND PROJECT ENGINEER Part 2 PROJECT LOCATION AND DESCRIPTION Project Owner _____________________________ Phone ___________________________________ Address __________________________________ _________________________________________ Project Engineer ___________________________ Company _________________________________ Phone ___________________________________ Project Name __________________________ CED Permit # ________________________ Location Township ________________ Range __________________ Section _________________ Site Address __________________________ _____________________________________ Part 3 TYPE OF PERMIT APPLICATION Part 4 OTHER REVIEWS AND PERMITS  Land Use (e.g., Subdivision / Short Subd.)  Building (e.g., M/F / Commercial / SFR)  Grading  Right-of-Way Use  Other _______________________  DFW HPA  COE 404  DOE Dam Safety  FEMA Floodplain  COE Wetlands  Other ________  Shoreline Management  Structural Rockery/Vault/_____  ESA Section 7 Part 5 PLAN AND REPORT INFORMATION Technical Information Report Site Improvement Plan (Engr. Plans) Type of Drainage Review (check one): Date (include revision dates): Date of Final:  Full  Targeted  Simplified  Large Project  Directed __________________ __________________ __________________ Plan Type (check one): Date (include revision dates): Date of Final:  Full  Modified  Simplified __________________ __________________ __________________ Schneider Family Homes 6510 Southcenter Blvd #1 Tukwila, WA 98188 Brandon Loucks ESM Consulting Engineers (253) 838-6113 Sophie Jo Short Plat 23 N 05 E 19 x x x x x REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-2 Part 6 SWDM ADJUSTMENT APPROVALS Type (circle one): Standard / Blanket Description: (include conditions in TIR Section 2) ____________________________________________________________________________________ ____________________________________________________________________________________ ____________________________________________________________________________________ Approved Adjustment No. ______________________ Date of Approval: _______________________ Part 7 MONITORING REQUIREMENTS Monitoring Required: Yes / No Start Date: _______________________ Completion Date: _______________________ Describe: _________________________________ _________________________________________ _________________________________________ Re: SWDM Adjustment No. ________________ Part 8 SITE COMMUNITY AND DRAINAGE BASIN Community Plan: ____________________________________________________________________ Special District Overlays: ______________________________________________________________ Drainage Basin: _____________________________________________________________________ Stormwater Requirements: _____________________________________________________________ Part 9 ONSITE AND ADJACENT SENSITIVE AREAS  River/Stream ________________________  Lake ______________________________  Wetlands ____________________________  Closed Depression ____________________  Floodplain ___________________________  Other _______________________________ _______________________________  Steep Slope __________________________  Erosion Hazard _______________________  Landslide Hazard ______________________  Coal Mine Hazard ______________________  Seismic Hazard _______________________  Habitat Protection ______________________  _____________________________________ REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-3 Part 10 SOILS Soil Type ______________________ ______________________ ______________________ ______________________ Slopes ________________________ ________________________ ________________________ ________________________ Erosion Potential _________________________ _________________________ _________________________ _________________________  High Groundwater Table (within 5 feet)  Other ________________________________  Sole Source Aquifer  Seeps/Springs  Additional Sheets Attached Part 11 DRAINAGE DESIGN LIMITATIONS REFERENCE  Core 2 – Offsite Analysis_________________  Sensitive/Critical Areas__________________  SEPA________________________________  LID Infeasibility________________________  Other________________________________  _____________________________________ LIMITATION / SITE CONSTRAINT _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________ _______________________________________  Additional Sheets Attached Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Threshold Discharge Area: (name or description) Core Requirements (all 9 apply): Discharge at Natural Location Number of Natural Discharge Locations: Offsite Analysis Level: 1 / 2 / 3 dated:__________________ Flow Control (include facility summary sheet) Standard: _______________________________ or Exemption Number: ____________ Conveyance System Spill containment located at: _____________________________ Erosion and Sediment Control / Construction Stormwater Pollution Prevention CSWPP/CESCL/ESC Site Supervisor: _____________________ Contact Phone: _________________________ After Hours Phone: _________________________ Maintenance and Operation Responsibility (circle one): Private / Public If Private, Maintenance Log Required: Yes / No Financial Guarantees and Liability Provided: Yes / No 09/26/2023 Detention Vault #1 TBD 5%NoBeaurite REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-4 Part 12 TIR SUMMARY SHEET (provide one TIR Summary Sheet per Threshold Discharge Area) Water Quality (include facility summary sheet) Type (circle one): Basic / Sens. Lake / Enhanced Basic / Bog or Exemption No. _______________________ On-site BMPs Describe: Special Requirements (as applicable): Area Specific Drainage Requirements Type: SDO / MDP / BP / Shared Fac. / None Name: ________________________ Floodplain/Floodway Delineation Type (circle one): Major / Minor / Exemption / None 100-year Base Flood Elevation (or range): _______________ Datum: Flood Protection Facilities Describe: Source Control (commercial / industrial land use) Describe land use: Describe any structural controls: Oil Control High-Use Site: Yes / No Treatment BMP: _________________________________ Maintenance Agreement: Yes / No with whom? _____________________________________ Other Drainage Structures Describe: #1e REFERENCE 8-A: TECHNICAL INFORMATION REPORT (TIR) WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 2022 City of Renton Surface Water Design Manual 6/22/2022 Ref 8-A-5 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  Control Pollutants  Protect Existing and Proposed BMPs/Facilities  Maintain Protective BMPs / Manage Project MINIMUM ESC REQUIREMENTS AFTER CONSTRUCTION  Stabilize exposed surfaces  Remove and restore Temporary ESC Facilities  Clean and remove all silt and debris, ensure operation of Permanent BMPs/Facilities, restore operation of BMPs/Facilities as necessary  Flag limits of sensitive areas and open space preservation areas  Other _______________________ Part 14 STORMWATER FACILITY DESCRIPTIONS (Note: Include Facility Summary and Sketch) Flow Control Description Water Quality Description On-site BMPs Description  Detention  Infiltration  Regional Facility  Shared Facility  Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________  Vegetated Flowpath  Wetpool  Filtration  Oil Control  Spill Control  Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________  Full Dispersion  Full Infiltration  Limited Infiltration  Rain Gardens  Bioretention  Permeable Pavement  Basic Dispersion  Soil Amendment  Perforated Pipe Connection  Other _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ x x x x x x x x x x x x x x Vault REFERENCE 8: PLAN REVIEW FORMS AND WORKSHEET TECHNICAL INFORMATION REPORT (TIR) WORKSHEET 6/22/2022 2022 City of Renton Surface Water Design Manual 8-A-6 Part 15 EASEMENTS/TRACTS Part 16 STRUCTURAL ANALYSIS  Drainage Easement  Covenant  Native Growth Protection Covenant  Tract  Other ____________________________  Cast in Place Vault  Retaining Wall  Rockery > 4′ High  Structural on Steep Slope  Other _______________________________ Part 17 SIGNATURE OF PROFESSIONAL ENGINEER I, or a civil engineer under my supervision, have visited the site. Actual site conditions as observed were incorporated into this worksheet and the attached Technical Information Report. To the best of my knowledge the information provided here is accurate. ____________________________________________________________________________________ Signed/Date 02/20/2025 x Shared Access King Vicinity Map Date: 9/25/2023 Notes: The information included on this map has been compiled by King County staff from a variety of sources and is subject to changewithout notice. King County makes no representations or warranties, express or implied, as to accuracy, completeness, timeliness,or rights to the use of such information. This document is not intended for use as a survey product. King County shall not be liablefor any general, special, indirect, incidental, or consequential damages including, but not limited to, lost revenues or lost profitsresulting from the use or misuse of the information contained on this map. Any sale of this map or information on this map isprohibited except by written permission of King County.± SITE Figure 1.2 - L L CFederal Way, WA 9800333400 8th Ave S, Suite 205C O N S U L T I N G E N G I N E E R SSCHNEIDER HOMESSOPHIE JO SHORT PLATFIGURE 1.3A - PREDEVELOPED BASIN MAP -BEFORE MITIGATION TRADE - SCALE: 1" = 30' n 21ST ST S SMITHERS AVE S L L CFederal Way, WA 9800333400 8th Ave S, Suite 205C O N S U L T I N G E N G I N E E R SSCHNEIDER HOMESSOPHIE JO SHORT PLATFIGURE 1.3B - PREDEVELOPED BASIN MAP -AFTER MITIGATION TRADE - SCALE: 1" = 30' n 21ST ST S SMITHERS AVE S 1 3TRACT A2 L L CFederal Way, WA 9800333400 8th Ave S, Suite 205C O N S U L T I N G E N G I N E E R SSCHNEIDER HOMESSOPHIE JO SHORT PLATFIGURE 1.3C - DEVELOPED BASIN MAP -AFTER MITIGATION TRADE - SCALE: 1" = 30' n 21ST ST S SMITHERS AVE S Approximate Site Location Not to Scale DE-CIVIL, PLLC P.O. Box 446 Tacoma, WA 98401 Ph (253) 228-0513 www.de-civil.com USDA Web Soil Survey Schneider SP 7XX S 21st Street Renton County, Washington Job No: 17-166 September 2017 Figure 3 Sophie Jo Short Plat Page 16 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 2. Conditions and Requirements Summary The project is subject to a Full Drainage Review according to Section 1.1.2.4 of the RSWDM. The proposed development will result in greater than 2,000 sf of new plus replaced impervious surfaces but less than 50 acres of new impervious surface. A Full Drainage Review consists of reviewing Core Requirements #1-9 and Special Requirements #1-6 as outlined in Table 1.1.2.A of the RSWDM. Review of the 9 Core Requirements and 5 Special Requirements This section describes how the project will meet the RSWDM Core and Special Requirements. Core Requirement No. 1 Discharge at the Natural Location The project site is made up of a single threshold discharge area with one natural discharge location. The site naturally drains toward the northeastern corner of the property. All runoff generated from the developed basin will discharge to the northeast corner of the site and enter an existing storm system. See Figure 1.3A for the natural discharge location. Core Requirement No. 2 Off-site Analysis An off-site analysis of the project has been completed and documented in Section 3 of this report. Core Requirement No. 3 Flow Control The site is located within a Conservation Flow Control Area, matching forested site conditions, requiring at minimum Level 2 flow control standards per Section 1.2.3.1.B of the RSWDM and the City of Renton Flow Control Application map. The flow control standard will be met through the use of an underground detention facility in a shared access tract to release stormwater at approved rates to the natural discharge location. Refer to Section 4 for more information. Core Requirement No. 4 Conveyance System The new conveyance network has been analyzed and is designed with sufficient capacity to convey and contain the 25-year and 100-year peak flow events. Stormwater conveyance calculations are provided in Section 5 of this report. Core Requirement No. 5 Erosion and Sediment Control Erosion and sediment controls to prevent the transport of sediment from the project site to downstream drainage facilities, water resources, and adjacent properties will be provided on the construction plans and discussed the Erosion and Sediment Control Report (CSWPPP) in Appendix C. Core Requirement No. 6 Maintenance and Operations The Operations and Maintenance manual is included in Appendix D of this report. Core Requirement No. 7 Financial Guarantees and Liability All drainage facilities constructed or modified for projects will comply with the financial guarantee requirement. Financial guarantees will be provided to the city as required. Sophie Jo Short Plat Page 17 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Core Requirement No. 8 Water Quality The proposed project, a single-family development, is located within a Basic WQ treatment area. After analysis of the proposed and future build-out land use areas, the development falls under Core Requirement #8, Exemption #1, less than 5,000 sf of new plus replaced PGIS will be created and less than 3/4 acre of new PGPS will be added. Refer to Table 4.2 for a breakdown of the new plus replaced PGIS area proposed. Core Requirement No. 9 Flow Control BMP’s All applicable Flow Control BMPs are listed and discussed in Section 4 of this report. Special Requirement No. 1 Other Adopted Area-Specific Requirements There are no known master drainage plans, basin plans, salmon conservation plans, stormwater compliance plans, flood hazard reduction plan updates, or shared facility drainage plans for this project. Special Requirement No. 1 does not apply. Special Requirement No. 2 Flood Hazard Area Delineation There is no known flood hazard on or around the project site. Special Requirement No. 2 does not apply. Special Requirement No. 3 Flood Protection Facilities The developed project site is not protected by an existing flood protection facility. The proposed site improvements do not include the modification of an existing flood protection facility. Special Requirement No. 3 does not apply. Special Requirement No. 4 Source Control The site is a residential development and is not subject to this requirement. Special Requirement No. 4 does not apply. Special Requirement No. 5 Oil Control The project does not have a “high-use site” characteristic and is not a redevelopment of a high-use site. Special Requirement No. 5 does not apply. A “high-use site” is a commercial or industrial site that typically generates or is subject to runoff containing high concentrations of oil due to high traffic turnover, on-site vehicle or heavy or stationary equipment’s use, or the frequent transfer of liquid petroleum or coal derivative products. Special Requirement No. 6 Aquifer Protection Area The project is not located within an aquifer protection area. Special Requirement No. 6 does not apply. Sophie Jo Short Plat Page 18 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 3. Level 1 Off-Site Analysis This narrative is to provide a Level 1 Downstream Analysis for the proposed Sophie Jo Short Plat development per Core Requirement #2, Section 1.2.2 of the RSWDM. The analysis is to identify and evaluate offsite flooding, erosion, and water quality problems that may be created or aggravated by the proposed project. The primary component of this offsite analysis is the downstream corridor. The second component is to evaluate the upstream drainage system to verify any offsite run-on that may impact the project. The following Level 1 downstream analysis is a qualitative survey of the downstream system of the project site and is composed of the following four tasks: Task 1 – Define and map the study area Task 2 – Downstream Resource Review for 1-mile downstream Task 3 – Field Inspection Task 4 – Drainage System Description and Problem Descriptions Task 1: Study Area Definition and Maps The drainage study area is approximately a one-mile-long path encompassing the site’s downstream corridor. See Figure 3.2 for a map of the basic study area. The study area also includes a 1/4-mile downstream field investigation of stormwater released from the project site. See Figure 1.3A for the Existing Site Conditions and Figure 3.3 for a map of the downstream field investigation. Task 2: Resource Review Flow Control Map According to the City of Renton Flow Control Applications Map, the project is located within the Conservation Flow Control Area, matching forested site conditions, and required to comply with Level 2 Flow Control Standards. Site Soils A geotechnical study has been completed by Development Engineering, PLLC., dated September 7, 2017. Three exploration pits were dug across the project site. See Figure 1.4 for the Soils Map provided by Development Engineering for test pit locations. In summary, the three test pits had uniform subsurface conditions that confirmed the general geological mapping stratigraphy. The soils generally consisted of a minimum of 24 to 36 inches of weathered silty sand and gravel over a dense sandstone layer. No groundwater seepage was observed in any of the test pits, although based on soil observations it is anticipated that during periods of heavy rainfall the upper soils would become saturated. Based on the soil findings, the subsurface conditions observed in the test pits are not favorable for infiltration of significant volumes of project stormwater as stated in the geotechnical study. This is due primarily to the site soil’s relatively high fines content, and shallow groundwater observed in the test pits. A copy of Development Engineering’s report has been included in Appendix C of this report. Sophie Jo Short Plat Page 19 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Resource Overview According to available information at the time of writing: Drainage Basin: The site drains into the S 21st ST Right of Way Stormwater Conveyance System. Streams: There are no known mapped or identified streams through or adjacent to the project site Erosion Hazard: None mapped. According to the Geotechnical report prepared by Development Engineering, dated September 07, 2017, the site is not considered an erosion hazard area as defined by the City of Renton. Landslide Hazard Area: None mapped. According to the Geotechnical report prepared by Development Engineering, dated September 07, 2017, the site does not contain Landslide Hazard Areas as defined by City of Renton. Lakes: None mapped 100 Year Floodplain The Federal Emergency Management Agency prepared maps for all areas within the City of Federal Way. These maps can be found on the FEMA website. Panel #53033C0979G, effective 08/19/2020 depicts the areas, if any, subject to flooding in the vicinity of this project. By inspection of this map, the project is located in Zone X, which is designated as areas outside the 0.2 percent annual chance floodplain. Downstream Drainage Complaints Relevant drainage complaints within the downstream corridor within the last 10-years were searched. After searching for publicly documented complaints, it was found that there are currently no relevant open or closed drainage complaints from the last 10 years. Water Quality Assessment The Department of Ecology Water Quality Assessment 303(d)/305(b) lists were reviewed to see if there are any known downstream water quality concerns. Waters whose beneficial uses are impaired by pollutants that require a water improvement are placed in the polluted water category (Category 5) and put on the 303(d) list. The 305(b) lists all waters and all categories. Pollutants of concern could be Bacteria, Dissolved oxygen, temperature, metals, phosphorus, turbidity, or high pH levels. Discharge from the project site is tributary to an unnamed Creek approximately 2,000 feet downstream of the project (tributary to Lake Washington). According to the assessment, pollutants of this unnamed creek are classified as Category 5. Category 5 parameters are: Bioassessment indicating degraded biological integrity. Designated water quality problems There are no designated water quality problems known at this time. Downstream Corridor The downstream corridor consists of one flow path, flowing east on S 21st Street’s closed conveyance system for 270 ft before entering the Benson Dr South’s closed conveyance system. The stormwater travels north towards Lake Washington for roughly a quarter mile Sophie Jo Short Plat Page 20 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 before being deposited into a densely forested area. After this point, water exiting the densely forested area will collect in an unnamed stream to be later collected by a series of conveyance systems before entering Lake Washington. The following is a narrative of the two natural downstream flow paths and combined flow path documented during the field analysis. Task 3: Field Inspection (Level 1 Inspection) A site visit was conducted on September 26, 2023, by ESM Consulting Engineers for the purpose of analyzing the project site and its upstream and downstream corridors. The weather conditions were heavy rain and thunderstorms, approximately 50°F. The ground surface was wet. Continuous flow was observed through the downstream conveyance network from upstream tributaries. A description of the drainage path is provided below. Refer to Figure 3.3 at the end of this section for a map of the downstream reaches and point locations. Upstream and onsite runoff The project site has limited potential for upstream run-on. Based on the topography conditions, the project parcel receives upstream run-on from adjacent properties. The project parcel is covered in moderately dense to dense forest areas consisting of young and mature trees. The entire area including the project property and adjacent roadways are tributary to Lake Washington. There is a channel running through roadside edges of the property and presumed that most stormwater is conveyed east through this channel into the S 21st St right-of-way at the natural discharge location. Sophie Jo Short Plat Page 21 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Upstream Inspection Pictures taken at Points 1-3 on Smithers Ave S are shown below. Additional points along the adjacent right-of-way of the existing stormwater conveyance system are also shown throughout the field investigation narrative. Refer to Figure 3.3 for a map of point locations. Photo Photo Description Point #1 – Looking north along Smithers Ave S. Point #2 – Looking north along Smithers Ave S. Sophie Jo Short Plat Page 22 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Point #3 – Looking south at the Smithers S Discharge into the property. Pictures taken at Points 4-9 on the Property are shown below. Point #4 – Looking north at the start of the existing conveyance ditch on site. Sophie Jo Short Plat Page 23 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Point #5 – Rounding the southeast corner of the intersection between S 21st St and Smithers Ave S along the on-site conveyance ditch. Point #6 – Looking east along S 21st St. Sophie Jo Short Plat Page 24 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Point #7 - Looking east along S 21st St. Point #8 - Looking east along S 21st St. Sophie Jo Short Plat Page 25 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Point #9 - Looking south at the Discharge point of the Property into the conveyance network of S 21st St. Sophie Jo Short Plat Page 26 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Natural Discharge Point #1 Reach 1A (0’ –270’) – Upon leaving the site, stormwater enters in the S 21st St right-of-way conveyance network through an inlet (see Point #9) to a catch basin along the roadway (Point #10). This inlet is the Discharge Point for the site. From this point, stormwater heads east along S 21st St towards Benson Dr S. No signs of any conveyance nuisances or flooding problems were observed. Photo Photo Description Point #10 – Discharged stormwater from site enters S 21st St conveyance system heading east along S 21st St. Sophie Jo Short Plat Page 27 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Point #11 – looking east along S 21st St. Point #12 – looking east along S 21st St heading to the intersect with Benson Dr S. Sophie Jo Short Plat Page 28 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Reach 2 (270’ – 1500’) – Stormwater enters the Benson Dr S conveyance system and starts heading north along the Benson Dr S right of way. The Benson Dr S conveyance system discharges into a densely forested area to connect into a stream later downstream. Photo Photo Description Point #13 – Looking northeast at the intersection of S 21st St and Benson Dr S Point #14 – Looking north along Benson Dr S. Sophie Jo Short Plat Page 29 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Point #15 - Looking north along Benson Dr S. Point #16 – Looking east into the densely forested area assumed to be the discharge point for the Benson Dr S conveyance system. Sophie Jo Short Plat Page 30 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Task 4: Drainage Description and Problem Descriptions The downstream drainage system is largely comprised of a 12” tightline system. See Task 3 for a narrative of the downstream flow path for a quarter mile downstream of the site and a description of each reach. Downstream Drainage Problems There are no known or observed conveyance system nuisance problems, severe erosion, or flooding problems. Downstream Water Quality Problems Discussed in Task 2 of the Offsite Analysis, a biological integrity problem was noted approximately half a mile downstream. A detailed parameter has not been identified. This potential water quality problem is beyond the quarter mile threshold to warrant mitigation as suggested in Section 1.2.2.3 of the RSWDM. See Figure 3.1 below for a map of the classified 303(d) areas downstream of the project site. Figure 3.1 – Water Quality Assessment King Date: 10/2/2023 Notes: The information included on this map has been compiled by King County staff from a variety of sources and issubject to change without notice. King County makes no representations or warranties, express or implied,as to accuracy, completeness, timeliness, or rights to the use of such information. This document is not intendedfor use as a survey product. King County shall not be liable for any general, special, indirect, incidental, orconsequential damages including, but not limited to, lost revenues or lost profits resulting from the use or misuseof the information contained on this map. Any sale of this map or information on this map is prohibited except bywritten permission of King County. Legend Parcels Potentiallandslide hazardareas (2016, seeexplanation--->) Erosion hazard(1990 SAO) Seismic hazard(1990 SAO) Coal mine hazard(1990 SAO) Stream (1990 SAO) class 1 class 2 perennial class 2 salmonid class 3 unclassified Wetland (1990SAO) Sensitive areanotice on title FEMA floodway FEMA 100 yearfloodplain FEMA 500 yearfloodplain FEMA area withreduced risk dueto levee Drainagecomplaints Figure 3.2 - Downstream Study Area ± 1/4 Mile Downstream 1/2 Mile Downstream 1 Mile Downstream Site 1995-0868 Type: WQA Problem: DUMPING Closed: 4/21/1996 2012-0717 Type: CUST Problem: WQAI Closed: 12/18/2012 2,257 188 Figure 3.3 - Field Study Area This map is a user generated static output from an Internet mapping site and is for reference only. Data layers that appear on this map may or may not be accurate, current, or otherwise reliable. Field conditions were Thunderstorms and Heavy Rain. Figure corresponds to narrative written for downstream analysis. 10/2/2023 Legend 128064 THIS MAP IS NOT TO BE USED FOR NAVIGATION Feet Notes 128 WGS_1984_Web_Mercator_Auxiliary_Sphere Information Technology - GIS RentonMapSupport@Rentonwa.gov City and County Labels Parcels Discharge Point Public Discharge Point Private Discharge Point Pipe Public Pipe Private Pipe Public Culvert Private Culvert Public Roofdrain Private Roofdrain Open Drains Facility Outline Streets Points of Interest Parks Waterbodies Point #10 Point #11 Point #12 Point #13 Point #14 Point #15 Point #16 Site 1/4 Mile Downstream Sophie Jo Short Plat Page 33 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 4. Flow Control & Water Quality Facility Analysis and Design 4.1 Existing Site Hydrology During the site investigation, it was found, the site is primarily covered in medium dense forest with large amounts of thorny bushes and underbrush. The water that currently flows onto the site is carried by a manmade ditch along Smithers Ave S and S 21st St. This ditch intercepts and conveys stormwater from the parcels located south of the project site and discharges it into the Zetterberg Project conveyance system at the natural discharge location at the northeast corner of the property. 4.2 Developed Site Hydrology The project proposes storm water collection and flow control prior to site discharge through the use of a detention facility and a closed conveyance network for all rooftop, driveway, and roadway runoff. The storm network will collect virtually all runoff on the project property and convey it to the detention facility. For stormwater within the existing public right-of-way, careful consideration was given to what areas are to be tributary to the detention facility upon completion of the right-of-way improvements. Each roadway adjacent to the development includes roadway widening as well as new curb, roadside planter strips, and sidewalk. A discussion of the proposed storm network along each road is described below. Smither Ave S: Smithers Ave S is tributary to a few acres of stormwater that is collected into the existing Smithers Ave roadside ditch. The project proposes to replace the existing ditch on the east side of Smithers Ave, with a closed conveyance pipe. The conveyance network proposed along Smithers Ave will bypass the proposed detention facility. This will eliminate any issue if parcels along Smithers Ave are developed in the future. To compensate for Smithers Ave improvements bypass area, the Target surfaces in Smithers Ave will be 'traded' for similar, non-target surfaces in S 21st St. S 21st St: The existing roadway is assumed to be crested along its surveyed centerline, resulting in a sheet flow runoff from half of the adjacent S 21st St onto the project site. The project proposes to collect a majority of this existing runoff, a non-target surface, in combination with any new target surfaces along S 21st St and route to the detention facility. This trade will allow for the unmitigated bypass from Smithers Ave S and a small amount of unmitigated bypass of target surfaces in S 21st S right-of-way east of the detention facility. The proposed detention facility is located within a stormwater easement between lots 2 and 3 of the project. Refer to Section 4.3 for a discussion of the flow control and treatment performance standards. Impervious and pervious areas were estimated based on a combination of zoning requirements and proposed site features. All proposed work within the existing and future rights-of-way were estimated based on the proposed surface types. The single-family lot impervious areas were estimated based on the 65% maximum allowed by zoning. Sophie Jo Short Plat Page 34 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 The following tables represent the pre-developed and developed runoff/discharge conditions for the project. Refer to Figures 1.3A and 13.B for maps of the existing conditions before and after the mitigation trade, and Figure 1.3C for a map of the proposed conditions. Table 4.1 – Historic Conditions Basin Total (SF) C, Forest (SF) Impervious, Flat (SF) C, Lawn, Flat (SF) Total Non - PGIS PGIS Before Mitigation Trade Site 28,786 (0.661) 28,786 - - - - After Mitigation Trade Site 28,856 (0.662) 28,856 - - - - Difference (After - Before) Site +70 (+0.002) +70 (+0.002) - - - - Table 4.2 – Developed Conditions Basin* Total (SF) C, Forest (SF) Impervious, Flat (SF) C, Lawn, Flat (SF) Total Non - PGIS PGIS** Before Mitigation Trade Facility Lots* 17,871 - 12,817 10,867 1,950 5,054 Tract A** 2,819 - 1,458 - 1,458 1,361 Frontage** 3,412 - 1,912 1,252 660 1,500 Frontage Bypass 4,684 - 3,041 2,197 844 1,643 Total 28,786 (0.661) - 19,228 (0.442) 14,316 (0.329) 4,912*** (0.113) 9,558 (0.219) After Mitigation Trade Facility Lots* 17,871 - 12,817 10,867 1,950 5,054 Tract A** 2,819 - 1,458 - 1,458 1,361 Frontage** 6,523 - 5,023 1,252 3,771 1,500 Frontage Bypass 1,643 - - - - 1,643 Total 28,856 (0.662) - 19,298 (0.443) 12,119 (0.278) 7,179 (0.165) 9,558 (0.219) Difference (After - Before) Facility +3,111 - +3,111 - +3,111 - Bypass -3,041 - -3,041 -2,197 -844 - Total +70 (+0.002) - +70 (+0.002) -2,197 (-0.050) +2,267 (+0.052) - (0.00) *65% impervious coverage per zoning, assumes 650 sf for each driveway on lots 1-3. (Lot 1: 5864sf x 65% = 3812sf, Lot 2: 6040sf x 65% = 3926sf, Lot 3: 5968sf x 65% = 3879sf). **Includes assumed future driveway approaches within frontage improvements and future 20’ driveways within Tract A. ***Total proposed new plus replaced PGIS. Sophie Jo Short Plat Page 35 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 4.3 Performance Standards Flow Control The stormwater facility onsite is designed to mitigate runoff generated from the project per the requirements of the RSWDM. The King County Flow Control Applications Map provides the area-specific flow control facility standard. The project site falls within the Conservation Flow Control Area. Conservation Flow Control areas are to apply the Level 2 flow control standard. The Level 2 flow control standard is to match developed discharge durations to predeveloped durations for the range of predeveloped discharge rates from 50% of the 2- year peak flow up to the full 50-year peak flow. Also match developed peak discharge rates to predeveloped peak discharge rates for the 2- and 10- year return periods. This also assumes historic site conditions as the predeveloped condition. The project site is made up of 3 lots,1 tract, and improvements to the existing public right- of-way. The project specific target surfaces subject to flow control are equal to all the new plus replaced surface areas. The flow control basin, however, will consist partly of non-target areas through a mitigation trade per Section 1.2.3.2.G of the RSWDM. This section states a project’s flow control facility may be designed to mitigate an existing developed non-target surface area in trade for not mitigating part of the project target surface area, provided that all of the following conditions are met: • The non-target surface area must have runoff discharge characteristics (peak flow and volume) equivalent to those of the target surface area for which mitigation is being traded. Response: Condition is met by trading a greater than or equal amount of impervious surface and a greater than or equal amount of like impervious surface. • Runoff from both the target surface area being traded and the flow control facility must converge prior to discharge of the runoff from the target surface area being traded onto private property without an easement or through any area subject to erosion. Response: All runoff from target and non-target converges in the area of the natural discharge location. • The net effect in terms of flow control at the point of convergence downstream must be the same with or without the mitigation trade. Response: Condition is met by detaining an area equal to or greater than the target surfaces. • The undetained runoff from the target surface area being traded must not create a significant adverse impact to the downstream drainage systems, salmonid habitat, or properties prior to convergence with runoff from the flow control facility. Response: Due to the mitigation trade, the undetained runoff will have very minimal impact to the downstream system. The undetained runoff is being compensated for by detaining other contributing flows to the downstream system not currently detained. To confirm the Level 2 flow control standard have been met, the Western Washington Hydrology Model Version 2012 (WWHM), an approved model per 3.2.3 of the RSWDM, has been utilized to determine the required volume of the detention system with the proposed control structure outlet dimensions. Sophie Jo Short Plat Page 36 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Bypass On some sites, topography can make it difficult or costly to collect all target surface runoff for conveyance to the onsite flow control facility. Section 1.2.3.2.E of the RSWDM allows for bypass of the flow control facility. Compensatory mitigation by the flow control facility must be provided so that the net effect at the point of convergence downstream is the same with or without the bypass. After the proposed mitigation trade, there is a small portion of bypass leaving the site unmitigated. This bypassed area is the proposed planter strip along S 21st St and Smithers Ave S. The planter strip area was not traded in the mitigation trade due only trading impervious areas. Alternative Detention System The proposed Private flow control facility is made up of AquaCell© modules is a manufactured system. This system has properties in common with traditional underground concrete detention vaults but does not conform to the standards adopted from the established standards for a traditional vault system. There are many similar systems, (RTank for example) installed within the city. Per the Section 5.1.8 of the RSWDM, these alternative systems may be approved provided the design criteria set forth in Section 5.1.8.1 of the RSWDM: • Alternative detention system shall be designed as flow-through system to promote sediment remove and facilitate maintenance. Response: As much as practical, runoff will enter the flow control facility from the opposite side of the control construction to provide a flow-through facility as much as practical. • Outflow control structures shall be as detailed in Section 5.1.4. Response: The outflow control structure has been designed according • Maximum depth from finished grade to invert shall be 20 feet. Response: Depth of the facility from finish grade is approximately 9 feet. • Access openings required within 50 feet from any location in the facility and within 5 feet of each terminal end. Response: Maintenance ports as recommended by the manufacturer are proposed. There are systems in place to provide thorough cleaning of the system when necessary. • All access opening, except those covered by removable panels, shall have round, solid locking covers. Response: The maintenance ports will be covered by solid locking covers. • All access openings must be readily accessible by maintenance vehicles. Response: All access ports will be on or adjacent to the shared driveway within Tract A. Discharge There is one discharge location on the property. The discharge location will be directly connected to the existing conveyances system at the east end of the property. Sophie Jo Short Plat Page 37 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Water Quality Stormwater treatment is not required for this project as the new and replaced PGIS does not exceed more than 5,000 sf and therefore qualifies for Surface Area Exemption #1 according to Section 1.2.8. of the RSWDM. 𝑄=𝐶𝐴√2𝑖� Where Q = flow (cfs) C = coefficient of discharge (0.62 for plate orifice) A = Area of orifice (sf) g = gravity (32.2 ft/sec2) h = hydraulic head (ft) Table 4.3A – Control Riser Summary Element Diameter Stage Live Storage Depth - 5.25 First Orifice .470” 0.00 Second Orifice 33/64” 2.70 Third Orifice 5/8” 3.50 Riser Diameter 12” - 4.4 Flow Control System Table 4.5 in this section provides the Developed flow control Basin for the Detention Analysis in WWHM. Table 4.1 in Section 4.2 provides the historic conditions for the natural discharge area with a total area equal to the developed flow control basin. See Appendix A for a copy of the WWHM output. The proposed detention system will consist of and AquaCell Detention system, with a 2- foot gravel perimeter, and a Type II 54” catch basin housing the control riser. The proposed detention facility is within the Tract A of the short plat. The Western Washington Hydrology Model (WWHM) was used to confirm the stormwater detention system volume is adequate to comply with Level 2 flow control standards. WWHM output can be found in Appendix A. A stage-storage table, Table 4.4, was generated based on the proposed system to check the provided volume against the flow control standards. After analysis of the proposed system, it was found to meet or exceed the Level 2 flow control standards for the natural discharge area. Detention Facility Summary Stormwater detention facility is proposed to detain stormwater temporarily as a result of the controlled and reduced developed flow rates. The required volume of the facility is based on several governing factors. This includes the size of the contributing basin, the type of ground cover, and any applicable flow control BMP facility sizing credits listed in Table 5.2.2.A of the RSWDM. The live storage depth of the facility is 5.25 feet. Additionally, 7.5 inches of freeboard has been provided above the top of live storage as well nine inches of sediment storage below the bottom of live storage. Sophie Jo Short Plat Page 38 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 The following sections provide a detailed summary of the overflow, downstream conveyance analysis and control riser, components for the detention facility. Control Riser (primary discharge control) The control structures will be the primary control of stormwater discharge up to a selected flow rate to achieve flow control performance standards. Flow through these orifices are analyzed in WWHM at any given elevation through the following equations as listed in Section 5.2.4.2 of the SWDM. 𝑄=𝐶𝐴√2𝑖�, (Orifice) Where, C = 0.62, A = Area of orifice in feet, g = 32.2 (gravity constant) h = headwater elevation in feet 𝑄𝑤𝑒�ℎ𝑟=9.739𝐶𝐻 3 2 (Weir) (Figure 5.1.4.H SWDM) Where D = the diameter of the riser (12 inches) Table 4.4 – Proposed Stage Storage Stage (ft) Aquacell Storage Area (sf) Aquacell Storage @ 95.62% Voids (cf) Gravel Storage Area (sf) Gravel Storage @ 40% Voids (cf) Accumulative Storage Volume (cf) 0 1,914 0.000 425 0.000 0 1 1,914 1,830 425 170 2,000 2 1,914 3,660 425 340 4,000 3 1,914 5,491 425 510 6,001 4 1,914 7,321 425 680 8,001 5 1,941 9,151 425 850 10,001 5.25 1,914 9,608 425 893 10,501 The predeveloped, developed and mitigated project site flow rates are provided in Table 4.5 below to compare the developed peak discharge rates to predeveloped peak discharge rates for the 2- and 10- year return periods as required by the Level 2 Flow Control standard. Table 4.5 – Return-Flow, Natural Discharge Return Period Predeveloped (cfs) Developed (cfs) Mitigated (cfs) 2-Year 0.021 0.182 0.014 10-Year 0.039 0.273 0.026 100-Year 0.054 0.399 0.049 Sophie Jo Short Plat Page 39 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 The analyzed and proposed storage volume is provided in Table 4.6 below. Table 4.6 – Volumes Detention Facility Primary Overflow The primary overflow is the top of the riser, 12-inch diameter (D=1.0’). The overflow is intended as a safety measure if any of the orifices are plugged. The bottom of the weir (top of riser) is set at the peak detention volume storage depth. The riser must be designed to provide for the primary overflow of the developed 100-year peak flow, Q100, discharge from the detention facility according to Section 5.1.4.1 of the RSWDM. The 100-year peak flow is provided in Tables 4.5. The freeboard necessary above the top of the riser to allow for primary overflow is determined from the Weir equation as shown below. Vault Developed Q100 = 9.739(D)(H3/2) 0.399 = 9.739(1)(H3/2) H = 0.119 ft = 1.42 inches The facility provides a minimum of 0.5’ of freeboard above the hydraulic head during flow to provide adequate room for the 100-year flow event. Detention Vault Downstream Pipe Conveyance The capacity of the outlet pipe from the control structure has also been checked as a safety measure if the primary overflow becomes active. The capacity of the downstream pipe should be greater than the developed 100-year design flow. The 100-year design flow can be found in Table 4.5 above. To calculate the capacity of the downstream pipe(s), Manning’s equation was used to directly solve for the capacity of the pipe, assuming a full flowing pipe. The proposed downstream pipes are to be installed with a minimum slope of 0.50 percent. Manning’s Equation (Eq 4-2 RSWDM) Q = (1.49/n)AR2/3S1/2 Where, Q = Pipe capacity (cfs) A = Wetted area (sf), 𝜋𝑟2 n = Manning roughness coefficient, 0.012 (Table 4.2.1.D RSWDM) R = hydraulic radius, d/4 for full flowing pipe d = Pipe Diameter S = slope of the pipe Pipe Capacity of a 12” diameter pipe @ 0.5% min Slope d=1.0 ft A=3.14*0.52=0.7854 sf Description Volume (ac-ft) Volume (cu-ft) Modeled, WWHM 0.240 10,496 Proposed 0.241 10,501 Sophie Jo Short Plat Page 40 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 R=1.0/4=0.25 ft S=0.005 Qcapacity=(1.49/0.012)(0.7854)(0.252/3)(0.0051/2) = 2.735 cfs A 12” diameter discharge pipe with a 0.5 percent slope has sufficient capacity to convey the 100-year developed flow, of 0.399 cfs (See Table 4.5) 4.5 Water Quality System: Development falls under Surface Area Exemption #1. Refer to section 4.3 for further details. 4.6 Flow Control BMPs (Core Requirement #9): On-Site BMPs were evaluated for the project site as outlined in the RSWDM under Section 1.2.9.3.1 – subdivision projects on sites less than 5 acres in size OR within the Urban Growth Area. Target surfaces for application of Core Requirement #9 include new impervious surfaces, new pervious surfaces, and replaced impervious surfaces. Implementation of flow control BMPs for each lot will be deferred until a permit is obtained for building construction on each lot. The BMP’s required for the plat infrastructure per RSWDM Section 1.2.9.4 (e.g., road and sidewalk etc.) are described in order of precedence below with feasibility determined. Requirement #1 Full Dispersion (RSWDM Section C.2.1) has been evaluated for the project site. There is insufficient onsite native vegetated flow path to which target impervious surfaces may be dispersed. Therefore, minimum design requirement #1 (specified in Section C.2.1.1 of the RSWDM) cannot be met; hence, this BMP is infeasible for the project site. Requirement #2 Full Infiltration (Section C.2.2 or Section 5.2of the RSWDM, whichever is applicable) has been evaluated. A geotechnical study has been completed by Development Engineering, PLLC dated September 07, 2017. Based on the soil findings, the subsurface conditions observed in the test pits are not favorable for infiltration of significant volumes of project stormwater as stated in the geotechnical study. This is due primarily to the site soil’s relatively high fines content, and shallow groundwater observed in the test pits. Therefore, the Soils requirement (specified in RSWDM Section 5.2.1 - Soils) cannot be met; hence, this BMP is infeasible for the project site. Limited Infiltration (RSWDM Section C.2.3) is subject to the same minimum design requirements as Full Infiltration (per RSWDM Section C.2.3.2). Since Full Infiltration has been deemed infeasible, Limited Infiltration is also infeasible for this project site. Bioretention (RSWDM Section C2.6) is not a suitable BMP for this project site. In order to satisfy Core Requirement #9, bioretention facilities are not allowed to have an under- drain (per RSWDM Section C.2.6.1.5). Because infiltration is infeasible onsite, the draw- down time for any bioretention facilities would likely exceed 24-hours and is estimated to enable mosquito breeding (RSWDM Section C.2.6: Ponding Depth and Surface Water Draw-Down). Permeable Pavement (RSWDM Section C.2.7) is not a suitable BMP for this project site due to existing shallow till layer that will restrict the percolations of water. Sophie Jo Short Plat Page 41 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Requirement #3 Basic Dispersion (RSWDM Section C.2.4) has been evaluated for the project site. Most stormwater from the new meandering sidewalks will disperse through the adjacent vegetation. Most new plat infrastructure including new road, curb, gutter, and sidewalk will flow to the proposed conveyance system within the right-of-way without opportunity for basic dispersion. Requirement #4 All new pervious surfaces will be amended in accordance with section C.2.13 of the 2022 RSWDM and City of Renton STD plan 264.00 to satisfy the requirements specified therein (notes will be included on the final landscape plans). Sophie Jo Short Plat Page 42 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 5. Conveyance System Analysis and Design Onsite Conveyance System: Runoff from the developed project site will be collected from the developed lot lawns, roofs, and new access road by the proposed conveyance system located throughout the project. The proposed stormwater drainage system is composed of catch basin structures with 6- inch diameter pipes for roof drains and 12-inch diameter pipes for the proposed storm system. The proposed stormwater drainage system has been designed to convey the 25 and 100- year peak flow rates generated by the developed tributary basin to ensure no overtopping. Rational Method To determine the runoff flow events, QR, the Rational Method as directed by Table 3.2 of the RSWDM is used. This method is appropriate for tributary areas less than 10 acres that are largely undetained. The Rational Method equations found in Section 3.2.1 of the RSWDM are summarized below and the calculated Q25 and Q100 flow rates based on the developed basin provided in Table 4.5. QR = CIRA Where QR = Peak Flow for a storm return frequency R, cfs C = estimated runoff coefficient Cimpervious = 0.90 Cpervious = 0.25 IR = peak rainfall intensity, in/hr A = drainage subbasin area, acres “IR” Peak Rainfall Intensity IR = (PR)(iR) Where PR = the total precipitation at the project site for the 24-hour duration storm event for the given return frequency. The 25-year and 100- year precipitation value is found in Figures 3.2.1.C and 3.2.1.D of the RSWDM. P25 = 3.4 inches P100 = 4.2 inches iR = the unit peak rainfall intensity factor The unit peak rainfall intensity factor, iR is determined by the following equation: iR = (aR)(Tc)(-bR) Where Tc = time of concentration (minutes), assumed minimum, 6.3 minutes aR, bR = coefficients from RSWDM Table 3.2.1.B used to adjust the equation for the design storm frequency. a25 = 2.66, b25 = 0.65 a100 = 2.61, b100 = 0.63 i25 = (2.66)(6.3)(-0.65) = 0.804 i100 = (2.61)(6.3)(-0.63) = 0.819 I25 = (3.4)(0.804) = 2.734 in/hr I100 = (4.2)(0.819) = 3.437 in/hr Sophie Jo Short Plat Page 43 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 Conveyance Capacity The new conveyance network has been analyzed and designed with sufficient capacity to convey and contain the required 25-year minimum per RSWDM Section 1.2.4.1. Pipe system structures may overtop for runoff events that exceed the 25-year design capacity, provided the overtop from a 100-year runoff event does not create or aggravate a severe flooding problem or severe erosion problem. The conveyance capacity of the proposed system will use two methods of hydraulic analysis using Manning’s Equation as outlined in Section 4.2.1.2 of the RSWDM. First, the Uniform Flow Analysis method is used to preliminarily size the pipes based on capacity and the calculated design flows. Second, a backwater analysis is completed to check system capacity of the storm network. Uniform Flow Analysis Each pipe within the system is sized and sloped such that its barrel capacity at normal full flow, Qcapacity, (computer by Manning’s equation) is equal to or greater than the design flow, QR. Qcapacity =1.49 𝑛𝐴 𝑄2 3⁄ 𝑄1 2⁄ Where QCapacity = discharge capacity of pipe A = cross sectional area of flow, sf, assume full n = Manning roughness coefficient, 0.013 (RSWDM Table 4.2.1.D) R = hydraulic radius = Pipe Diameter/4 for full flowing pipe, ft S = pipe slope, ft/ft Qcapacity of each pipe compared to the accumulated flow for both the 25-year and 100- year design flows can be found as a percentage, in the last column on Table 5.1A and Table 5.1B Backwater Analysis The backwater analysis demonstrates that the conveyance network can contain the headwater surface (hydraulic grade line) for the design peak flow rate. Structures are allowed to overtop for the 100-year peak flow; however, the storm system for this project proposes to contain up to the 100-year peak flow. A backwater profile was calculated (hydraulic grade line) through the proposed pipe system. The head loss in each pipe segment due to barrel friction and other head loses are added to that segments tailwater elevation. A tailwater elevation was set for this pipe network. It is set at the downstream end of the proposed pipes, “ECB”. The tailwater elevation was set at the top of the inlet pipe to the structure at the existing CB at the East end of the project. A second tailwater elevation was set at the detention facility inlet. The tailwater elevation in the facility was assumed to be the top of live storage. Sophie Jo Short Plat Page 44 February 20, 2025 Technical Information Report PR24-000024, LUA24-000081 The backwater calculations sheet outlined in Figure 4.2.1.H of the RSWDM was followed as a template for the conveyance calculations. The analysis is provided on the following Figures and Tables: Figure 5.1A – Onsite Conveyance Basin Map Figure 5.1B – Offsite Conveyance Basin Map Table 5.1 – Input Values Table 5.2A - 25-Year Conveyance Table 5.2B - 100-Year Conveyance Table 5.3A - 25-Year Backwater Table 5.3B - 100-Year Backwater S S S DRAWING:JOB NO.DATE:DRAWN:SHEET OF(425) 297-9900(253) 838-6113www.esmcivil.comLand PlanningLandscape ArchitectureLand SurveyingProject ManagementPublic WorksCivil EngineeringΚ Κ ΒΕδχδθκ ςξ+ ς≅ 87//2223// 7σγ ≅υδ Ρ+ Ρτησδ 1/4Β Ν Μ Ρ Τ Κ Σ Η Μ Φ ∆ Μ Φ Η Μ ∆ ∆ Θ ΡFEDERAL WAYLYNNWOODΡΒΓΜ∆ΗΧ∆Θ ΓΝΛ∆ΡΡΝΟΓΗ∆ ΙΝ ΡΓΝΘΣ ΟΚ≅ΣFIGURE 5.1A - ONSITE CONVEYANCE BASIN MAP2185-001-021BS-01CJR03/22/20221 1 µ ΡΒ≅Κ∆9 0! < 0 2/ 15 30 ΒΝΜΥ∆Ξ≅ΜΒ∆ Α≅ΡΗΜ Λ≅Ο ΣΓΘ∆ΡΓΝΚΧ ΧΗΡΒΓ≅ΘΦ∆ ≅Θ∆≅ ∀0 Ο≅ΘΒ∆Κ ∀6821//,//64 ΕΗΦΤΘ∆ 4−0≅SMITHERS AVE S1 2 3 BASIN 5 BASIN 6TRACT A CONVEYANCE BASIN AREAS SURFACE COVERAGE BASIN 3 BASIN 5 BASIN 6 {\C2; PERVIOUS/GRASS (SF)}590 911 590 {\C2; IMPERVIOUS (SF)}1,981 3,089 1,934 TOTAL (SF)2,571 4,000 2,524 S 21ST ST 7222000106 7222000105 9888200010 9888200020RIDGEDETENTIONFACILITY SOUTH OFFSITE BASINSEE FIGURE 5.1B BASIN 3 PPOWER VAULT ΚΝΣ ≅Θ∆≅DRAWING:JOB NO.DATE:DRAWN:SHEET OF(425) 297-9900(253) 838-6113www.esmcivil.comLand PlanningLandscape ArchitectureLand SurveyingProject ManagementPublic WorksCivil EngineeringΚ Κ ΒΕδχδθκ ςξ+ ς≅ 87//2223// 7σγ ≅υδ Ρ+ Ρτησδ 1/4Β Ν Μ Ρ Τ Κ Σ Η Μ Φ ∆ Μ Φ Η Μ ∆ ∆ Θ ΡFEDERAL WAYLYNNWOOD\\\\esm8\\ENGR\\ESM-JOBS\\441\\004\\023\\StormReport\\Resources\\CAD Basin Maps\\Figure 5.1B - UPSTREAM BASIN MAP.dwg2/20/2025 11:29 AMPlotted:File:Plotted By: Brandon LoucksΡΒΓΜ∆ΗΧ∆Θ ΓΝΛ∆ΡΡΝΟΓΗ∆ ΙΝ ΡΓΝΘΣ ΟΚ≅ΣFIGURE 5.1B - OFFSITE CONVEYANCE BASIN MAP441-004-023DEVON WATERMAN10/24/20231 1 ΡΒ≅Κ∆9 0! < 0 5/ 30 60 µ 10ΡΣ ΡΣ Ρ ΡΛΗΣΓ∆ΘΡ ≅Υ∆ ΡΤΟΡΣΘ∆≅Λ ΒΝΜΥ∆Ξ≅ΜΒ∆ Α≅ΡΗΜ Λ≅Ο ΣΓΘ∆ΡΓΝΚΧ ΧΗΡΒΓ≅ΘΦ∆ ≅Θ∆≅ ∀0 Ο≅ΘΒ∆Κ ∀6821//,//64 ΕΗΦΤΘ∆ 4−0Α SOUTH OFFSITE BASIN45,719 SF *ASSUMES %65 MAX SURFACECOVERAGE PER ZONING CONVEYANCE BASIN AREAS SURFACE COVERAGE BASIN 4 {\C2; PERVIOUS/GRASS (SF)}16,002 {\C2; IMPERVIOUS (SF)}29,717 TOTAL (SF)45,719 BASIN 4 1 2 3 Table 5.1 - Input Values NODETypeRim Elevation (ft)I.E. (ft)Depth (ft)Pervious (sf)Impervious (sf)Pervious (ac)Impervious (ac)Total (ac)25-yr Flows (cfs) WWHM100-yr Flows (cfs) WWHMVault 1 1 212.00 204.50 7.50 0 0 0.00 0.00 0.00 CB 5 1 210.54 206.73 3.81 911 3,089 0.02 0.07 0.09 CB 6 1 210.83 206.00 4.83 590 1,934 0.01 0.04 0.06 CB 1 2 210.68 203.97 6.71 0 0 0.00 0.00 0.00 CB 2 1 210.32 205.91 4.41 0 0 0.00 0.00 0.00 CB 3 1 210.25 206.28 3.97 590 1,981 0.01 0.05 0.06 CB 4 1 210.95 206.94 4.01 16,002 29,717 0.37 0.68 1.05 EX CB 2 209.75 203.52 6.23 0 3,365 0.00 0.08 0.08 CB 7 1 211.70 204.25 7.45 0 0 0.00 0.00 0.00 0.0344 0.0489 Table 5.2A - Uniform Flow Analysis (25-year Event)CB (From)CB (To)Accumulative Pervious(ac)Accumulative Impervious(ac)Total(ac)Length(ft)Accumulative Q-25-yr Flow(cfs)Pipe Diameter(in)Pipe Diameter(ft)Area(sf)Wet Perimeter(ft)Hydraulic Radius(ft)Slope(ft/ft)"n" ValueQCapacity(cfs)Vel at 25-yr Cap(ft/s)25-yr % Cap(cfs)CB 5 CB 6 0.02 0.07 0.09 147 0.1888 12 1.00 0.79 3.14 0.25 0.0050 0.013 2.52 3.21 7.50% CB 6 Vault 1 0.03 0.12 0.15 25 0.3073 12 1.00 0.79 3.14 0.25 0.0600 0.013 8.75 11.14 3.51% CB 4 CB 3 0.37 0.68 1.05 66 1.9297 12 1.00 0.79 3.14 0.25 0.0100 0.013 3.57 4.55 54.02% CB 3 CB 2 0.38 0.73 1.11 37 2.0508 12 1.00 0.79 3.14 0.25 0.0100 0.013 3.57 4.55 57.41% CB 2 CB 1 0.38 0.73 1.11 194 2.0508 12 1.00 0.79 3.14 0.25 0.0100 0.013 3.57 4.55 57.41% CB 7 CB 1 0.00 0.00 0.00 28 0.0344 12 1.00 0.79 3.14 0.25 0.0100 0.013 3.57 4.55 0.96% CB 1 EX CB 0.38 0.73 1.11 87 2.0853 12 1.00 0.79 3.14 0.25 0.0052 0.013 2.57 3.27 81.16% Table 5.2B - Uniform Flow Analysis (100-year Event)CB (From)CB (To)Accumulative Pervious(ac)Accumulative Impervious(ac)Total(ac)Length(ft)Accumulative Q-25-yr Flow(cfs)Pipe Diameter(in)Pipe Diameter(ft)Area(sf)Wet Perimeter(ft)Hydraulic Radius(ft)Slope(ft/ft)"n" ValueQCapacity(cfs)Vel at 25-yr Cap(ft/s)25-yr % Cap(cfs)CB 5 CB 6 0.02 0.07 0.09 147 0.2204 12 1.00 0.79 3.14 0.25 0.0050 0.013 2.52 3.21 8.76% CB 6 Vault 1 0.03 0.12 0.15 25 0.3588 12 1.00 0.79 3.14 0.25 0.0600 0.013 8.75 11.14 4.10% CB 4 CB 3 0.37 0.68 1.05 66 2.2533 12 1.00 0.79 3.14 0.25 0.0100 0.013 3.57 4.55 63.08% CB 3 CB 2 0.38 0.73 1.11 37 2.3948 12 1.00 0.79 3.14 0.25 0.0100 0.013 3.57 4.55 67.04% CB 2 CB 1 0.38 0.73 1.11 194 2.3948 12 1.00 0.79 3.14 0.25 0.0100 0.013 3.57 4.55 67.04% CB 7 CB 1 0.00 0.00 0.00 28 0.0489 12 1.00 0.79 3.14 0.25 0.0100 0.013 3.57 4.55 1.37% CB 1 EX CB 0.38 0.73 1.11 87 2.4436 12 1.00 0.79 3.14 0.25 0.0052 0.013 2.57 3.27 95.11% Table 5.3A - Backwater Analysis (25-year Event) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 CB (From)CB (To)Q(cfs)Length(ft)Pipe Size(in) "n"ValueOutlet Elev(ft)Inlet Elev(ft)Barrel Area(sf)Barrel Vel(ft/s)Barrel Vel Head(ft/s)TW Elev*(ft)Friction Loss(fT)Entr HGL Elev(ft)Entr Head Loss(ft)Exit Head Loss(ft)Outlt Contr Elev(ft)Inlet Contr Elev(ft)Critical Velocity(fps)Critical Depth(ft)Appr Vel Head(ft)Bend(°)Bend Head Loss(ft)Q1(cfs)Q3(cfs)Junc Head Loss(ft)HW Elev(ft)Upstream CB RIM Elev(ft)CB RIM - HW Elev(ft)EX CB CB 1 2.085 90 12 0.011 203.52 203.97 0.79 2.66 0.11 204.52 0.22 204.97 0.05 0.11 205.13 204.07 1.995 0.178 -0.11 90.0 0.14 0.0344 2.05 0.00 205.17 210.68 5.51 CB 1 CB 7 0.034 32 12 0.011 203.97 204.25 0.79 0.04 0.00 205.17 0.00 205.25 0.00 0.00 205.25 204.43 2.274 0.228 0.00 0.0 0.00 0.00 205.25 211.70 6.45 CB 1 CB 2 2.051 191 12 0.011 203.97 205.91 0.79 2.61 0.11 205.17 0.45 206.91 0.05 0.11 207.07 206.05 4.034 0.603 -0.11 67.5 0.10 2.0508 0.00 207.06 210.32 3.26 CB 2 CB 3 2.051 37 12 0.011 205.91 206.28 0.79 2.61 0.11 207.06 0.09 207.28 0.05 0.11 207.44 206.80 4.072 0.610 -0.11 22.5 0.01 1.9297 0.31 0.01 207.36 210.25 2.89 CB 3 CB 4 1.930 66 12 0.011 206.28 206.94 0.79 2.46 0.09 207.36 0.14 207.94 0.05 0.09 208.08 207.25 4.072 0.610 -0.09 0.0 0.00 0.00 207.99 210.95 2.96 Vault 1 CB 6 0.307 23 12 0.011 204.50 206.00 0.79 0.39 0.00 209.50 0.00 209.50 0.00 0.00 209.50 206.23 2.274 0.228 0.00 90.0 0.00 0.1888 0.00 0.00 209.51 210.83 1.324 CB 6 CB 5 0.189 150 12 0.011 206.00 206.73 0.79 0.24 0.00 209.51 0.00 209.51 0.00 0.00 209.51 206.86 4.304 0.656 0.00 0.0 0.00 0.00 209.51 210.54 1.031 *EX CB TW = TOP OF PIPE ELEVATION *VAULT 1 TW = TOP OF STORAGE ELEVATION 2/20/2025 Table 5.3B - Backwater Analysis (100-year Event) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 CB (From)CB (To)Q(cfs)Length(ft)Pipe Size(in) "n"ValueOutlet Elev(ft)Inlet Elev(ft)Barrel Area(sf)Barrel Vel(ft/s)Barrel Vel Head(ft/s)TW Elev*(ft)Friction Loss(fT)Entr HGL Elev(ft)Entr Head Loss(ft)Exit Head Loss(ft)Outlt Contr Elev(ft)Inlet Contr Elev(ft)Critical Velocity(ft)Critical Depth(ft)Appr Vel Head(ft)Bend(°)Bend Head Loss(ft)Q1(cfs)Q3(cfs)Junc Head Loss(ft)HW Elev(ft)Upstream CB RIM Elev(ft)CB RIM - HW Elev(ft)EX CB CB 1 2.444 87 12 0.011 203.52 203.97 0.785 3.111 0.150 204.52 0.290 204.97 0.075 0.150 205.20 204.10 2.078 0.192 -0.150 90 0.20 0.05 2.39 0.00 205.25 210.68 5.43 CB 1 CB 7 0.049 28 12 0.011 203.97 204.25 0.785 0.062 0.000 205.25 0.000 205.25 0.000 0.000 205.25 204.47 2.374 0.247 0.000 0 0.00 0.00 205.25 211.70 6.45 CB 1 CB 2 2.395 194 12 0.011 203.97 205.91 0.785 3.049 0.144 205.25 0.621 206.91 0.072 0.144 207.13 206.08 4.287 0.653 -0.144 67.5 0.13 2.39 0.00 207.11 210.32 3.21 CB 2 CB 3 2.395 37 12 0.011 205.91 206.28 0.785 3.049 0.144 207.11 0.119 207.28 0.072 0.144 207.50 206.87 4.331 0.661 -0.144 22.5 0.02 2.25 0.36 0.02 207.39 210.25 2.86 CB 3 CB 4 2.253 66 12 0.011 206.28 206.94 0.785 2.869 0.128 207.39 0.187 207.94 0.064 0.128 208.13 207.29 4.331 0.661 -0.128 0 0.00 0.00 208.01 210.95 2.94 Vault 1 CB 6 0.359 25 12 0.011 204.5 206 0.785 0.457 0.003 209.50 0.002 209.50 0.002 0.003 209.51 206.23 2.374 0.247 -0.003 90 0.00 0.22 0.00 0.00 209.51 210.83 1.322 CB 6 CB 5 0.220 147 12 0.011 206 206.73 0.785 0.281 0.001 209.51 0.004 209.51 0.001 0.001 209.51 206.87 4.603 0.71 -0.001 0 0.00 0.00 209.51 210.54 1.028 *EX CB TW = TOP OF PIPE ELEVATION *VAULT 1 TW = TOP OF STORAGE ELEVATION Sophie Jo Short Plat Page 51 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 6. Special Reports and Studies Geotechnical Study Geotechnical Assessment Report, Sophie Jo Short Plat, September 7, 2017; prepared by Development Engineering, PLLC., This study has been included in Appendix B of this report. Geotechnical Assessment: Mine Hazard Geotechnical Letter, Proposed Short Plat, December 28, 2023; prepared by DE-Civil, PLLC., This study has been included in Appendix B of this report. Sophie Jo Short Plat Page 52 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 7. Other Permits Building permits will be required for this project, together with permits for utility connections. Washington State Department of Ecology – Notice of Intent (NPDES) Sophie Jo Short Plat Page 53 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 8. ESC Analysis and Design The Erosion and Sedimentation Control analysis (CSWPPP) has been provided in Appendix C of this report. Sophie Jo Short Plat Page 54 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 9. Bond Quantities, Facility Summaries, and Declaration of Covenant The Bond Quantities worksheet, Facility Summaries, and Declaration of Covenant will be provided to the City upon request. Sophie Jo Short Plat Page 55 February 14, 2025 Technical Information Report PR24-000024, LUA24-000081 10. Operations and Maintenance The Operations and Maintenance manual has been provided in Appendix D of this report. Appendix A – Hydrology Model Output WWHM2012 PROJECT REPORT Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 2 General Model Information WWHM2012 Project Name:Sophie Jo Short Plat Vault 09-23-24 Site Name:Sophie Jo Site Address: City: Report Date:10/11/2024 Gage:Seatac Data Start:1948/10/01 Data End:2009/09/30 Timestep:15 Minute Precip Scale:1.000 Version Date:2024/06/28 Version:4.3.1 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Low Flow Threshold for POC2:50 Percent of the 2 Year High Flow Threshold for POC2:50 Year Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 3 Landuse Basin Data Predeveloped Land Use Predeveloped After Mitigation Trade Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 0.662 Pervious Total 0.662 Impervious Land Use acre Impervious Total 0 Basin Total 0.662 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 1 POC 1 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 4 Predeveloped Bypass Bypass:No GroundWater:No Pervious Land Use acre C, Forest, Flat 0.035 Pervious Total 0.035 Impervious Land Use acre Impervious Total 0 Basin Total 0.035 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 1 POC 1 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 5 Not Included Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.22 Pervious Total 0.22 Impervious Land Use acre ROADS FLAT 0.441 Impervious Total 0.441 Basin Total 0.661 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 2 POC 2 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 6 Mitigated Land Use Vault: Tributary Area Bypass:No GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.22 Pervious Total 0.22 Impervious Land Use acre ROADS FLAT 0.441 Impervious Total 0.441 Basin Total 0.661 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: Vault 1 Vault 1POC 2POC 2 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 7 Dev Bypass Area Bypass:Yes GroundWater:No Pervious Land Use acre C, Lawn, Flat 0.035 Pervious Total 0.035 Impervious Land Use acre Impervious Total 0 Basin Total 0.035 Element Flow Componants: Surface Interflow Groundwater Componant Flows To: POC 1 POC 1 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 8 Routing Elements Predeveloped Routing Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 9 Mitigated Routing Vault 1 Width:34 ft. Length:58.8 ft. Depth:6.25 ft. Discharge Structure Riser Height:5.25 ft. Riser Diameter:12 in. Orifice 1 Diameter:0.470 in.Elevation:0 ft. Orifice 2 Diameter:0.516 in.Elevation:2.7 ft. Orifice 3 Diameter:0.625 in.Elevation:3.5 ft. Element Outlets: Outlet 1 Outlet 2 Outlet Flows To: Vault Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.045 0.000 0.000 0.000 0.0694 0.045 0.003 0.001 0.000 0.1389 0.045 0.006 0.002 0.000 0.2083 0.045 0.009 0.002 0.000 0.2778 0.045 0.012 0.003 0.000 0.3472 0.045 0.015 0.003 0.000 0.4167 0.045 0.019 0.003 0.000 0.4861 0.045 0.022 0.004 0.000 0.5556 0.045 0.025 0.004 0.000 0.6250 0.045 0.028 0.004 0.000 0.6944 0.045 0.031 0.005 0.000 0.7639 0.045 0.035 0.005 0.000 0.8333 0.045 0.038 0.005 0.000 0.9028 0.045 0.041 0.005 0.000 0.9722 0.045 0.044 0.005 0.000 1.0417 0.045 0.047 0.006 0.000 1.1111 0.045 0.051 0.006 0.000 1.1806 0.045 0.054 0.006 0.000 1.2500 0.045 0.057 0.006 0.000 1.3194 0.045 0.060 0.006 0.000 1.3889 0.045 0.063 0.007 0.000 1.4583 0.045 0.066 0.007 0.000 1.5278 0.045 0.070 0.007 0.000 1.5972 0.045 0.073 0.007 0.000 1.6667 0.045 0.076 0.007 0.000 1.7361 0.045 0.079 0.007 0.000 1.8056 0.045 0.082 0.008 0.000 1.8750 0.045 0.086 0.008 0.000 1.9444 0.045 0.089 0.008 0.000 2.0139 0.045 0.092 0.008 0.000 2.0833 0.045 0.095 0.008 0.000 2.1528 0.045 0.098 0.008 0.000 2.2222 0.045 0.102 0.008 0.000 2.2917 0.045 0.105 0.009 0.000 2.3611 0.045 0.108 0.009 0.000 2.4306 0.045 0.111 0.009 0.000 2.5000 0.045 0.114 0.009 0.000 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 10 2.5694 0.045 0.117 0.009 0.000 2.6389 0.045 0.121 0.009 0.000 2.7083 0.045 0.124 0.010 0.000 2.7778 0.045 0.127 0.012 0.000 2.8472 0.045 0.130 0.012 0.000 2.9167 0.045 0.133 0.013 0.000 2.9861 0.045 0.137 0.014 0.000 3.0556 0.045 0.140 0.014 0.000 3.1250 0.045 0.143 0.015 0.000 3.1944 0.045 0.146 0.015 0.000 3.2639 0.045 0.149 0.016 0.000 3.3333 0.045 0.153 0.016 0.000 3.4028 0.045 0.156 0.017 0.000 3.4722 0.045 0.159 0.017 0.000 3.5417 0.045 0.162 0.020 0.000 3.6111 0.045 0.165 0.021 0.000 3.6806 0.045 0.168 0.023 0.000 3.7500 0.045 0.172 0.024 0.000 3.8194 0.045 0.175 0.025 0.000 3.8889 0.045 0.178 0.026 0.000 3.9583 0.045 0.181 0.027 0.000 4.0278 0.045 0.184 0.028 0.000 4.0972 0.045 0.188 0.028 0.000 4.1667 0.045 0.191 0.029 0.000 4.2361 0.045 0.194 0.030 0.000 4.3056 0.045 0.197 0.031 0.000 4.3750 0.045 0.200 0.031 0.000 4.4444 0.045 0.204 0.032 0.000 4.5139 0.045 0.207 0.033 0.000 4.5833 0.045 0.210 0.033 0.000 4.6528 0.045 0.213 0.034 0.000 4.7222 0.045 0.216 0.035 0.000 4.7917 0.045 0.219 0.035 0.000 4.8611 0.045 0.223 0.036 0.000 4.9306 0.045 0.226 0.036 0.000 5.0000 0.045 0.229 0.037 0.000 5.0694 0.045 0.232 0.037 0.000 5.1389 0.045 0.235 0.038 0.000 5.2083 0.045 0.239 0.039 0.000 5.2778 0.045 0.242 0.088 0.000 5.3472 0.045 0.245 0.359 0.000 5.4167 0.045 0.248 0.744 0.000 5.4861 0.045 0.251 1.173 0.000 5.5556 0.045 0.255 1.581 0.000 5.6250 0.045 0.258 1.910 0.000 5.6944 0.045 0.261 2.130 0.000 5.7639 0.045 0.264 2.300 0.000 5.8333 0.045 0.267 2.449 0.000 5.9028 0.045 0.270 2.588 0.000 5.9722 0.045 0.274 2.721 0.000 6.0417 0.045 0.277 2.847 0.000 6.1111 0.045 0.280 2.968 0.000 6.1806 0.045 0.283 3.084 0.000 6.2500 0.045 0.286 3.195 0.000 6.3194 0.048 0.293 3.303 0.000 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:00 AM Page 11 Analysis Results POC 1 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #1 Total Pervious Area:0.697 Total Impervious Area:0 Mitigated Landuse Totals for POC #1 Total Pervious Area:0.255 Total Impervious Area:0.441 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #1 Return Period Flow(cfs) 2 year 0.020492 5 year 0.032184 10 year 0.03881 25 year 0.04583 50 year 0.050173 100 year 0.053868 Flow Frequency Return Periods for Mitigated. POC #1 Return Period Flow(cfs) 2 year 0.013626 5 year 0.020746 10 year 0.026326 25 year 0.034431 50 year 0.041278 100 year 0.048857 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #1 Year Predeveloped Mitigated 1949 0.020 0.012 1950 0.025 0.014 1951 0.045 0.034 1952 0.014 0.008 1953 0.012 0.010 1954 0.018 0.010 1955 0.028 0.010 1956 0.022 0.018 1957 0.018 0.010 1958 0.020 0.012 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:29 AM Page 12 1959 0.017 0.010 1960 0.031 0.028 1961 0.017 0.016 1962 0.011 0.008 1963 0.015 0.010 1964 0.019 0.014 1965 0.014 0.017 1966 0.013 0.010 1967 0.028 0.014 1968 0.017 0.010 1969 0.017 0.010 1970 0.014 0.010 1971 0.015 0.012 1972 0.034 0.027 1973 0.015 0.017 1974 0.017 0.011 1975 0.022 0.011 1976 0.016 0.010 1977 0.002 0.008 1978 0.014 0.014 1979 0.009 0.008 1980 0.032 0.029 1981 0.013 0.010 1982 0.024 0.022 1983 0.022 0.011 1984 0.014 0.009 1985 0.008 0.009 1986 0.036 0.016 1987 0.031 0.026 1988 0.012 0.009 1989 0.008 0.009 1990 0.066 0.030 1991 0.040 0.026 1992 0.015 0.014 1993 0.016 0.009 1994 0.005 0.007 1995 0.023 0.016 1996 0.048 0.033 1997 0.040 0.033 1998 0.009 0.010 1999 0.038 0.027 2000 0.016 0.014 2001 0.003 0.007 2002 0.017 0.017 2003 0.022 0.010 2004 0.029 0.033 2005 0.021 0.010 2006 0.024 0.018 2007 0.049 0.039 2008 0.063 0.032 2009 0.031 0.018 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #1 Rank Predeveloped Mitigated 1 0.0657 0.0388 2 0.0629 0.0339 3 0.0488 0.0330 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:29 AM Page 13 4 0.0480 0.0330 5 0.0451 0.0326 6 0.0401 0.0320 7 0.0396 0.0299 8 0.0376 0.0293 9 0.0355 0.0283 10 0.0336 0.0275 11 0.0318 0.0274 12 0.0314 0.0259 13 0.0309 0.0255 14 0.0305 0.0225 15 0.0287 0.0183 16 0.0282 0.0180 17 0.0279 0.0177 18 0.0251 0.0173 19 0.0245 0.0172 20 0.0243 0.0168 21 0.0228 0.0162 22 0.0224 0.0159 23 0.0224 0.0157 24 0.0222 0.0143 25 0.0219 0.0141 26 0.0206 0.0139 27 0.0204 0.0139 28 0.0201 0.0138 29 0.0194 0.0136 30 0.0181 0.0119 31 0.0177 0.0118 32 0.0175 0.0118 33 0.0174 0.0111 34 0.0174 0.0106 35 0.0172 0.0105 36 0.0170 0.0105 37 0.0166 0.0105 38 0.0162 0.0105 39 0.0159 0.0105 40 0.0158 0.0104 41 0.0153 0.0104 42 0.0153 0.0104 43 0.0150 0.0103 44 0.0147 0.0103 45 0.0142 0.0102 46 0.0142 0.0101 47 0.0140 0.0099 48 0.0139 0.0098 49 0.0135 0.0096 50 0.0133 0.0095 51 0.0127 0.0092 52 0.0124 0.0088 53 0.0115 0.0087 54 0.0107 0.0087 55 0.0091 0.0087 56 0.0086 0.0082 57 0.0081 0.0082 58 0.0080 0.0080 59 0.0053 0.0077 60 0.0028 0.0074 61 0.0019 0.0067 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:29 AM Page 14 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:29 AM Page 15 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0102 17579 15607 88 Pass 0.0106 16196 13019 80 Pass 0.0111 14970 11862 79 Pass 0.0115 13864 11285 81 Pass 0.0119 12831 10793 84 Pass 0.0123 11813 10346 87 Pass 0.0127 10904 9845 90 Pass 0.0131 10134 9293 91 Pass 0.0135 9385 8712 92 Pass 0.0139 8739 8166 93 Pass 0.0143 8162 7634 93 Pass 0.0147 7593 7107 93 Pass 0.0151 7069 6566 92 Pass 0.0155 6594 5935 90 Pass 0.0159 6147 5270 85 Pass 0.0163 5781 4701 81 Pass 0.0167 5437 4211 77 Pass 0.0171 5099 3773 73 Pass 0.0175 4808 3424 71 Pass 0.0179 4528 3089 68 Pass 0.0183 4252 2778 65 Pass 0.0187 4019 2594 64 Pass 0.0191 3788 2451 64 Pass 0.0195 3546 2363 66 Pass 0.0199 3339 2310 69 Pass 0.0203 3138 2254 71 Pass 0.0207 2952 2188 74 Pass 0.0211 2787 2106 75 Pass 0.0215 2599 2036 78 Pass 0.0219 2447 1963 80 Pass 0.0223 2308 1897 82 Pass 0.0227 2162 1834 84 Pass 0.0232 2026 1758 86 Pass 0.0236 1900 1686 88 Pass 0.0240 1790 1614 90 Pass 0.0244 1687 1524 90 Pass 0.0248 1587 1428 89 Pass 0.0252 1483 1350 91 Pass 0.0256 1379 1259 91 Pass 0.0260 1292 1177 91 Pass 0.0264 1221 1111 90 Pass 0.0268 1154 1046 90 Pass 0.0272 1098 974 88 Pass 0.0276 1048 898 85 Pass 0.0280 997 840 84 Pass 0.0284 930 764 82 Pass 0.0288 884 704 79 Pass 0.0292 837 604 72 Pass 0.0296 789 535 67 Pass 0.0300 743 497 66 Pass 0.0304 713 446 62 Pass 0.0308 668 390 58 Pass 0.0312 632 349 55 Pass Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:29 AM Page 16 0.0316 595 307 51 Pass 0.0320 566 256 45 Pass 0.0324 539 212 39 Pass 0.0328 496 174 35 Pass 0.0332 473 146 30 Pass 0.0336 435 135 31 Pass 0.0340 399 121 30 Pass 0.0344 366 116 31 Pass 0.0348 348 112 32 Pass 0.0353 323 107 33 Pass 0.0357 296 103 34 Pass 0.0361 272 89 32 Pass 0.0365 256 75 29 Pass 0.0369 235 61 25 Pass 0.0373 217 52 23 Pass 0.0377 195 44 22 Pass 0.0381 180 37 20 Pass 0.0385 158 28 17 Pass 0.0389 145 0 0 Pass 0.0393 129 0 0 Pass 0.0397 119 0 0 Pass 0.0401 109 0 0 Pass 0.0405 97 0 0 Pass 0.0409 91 0 0 Pass 0.0413 82 0 0 Pass 0.0417 76 0 0 Pass 0.0421 69 0 0 Pass 0.0425 61 0 0 Pass 0.0429 54 0 0 Pass 0.0433 48 0 0 Pass 0.0437 41 0 0 Pass 0.0441 38 0 0 Pass 0.0445 33 0 0 Pass 0.0449 27 0 0 Pass 0.0453 22 0 0 Pass 0.0457 21 0 0 Pass 0.0461 20 0 0 Pass 0.0465 19 0 0 Pass 0.0469 17 0 0 Pass 0.0473 14 0 0 Pass 0.0478 12 0 0 Pass 0.0482 9 0 0 Pass 0.0486 4 0 0 Pass 0.0490 3 0 0 Pass 0.0494 3 0 0 Pass 0.0498 3 0 0 Pass 0.0502 3 0 0 Pass Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:29 AM Page 17 Water Quality Water Quality BMP Flow and Volume for POC #1 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:29 AM Page 18 POC 2 + Predeveloped x Mitigated Predeveloped Landuse Totals for POC #2 Total Pervious Area:0.22 Total Impervious Area:0.441 Mitigated Landuse Totals for POC #2 Total Pervious Area:0.22 Total Impervious Area:0.441 Flow Frequency Method:Log Pearson Type III 17B Flow Frequency Return Periods for Predeveloped. POC #2 Return Period Flow(cfs) 2 year 0.182261 5 year 0.235852 10 year 0.272948 25 year 0.321775 50 year 0.359629 100 year 0.398793 Flow Frequency Return Periods for Mitigated. POC #2 Return Period Flow(cfs) 2 year 0.182261 5 year 0.235852 10 year 0.272948 25 year 0.321775 50 year 0.359629 100 year 0.398793 Annual Peaks Annual Peaks for Predeveloped and Mitigated. POC #2 Year Predeveloped Mitigated 1949 0.250 0.250 1950 0.240 0.240 1951 0.155 0.155 1952 0.123 0.123 1953 0.133 0.133 1954 0.149 0.149 1955 0.165 0.165 1956 0.163 0.163 1957 0.194 0.194 1958 0.147 0.147 1959 0.143 0.143 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:58 AM Page 19 1960 0.161 0.161 1961 0.163 0.163 1962 0.133 0.133 1963 0.158 0.158 1964 0.147 0.147 1965 0.202 0.202 1966 0.127 0.127 1967 0.223 0.223 1968 0.253 0.253 1969 0.184 0.184 1970 0.170 0.170 1971 0.203 0.203 1972 0.228 0.228 1973 0.117 0.117 1974 0.190 0.190 1975 0.197 0.197 1976 0.147 0.147 1977 0.143 0.143 1978 0.180 0.180 1979 0.243 0.243 1980 0.259 0.259 1981 0.188 0.188 1982 0.275 0.275 1983 0.210 0.210 1984 0.138 0.138 1985 0.189 0.189 1986 0.158 0.158 1987 0.241 0.241 1988 0.142 0.142 1989 0.178 0.178 1990 0.382 0.382 1991 0.291 0.291 1992 0.136 0.136 1993 0.114 0.114 1994 0.119 0.119 1995 0.166 0.166 1996 0.192 0.192 1997 0.182 0.182 1998 0.170 0.170 1999 0.378 0.378 2000 0.182 0.182 2001 0.187 0.187 2002 0.246 0.246 2003 0.191 0.191 2004 0.350 0.350 2005 0.161 0.161 2006 0.145 0.145 2007 0.342 0.342 2008 0.286 0.286 2009 0.218 0.218 Ranked Annual Peaks Ranked Annual Peaks for Predeveloped and Mitigated. POC #2 Rank Predeveloped Mitigated 1 0.3823 0.3823 2 0.3777 0.3777 3 0.3500 0.3500 4 0.3416 0.3416 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:58 AM Page 20 5 0.2910 0.2910 6 0.2857 0.2857 7 0.2752 0.2752 8 0.2588 0.2588 9 0.2526 0.2526 10 0.2497 0.2497 11 0.2461 0.2461 12 0.2435 0.2435 13 0.2415 0.2415 14 0.2404 0.2404 15 0.2281 0.2281 16 0.2231 0.2231 17 0.2179 0.2179 18 0.2096 0.2096 19 0.2034 0.2034 20 0.2022 0.2022 21 0.1965 0.1965 22 0.1941 0.1941 23 0.1923 0.1923 24 0.1913 0.1913 25 0.1900 0.1900 26 0.1890 0.1890 27 0.1884 0.1884 28 0.1868 0.1868 29 0.1836 0.1836 30 0.1824 0.1824 31 0.1823 0.1823 32 0.1798 0.1798 33 0.1779 0.1779 34 0.1704 0.1704 35 0.1703 0.1703 36 0.1657 0.1657 37 0.1651 0.1651 38 0.1634 0.1634 39 0.1632 0.1632 40 0.1611 0.1611 41 0.1608 0.1608 42 0.1580 0.1580 43 0.1578 0.1578 44 0.1553 0.1553 45 0.1486 0.1486 46 0.1474 0.1474 47 0.1474 0.1474 48 0.1469 0.1469 49 0.1450 0.1450 50 0.1434 0.1434 51 0.1426 0.1426 52 0.1423 0.1423 53 0.1375 0.1375 54 0.1363 0.1363 55 0.1335 0.1335 56 0.1334 0.1334 57 0.1270 0.1270 58 0.1234 0.1234 59 0.1187 0.1187 60 0.1169 0.1169 61 0.1139 0.1139 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:58 AM Page 21 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:58 AM Page 22 Duration Flows The Facility PASSED Flow(cfs)Predev Mit Percentage Pass/Fail 0.0911 1676 1676 100 Pass 0.0938 1518 1518 100 Pass 0.0966 1353 1353 100 Pass 0.0993 1217 1217 100 Pass 0.1020 1098 1098 100 Pass 0.1047 997 997 100 Pass 0.1074 924 924 100 Pass 0.1101 828 828 100 Pass 0.1128 753 753 100 Pass 0.1155 695 695 100 Pass 0.1183 646 646 100 Pass 0.1210 588 588 100 Pass 0.1237 548 548 100 Pass 0.1264 510 510 100 Pass 0.1291 464 464 100 Pass 0.1318 427 427 100 Pass 0.1345 397 397 100 Pass 0.1372 370 370 100 Pass 0.1399 354 354 100 Pass 0.1427 326 326 100 Pass 0.1454 302 302 100 Pass 0.1481 282 282 100 Pass 0.1508 260 260 100 Pass 0.1535 242 242 100 Pass 0.1562 224 224 100 Pass 0.1589 207 207 100 Pass 0.1616 197 197 100 Pass 0.1644 186 186 100 Pass 0.1671 172 172 100 Pass 0.1698 162 162 100 Pass 0.1725 151 151 100 Pass 0.1752 141 141 100 Pass 0.1779 132 132 100 Pass 0.1806 125 125 100 Pass 0.1833 113 113 100 Pass 0.1861 108 108 100 Pass 0.1888 103 103 100 Pass 0.1915 98 98 100 Pass 0.1942 91 91 100 Pass 0.1969 84 84 100 Pass 0.1996 81 81 100 Pass 0.2023 77 77 100 Pass 0.2050 76 76 100 Pass 0.2078 76 76 100 Pass 0.2105 70 70 100 Pass 0.2132 65 65 100 Pass 0.2159 63 63 100 Pass 0.2186 60 60 100 Pass 0.2213 58 58 100 Pass 0.2240 55 55 100 Pass 0.2267 51 51 100 Pass 0.2294 48 48 100 Pass 0.2322 45 45 100 Pass Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:58 AM Page 23 0.2349 41 41 100 Pass 0.2376 39 39 100 Pass 0.2403 38 38 100 Pass 0.2430 33 33 100 Pass 0.2457 31 31 100 Pass 0.2484 29 29 100 Pass 0.2511 26 26 100 Pass 0.2539 25 25 100 Pass 0.2566 23 23 100 Pass 0.2593 21 21 100 Pass 0.2620 21 21 100 Pass 0.2647 20 20 100 Pass 0.2674 18 18 100 Pass 0.2701 17 17 100 Pass 0.2728 17 17 100 Pass 0.2756 13 13 100 Pass 0.2783 13 13 100 Pass 0.2810 12 12 100 Pass 0.2837 12 12 100 Pass 0.2864 10 10 100 Pass 0.2891 9 9 100 Pass 0.2918 8 8 100 Pass 0.2945 8 8 100 Pass 0.2973 8 8 100 Pass 0.3000 8 8 100 Pass 0.3027 8 8 100 Pass 0.3054 8 8 100 Pass 0.3081 8 8 100 Pass 0.3108 7 7 100 Pass 0.3135 7 7 100 Pass 0.3162 7 7 100 Pass 0.3189 7 7 100 Pass 0.3217 7 7 100 Pass 0.3244 7 7 100 Pass 0.3271 7 7 100 Pass 0.3298 7 7 100 Pass 0.3325 6 6 100 Pass 0.3352 5 5 100 Pass 0.3379 5 5 100 Pass 0.3406 5 5 100 Pass 0.3434 4 4 100 Pass 0.3461 4 4 100 Pass 0.3488 3 3 100 Pass 0.3515 2 2 100 Pass 0.3542 2 2 100 Pass 0.3569 2 2 100 Pass 0.3596 2 2 100 Pass Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:58 AM Page 24 Water Quality Water Quality BMP Flow and Volume for POC #2 On-line facility volume:0 acre-feet On-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Off-line facility target flow:0 cfs. Adjusted for 15 min:0 cfs. Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:58 AM Page 25 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 26 Appendix Predeveloped Schematic Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 27 Mitigated Schematic Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 28 Predeveloped UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 Sophie Jo Short Plat Vault 09-23-24.wdm MESSU 25 PreSophie Jo Short Plat Vault 09-23-24.MES 27 PreSophie Jo Short Plat Vault 09-23-24.L61 28 PreSophie Jo Short Plat Vault 09-23-24.L62 30 POCSophie Jo Short Plat Vault 09-23-241.dat 31 POCSophie Jo Short Plat Vault 09-23-242.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 10 PERLND 16 IMPLND 1 COPY 501 COPY 502 DISPLY 1 DISPLY 2 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Predeveloped After Mitiga MAX 1 2 30 9 2 Not Included MAX 1 2 31 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 502 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 10 C, Forest, Flat 1 1 1 1 27 0 16 C, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 10 0 0 1 0 0 0 0 0 0 0 0 0 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 29 16 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 10 0 0 4 0 0 0 0 0 0 0 0 0 1 9 16 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 10 0 0 0 0 0 0 0 0 0 0 0 16 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 10 0 4.5 0.08 400 0.05 0.5 0.996 16 0 4.5 0.03 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 10 0 0 2 2 0 0 0 16 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 10 0.2 0.5 0.35 6 0.5 0.7 16 0.1 0.25 0.25 6 0.5 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 10 0 0 0 0 2.5 1 0 16 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 4 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 30 # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Predeveloped After Mitigation Trade*** PERLND 10 0.662 COPY 501 12 PERLND 10 0.662 COPY 501 13 Predeveloped Bypass*** PERLND 10 0.035 COPY 501 12 PERLND 10 0.035 COPY 501 13 Not Included*** PERLND 16 0.22 COPY 502 12 PERLND 16 0.22 COPY 502 13 IMPLND 1 0.441 COPY 502 15 ******Routing****** END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 COPY 502 OUTPUT MEAN 1 1 48.4 DISPLY 2 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* END PRINT-INFO Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 31 HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 501 OUTPUT MEAN 1 1 48.4 WDM 501 FLOW ENGL REPL COPY 502 OUTPUT MEAN 1 1 48.4 WDM 502 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 END MASS-LINK END RUN Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 32 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1948 10 01 END 2009 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 Sophie Jo Short Plat Vault 09-23-24.wdm MESSU 25 MitSophie Jo Short Plat Vault 09-23-24.MES 27 MitSophie Jo Short Plat Vault 09-23-24.L61 28 MitSophie Jo Short Plat Vault 09-23-24.L62 31 POCSophie Jo Short Plat Vault 09-23-242.dat 30 POCSophie Jo Short Plat Vault 09-23-241.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 16 IMPLND 1 RCHRES 1 COPY 502 COPY 1 COPY 501 COPY 601 DISPLY 2 DISPLY 1 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 2 Vault: Tributary Area MAX 1 2 31 9 1 Vault 1 MAX 1 2 30 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 502 1 1 501 1 1 601 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 16 C, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 33 # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 16 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 16 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 16 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 16 0 4.5 0.03 400 0.05 0.5 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 16 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 16 0.1 0.25 0.25 6 0.5 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 16 0 0 0 0 2.5 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 4 1 9 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 34 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** Vault: Tributary Area*** PERLND 16 0.22 RCHRES 1 2 PERLND 16 0.22 RCHRES 1 3 IMPLND 1 0.441 RCHRES 1 5 Vault: Tributary Area*** PERLND 16 0.22 COPY 502 12 PERLND 16 0.22 COPY 502 13 IMPLND 1 0.441 COPY 502 15 Dev Bypass Area*** PERLND 16 0.035 COPY 501 12 PERLND 16 0.035 COPY 601 12 PERLND 16 0.035 COPY 501 13 PERLND 16 0.035 COPY 601 13 ******Routing****** PERLND 16 0.22 COPY 1 12 IMPLND 1 0.441 COPY 1 15 PERLND 16 0.22 COPY 1 13 RCHRES 1 1 COPY 501 16 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 502 OUTPUT MEAN 1 1 48.4 DISPLY 2 INPUT TIMSER 1 COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Vault 1 1 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 END ACTIVITY Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 35 PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 0 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.01 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES FTABLE 1 91 4 Depth Area Volume Outflow1 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (ft/sec) (Minutes)*** 0.000000 0.045895 0.000000 0.000000 0.069444 0.045895 0.003187 0.001580 0.138889 0.045895 0.006374 0.002234 0.208333 0.045895 0.009562 0.002736 0.277778 0.045895 0.012749 0.003159 0.347222 0.045895 0.015936 0.003532 0.416667 0.045895 0.019123 0.003869 0.486111 0.045895 0.022310 0.004179 0.555556 0.045895 0.025497 0.004468 0.625000 0.045895 0.028685 0.004739 0.694444 0.045895 0.031872 0.004995 0.763889 0.045895 0.035059 0.005239 0.833333 0.045895 0.038246 0.005472 0.902778 0.045895 0.041433 0.005696 0.972222 0.045895 0.044620 0.005911 1.041667 0.045895 0.047808 0.006118 1.111111 0.045895 0.050995 0.006319 1.180556 0.045895 0.054182 0.006513 1.250000 0.045895 0.057369 0.006702 1.319444 0.045895 0.060556 0.006886 1.388889 0.045895 0.063743 0.007065 1.458333 0.045895 0.066931 0.007239 1.527778 0.045895 0.070118 0.007409 1.597222 0.045895 0.073305 0.007576 1.666667 0.045895 0.076492 0.007739 1.736111 0.045895 0.079679 0.007898 1.805556 0.045895 0.082867 0.008055 1.875000 0.045895 0.086054 0.008208 1.944444 0.045895 0.089241 0.008359 2.013889 0.045895 0.092428 0.008507 2.083333 0.045895 0.095615 0.008652 2.152778 0.045895 0.098802 0.008795 2.222222 0.045895 0.101990 0.008936 2.291667 0.045895 0.105177 0.009075 2.361111 0.045895 0.108364 0.009211 Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 36 2.430556 0.045895 0.111551 0.009346 2.500000 0.045895 0.114738 0.009478 2.569444 0.045895 0.117925 0.009609 2.638889 0.045895 0.121113 0.009738 2.708333 0.045895 0.124300 0.010525 2.777778 0.045895 0.127487 0.012006 2.847222 0.045895 0.130674 0.012887 2.916667 0.045895 0.133861 0.013601 2.986111 0.045895 0.137049 0.014224 3.055556 0.045895 0.140236 0.014787 3.125000 0.045895 0.143423 0.015307 3.194444 0.045895 0.146610 0.015795 3.263889 0.045895 0.149797 0.016256 3.333333 0.045895 0.152984 0.016695 3.402778 0.045895 0.156172 0.017115 3.472222 0.045895 0.159359 0.017519 3.541667 0.045895 0.162546 0.020074 3.611111 0.045895 0.165733 0.021822 3.680556 0.045895 0.168920 0.023159 3.750000 0.045895 0.172107 0.024312 3.819444 0.045895 0.175295 0.025351 3.888889 0.045895 0.178482 0.026310 3.958333 0.045895 0.181669 0.027208 4.027778 0.045895 0.184856 0.028057 4.097222 0.045895 0.188043 0.028866 4.166667 0.045895 0.191230 0.029642 4.236111 0.045895 0.194418 0.030388 4.305556 0.045895 0.197605 0.031108 4.375000 0.045895 0.200792 0.031805 4.444444 0.045895 0.203979 0.032482 4.513889 0.045895 0.207166 0.033141 4.583333 0.045895 0.210354 0.033782 4.652778 0.045895 0.213541 0.034408 4.722222 0.045895 0.216728 0.035020 4.791667 0.045895 0.219915 0.035619 4.861111 0.045895 0.223102 0.036205 4.930556 0.045895 0.226289 0.036780 5.000000 0.045895 0.229477 0.037345 5.069444 0.045895 0.232664 0.037899 5.138889 0.045895 0.235851 0.038443 5.208333 0.045895 0.239038 0.038979 5.277778 0.045895 0.242225 0.088614 5.347222 0.045895 0.245412 0.359885 5.416667 0.045895 0.248600 0.743968 5.486111 0.045895 0.251787 1.173262 5.555556 0.045895 0.254974 1.581565 5.625000 0.045895 0.258161 1.910384 5.694444 0.045895 0.261348 2.130744 5.763889 0.045895 0.264536 2.300834 5.833333 0.045895 0.267723 2.449030 5.902778 0.045895 0.270910 2.588659 5.972222 0.045895 0.274097 2.721058 6.041667 0.045895 0.277284 2.847246 6.111111 0.045895 0.280471 2.968025 6.180556 0.045895 0.283659 3.084038 6.250000 0.045895 0.286846 3.195809 END FTABLE 1 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 1 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 1 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP END EXT SOURCES EXT TARGETS Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 37 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** COPY 2 OUTPUT MEAN 1 1 48.4 WDM 702 FLOW ENGL REPL COPY 502 OUTPUT MEAN 1 1 48.4 WDM 802 FLOW ENGL REPL COPY 602 OUTPUT MEAN 1 1 48.4 WDM 902 FLOW ENGL REPL RCHRES 1 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1001 STAG ENGL REPL COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL COPY 601 OUTPUT MEAN 1 1 48.4 WDM 901 FLOW ENGL REPL END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 2 PERLND PWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 2 MASS-LINK 3 PERLND PWATER IFWO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 3 MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 MASS-LINK 16 RCHRES ROFLOW COPY INPUT MEAN END MASS-LINK 16 END MASS-LINK END RUN Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 38 Predeveloped HSPF Message File Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 39 Mitigated HSPF Message File Sophie Jo Short Plat Vault 09-23-24 10/11/2024 9:39:59 AM Page 40 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2024; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com Appendix B – Geotechnical Report DEVELOPMENT ENGINEERING, PLLC P.O. Box 446 Tacoma, WA 98401 Ph (253) 228-0513 www.de-civil.com September 7, 2017 Schneider Homes, Inc. 6510 Southcenter Blvd #1 Tukwila, WA 98188 Attn: Mr. Harry Schneider Geologic Assessment Report Proposed Short Plat 7XX S 21st Street Renton, Washington PN: 7222000110 Job: 17-166 Schneider.GR INTRODUCTION This letter and design report presents the results of our subsurface explorations for the proposed short plat to be located at 7XX S 21st Street in the City of Renton, Washington. The general location of the site is shown on the attached Site Vicinity Map, Figure 1. Our understanding of the project is based on our discussions with yourself, our September 4, 2017 site visit, and our experience in the area. We understand that you are proposing to subdivide the property into 3 lots in order to construct new residences on each of the sites. We anticipate that the proposed residence(s) will be a constructed with conventional wood-framing, supported on spread and continuous foundations. SCOPE We understand that the City of Renton is requesting a geotechnical report to address stormwater management and other design issues related to the site development. The purpose of our services is to evaluate the surface and subsurface conditions at the site as a basis for providing engineering recommendations for the development of the site. Specifically, our scope of services for the project included the following: 1. Reviewing the available geologic, hydrogeologic and geotechnical data for the site area. 2. Performing a geological reconnaissance of the site to assess the site’s soil, groundwater and subsurface conditions. 3. Exploring shallow subsurface conditions at the site by monitoring the excavation of two test pits across the site. 4. Evaluating the engineering characteristics of the soils encountered at the site, as appropriate. 5. Providing geotechnical recommendations for site infiltration site grading including site preparation, subgrade reparation, fill placement criteria, suitability of on-site soils for use as structural fill, temporary and permanent cut and fill slopes, drainage and erosion control measures. 6. Providing site-specific seismic criteria based on the subsurface conditions encountered at the site. 7. Preparing a written report summarizing our observations, conclusions and recommendations along with the supporting data. Subsurface explorations or laboratory testing were completed as part of this assessment. 17-166 Schneider.GR September 7, 2017 Page 2 SITE CONDITIONS Surface Conditions The subject parcel is located at 7XX S 21st Street in the City of Renton, Washington. The site consists of a single parcel that is rectangular in shape, approximately 290 feet in length (west to east) by 70 feet in width (north to South) and encompasses an area of approximately 0.46 acres. The site is an existing lot of record that is currently undeveloped and is well vegetated with trees, grasses and brush. Access to the site will be from a private driveway from S 21st Street, see Figure 2 Site Plan. The parcel is nearly level with a slight slope to the north, site grades are generally less than 5 percent with less than 5 feet of elevation change across the lot. No surface water or seepage was observed on the site at the time of our first site visit, however we did observe signs of a potentially high groundwater in the upper soils of the site, see below for more information. No evidence of erosion, soil movement, landslide activity or deep-seated slope instability was observed at the site or within 300 feet of the site at the time of our site visit. Site Soils The USDA Natural Resource Conservation Service Web Soil Survey for King County mapped the soils in the area of the site as Beausite gravelly sandy loam (BeC). The Beausite soils are a gravelly sandy loam, formed from glacial deposits overlying sandstone bedrock on slopes of 6 to 15 percent slope and are listed as having a “moderate” erosion potential, see Figure 3 USDA Soil Map. Site Geology The Geological Map of the Renton Quadrangle, King County, Washington by D. R. Mullineaux, 1965 indicates the site is underlain by glacial till (Qvt). These glacial soils were deposited during the latest stage of the most recent Vashon Stade of the Fraser Glaciation, approximately 12,000 to 15,000 years ago. These soils are characterized as mix of silt, sand with gravel which were overridden by the glacial ice. As such, these soils are generally very dense exhibiting high strength and low compressibility characteristics. An excerpt of the above referenced map is included as Figure 4. Based on our site observations the near surface soils at the site are most consistent with the USDA mapped soils. Subsurface Explorations On September 4, 2017 we visited the site and observed the excavation of three test pits to a maximum depth of 6 feet for the purpose of determining infiltration feasibility for the project, soil samples were collected for later analysis in our lab. The test pits were excavated by a track mounted excavator operated by a licensed earthwork contractor. The test pits were located in the field by our representative by pacing from existing site features such as property corners and adjacent roadways and fences. The approximate location of the test pits are indicated on the attached Site Plan as Figure 2. A geotechnical engineer from our office logged the subsurface conditions encountered in each test pit, obtained representative soil samples, and observed pertinent site features. Representative soil samples obtained from the test pits were placed in sealed plastic bags and taken to our laboratory for further examination and testing, as deemed appropriate. Based on our experience in the area and extent of our explorations in the area it is our opinion that the soils encountered in the test pits are generally representative of the soils at the site. 17-166 Schneider.GR September 7, 2017 Page 3 Because the soils encountered were consistent between the test sites and other exposed site soils and the soil mapping, it is our opinion that no additional soils tests required to evaluate the subsurface conditions at the site. The explorations performed as part of this evaluation indicate conditions only at the specific locations and that the actual condition in other locations could vary. Furthermore, the nature and extent of any such variations would not become evident until additional explorations are performed or until construction activities have begun. Subsurface Conditions Our test pits encountered uniform subsurface conditions that confirmed the general geological mapping stratigraphy. The site soils generally consisted of a minimum of 24 to 36 inches of weathered silty sand and gravel over a dense sandstone layer. Test pit #2 showed signs of a shallow fill layer (approximately 12 to 18 inches). Based on our review of our test pits, the upper weathered site soils in the area of development are consistent with the Beausite soils. The soils encountered were visually classified in accordance with the Unified Soil Classification System (USCS) described on Figure 5. The test pit logs are included as Figures 6. Groundwater Conditions No groundwater seepage was observed in any of the test pits. Although based on our observations we anticipate that during periods of heavy rainfall the upper soils would become saturated. Perched groundwater typically develops when the vertical infiltration of precipitation through a more permeable soil is slowed at depth by a deeper, less permeable soil type. We expect that perched groundwater will develop seasonally atop the shallow sandstone layer. Based on the observed mottling and nature of the near surface soils, we anticipate fluctuations in the local groundwater levels will occur in response to precipitation patterns, off-site construction activities, and site utilization. CONCLUSIONS Based on our site observations, subsurface explorations and engineering analysis, it is our opinion that the proposed development is feasible from a geotechnical standpoint. The residences may be supported on new conventional spread footings or floor slabs bearing on competent native soils or on structural fill placed above these native soils. We understand that grading at the site will be minimal, and will consist primarily of excavating the footings for the proposed residence(s), site utilities, and the stormwater facilities. If grading activities will take place during the winter season, the owner should be prepared to import free-draining granular material for use as structural fill and backfill. Proper surface drainage and erosion control measures will reduce the risk for future erosion at the site. Site Preparation Areas to be graded should be cleared of deleterious matter including any existing structures, foundations, abandoned utility lines, debris and vegetation. The portions of the site covered with vegetation should be stripped of any forest duff and organic-laden soils. Based on our test pits we anticipate stripping depths to be on the order of 6 to 18 inches. These materials can be stockpiled and later used for erosion control. Material that cannot be utilized on the site should be removed from the site. Where placement of fill material is required, the stripped/exposed subgrade areas should be compacted to a firm and unyielding surface prior to placement of any fill. Excavations for debris 17-166 Schneider.GR September 7, 2017 Page 4 removal should be backfilled with structural fill compacted to the densities described in the “Structural Fill” section of this report. We recommend that a member of our staff evaluate the exposed subgrade conditions after removal of vegetation and topsoil stripping is completed and prior to placement of structural fill. The exposed subgrade soil should be proof-rolled with heavy rubber-tired equipment during dry weather or probed with a 1/2-inch-diameter steel rod during wet weather conditions. Any soft, loose or otherwise unsuitable areas delineated during proof-rolling or probing should be recompacted, if practical, or over-excavated and replaced with structural fill, based on the recommendations of our site representative. The areas of old fill material should be evaluated during grading operations to determine if they need mitigation; recompaction or removal. Structural Fill All material placed as fill associated with mass grading, as utility trench backfill, under building areas, or under asphalt pavement should be placed as structural fill. The structural fill should be placed in horizontal lifts of appropriate thickness to allow adequate and uniform compaction of each lift. Fill should be compacted to at least 95 percent of MDD (maximum dry density as determined in accordance with ASTM D-1557). The appropriate lift thickness will depend on the fill characteristics and compaction equipment used. We recommend that the appropriate lift thickness be evaluated by our field representative during construction. We recommend that our representative be present during site grading activities to observe the work and perform field density tests. The suitability of material for use as structural fill will depend on the gradation and moisture content of the soil. As the amount of fines (material passing US No. 200 sieve) increases, soil becomes increasingly sensitive to small changes in moisture content and adequate compaction becomes more difficult to achieve. During wet weather, we recommend use of well-graded sand and gravel with less than 5 percent (by weight) passing the US No. 200 sieve based on that fraction passing the 3/4-inch sieve, such as Gravel Backfill for Walls (9-03.12(2)). If prolonged dry weather prevails during the earthwork and foundation installation phase of construction, higher fines content (up to 10 to 12 percent) will be acceptable. Material placed for structural fill should be free of debris, organic matter, trash and cobbles greater than 6-inches in diameter. The moisture content of the fill material should be adjusted as necessary for proper compaction. Suitability of On-Site Materials as Fill During dry weather construction, any non-organic on-site soil may be considered for use as structural fill; provided it meets the criteria described above in the structural fill section and can be compacted as recommended. If the soil material is over-optimum in moisture content when excavated, it will be necessary to aerate or dry the soil prior to placement as structural fill. We generally did not observe the site soils to be excessively moist at the time of our subsurface exploration program. The native weathered and glacial till soils in the site generally consisted of silty gravel with fine sand. These soils are generally comparable to “common borrow” material and will be suitable for use as structural fill provided the moisture content is maintained within 3 percent of the optimum moisture level. However, because of the high fines content, the till soils encountered across the site will likely be unsuitable during extended periods of wet weather. We recommend that completed graded-areas be restricted from traffic or protected prior to wet weather conditions. The graded areas may be protected by paving, placing asphalt-treated base, a 17-166 Schneider.GR September 7, 2017 Page 5 layer of free-draining material such as pit run sand and gravel or clean crushed rock material containing less than 5 percent fines, or some combination of the above. Temporary Excavations All job site safety issues and precautions are the responsibility of the contractor providing services/work. The following cut/fill slope guidelines are provided for planning purposes only. Temporary cut slopes will likely be necessary during grading operations or utility installation. All excavations at the site associated with confined spaces, such as utility trenches and retaining walls, must be completed in accordance with local, state, or federal requirements. Based on current Washington Industrial Safety and Health Act (WISHA, WAC 296-155-66401) regulations, the shallow upper soils on the site would be classified as Type C soils, whereas the very dense sandstone soils would be classified as Type A soils. According to WISHA, for temporary excavations of less than 20 feet in depth, the side slopes in Type A soils should be laid back at a slope inclination of ¾H:1V (Horizontal: Vertical) and Type C soils should be laid back at a slope inclination of 1½H:1V or flatter from the toe to the crest of the slope. It should be recognized that slopes of this nature do ravel and require occasional maintenance. All exposed slope faces should be covered with a durable reinforced plastic membrane, jute matting, or other erosion control mats during construction to prevent slope raveling and rutting during periods of precipitation. These guidelines assume that all surface loads are kept at a minimum distance of at least one half the depth of the cut away from the top of the slope and that significant seepage is not present on the slope face. Flatter cut slopes will be necessary where significant raveling or seepage occurs, or if construction materials will be stockpiled along the slope crest. Where it is not feasible to slope the site soils back at these inclinations, a retaining structure should be considered. Where retaining structures are greater than 4-feet in height (bottom of footing to top of structure) or have slopes of greater than 15 percent above them, they should be engineered. This information is provided solely for the benefit of the owner and other design consultants, and should not be construed to imply that Development Engineering, PLLC assumes responsibility for job site safety. It is understood that job site safety is the sole responsibility of the project contractor. Foundation Support Based on the subsurface soil conditions encountered across the site, we recommend that spread footings for the new residences be founded on dense to very dense native soils or on structural fill that extends to suitable native soils. Given the presence of fill material on the site it is anticipated that some footings may be located in areas where existing fill material is present. Provided the exposed soils area evaluated and verified by a representative from our office at time of construction to be suitable to support the design loads we do not anticipate that the presence of the fill material on site will be a detrimental factor to the site development. We do not recommend that footings be supported on a mix of sandstone and weathered material. If areas of sandstone are exposed we recommend that those areas are over excavated a minimum of 12 inches and brought back to grade with structural fill. The soil at the base of the footing excavations should be disturbed as little as possible. All loose, soft or unsuitable material should be removed or recompacted, as appropriate. A representative from our firm should observe the foundation excavations to determine if suitable bearing surfaces have been prepared, particularly in the areas where the foundation will be situated on fill material. 17-166 Schneider.GR September 7, 2017 Page 6 We recommend a minimum width of 2 feet for isolated footings and at least 16 inches for continuous wall footings. All footing elements should be embedded at least 18 inches below grade for frost protection. Footings founded as described above can be designed using an allowable soil bearing capacity of 2,000psf (pounds per square foot) for combined dead and long-term live loads. For deeper footings supported entirely on the sandstone a bearing capacity of 5,000psf may be used. The weight of the footing and any overlying backfill may be neglected. The allowable bearing value may be increased by one-third for transient loads such as those induced by seismic events or wind loads. Lateral loads may be resisted by friction on the base of footings and floor slabs and as passive pressure on the sides of footings. We recommend that an allowable coefficient of friction of 0.40 be used to calculate friction between the concrete and the underlying soil. Passive pressure may be determined using an allowable equivalent fluid density of 300 pcf (pounds per cubic foot). Factors of safety have been applied to these values. We estimate that settlements of footings designed and constructed as recommended will be less than 1 inch, for the anticipated load conditions, with differential settlements between comparably loaded footings of 1/2 inch or less. Most of the settlements should occur essentially as loads are being applied. However, disturbance of the foundation subgrade during construction could result in larger settlements than predicted. Floor Slab Support Slabs-on-grade, if constructed, should be supported on the medium dense native soils or on structural fill prepared as described above. Any areas of old fill material should be evaluated during grading activity for suitability of structural support. Areas of significant organic debris should be removed. We recommend that floor slabs be directly underlain by a capillary break material with minimum 6- inch thickness of coarse sand, pea gravel, or gravel containing less than 3 percent fines. The drainage material should be placed in one lift and compacted to an unyielding condition. A synthetic vapor barrier is recommended to control moisture migration through the slabs. This is of particular importance where the foundation elements are underlain by the silty till, or where moisture migration through the slab is an issue, such as where adhesives are used to anchor carpet or tile to the slab. A subgrade modulus of 400 kcf (kips per cubic foot) may be used for floor slab design. We estimate that settlement of the floor slabs designed and constructed as recommended, will be 1/2 inch or less over a span of 50 feet. Site Drainage All ground surfaces, pavements and sidewalks at the site should be sloped away from structures. The lot should also be carefully graded to ensure positive drainage away from all structures and property lines. Surface water runoff from the roof area, driveways, perimeter footing drains, and wall drains, should be collected, tightlined, and conveyed to an appropriate discharge point. Based on our site evaluation, it is our opinion that the infiltration of stormwater at the site not feasible on the site. Further, based on our understanding of the current City of Renton Stormwater Management Manual, it will likely be necessary to visit the site and perform additional explorations and possibly at least one full scale “Pilot Infiltration Test” (PIT) between December 1 and April 30 (winter months) in order to determine seasonal groundwater levels and infiltration feasibility. Since our field final work was done in early Suptember we recommend that we revisit our Site Drainage 17-166 Schneider.GR September 7, 2017 Page 7 recommendations once this additional field work is complete. For preliminary design purposes we are not recommending that infiltration be pursued. LID Feasibility The following table presents our recommendations for various Best Management Practices (BMP’s) for various Low Impact Development (LID) BMP’s. BMP Viable Limitations or Infeasibility Criteria Lawn and Landscape Areas T5.13: Post Construction Soil Quality and Depth Yes None. Roofs T5.30: Full Dispersion No The site does not have sufficient dispersion area. T5.10A: Downspout full infiltration systems. No Infiltration appears to be infeasible due to a high groundwater table. Bio Retention No This BMP also has limited feasibility for the same general reasons as for full infiltration. T5.10B Downspout Dispersion systems Limited This BMP may be feasible depending on final lot configurations. T5.10C Perforate stub connections Limited Similar to the infiltration systems there will be limited depths of soil for the connection to ensure that it is at least 1 foot above the till layers. Other Hard Surfaces T5.30 Full Dispersion No The site does not have sufficient dispersion area. T5.15 Permeable Surfacing No The soils in the areas of the proposed pavement included a very shallow groundwater depth which does not allow for the required 12 inches of separation between the bottom of the pavement section and the groundwater. Further, given the silty nature of the site soils, permeable surfacing would not be sufficiently supported and would likely fail in a short period of time. Bio Retention No This BMP also has limited feasibility for the same general reasons as for full infiltration. T5.12: Sheet Flow Dispersion T5.11 Concentrated flow dispersion Limited No flooding or erosion impacts are anticipated. However, this BMP may be feasible dependent on the final lot configurations and the available areas for dispersion of runoff. LIMITATIONS We have prepared this report for Schneider Homes, Inc, and other members of the design team for use in evaluating a portion of this project. Subsurface conditions described herein are based on our observations of exposed soils on the parcel. This report may be made available to regulatory agencies or others, but this report and conclusions should not be construed as a warranty of subsurface conditions. Subsurface conditions can vary over short distances and can change with time. 17-166 Schneider.GR September 7, 2017 Page 8 Within the limitations of scope, schedule and budget, our services have been executed in accordance with generally accepted practices in this area at the time this report was prepared. No warranty, express or implied, should be understood. We trust this is sufficient for your current needs. Should you have any questions, or require additional information, please contact us at your earliest convenience. Respectfully submitted, Development Engineering, PLLC Glen Coad, PE Owner WGC DocID:17-166 Schneider.GR Attachments: Figure 1: Vicinity Map Figure 2: Site Plan Figure 3: SCS Soil Survey Figure 4: USGS Geology Map Figure 5: Soils Classification Chart Figure 6: Test Pit Logs Approximate Site Location Not to Scale DE-CIVIL, PLLC P.O. Box 446 Tacoma, WA 98401 Ph (253) 228-0513 www.de-civil.com Site Vicinity Map Schneider SP 7XX S 21st Street Renton County, Washington Job No: 17-166 September 2017 Figure 1 DEVELOPMENT ENGINEERING, PLLC P.O. Box 446 Tacoma, WA 98401 Ph (253) 228-0513 www.de-civil.com Approximate Test Pit Location Site Plan Schneider SP 7XX S 21st Street Renton County, Washington Job No: 17-166 September 2017 Figure 2 TP-1 TP-2 TP-3 TP-1 Approximate Site Location Not to Scale DE-CIVIL, PLLC P.O. Box 446 Tacoma, WA 98401 Ph (253) 228-0513 www.de-civil.com USDA Web Soil Survey Schneider SP 7XX S 21st Street Renton County, Washington Job No: 17-166 September 2017 Figure 3 Approximate Site Location Not to Scale DE-CIVIL, PLLC P.O. Box 446 Tacoma, WA 98401 Ph (253) 228-0513 www.de-civil.com USGS Geologic Map Schneider SP 7XX S 21st Street Renton County, Washington Job No: 17-166 September 2017 Figure 4 DEVELOPMENT ENGINEERING, PLLC P.O. Box 446 Tacoma, WA 98401 Ph (253) 228-0513 www.de-civil.com Soil Classification Chart Schneider SP 7XX S 21st Street Renton County, Washington Job No: 17-166 September 2017 Figure 5 ` Test Pit TP-1 Location: (See Figure 2) Depth (ft.) Soil Type Description 0 – 0.5 Topsoil 0.5 – 5.0 SM Brown silty sand and gravel (cemented, dense) 5.0 – 6.0 Tan Sandstone (fractured) Terminated at 6.0 feet below ground surface. No caving observed. Evidence of seasonal groundwater at 6 inches. Test Pit TP-2 Location: (See Figure 2) Depth (ft.) Soil Type Description 0 – 1.0 Brown silty SAND with gravel Fill (asphalt and concrete debris) 1.0 – 2.5 SM Brown silty SAND w/ gravel, (weakly cemented, dense) 2.5 – 7.0 ML grey SILT w/sand & gravel, (stiff) 7.0 – 8.0 tan Sandstone (fractured) Terminated at 8.0 feet below ground surface. No caving observed. Evidence of seasonal groundwater at 12 inches. Test Pit TP-3 Location: (See Figure 2) Depth (ft.) Soil Type Description 0 – 0.5 Top soil 0.5 – 2.0 SM Brown silty SAND w/ gravel, (weakly cemented, dense) 2.0 – 4.5 ML grey SILT w/sand & gravel, (stiff) 4.5 – 6.0 tan Sandstone (fractured) Terminated at 6.0 feet below ground surface. No caving observed. Evidence of seasonal groundwater at 12 inches. Logged by WGC, 9/4/17 DE-CIVIL, PLLC P.O. Box 446 Tacoma, WA 98401 Ph (253) 228-0513 www.de-civil.com Test Pit Logs Schneider SP 7XX S 21st Street Renton County, Washington Job No: 17-166 September 2017 Figure 6 Appendix C – CSWPPP Construction Stormwater General Permit Stormwater Pollution Prevention Plan (SWPPP) for Sophie Jo Short Plat S 21st Street, Renton, WA 98055 Prepared for: Schneider Homes, Inc Permittee / Owner Developer Operator / Contractor Schneider Homes, Inc 6510 Southcenter Blvd, Suite 100 Tukwila, WA 98188 Schneider Homes, Inc 6510 Southcenter Blvd, Suite 100 Tukwila, WA 98188 TBD Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number TBD TBD TBD SWPPP Prepared By Name Organization Contact Phone Number Brandon Loucks, P.E. ESM Consulting Engineers (253) 838-6113 SWPPP Preparation Date 06/06/2024 Approximate Project Construction Dates Start Date End Date September 2024 September 2026 P a g e | 1 Table of Contents 1 Project Information .............................................................................................................. 4 1.1 Existing Conditions ...................................................................................................... 4 1.2 Proposed Construction Activities .................................................................................. 5 2 Construction Stormwater Best Management Practices (BMPs) ........................................... 6 2.1 The 13 Elements .......................................................................................................... 6 2.1.1 Element 1: Preserve Vegetation / Mark Clearing Limits ........................................ 6 2.1.2 Element 2: Establish Construction Access ............................................................ 7 2.1.3 Element 3: Control Flow Rates ............................................................................. 8 2.1.4 Element 4: Install Sediment Controls .................................................................... 9 2.1.5 Element 5: Stabilize Soils ....................................................................................10 2.1.6 Element 6: Protect Slopes....................................................................................11 2.1.7 Element 7: Protect Drain Inlets ............................................................................12 2.1.8 Element 8: Stabilize Channels and Outlets ..........................................................13 2.1.9 Element 9: Control Pollutants ...............................................................................14 2.1.10 Element 10: Control Dewatering ..........................................................................18 2.1.11 Element 11: Maintain BMPs .................................................................................19 2.1.12 Element 12: Manage the Project ..........................................................................20 2.1.13 Element 13: Protect Low Impact Development (LID) BMPs .................................22 3 Pollution Prevention Team .................................................................................................23 4 Monitoring and Sampling Requirements ............................................................................24 4.1 Site Inspection ............................................................................................................24 5 Reporting and Record Keeping ..........................................................................................24 5.1 Record Keeping ..........................................................................................................24 5.1.1 Site Log Book ......................................................................................................24 5.1.2 Records Retention ...............................................................................................24 5.1.3 Updating the SWPPP ...........................................................................................25 5.2 Reporting ....................................................................................................................25 5.2.1 Discharge Monitoring Reports ..............................................................................25 5.2.2 Notification of Noncompliance ..............................................................................25 P a g e | 2 List of Tables Table 1 – Summary of Site Pollutant Constituents ...................... Error! Bookmark not defined. Table 2 – Pollutants ..................................................................................................................14 Table 3 – pH-Modifying Sources ...............................................................................................16 Table 4 – Dewatering BMPs ......................................................................................................18 Table 5 – Management .............................................................................................................20 Table 6 – BMP Implementation Schedule .................................................................................21 Table 7 – Team Information ......................................................................................................23 List of Appendices Appendix/Glossary A. Site Map B. BMP Detail C. Correspondence D. Site Inspection Form E. Construction Stormwater General Permit (CSWGP) F. 303(d) List Waterbodies / TMDL Waterbodies Information G. Contaminated Site Information H. Engineering Calculations P a g e | 3 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 P a g e | 4 1 Project Information Project/Site Name: Sophie Jo Short Plat Street/Location: S 21st Street City: City of Renton State: WA Zip code: 98055 Subdivision: N/A Receiving waterbody: An unnamed creek (tributary to Lake Washington) 1.1 Existing Conditions Total acreage (including support activities such as off-site equipment staging yards, material storage areas, borrow areas). Total site acreage: 0.51 ac Disturbed acreage: 0.51 ac Existing structures: The project site was previously developed with single-family residence with access driveway. The single-family home has since been demolished. Landscape Topography: There is approximately 7 feet of elevation drop across the site from south to the north. Drainage patterns: The site drains to the north and to the east. Site flows discharge into the existing city storm system near the northeast corner of the property. Existing Vegetation: Vegetation consists primarily of grass, scattered brambles and mature trees. Critical Areas: The site does not contain any critical areas and is not adjacent to any critical areas. List of known impairments for 303(d) listed or Total Maximum Daily Load (TMDL) for the receiving waterbody: None known. P a g e | 5 1.2 Proposed Construction Activities Description of site development (example: subdivision): The project proposes to subdivide this parcel into three (3) single-family residences with driveways, walkways, and utility services; frontage improvements will be required along S 21st Street. Description of construction activities (example: site preparation, demolition, excavation): Construction activities include site clearing, site preparation, erosion and sedimentation control installation, stormwater and other utility appurtenance installation, asphalt paving and landscaping. Description of site drainage including flow from and onto adjacent properties. Must be consistent with Site Map in Appendix A: The existing parcels to the south, developed as single-family residences, are upstream of the site. Portions of these adjacent parcels drain into the site. All other stormwater runoff drains toward an existing roadside ditch located north of the parcel. Description of final stabilization (example: extent of revegetation, paving, landscaping): Final stabilization will be provided by the proposed paved road and sidewalk/landscape areas. Contaminated Site Information: Proposed activities regarding contaminated soils or groundwater (example: on-site treatment system, authorized sanitary sewer discharge): Contaminated soils are not anticipated to be present on site. P a g e | 6 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 13 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. A silt fence will be installed around the perimeter of the project site to mark the limits of construction as well as protect surrounding properties from any possible sediment laden runoff. Grading will occur around the perimeter of the disturbed area to insure there is no runoff of any ponded stormwater. List and describe BMPs: BMP C233: Silt Fence Installation Schedules: Beginning of Project Inspection and Maintenance plan: Silt Fence Maintenance • Repair any damage immediately. • Intercept and convey all evident concentrated flows uphill of the silt fence to a sediment pond. • Check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the trapped sediment. • Remove sediment deposits when the deposit reaches approximately one-third the height of the silt fence or install a second silt fence. • Replace filter fabric that has deteriorated due to ultraviolet breakdown. Responsible Staff: Contractor/CESCL P a g e | 7 2.1.2 Element 2: Establish Construction Access The existing access point to the site is paved and will be used as access to the site. To minimize the tracking of sediment onto public roads, street sweeping, and street cleaning may be necessary to prevent sediment from being tracked onto public roads and the site’s shared access driveway. If necessary, roads shall be swept daily should sediment collect on them. Site designated areas will be used for construction equipment and storage in order to keep equipment on paved areas as much as possible. Inspection and Maintenance plan: Construction Entrance Maintenance • If sediment is being tracked onto pavement, then alternative measures to keep the streets free of sediment shall be used. This may include street sweeping or the installation of a wheel wash. • Any sediment that is tracked onto pavement shall be removed by shoveling or street sweeping. The sediment collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by washing down the street, except when high efficiency sweeping is ineffective and there is a threat to public safety. If it is necessary to wash the streets, the construction of a small sump to contain the wash water shall be considered. The sediment would then be washed into the sump where it can be controlled. • Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non-high efficiency mechanical sweeper because this creates dust and throws soils into storm systems or conveyance ditches. Responsible Staff: Contractor/CESCL P a g e | 8 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 with the following BMPs as needed. The project site is located west of the Cascade Mountain Crest. As such, the project must comply with Minimum Requirement 7 (Ecology 2012). 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: This element is not anticipated to be necessary for this project because the project site is very flat and relatively small. Flow rates during storm events will be relatively minimal. Generated surface water during construction will be captured and tightlined by the existing stormwater network. P a g e | 9 2.1.4 Element 4: Install Sediment Controls Constructing the silt fence and the sediment control pond are the first steps to create the necessary gradients for flow to the pond and to prevent off site discharge of sediment. Rock check dams and v-ditches will be used to convey stormwater runoff into the sediment pond and collect out sediment. The sediment pond is expected to be adequate for sediment control prior to discharge to the existing storm system. The surface area requirements for the TESC pond are met with the designed TESC plan and it is not expected that further treatment or other sediment controlling measures are necessary. However, if the proposed sediment controls are ineffective as determined by the CESCL, they will promptly initiate the implementation of one or more of the alternative BMPs listed in Appendix B. List and describe BMPs: BMP C233: Silt Fence Installation Schedules: Beginning of Project Inspection and Maintenance plan: Silt Fence Maintenance • Repair any damage immediately. • Intercept and convey all evident concentrated flows uphill of the silt fence to a sediment pond. • Check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the trapped sediment. • Remove sediment deposits when the deposit reaches approximately one-third the height of the silt fence or install a second silt fence. • Replace filter fabric that has deteriorated due to ultraviolet breakdown. Responsible Staff: Contractor/CESCL P a g e | 10 2.1.5 Element 5: Stabilize Soils Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. In general, cut and fill slopes will be stabilized as soon as possible, and soil stockpiles will be stabilized through hydroseeding. 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. To minimize soil compaction, a construction entrance will be used and a construction staging area will keep heavy equipment and machinery off unpaved areas as much as possible. 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: September 2023 End date: September 2025 Will you construct during the wet season? Yes No List and describe BMPs: BMP C140: Dust Control Installation Schedules: After grading where the number of days where soils can be left exposed is 7 days during the dry season and 2 days during the wet season. Inspection and Maintenance plan: Dust Control Maintenance • Respray area as necessary to keep dust to a minimum. Responsible Staff: Contractor/CESCL P a g e | 11 2.1.6 Element 6: Protect Slopes Will steep slopes be present at the site during construction? Yes No All cut and fill slopes will be designed, constructed, and protected in a manner that minimizes erosion. List and describe BMPs: The project site will be subject to very minimal slopes if any. Slope protection BMPs are not anticipated. Refer to the BMP documentation (included in Appendix B) for a full description of Inspection and Maintenance for individual BMPs. P a g e | 12 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. 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. If this is deemed ineffective by the CESCL, additional BMPs may be necessary, as listed in Appendix B. Inlet protection is the last component of a treatment train and protection of drain inlets include additional sediment and erosion control measures. Inlet protection devices will be cleaned (or removed and replaced), when sediment has filled the device by one third (1/3) or as specified by the manufacturer. List and describe BMPs: BMP C220: Storm Drain Inlet Protection Installation Schedules: Beginning of Project Inspection and Maintenance plan: Storm Drain Inlet Protection Maintenance • Inspect catch basin filters frequently, especially after storm events. Clean and replace clogged inserts. For systems with clogged stone filters: pull away the stones from the inlet and clean or replace. An alternative approach would be to use the clogged stone as fill and put fresh stone around the inlet. • Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly over the surrounding land area or stockpile and stabilize as appropriate. • Inlets to be inspected weekly and a minimum of daily during storm events. Responsible Staff: Contractor/CESCL P a g e | 13 2.1.8 Element 8: Stabilize Channels and 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. List and describe BMPs: This element and associated BMPs to stabilize channels and outlets are not anticipated. No temporary or permanent conveyance channels are proposed. P a g e | 14 2.1.9 Element 9: Control Pollutants The following pollutants are anticipated to be present on-site: Table 2 – Pollutants Pollutant (List pollutants and source, if applicable) Hydraulic fluid - May be present on site with construction equipment. Diesel - May be present on site with construction equipment. Motor Oil - May be present on site with construction equipment. 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. Chemicals, liquid products, petroleum products, and other polluting materials will be kept covered, stored appropriately, and locked when not in use to prevent vandalism or misuse of these materials that may pollute state waters. 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. • 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). 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). List and describe BMPs: BMP C151: Concrete Handling P a g e | 15 Installation Schedules: TBD Inspection and Maintenance plan: Concrete Handling Maintenance • Check containers for holes in the liner daily during concrete pours and repair the same day. Responsible Staff: Contractor/CESCL Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site? Yes No In order to prevent spills and minimize risk, the following list should be applied • Temporary storage area should be located away from vehicular traffic, near the construction entrance(s), and away from waterways or storm drains. • Material Safety Data Sheets (MSDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers. • Hazardous material storage on-site should be minimized. • Hazardous materials should be handled as infrequently as possible. • During the wet weather season (Oct 1 – April 30), consider storing materials in a covered area. • Materials should be stored in secondary containments, such as earthen dike, horse trough, or even a children’s wading pool for non-reactive materials such as detergents, oil, grease, and paints. Small amounts of material may be secondarily contained in “bus boy” trays or concrete mixing trays. • Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a pallet and, when possible, and within secondary containment. • If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of drums, preventing water from collecting. • Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be stored in approved containers and drums and shall not be overfilled. Containers and drums shall be stored in temporary secondary containment facilities. List and describe BMPs: BMP C153: Material Delivery, Storage and Containment Installation Schedules: As material delivery, storage, and containment occur Inspection and Maintenance plan: The spill kit should include, at a minimum: • 1-Water Resistant Nylon Bag P a g e | 16 • 3-Oil Absorbent Socks 3”x 4’ • 2-Oil Absorbent Socks 3”x 10’ • 12-Oil Absorbent Pads 17”x19” • 1-Pair Splash Resistant Goggles • 3-Pair Nitrile Gloves • 10-Disposable Bags with Ties • Instructions Responsible Staff: Contractor/CESCL Will wheel wash or tire bath system BMPs be used during construction? Yes No Will pH-modifying sources be present on-site? 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 Recycled concrete stockpiles Other (i.e., calcium lignosulfate) [please describe: ] P a g e | 17 List and describe BMPs: BMP C151: Concrete Handling Installation Schedules: TBD Inspection and Maintenance plan: Concrete Handling Maintenance • Check containers for holes in the liner daily during concrete pours and repair the same day. Responsible Staff: Contractor/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. Will uncontaminated water from water-only based shaft drilling for construction of building, road, and bridge foundations be infiltrated provided the wastewater is managed in a way that prohibits discharge to surface waters? Yes No P a g e | 18 2.1.10 Element 10: Control Dewatering Dewatering is not anticipated to be needed for the construction site however, BMPs from Appendix B may be implemented by the CESCL if necessary. Table 4 – Dewatering BMPs Infiltration Transport off-site in a vehicle (vacuum truck for legal disposal) Ecology-approved on-site chemical treatment or other suitable treatment technologies Sanitary or combined sewer discharge with local sewer district approval (last resort) Use of sedimentation bag with discharge to ditch or swale (small volumes of localized dewatering) List and describe BMPs: BMP C251: Construction Stormwater Filtration Installation Schedules: As dewatering is needed Inspection and Maintenance plan: • Screen, bag, and fiber filters must be cleaned and/or replaced when they become clogged. Responsible Staff: Contractor/CESCL P a g e | 19 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. P a g e | 20 2.1.12 Element 12: Manage the Project The project will be managed based on the following principles: • Projects will be phased to the maximum extent practicable and seasonal work limitations will be taken into account. • Inspection and monitoring: o Inspection, maintenance and repair of all BMPs will occur as needed to ensure performance of their intended function. o Site inspections and monitoring will be conducted in accordance with Special Condition S4 of the CSWGP. Sampling locations are indicated on the Site Map. Sampling station(s) are located in accordance with applicable requirements of the CSWGP. • Maintain an updated SWPPP. o 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. 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) P a g e | 21 Table 6 – BMP Implementation Schedule Phase of Construction Project Stormwater BMPs Date Wet/Dry Season Beginning of project BMP C233: Silt Fence September 2024 Wet After Storm Drain Inlet Construction BMP C220: Storm Drain Inlet Protection After grading BMP C120: Temporary and Permanent Seeding September 2024- September 2026 Dry/Wet BMP C121: Mulching BMP C140: Dust Control During concrete/saw cutting and surfacing BMP C151: Concrete Handling September 2024- September 2026 Dry/Wet BMP C152: Sawcutting and Surfacing Pollution Prevention During material delivery, storage, and containment BMP C153: Material Delivery, Storage and Containment September 2024- September 2026 Dry/Wet If dewatering is needed BMP C251: Construction Stormwater Filtration September 2024- September 2026 Dry/Wet P a g e | 22 2.1.13 Element 13: Protect Low Impact Development (LID) BMPs There are no permanent stormwater BMPs for this project. P a g e | 23 3 Pollution Prevention Team Table 7 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) TBD TBD Resident Engineer Brandon Loucks (253) 838-6113 Emergency Ecology Contact Kendra Henderson (360) 870-6757 Emergency Permittee/ Owner Contact TBD TBD Non-Emergency Owner Contact TBD TBD Monitoring Personnel TBD TBD Ecology Regional Office Northwest Regional Office (425) 649-7098 P a g e | 24 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. 4.1 Site Inspection 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 discharge point(s) to the sanitary sewer are indicated on the Site Map (see Appendix A) and in accordance with the applicable requirements of the CSWGP. 5 Reporting and Record Keeping 5.1 Record Keeping 5.1.1 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 5.1.2 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 P a g e | 25 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. 5.1.3 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. 5.2 Reporting 5.2.1 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 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. 5.2.2 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 notified within 24-hours of the failure to comply by calling the applicable Regional office ERTS phone number (Regional office number 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. • Kendra Henderson at (360) 870-6757 for King County P a g e | 26 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. P a g e | 27 Appendix/Glossary A. Site Map CONTOUR INTERVAL = 1'SCALE: 1" = 20'nSMITHERS AVE S S 21ST ST12TRACT A 3BURNETT PL S LEGENDAPPROXIMATEEARTHWORK QUANTITIESDETENTION VOLUMES(LIVE STORAGE)Federal Way, WA 98003Suite 205L L C33400 8th Avenue SouthC O N S U L T I N G E N G I N E E R SCITY OFRENTONIN COMPLIANCE WITH CITY OF RENTON STANDARDSSOPHIE JO SHORT PLATGRADING & T.E.S.C. PLANUTILITY PERMIT #SOPHIE JO SHORT PLAT P a g e | 28 B. BMP Detail Please see following pages for appropriate BMP details from the 2012 Stormwater Management Manual for Western Washington amended in 2014. Below is a list of Alternative BMPs that can be used if the BMPs listed in the body of this document are deemed ineffective by the CESCL. Element #1 - Mark Clearing Limits BMP C233: Silt Fence Element #2 - Establish Construction Access BMP C105: Stabilized Construction Entrance BMP C107: Construction Road/Parking Area Stabilization Element #3 - Control Flow Rates N/A Element #4 - Install Sediment Controls BMP C233: Silt Fence Element #5 - Stabilize Soils BMP C120: Temporary and Permanent Seeding BMP C121: Mulching BMP C140: Dust Control Element #6 - Protect Slopes BMP C120: Temporary and Permanent Seeding Element #7 - Protect Drain Inlets BMP C220: Storm Drain Inlet Protection Element #8 - Stabilize Channels and Outlets N/A Element #9 - Control Pollutants BMP C151: Concrete Handling BMP C152: Sawcutting and Surfacing Pollution Prevention BMP C153: Material Delivery, Storage and Containment Element #10 - Control Dewatering BMP C251: Construction Stormwater Filtration Element #11 - Maintain BMPs BMP C160: Erosion and Sedimentation Control Lead Element #12 - Manage the Project BMP C160: Erosion and Sediment Control Lead BMP C162: Scheduling Element #13: Protect Low Impact Development N/A BMP C105: Stabilized Construction Access Purpose Stabilized construction accesses are established to reduce the amount of sediment transported onto paved roads outside the project site by vehicles or equipment. This is done by constructing a sta- bilized pad of quarry spalls at entrances and exits for project sites. Conditions of Use Construction accesses shall be stabilized wherever traffic will be entering or leaving a construction site if paved roads or other paved areas are within 1,000 feet of the site. For residential subdivision construction sites, provide a stabilized construction access for each res- idence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of sufficient length/width to provide vehicle access/parking, based on lot size and configuration. On large commercial, highway, and road projects, the designer should include enough extra mater- ials in the contract to allow for additional stabilized accesses not shown in the initial Construction SWPPP. It is difficult to determine exactly where access to these projects will take place; additional materials will enable the contractor to install them where needed. Design and Installation Specifications See Figure II-3.1: Stabilized Construction Access for details. Note: the 100’ minimum length of the access shall be reduced to the maximum practicable size when the size or configuration of the site does not allow the full length (100’). Construct stabilized construction accesses with a 12-inch thick pad of 4-inch to 8-inch quarry spalls, a 4-inch course of asphalt treated base (ATB), or use existing pavement. Do not use crushed con- crete, cement, or calcium chloride for construction access stabilization because these products raise pH levels in stormwater and concrete discharge to waters of the State is prohibited. A separation geotextile shall be placed under the spalls to prevent fine sediment from pumping up into the rock pad. The geotextile shall meet the standards listed in Table II-3.2: Stabilized Con- struction Access Geotextile Standards. Geotextile Property Required Value Grab Tensile Strength (ASTM D4751)200 psi min. Table II-3.2: Stabilized Construction Access Geotextile Standards 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 275 Geotextile Property Required Value Grab Tensile Elongation (ASTM D4632)30% max. Mullen Burst Strength (ASTM D3786-80a)400 psi min. AOS (ASTM D4751)20-45 (U.S. standard sieve size) Table II-3.2: Stabilized Construction Access Geotextile Standards (continued) l Consider early installation of the first lift of asphalt in areas that will be paved; this can be used as a stabilized access. Also consider the installation of excess concrete as a stabilized access. During large concrete pours, excess concrete is often available for this purpose. l Fencing (see BMP C103: High-Visibility Fence) shall be installed as necessary to restrict traffic to the construction access. l Whenever possible, the access shall be constructed on a firm, compacted subgrade. This can substantially increase the effectiveness of the pad and reduce the need for maintenance. l Construction accesses should avoid crossing existing sidewalks and back of walk drains if at all possible. If a construction access must cross a sidewalk or back of walk drain, the full length of the sidewalk and back of walk drain must be covered and protected from sediment leaving the site. Alternative Material Specification WSDOT has raised safety concerns about the Quarry Spall rock specified above. WSDOT observes that the 4-inch to 8-inch rock sizes can become trapped between Dually truck tires, and then released off-site at highway speeds. WSDOT has chosen to use a modified specification for the rock while continuously verifying that the Stabilized Construction Access remains effective. To remain effective, the BMP must prevent sediment from migrating off site. To date, there has been no per- formance testing to verify operation of this new specification. Jurisdictions may use the alternative specification, but must perform increased off-site inspection if they use, or allow others to use, it. Stabilized Construction Accesses may use material that meets the requirements of WSDOT's Stand- ard Specifications for Road, Bridge, and Municipal Construction Section 9-03.9(1) (WSDOT, 2016) for ballast except for the following special requirements. The grading and quality requirements are listed in Table II-3.3: Stabilized Construction Access Alternative Material Requirements. Sieve Size Percent Passing 2½″99-100 Table II-3.3: Stabilized Construction Access Alternative Material Requirements 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 276 Sieve Size Percent Passing 2″65-100 ¾″40-80 No. 4 5 max. No. 100 0-2 % Fracture 75 min. Table II-3.3: Stabilized Construction Access Alternative Material Requirements (continued) l All percentages are by weight. l The sand equivalent value and dust ratio requirements do not apply. l The fracture requirement shall be at least one fractured face and will apply the combined aggregate retained on the No. 4 sieve in accordance with FOP for AASHTO T 335. Maintenance Standards Quarry spalls shall be added if the pad is no longer in accordance with the specifications. l If the access is not preventing sediment from being tracked onto pavement, then alternative measures to keep the streets free of sediment shall be used. This may include replace- ment/cleaning of the existing quarry spalls, street sweeping, an increase in the dimensions of the access, or the installation of BMP C106: Wheel Wash. l Any sediment that is tracked onto pavement shall be removed by shoveling or street sweep- ing. The sediment collected by sweeping shall be removed or stabilized on site. The pavement shall not be cleaned by washing down the street, except when high efficiency sweeping is inef- fective and there is a threat to public safety. If it is necessary to wash the streets, the con- struction of a small sump to contain the wash water shall be considered. The sediment would then be washed into the sump where it can be controlled. l Perform street sweeping by hand or with a high efficiency sweeper. Do not use a non-high effi- ciency mechanical sweeper because this creates dust and throws soils into storm systems or conveyance ditches. l Any quarry spalls that are loosened from the pad, which end up on the roadway shall be removed immediately. l If vehicles are entering or exiting the site at points other than the construction access(es), BMP C103: High-Visibility Fence shall be installed to control traffic. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 277 l Upon project completion and site stabilization, all construction accesses intended as per- manent access for maintenance shall be permanently stabilized. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 278 Figure II-3.1: Stabilized Construction Access 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 279 Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C106: Wheel Wash Purpose Wheel washes reduce the amount of sediment transported onto paved roads by washing dirt from the wheels of motor vehicles prior to the motor vehicles leaving the construction site. Conditions of Use l Use a wheel wash when BMP C105: Stabilized Construction Access is not preventing sed- iment from being tracked off site. l Wheel washing is generally an effective BMP when installed with careful attention to topo- graphy. For example, a wheel wash can be detrimental if installed at the top of a slope abut- ting a right-of-way where the water from the dripping truck can run unimpeded into the street. l Pressure washing combined with an adequately sized and surfaced pad with direct drainage to a large 10-foot x 10-foot sump can be very effective. l Wheel wash wastewater is not stormwater. It is commonly called process water, and must be discharged to a separate on-site treatment system that prevents discharge to waters of the State, or to the sanitary sewer with local sewer district approval. l Wheel washes may use closed-loop recirculation systems to conserve water use. l Wheel wash wastewater shall not include wastewater from concrete washout areas. l When practical, the wheel wash should be placed in sequence with BMP C105: Stabilized Construction Access. Locate the wheel wash such that vehicles exiting the wheel wash will enter directly onto BMP C105: Stabilized Construction Access. In order to achieve this, BMP C105: Stabilized Construction Access may need to be extended beyond the standard install- ation to meet the exit of the wheel wash. Design and Installation Specifications Suggested details are shown in Figure II-3.2: Wheel Wash. The Local Permitting Authority may allow other designs. A minimum of 6 inches of asphalt treated base (ATB) over crushed base mater- ial or 8 inches over a good subgrade is recommended to pave the wheel wash. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 280 Use a low clearance truck to test the wheel wash before paving. Either a belly dump or lowboy will work well to test clearance. Keep the water level from 12 to 14 inches deep to avoid damage to truck hubs and filling the truck tongues with water. Midpoint spray nozzles are only needed in extremely muddy conditions. Wheel wash systems should be designed with a small grade change, 6- to 12-inches for a 10-foot- wide pond, to allow sediment to flow to the low side of pond to help prevent re-suspension of sed- iment. A drainpipe with a 2- to 3-foot riser should be installed on the low side of the pond to allow for easy cleaning and refilling. Polymers may be used to promote coagulation and flocculation in a closed-loop system. Polyacrylamide (PAM) added to the wheel wash water at a rate of 0.25 - 0.5 pounds per 1,000 gallons of water increases effectiveness and reduces cleanup time. If PAM is already being used for dust or erosion control and is being applied by a water truck, the same truck can be used to change the wash water. Maintenance Standards The wheel wash should start out each day with fresh water. The wheel wash water should be changed a minimum of once per day. On large earthwork jobs where more than 10-20 trucks per hour are expected, the wheel wash water will need to be changed more often. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 281 Figure II-3.2: Wheel Wash 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 282 BMP C107: Construction Road / Parking Area Stabilization Purpose Stabilizing roads, parking areas, and other on-site vehicle transportation routes immediately after grading reduces erosion caused by construction traffic or stormwater runoff. Conditions of Use Roads and parking areas shall be stabilized wherever they are constructed, whether permanent or temporary, for use by construction traffic. BMP C103: High-Visibility Fence shall be installed, if necessary, to limit the access of vehicles to only those roads and parking areas that are stabilized. Design and Installation Specifications l On areas that will receive asphalt as part of the project, install the first lift as soon as possible. l A 6-inch depth of 2- to 4-inch crushed rock, gravel base, or crushed surfacing base course shall be applied immediately after grading or utility installation. A 4-inch course of asphalt treated base (ATB) may also be used, or the road/parking area may be paved. It may also be possible to use cement or calcium chloride for soil stabilization. If cement or cement kiln dust is used for roadbase stabilization, pH monitoring and BMP C252: Treating and Disposing of High pH Water is necessary to evaluate and minimize the effects on stormwater. If the area will not be used for permanent roads, parking areas, or structures, a 6-inch depth of hog fuel may also be used, but this is likely to require more maintenance. Whenever possible, con- struction roads and parking areas shall be placed on a firm, compacted subgrade. l Temporary road gradients shall not exceed 15 percent. Roadways shall be carefully graded to drain. Drainage ditches shall be provided on each side of the roadway in the case of a crowned section, or on one side in the case of a super-elevated section. Drainage ditches shall be directed to a sediment control BMP. l Rather than relying on ditches, it may also be possible to grade the road so that runoff sheet- flows into a heavily vegetated area with a well-developed topsoil. Landscaped areas are not adequate. If this area has at least 50 feet of vegetation that water can flow through, then it is generally preferable to use the vegetation to treat runoff, rather than a sediment pond or trap. The 50 feet shall not include wetlands or their buffers. If runoff is allowed to sheetflow through adjacent vegetated areas, it is vital to design the roadways and parking areas so that no con- centrated runoff is created. l Storm drain inlets shall be protected to prevent sediment-laden water entering the drainage system (see BMP C220: Inlet Protection). Maintenance Standards Inspect stabilized areas regularly, especially after large storm events. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 283 Crushed rock, gravel base, etc., shall be added as required to maintain a stable driving surface and to stabilize any areas that have eroded. Following construction, these areas shall be restored to pre-construction condition or better to pre- vent future erosion. Perform street cleaning at the end of each day or more often if necessary. BMP C120: Temporary and Permanent Seeding Purpose Seeding reduces erosion by stabilizing exposed soils. A well-established vegetative cover is one of the most effective methods of reducing erosion. Conditions of Use Use seeding throughout the project on disturbed areas that have reached final grade or that will remain unworked for more than 30 days. The optimum seeding windows for western Washington are April 1 through June 30 and September 1 through October 1. Between July 1 and August 30 seeding requires irrigation until 75 percent grass cover is established. Between October 1 and March 30 seeding requires a cover of mulch or an erosion control blanket until 75 percent grass cover is established. Review all disturbed areas in late August to early September and complete all seeding by the end of September. Otherwise, vegetation will not establish itself enough to provide more than average pro- tection. Mulch is required at all times for seeding because it protects seeds from heat, moisture loss, and transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding. See BMP C121: Mulching for specifications. Seed and mulch all disturbed areas not otherwise vegetated at final site stabilization. Final sta- bilization means the completion of all soil disturbing activities at the site and the establishment of a permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement, riprap, gabions, or geotextiles) which will prevent erosion. See BMP T5.13: Post-Construction Soil Quality and Depth. Design and Installation Specifications General l Install channels intended for vegetation before starting major earthwork and hydroseed with a Bonded Fiber Matrix. For vegetated channels that will have high flows, install erosion control blankets over the top of hydroseed. Before allowing water to flow in vegetated channels, establish 75 percent vegetation cover. If vegetated channels cannot be established by seed 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 284 before water flow; install sod in the channel bottom — over top of hydromulch and erosion con- trol blankets. l Confirm the installation of all required surface water control measures to prevent seed from washing away. l Hydroseed applications shall include a minimum of 1,500 pounds per acre of mulch with 3 per- cent tackifier. See BMP C121: Mulching for specifications. l Areas that will have seeding only and not landscaping may need compost or meal-based mulch included in the hydroseed in order to establish vegetation. Re-install native topsoil on the disturbed soil surface before application. See BMP T5.13: Post-Construction Soil Quality and Depth. l When installing seed via hydroseeding operations, only about 1/3 of the seed actually ends up in contact with the soil surface. This reduces the ability to establish a good stand of grass quickly. To overcome this, consider increasing seed quantities by up to 50 percent. l Enhance vegetation establishment by dividing the hydromulch operation into two phases: o Phase 1- Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in the first lift. o Phase 2- Install the rest of the mulch and tackifier over the first lift. Or, enhance vegetation by: o Installing the mulch, seed, fertilizer, and tackifier in one lift. o Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per acre. o Hold straw in place with a standard tackifier. Both of these approaches will increase cost moderately but will greatly improve and enhance vegetative establishment. The increased cost may be offset by the reduced need for: o Irrigation. o Reapplication of mulch. o Repair of failed slope surfaces. This technique works with standard hydromulch (1,500 pounds per acre minimum) and Bon- ded Fiber Matrix/ Mechanically Bonded Fiber Matrix (BFM/MBFMs) (3,000 pounds per acre minimum). l Seed may be installed by hand if: o Temporary and covered by straw, mulch, or topsoil. o Permanent in small areas (usually less than 1 acre) and covered with mulch, topsoil, or erosion blankets. l The seed mixes listed in Table II-3.4: Temporary and Permanent Seed Mixes include 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 285 recommended mixes for both temporary and permanent seeding. l Apply these mixes, with the exception of the wet area seed mix, at a rate of 120 pounds per acre. This rate can be reduced if soil amendments or slow-release fertilizers are used. Apply the wet area seed mix at a rate of 60 pounds per acre. l Consult the local suppliers or the local conservation district for their recommendations. The appropriate mix depends on a variety of factors, including location, exposure, soil type, slope, and expected foot traffic. Alternative seed mixes approved by the local authority may be used, depending on the soil type and hydrology of the area. Common Name Latin Name % Weight % Purity % Germination Temporary Erosion Control Seed Mix A standard mix for areas requiring a temporary vegetative cover. Chewings or annual blue grass Festuca rubra var. commutata or Poa anna 40 98 90 Perennial rye Lolium perenne 50 98 90 Redtop or colonial bentgrass Agrostis alba or Agrostis tenuis 5 92 85 White dutch clover Trifolium repens 5 98 90 Landscaping Seed Mix A recommended mix for landscaping seed. Perennial rye blend Lolium perenne 70 98 90 Chewings and red fescue blend Festuca rubra var. commutata or Fes- tuca rubra 30 98 90 Low-Growing Turf Seed Mix A turf seed mix for dry situations where there is no need for watering. This mix requires very little main- tenance. Dwarf tall fescue (several varieties) Festuca arundin- acea var. 45 98 90 Dwarf perennial rye (Barclay) Lolium perenne var. barclay 30 98 90 Red fescue Festuca rubra 20 98 90 Colonial bentgrass Agrostis tenuis 5 98 90 Bioswale Seed Mix A seed mix for bioswales and other intermittently wet areas. Tall or meadow fes-Festuca arundin-75-80 98 90 Table II-3.4: Temporary and Permanent Seed Mixes 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 286 Common Name Latin Name % Weight % Purity % Germination cue acea or Festuca elatior Seaside/Creeping bentgrass Agrostis palustris 10-15 92 85 Redtop bentgrass Agrostis alba or Agrostis gigantea 5-10 90 80 Wet Area Seed Mix A low-growing, relatively non-invasive seed mix appropriate for very wet areas that are not regulated wet- lands. Consult Hydraulic Permit Authority (HPA) for seed mixes if applicable. Tall or meadow fes- cue Festuca arundin- acea or Festuca elatior 60-70 98 90 Seaside/Creeping bentgrass Agrostis palustris 10-15 98 85 Meadow foxtail Alepocurus praten- sis 10-15 90 80 Alsike clover Trifolium hybridum 1-6 98 90 Redtop bentgrass Agrostis alba 1-6 92 85 Meadow Seed Mix A recommended meadow seed mix for infrequently maintained areas or non-maintained areas where col- onization by native plants is desirable. Likely applications include rural road and utility right-of-way. Seed- ing should take place in September or very early October in order to obtain adequate establishment prior to the winter months. Consider the appropriateness of clover, a fairly invasive species, in the mix. Amending the soil can reduce the need for clover. Redtop or Oregon bentgrass Agrostis alba or Agrostis ore- gonensis 20 92 85 Red fescue Festuca rubra 70 98 90 White dutch clover Trifolium repens 10 98 90 Table II-3.4: Temporary and Permanent Seed Mixes (continued) Roughening and Rototilling l The seedbed should be firm and rough. Roughen all soil no matter what the slope. Track walk slopes before seeding if engineering purposes require compaction. Backblading or smoothing of slopes greater than 4H:1V is not allowed if they are to be seeded. l Restoration-based landscape practices require deeper incorporation than that provided by a simple single-pass rototilling treatment. Wherever practical, initially rip the subgrade to improve long-term permeability, infiltration, and water inflow qualities. At a minimum, 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 287 permanent areas shall use soil amendments to achieve organic matter and permeability per- formance defined in engineered soil/landscape systems. For systems that are deeper than 8 inches complete the rototilling process in multiple lifts, or prepare the engineered soil system per specifications and place to achieve the specified depth. Fertilizers l Conducting soil tests to determine the exact type and quantity of fertilizer is recommended. This will prevent the over-application of fertilizer. l Organic matter is the most appropriate form of fertilizer because it provides nutrients (includ- ing nitrogen, phosphorus, and potassium) in the least water-soluble form. l In general, use 10-4-6 N-P-K (nitrogen-phosphorus-potassium) fertilizer at a rate of 90 pounds per acre. Always use slow-release fertilizers because they are more efficient and have fewer environmental impacts. Do not add fertilizer to the hydromulch machine, or agit- ate, more than 20 minutes before use. Too much agitation destroys the slow-release coating. l There are numerous products available that take the place of chemical fertilizers. These include several with seaweed extracts that are beneficial to soil microbes and organisms. If 100 percent cottonseed meal is used as the mulch in hydroseed, chemical fertilizer may not be necessary. Cottonseed meal provides a good source of long-term, slow-release, available nitrogen. Bonded Fiber Matrix and Mechanically Bonded Fiber Matrix l On steep slopes use Bonded Fiber Matrix (BFM) or Mechanically Bonded Fiber Matrix (MBFM) products. Apply BFM/MBFM products at a minimum rate of 3,000 pounds per acre with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during application. Numerous products are available commercially. Most products require 24-36 hours to cure before rainfall and cannot be installed on wet or saturated soils. Generally, products come in 40-50 pound bags and include all necessary ingredients except for seed and fertilizer. l Install products per manufacturer's instructions. l BFMs and MBFMs provide good alternatives to blankets in most areas requiring vegetation establishment. Advantages over blankets include: o BFM and MBFMs do not require surface preparation. o Helicopters can assist in installing BFM and MBFMs in remote areas. o On slopes steeper than 2.5H:1V, blanket installers may require ropes and harnesses for safety. o Installing BFM and MBFMs can save at least $1,000 per acre compared to blankets. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 288 Maintenance Standards Reseed any seeded areas that fail to establish at least 75 percent cover (100 percent cover for areas that receive sheet or concentrated flows). If reseeding is ineffective, use an alternate method such as sodding, mulching, nets, or blankets. l Reseed and protect by mulch any areas that experience erosion after achieving adequate cover. Reseed and protect by mulch any eroded area. l Supply seeded areas with adequate moisture, but do not water to the extent that it causes run- off. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies BMP C121: Mulching Purpose Mulching soils provides immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and topsoil in place, and moderating soil temperatures. There are a variety of mulches that can be used. This section discusses only the most common types of mulch. Conditions of Use As a temporary cover measure, mulch should be used: l For less than 30 days on disturbed areas that require cover. l At all times for seeded areas, especially during the wet season and during the hot summer months. l During the wet season on slopes steeper than 3H:1V with more than 10 feet of vertical relief. Mulch may be applied at any time of the year and must be refreshed periodically. For seeded areas, mulch may be made up of 100 percent: l cottonseed meal; l fibers made of wood, recycled cellulose, hemp, or kenaf; 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 289 l compost; l or blends of these. Tackifier shall be plant-based, such as guar or alpha plantago, or chemical-based such as poly- acrylamide or polymers. Generally, mulches come in 40-50 pound bags. Seed and fertilizer are added at time of application. Recycled cellulose may contain polychlorinated biphenyl (PCBs). Ecology recommends that products should be evaluated for PCBs prior to use. Refer to BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use. PAM shall not be directly applied to water or allowed to enter a water body. Any mulch or tackifier product used shall be installed per the manufacturer’s instructions. Design and Installation Specifications For mulch materials, application rates, and specifications, see Table II-3.6: Mulch Standards and Guidelines. Consult with the local supplier or the local conservation district for their recom- mendations. Increase the application rate until the ground is 95% covered (i.e. not visible under the mulch layer). Note: Thickness may be increased for disturbed areas in or near sensitive areas or other areas highly susceptible to erosion. Where the option of “Compost” is selected, it should be a coarse compost that meets the size grad- ations listed in Table II-3.5: Size Gradations of Compost as Mulch Material when tested in accord- ance with Test Method 02.02-B found in Test Methods for the Examination of Composting and Compost (Thompson, 2001). Sieve Size Percent Passing 3"100% 1"90% - 100% 3/4"70% - 100% 1/4"40% - 100% Table II-3.5: Size Gradations of Compost as Mulch Material Mulch used within the ordinary high-water mark of surface waters should be selected to minimize potential flotation of organic matter. Composted organic materials have higher specific gravities (densities) than straw, wood, or chipped material. Consult the Hydraulic Permit Authority (HPA) for mulch mixes if applicable. Maintenance Standards The thickness of the mulch cover must be maintained. Any areas that experience erosion shall be remulched and/or protected with a net or blanket. If the erosion problem is drainage related, then the problem shall be fixed and the eroded area remulched. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 290 Mulch Mater- ial Guideline Description Straw Quality Standards Air-dried; free from undesirable seed and coarse material. Application Rates 2"-3" thick; 5 bales per 1,000 sf or 2-3 tons per acre Remarks Cost-effective protection when applied with adequate thickness. Hand- application generally requires greater thickness than blown straw. The thickness of straw may be reduced by half when used in conjunction with seeding. In windy areas straw must be held in place by crimping, using a tackifier, or covering with netting. Blown straw always has to be held in place with a tackifier as even light winds will blow it away. Straw, however, has several deficiencies that should be considered when selecting mulch materials. It often introduces and/or encourages the propagation of weed species and it has no significant long-term benefits It should also not be used within the ordinary high-water elevation of surface waters (due to flot- ation). Hydromulch Quality Standards No growth inhibiting factors. Application Rates Approx. 35-45 lbs per 1,000 sf or 1,500 - 2,000 lbs per acre Remarks Shall be applied with hydromulcher. Shall not be used without seed and tackifier unless the application rate is at least doubled. Fibers longer than about 3/4 - 1 inch clog hydromulch equipment. Fibers should be kept to less than 3/4 inch. Compost Quality Standards No visible water or dust during handling. Must be produced per WAC 173- 350, Solid Waste Handling Standards, but may have up to 35% biosolids. Application Rates 2" thick min.; approx. 100 tons per acre (approx. 750 lbs per cubic yard) Remarks More effective control can be obtained by increasing thickness to 3". Excel- lent mulch for protecting final grades until landscaping because it can be dir- ectly seeded or tilled into soil as an amendment. Compost used for mulch has a coarser size gradation than compost used for BMP C125: Topsoiling / Composting or BMP T5.13: Post-Construction Soil Quality and Depth. It is more stable and practical to use in wet areas and during rainy weather conditions. Do not use near wetlands or near phosphorous impaired water bodies. Chipped Site Veget- ation Quality Standards Gradations from fines to 6 inches in length for texture, variation, and inter- locking properties. Include a mix of various sizes so that the average size is between 2- and 4- inches. Application Rates 2" thick min.; Table II-3.6: Mulch Standards and Guidelines 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 291 Mulch Mater- ial Guideline Description Remarks This is a cost-effective way to dispose of debris from clearing and grub- bing, and it eliminates the problems associated with burning. Generally, it should not be used on slopes above approx. 10% because of its tendency to be transported by runoff. It is not recommended within 200 feet of sur- face waters. If permanent seeding or planting is expected shortly after mulch, the decomposition of the chipped vegetation may tie up nutrients important to grass establishment. Note: thick application of this material over existing grass, herbaceous spe- cies, and some groundcovers could smother and kill vegetation. Wood- Based Mulch Quality Standards No visible water or dust during handling. Must be purchased from a supplier with a Solid Waste Handling Permit or one exempt from solid waste reg- ulations. Application Rates 2" thick min.; approx. 100 tons per acre (approx. 750 lbs. per cubic yard) Remarks This material is often called "wood straw" or "hog fuel". The use of mulch ultimately improves the organic matter in the soil. Special caution is advised regarding the source and composition of wood-based mulches. Its preparation typically does not provide any weed seed control, so evidence of residual vegetation in its composition or known inclusion of weed plants or seeds should be monitored and prevented (or minimized). Wood Strand Mulch Quality Standards A blend of loose, long, thin wood pieces derived from native conifer or deciduous trees with high length-to-width ratio. Application Rates 2" thick min. Remarks Cost-effective protection when applied with adequate thickness. A min- imum of 95-percent of the wood strand shall have lengths between 2 and 10-inches, with a width and thickness between 1/16 and 1/2-inches. The mulch shall not contain resin, tannin, or other compounds in quantities that would be detrimental to plant life. Sawdust or wood shavings shall not be used as mulch. [Specification 9-14.4(4) from the Standard Specifications for Road, Bridge, and Municipal Construction (WSDOT, 2016) Table II-3.6: Mulch Standards and Guidelines (continued) 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 292 BMP C140: Dust Control Purpose Dust control prevents wind transport of dust from disturbed soil surfaces onto roadways, drainage ways, and surface waters. Conditions of Use Use dust control in areas (including roadways) subject to surface and air movement of dust where on-site or off-site impacts to roadways, drainage ways, or surface waters are likely. Design and Installation Specifications l Vegetate or mulch areas that will not receive vehicle traffic. In areas where planting, mulching, or paving is impractical, apply gravel or landscaping rock. l Limit dust generation by clearing only those areas where immediate activity will take place, leaving the remaining area(s) in the original condition. Maintain the original ground cover as long as practical. l Construct natural or artificial windbreaks or windscreens. These may be designed as enclos- ures for small dust sources. l Sprinkle the site with water until the surface is wet. Repeat as needed. To prevent carryout of mud onto the street, refer to BMP C105: Stabilized Construction Access and BMP C106: Wheel Wash. l Irrigation water can be used for dust control. Irrigation systems should be installed as a first step on sites where dust control is a concern. l Spray exposed soil areas with a dust palliative, following the manufacturer’s instructions and cautions regarding handling and application. Used oil is prohibited from use as a dust sup- pressant. Local governments may approve other dust palliatives such as calcium chloride or PAM. l PAM (BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection) added to water at a rate of 0.5 pounds per 1,000 gallons of water per acre and applied from a water truck is more effect- ive than water alone. This is due to increased infiltration of water into the soil and reduced evaporation. In addition, small soil particles are bonded together and are not as easily trans- ported by wind. Adding PAM may reduce the quantity of water needed for dust control. Note that the application rate specified here applies to this BMP, and is not the same application rate that is specified in BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection, but the downstream protections still apply. Refer to BMP C126: Polyacrylamide (PAM) for Soil Erosion Protection for conditions of use. PAM shall not be directly applied to water or allowed to enter a water body. l Contact your local Air Pollution Control Authority for guidance and training on other dust con- trol measures. Compliance with the local Air Pollution Control Authority constitutes 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 313 compliance with this BMP. l Use vacuum street sweepers. l Remove mud and other dirt promptly so it does not dry and then turn into dust. l Techniques that can be used for unpaved roads and lots include: o Lower speed limits. High vehicle speed increases the amount of dust stirred up from unpaved roads and lots. o Upgrade the road surface strength by improving particle size, shape, and mineral types that make up the surface and base materials. o Add surface gravel to reduce the source of dust emission. Limit the amount of fine particles (those smaller than .075 mm) to 10 to 20 percent. o Use geotextile fabrics to increase the strength of new roads or roads undergoing recon- struction. o Encourage the use of alternate, paved routes, if available. o Apply chemical dust suppressants using the admix method, blending the product with the top few inches of surface material. Suppressants may also be applied as surface treatments. o Limit dust-causing work on windy days. o Pave unpaved permanent roads and other trafficked areas. Maintenance Standards Respray area as necessary to keep dust to a minimum. BMP C150: Materials on Hand Purpose Keep quantities of erosion prevention and sediment control materials on the project site at all times to be used for regular maintenance and emergency situations such as unexpected heavy rains. Hav- ing these materials on-site reduces the time needed to replace existing or implement new BMPs when inspections indicate that existing BMPs are not meeting the Construction SWPPP require- ments. In addition, contractors can save money by buying some materials in bulk and storing them at their office or yard. Conditions of Use l Construction projects of any size or type can benefit from having materials on hand. A small commercial development project could have a roll of plastic and some gravel available for immediate protection of bare soil and temporary berm construction. A large earthwork project, such as highway construction, might have several tons of straw, several rolls of plastic, flexible 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 314 pipe, sandbags, geotextile fabric and steel “T” posts. l Materials should be stockpiled and readily available before any site clearing, grubbing, or earthwork begins. A large contractor or project proponent could keep a stockpile of materials that are available for use on several projects. l If storage space at the project site is at a premium, the contractor could maintain the materials at their office or yard. The office or yard must be less than an hour from the project site. Design and Installation Specifications Depending on project type, size, complexity, and length, materials and quantities will vary. A good minimum list of items that will cover numerous situations includes: l Clear Plastic, 6 mil l Drainpipe, 6 or 8 inch diameter l Sandbags, filled l Straw Bales for mulching l Quarry Spalls l Washed Gravel l Geotextile Fabric l Catch Basin Inserts l Steel "T" Posts l Silt fence material l Straw Wattles Maintenance Standards l All materials with the exception of the quarry spalls, steel “T” posts, and gravel should be kept covered and out of both sun and rain. l Re-stock materials as needed. BMP C151: Concrete Handling Purpose Concrete work can generate process water and slurry that contain fine particles and high pH, both of which can violate water quality standards in the receiving water. Concrete spillage or concrete dis- charge to waters of the State is prohibited. Use this BMP to minimize and eliminate concrete, con- crete process water, and concrete slurry from entering waters of the State. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 315 Conditions of Use Any time concrete is used, utilize these management practices. Concrete construction project com- ponents include, but are not limited to: l Curbs l Sidewalks l Roads l Bridges l Foundations l Floors l Runways Disposal options for concrete, in order of preference are: 1. Off-site disposal 2. Concrete wash-out areas (see BMP C154: Concrete Washout Area) 3. De minimus washout to formed areas awaiting concrete Design and Installation Specifications l Wash concrete truck drums at an approved off-site location or in designated concrete washout areas only. Do not wash out concrete trucks onto the ground (including formed areas awaiting concrete), or into storm drains, open ditches, streets, or streams. Refer to BMP C154: Concrete Washout Area for information on concrete washout areas. o Return unused concrete remaining in the truck and pump to the originating batch plant for recycling. Do not dump excess concrete on site, except in designated concrete washout areas as allowed in BMP C154: Concrete Washout Area. l Wash small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheelbarrows) into designated concrete washout areas or into formed areas awaiting concrete pour. l At no time shall concrete be washed off into the footprint of an area where an infiltration fea- ture will be installed. l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir- ectly drain to natural or constructed stormwater conveyance or potential infiltration areas. l Do not allow washwater from areas, such as concrete aggregate driveways, to drain directly (without detention or treatment) to natural or constructed stormwater conveyances. l Contain washwater and leftover product in a lined container when no designated concrete washout areas (or formed areas, allowed as described above) are available. Dispose of con- tained concrete and concrete washwater (process water) properly. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 316 l Always use forms or solid barriers for concrete pours, such as pilings, within 15-feet of surface waters. l Refer to BMP C252: Treating and Disposing of High pH Water for pH adjustment require- ments. l Refer to the Construction Stormwater General Permit (CSWGP) for pH monitoring require- ments if the project involves one of the following activities: o Significant concrete work (as defined in the CSWGP). o The use of soils amended with (but not limited to) Portland cement-treated base, cement kiln dust or fly ash. o Discharging stormwater to segments of water bodies on the 303(d) list (Category 5) for high pH. Maintenance Standards Check containers for holes in the liner daily during concrete pours and repair the same day. BMP C152: Sawcutting and Surfacing Pollution Prevention Purpose Sawcutting and surfacing operations generate slurry and process water that contains fine particles and high pH (concrete cutting), both of which can violate the water quality standards in the receiving water. Concrete spillage or concrete discharge to waters of the State is prohibited. Use this BMP to minimize and eliminate process water and slurry created through sawcutting or surfacing from enter- ing waters of the State. Conditions of Use Utilize these management practices anytime sawcutting or surfacing operations take place. Saw- cutting and surfacing operations include, but are not limited to: l Sawing l Coring l Grinding l Roughening l Hydro-demolition l Bridge and road surfacing 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 317 Design and Installation Specifications l Vacuum slurry and cuttings during cutting and surfacing operations. l Slurry and cuttings shall not remain on permanent concrete or asphalt pavement overnight. l Slurry and cuttings shall not drain to any natural or constructed drainage conveyance includ- ing stormwater systems. This may require temporarily blocking catch basins. l Dispose of collected slurry and cuttings in a manner that does not violate ground water or sur- face water quality standards. l Do not allow process water generated during hydro-demolition, surface roughening or similar operations to drain to any natural or constructed drainage conveyance including stormwater systems. Dispose of process water in a manner that does not violate ground water or surface water quality standards. l Handle and dispose of cleaning waste material and demolition debris in a manner that does not cause contamination of water. Dispose of sweeping material from a pick-up sweeper at an appropriate disposal site. Maintenance Standards Continually monitor operations to determine whether slurry, cuttings, or process water could enter waters of the state. If inspections show that a violation of water quality standards could occur, stop operations and immediately implement preventive measures such as berms, barriers, secondary containment, and/or vacuum trucks. BMP C153: Material Delivery, Storage, and Containment Purpose Prevent, reduce, or eliminate the discharge of pollutants to the stormwater system or watercourses from material delivery and storage. Minimize the storage of hazardous materials on-site, store mater- ials in a designated area, and install secondary containment. Conditions of Use Use at construction sites with delivery and storage of the following materials: l Petroleum products such as fuel, oil and grease l Soil stabilizers and binders (e.g., Polyacrylamide) l Fertilizers, pesticides and herbicides l Detergents l Asphalt and concrete compounds 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 318 l Hazardous chemicals such as acids, lime, adhesives, paints, solvents, and curing compounds l Any other material that may be detrimental if released to the environment Design and Installation Specifications l The temporary storage area should be located away from vehicular traffic, near the con- struction entrance(s), and away from waterways or storm drains. l Safety Data Sheets (SDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers. l Hazardous material storage on-site should be minimized. l Hazardous materials should be handled as infrequently as possible. l During the wet weather season (Oct 1 – April 30), consider storing materials in a covered area. l Materials should be stored in secondary containments, such as an earthen dike, horse trough, or even a children’s wading pool for non-reactive materials such as detergents, oil, grease, and paints. Small amounts of material may be secondarily contained in “bus boy” trays or con- crete mixing trays. l Do not store chemicals, drums, or bagged materials directly on the ground. Place these items on a pallet and, when possible, within secondary containment. l If drums must be kept uncovered, store them at a slight angle to reduce ponding of rainwater on the lids to reduce corrosion. Domed plastic covers are inexpensive and snap to the top of drums, preventing water from collecting. l Liquids, petroleum products, and substances listed in 40 CFR Parts 110, 117, or 302 shall be stored in approved containers and drums and shall not be overfilled. Containers and drums shall be stored in temporary secondary containment facilities. l Temporary secondary containment facilities shall provide for a spill containment volume able to contain 10% of the total enclosed container volume of all containers, or 110% of the capa- city of the largest container within its boundary, whichever is greater. l Secondary containment facilities shall be impervious to the materials stored therein for a min- imum contact time of 72 hours. l Sufficient separation should be provided between stored containers to allow for spill cleanup and emergency response access. l During the wet weather season (Oct 1 – April 30), each secondary containment facility shall be covered during non-working days, prior to and during rain events. l Keep material storage areas clean, organized and equipped with an ample supply of appro- priate spill clean-up material (spill kit). l The spill kit should include, at a minimum: 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 319 o 1-Water Resistant Nylon Bag o 3-Oil Absorbent Socks 3”x 4’ o 2-Oil Absorbent Socks 3”x 10’ o 12-Oil Absorbent Pads 17”x19” o 1-Pair Splash Resistant Goggles o 3-Pair Nitrile Gloves o 10-Disposable Bags with Ties o Instructions Maintenance Standards l Secondary containment facilities shall be maintained free of accumulated rainwater and spills. In the event of spills or leaks, accumulated rainwater and spills shall be collected and placed into drums. These liquids shall be handled as hazardous waste unless testing determines them to be non-hazardous. l Re-stock spill kit materials as needed. BMP C154: Concrete Washout Area Purpose Prevent or reduce the discharge of pollutants from concrete waste to stormwater by conducting washout off-site, or performing on-site washout in a designated area. Conditions of Use Concrete washout areas are implemented on construction projects where: l Concrete is used as a construction material l It is not possible to dispose of all concrete wastewater and washout off-site (ready mix plant, etc.). l Concrete truck drums are washed on-site. Note that auxiliary concrete truck components (e.g. chutes and hoses) and small concrete handling equipment (e.g. hand tools, screeds, shovels, rakes, floats, trowels, and wheel- barrows) may be washed into formed areas awaiting concrete pour. At no time shall concrete be washed off into the footprint of an area where an infiltration feature will be installed. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 320 Design and Installation Specifications Implementation l Perform washout of concrete truck drums at an approved off-site location or in designated con- crete washout areas only. l Do not wash out concrete onto non-formed areas, or into storm drains, open ditches, streets, or streams. l Wash equipment difficult to move, such as concrete paving machines, in areas that do not dir- ectly drain to natural or constructed stormwater conveyance or potential infiltration areas. l Do not allow excess concrete to be dumped on-site, except in designated concrete washout areas as allowed above. l Concrete washout areas may be prefabricated concrete washout containers, or self-installed structures (above-grade or below-grade). l Prefabricated containers are most resistant to damage and protect against spills and leaks. Companies may offer delivery service and provide regular maintenance and disposal of solid and liquid waste. l If self-installed concrete washout areas are used, below-grade structures are preferred over above-grade structures because they are less prone to spills and leaks. l Self-installed above-grade structures should only be used if excavation is not practical. l Concrete washout areas shall be constructed and maintained in sufficient quantity and size to contain all liquid and concrete waste generated by washout operations. Education l Discuss the concrete management techniques described in this BMP with the ready-mix con- crete supplier before any deliveries are made. l Educate employees and subcontractors on the concrete waste management techniques described in this BMP. l Arrange for the contractor’s superintendent or Certified Erosion and Sediment Control Lead (CESCL) to oversee and enforce concrete waste management procedures. l A sign should be installed adjacent to each concrete washout area to inform concrete equip- ment operators to utilize the proper facilities. Contracts Incorporate requirements for concrete waste management into concrete supplier and subcontractor agreements. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 321 Location and Placement l Locate concrete washout areas at least 50 feet from sensitive areas such as storm drains, open ditches, water bodies, or wetlands. l Allow convenient access to the concrete washout area for concrete trucks, preferably near the area where the concrete is being poured. l If trucks need to leave a paved area to access the concrete washout area, prevent track-out with a pad of rock or quarry spalls (see BMP C105: Stabilized Construction Access). These areas should be far enough away from other construction traffic to reduce the likelihood of acci- dental damage and spills. l The number of concrete washout areas you install should depend on the expected demand for storage capacity. l On large sites with extensive concrete work, concrete washout areas should be placed in mul- tiple locations for ease of use by concrete truck drivers. Concrete Truck Washout Procedures l Washout of concrete truck drums shall be performed in designated concrete washout areas only. l Concrete washout from concrete pumper bins can be washed into concrete pumper trucks and discharged into designated concrete washout areas or properly disposed of off-site. Concrete Washout Area Installation l Concrete washout areas should be constructed as shown in the figures below, with a recom- mended minimum length and minimum width of 10 ft, but with sufficient quantity and volume to contain all liquid and concrete waste generated by washout operations. l Plastic lining material should be a minimum of 10 mil polyethylene sheeting and should be free of holes, tears, or other defects that compromise the impermeability of the material. l Lath and flagging should be commercial type. l Liner seams shall be installed in accordance with manufacturers’ recommendations. l Soil base shall be prepared free of rocks or other debris that may cause tears or holes in the plastic lining material. Maintenance Standards Inspection and Maintenance l Inspect and verify that concrete washout areas are in place prior to the commencement of con- crete work. l Once concrete wastes are washed into the designated washout area and allowed to harden, 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 322 the concrete should be broken up, removed, and disposed of per applicable solid waste reg- ulations. Dispose of hardened concrete on a regular basis. l During periods of concrete work, inspect the concrete washout areas daily to verify continued performance. o Check overall condition and performance. o Check remaining capacity (% full). o If using self-installed concrete washout areas, verify plastic liners are intact and side- walls are not damaged. o If using prefabricated containers, check for leaks. l Maintain the concrete washout areas to provide adequate holding capacity with a minimum freeboard of 12 inches. l Concrete washout areas must be cleaned, or new concrete washout areas must be con- structed and ready for use once the concrete washout area is 75% full. l If the concrete washout area is nearing capacity, vacuum and dispose of the waste material in an approved manner. l Do not discharge liquid or slurry to waterways, storm drains or directly onto ground. l Do not discharge to the sanitary sewer without local approval. l Place a secure, non-collapsing, non-water collecting cover over the concrete washout area prior to predicted wet weather to prevent accumulation and overflow of pre- cipitation. l Remove and dispose of hardened concrete and return the structure to a functional con- dition. Concrete may be reused on-site or hauled away for disposal or recycling. l When you remove materials from a self-installed concrete washout area, build a new struc- ture; or, if the previous structure is still intact, inspect for signs of weakening or damage, and make any necessary repairs. Re-line the structure with new plastic after each cleaning. Removal of Concrete Washout Areas l When concrete washout areas are no longer required for the work, the hardened concrete, slurries and liquids shall be removed and properly disposed of. l Materials used to construct concrete washout areas shall be removed from the site of the work and disposed of or recycled. l Holes, depressions or other ground disturbance caused by the removal of the concrete washout areas shall be backfilled, repaired, and stabilized to prevent erosion. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 323 Figure II-3.7: Concrete Washout Area with Wood Planks 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 324 Figure II-3.8: Concrete Washout Area with Straw Bales 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 325 Figure II-3.9: Prefabricated Concrete Washout Container w/Ramp 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 326 BMP C160: Certified Erosion and Sediment Control Lead Purpose The project proponent designates at least one person as the responsible representative in charge of erosion and sediment control (ESC), and water quality protection. The designated person shall be responsible for ensuring compliance with all local, state, and federal erosion and sediment control and water quality requirements. Construction sites one acre or larger that discharge to waters of the State must designate a Certified Erosion and Sediment Control Lead (CESCL) as the responsible representative. Conditions of Use A CESCL shall be made available on projects one acre or larger that discharge stormwater to sur- face waters of the state. Sites less than one acre may have a person without CESCL certification conduct inspections. The CESCL shall: l Have a current certificate proving attendance in an erosion and sediment control training course that meets the minimum ESC training and certification requirements established by Ecology. Ecology has provided the minimum requirements for CESCL course training, as well as a list of ESC training and certification providers at: https://ecology.wa.gov/Regulations-Permits/Permits-certifications/Certified-erosion-sed- iment-control OR l Be a Certified Professional in Erosion and Sediment Control (CPESC). For additional inform- ation go to: http://www.envirocertintl.org/cpesc/ Specifications l CESCL certification shall remain valid for three years. l The CESCL shall have authority to act on behalf of the contractor or project proponent and shall be available, or on-call, 24 hours per day throughout the period of construction. l The Construction SWPPP shall include the name, telephone number, fax number, and address of the designated CESCL. See II-2 Construction Stormwater Pollution Prevention Plans (Construction SWPPPs). l A CESCL may provide inspection and compliance services for multiple construction projects in the same geographic region, but must be on site whenever earthwork activities are 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 327 occurring that could generate release of turbid water. l Duties and responsibilities of the CESCL shall include, but are not limited to the following: o Maintaining a permit file on site at all times which includes the Construction SWPPP and any associated permits and plans. o Directing BMP installation, inspection, maintenance, modification, and removal. o Updating all project drawings and the Construction SWPPP with changes made. o Completing any sampling requirements including reporting results using electronic Dis- charge Monitoring Reports (WebDMR). o Facilitate, participate in, and take corrective actions resulting from inspections per- formed by outside agencies or the owner. o Keeping daily logs, and inspection reports. Inspection reports should include: n Inspection date/time. n Weather information; general conditions during inspection and approximate amount of precipitation since the last inspection. n Visual monitoring results, including a description of discharged stormwater. The presence of suspended sediment, turbid water, discoloration, and oil sheen shall be noted, as applicable. n Any water quality monitoring performed during inspection. n General comments and notes, including a brief description of any BMP repairs, maintenance or installations made as a result of the inspection. n A summary or list of all BMPs implemented, including observations of all erosion/sediment control structures or practices. The following shall be noted: 1. Locations of BMPs inspected. 2. Locations of BMPs that need maintenance. 3. Locations of BMPs that failed to operate as designed or intended. 4. Locations of where additional or different BMPs are required. BMP C162: Scheduling Purpose Sequencing a construction project reduces the amount and duration of soil exposed to erosion by wind, rain, runoff, and vehicle tracking. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 328 Conditions of Use The construction sequence schedule is an orderly listing of all major land-disturbing activities together with the necessary erosion and sedimentation control measures planned for the project. This type of schedule guides the contractor on work to be done before other work is started so that serious erosion and sedimentation problems can be avoided. Following a specified work schedule that coordinates the timing of land-disturbing activities and the installation of control measures is perhaps the most cost-effective way of controlling erosion during construction. The removal of ground cover leaves a site vulnerable to erosion. Construction sequen- cing that limits land clearing, provides timely installation of erosion and sedimentation controls, and restores protective cover quickly can significantly reduce the erosion potential of a site. Design Considerations l Minimize construction during rainy periods. l Schedule projects to disturb only small portions of the site at any one time. Complete grading as soon as possible. Immediately stabilize the disturbed portion before grading the next por- tion. Practice staged seeding in order to revegetate cut and fill slopes as the work progresses. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 329 thickness is 2 feet. o For outlets at the base of steep slope pipes (pipe slope greater than 10 percent), use an engineered energy dissipator. o Filter fabric or erosion control blankets should always be used under riprap to prevent scour and channel erosion. See BMP C122: Nets and Blankets. l Bank stabilization, bioengineering, and habitat features may be required for disturbed areas. This work may require a Hydraulic Project Approval (HPA) from the Washington State Depart- ment of Fish and Wildlife. See I-2.11 Hydraulic Project Approvals. Maintenance Standards l Inspect and repair as needed. l Add rock as needed to maintain the intended function. l Clean energy dissipator if sediment builds up. BMP C220: Inlet Protection Purpose Inlet protection prevents coarse sediment from entering drainage systems prior to permanent sta- bilization of the disturbed area. Conditions of Use Use inlet protection at inlets that are operational before permanent stabilization of the disturbed areas that contribute runoff to the inlet. Provide protection for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless those inlets are preceded by a sediment trapping BMP. Also consider inlet protection for lawn and yard drains on new home construction. These small and numerous drains coupled with lack of gutters can add significant amounts of sediment into the roof drain system. If possible, delay installing lawn and yard drains until just before landscaping, or cap these drains to prevent sediment from entering the system until completion of landscaping. Provide 18-inches of sod around each finished lawn and yard drain. Table II-3.10: Storm Drain Inlet Protection lists several options for inlet protection. All of the methods for inlet protection tend to plug and require a high frequency of maintenance. Limit contributing drain- age areas for an individual inlet to one acre or less. If possible, provide emergency overflows with additional end-of-pipe treatment where stormwater ponding would cause a hazard. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 356 Type of Inlet Pro- tection Emergency Overflow Applicable for Paved/ Earthen Sur- faces Conditions of Use Drop Inlet Protection Excavated drop inlet protection Yes, temporary flooding may occur Earthen Applicable for heavy flows. Easy to maintain. Large area requirement: 30'x30'/acre Block and gravel drop inlet pro- tection Yes Paved or Earthen Applicable for heavy concentrated flows. Will not pond. Gravel and wire drop inlet pro- tection No Paved or Earthen Applicable for heavy concentrated flows. Will pond. Can withstand traffic. Catch basin filters Yes Paved or Earthen Frequent maintenance required. Curb Inlet Protection Curb inlet pro- tection with wooden weir Small capacity overflow Paved Used for sturdy, more compact install- ation. Block and gravel curb inlet pro- tection Yes Paved Sturdy, but limited filtration. Culvert Inlet Protection Culvert inlet sed- iment trap N/A N/A 18 month expected life. Table II-3.10: Storm Drain Inlet Protection Design and Installation Specifications Excavated Drop Inlet Protection Excavated drop inlet protection consists of an excavated impoundment around the storm drain inlet. Sediment settles out of the stormwater prior to entering the storm drain. Design and installation spe- cifications for excavated drop inlet protection include: l Provide a depth of 1-2 ft as measured from the crest of the inlet structure. l Slope sides of excavation should be no steeper than 2H:1V. l Minimum volume of excavation is 35 cubic yards. l Shape the excavation to fit the site, with the longest dimension oriented toward the longest inflow area. l Install provisions for draining to prevent standing water. l Clear the area of all debris. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 357 l Grade the approach to the inlet uniformly. l Drill weep holes into the side of the inlet. l Protect weep holes with screen wire and washed aggregate. l Seal weep holes when removing structure and stabilizing area. l Build a temporary dike, if necessary, to the down slope side of the structure to prevent bypass flow. Block and Gravel Filter A block and gravel filter is a barrier formed around the inlet with standard concrete blocks and gravel. See Figure II-3.17: Block and Gravel Filter. Design and installation specifications for block gravel fil- ters include: l Provide a height of 1 to 2 feet above the inlet. l Recess the first row of blocks 2-inches into the ground for stability. l Support subsequent courses by placing a pressure treated wood 2x4 through the block open- ing. l Do not use mortar. l Lay some blocks in the bottom row on their side to allow for dewatering the pool. l Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings. l Place gravel to just below the top of blocks on slopes of 2H:1V or flatter. l An alternative design is a gravel berm surrounding the inlet, as follows: o Provide a slope of 3H:1V on the upstream side of the berm. o Provide a slope of 2H:1V on the downstream side of the berm. o Provide a 1-foot wide level stone area between the gravel berm and the inlet. o Use stones 3 inches in diameter or larger on the upstream slope of the berm. o Use gravel ½- to ¾-inch at a minimum thickness of 1-foot on the downstream slope of the berm. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 358 Figure II-3.17: Block and Gravel Filter 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 359 Gravel and Wire Mesh Filter Gravel and wire mesh filters are gravel barriers placed over the top of the inlet. This method does not provide an overflow. Design and installation specifications for gravel and wire mesh filters include: l Use a hardware cloth or comparable wire mesh with ½-inch openings. o Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot bey- ond each side of the inlet structure. o Overlap the strips if more than one strip of mesh is necessary. l Place coarse aggregate over the wire mesh. o Provide at least a 12-inch depth of aggregate over the entire inlet opening and extend at least 18-inches on all sides. Catch Basin Filters Catch basin filters are designed by manufacturers for construction sites. The limited sediment stor- age capacity increases the amount of inspection and maintenance required, which may be daily for heavy sediment loads. To reduce maintenance requirements, combine a catch basin filter with another type of inlet protection. This type of inlet protection provides flow bypass without overflow and therefore may be a better method for inlets located along active rights-of-way. Design and install- ation specifications for catch basin filters include: l Provides 5 cubic feet of storage. l Requires dewatering provisions. l Provides a high-flow bypass that will not clog under normal use at a construction site. l Insert the catch basin filter in the catch basin just below the grating. Curb Inlet Protection with Wooden Weir Curb inlet protection with wooden weir is an option that consists of a barrier formed around a curb inlet with a wooden frame and gravel. Design and installation specifications for curb inlet protection with wooden weirs include: l Use wire mesh with ½-inch openings. l Use extra strength filter cloth. l Construct a frame. l Attach the wire and filter fabric to the frame. l Pile coarse washed aggregate against the wire and fabric. l Place weight on the frame anchors. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 360 Block and Gravel Curb Inlet Protection Block and gravel curb inlet protection is a barrier formed around a curb inlet with concrete blocks and gravel. See Figure II-3.18: Block and Gravel Curb Inlet Protection. Design and installation spe- cifications for block and gravel curb inlet protection include: l Use wire mesh with ½-inch openings. l Place two concrete blocks on their sides abutting the curb at either side of the inlet opening. These are spacer blocks. l Place a 2x4 stud through the outer holes of each spacer block to align the front blocks. l Place blocks on their sides across the front of the inlet and abutting the spacer blocks. l Place wire mesh over the outside vertical face. l Pile coarse aggregate against the wire to the top of the barrier. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 361 Figure II-3.18: Block and Gravel Curb Inlet Protection 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 362 Curb and Gutter Sediment Barrier Curb and gutter sediment barrier is a sandbag or rock berm (riprap and aggregate) 3 feet high and 3 feet wide in a horseshoe shape. See Figure II-3.19: Curb and Gutter Barrier. Design and installation specifications for curb and gutter sediment barrier include: l Construct a horseshoe shaped berm, faced with coarse aggregate if using riprap, 3 feet high and 3 feet wide, at least 2 feet from the inlet. l Construct a horseshoe shaped sedimentation trap on the upstream side of the berm. Size the trap to sediment trap standards for protecting a culvert inlet. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 363 Figure II-3.19: Curb and Gutter Barrier 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 364 Maintenance Standards l Inspect all forms of inlet protection frequently, especially after storm events. Clean and replace clogged catch basin filters. For rock and gravel filters, pull away the rocks from the inlet and clean or replace. An alternative approach would be to use the clogged rock as fill and put fresh rock around the inlet. l Do not wash sediment into storm drains while cleaning. Spread all excavated material evenly over the surrounding land area or stockpile and stabilize as appropriate. Approved as Functionally Equivalent Ecology has approved products as able to meet the requirements of this BMP. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept these products, or may require additional testing prior to consideration for local use. Products that Ecology has approved as functionally equivalent are available for review on Ecology’s website at: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-per- mittee-guidance-resources/Emerging-stormwater-treatment-technologies 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 365 BMP C233: Silt Fence Purpose Silt fence reduces the transport of coarse sediment from a construction site by providing a temporary physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use Silt fence may be used downslope of all disturbed areas. l Silt fence shall prevent sediment carried by runoff from going beneath, through, or over the top of the silt fence, but shall allow the water to pass through the fence. l Silt fence is not intended to treat concentrated flows, nor is it intended to treat substantial amounts of overland flow. Convey any concentrated flows through the drainage system to a sediment trapping BMP. l Do not construct silt fences in streams or use in V-shaped ditches. Silt fences do not provide an adequate method of silt control for anything deeper than sheet or overland flow. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 370 Figure II-3.22: Silt Fence 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 371 Design and Installation Specifications l Use in combination with other construction stormwater BMPs. l Maximum slope steepness (perpendicular to the silt fence line) 1H:1V. l Maximum sheet or overland flow path length to the silt fence of 100 feet. l Do not allow flows greater than 0.5 cfs. l Use geotextile fabric that meets the following standards. All geotextile properties listed below are minimum average roll values (i.e., the test result for any sampled roll in a lot shall meet or exceed the values shown in Table II-3.11: Geotextile Fabric Standards for Silt Fence): Geotextile Property Minimum Average Roll Value Polymeric Mesh AOS (ASTM D4751) 0.60 mm maximum for slit film woven (#30 sieve). 0.30 mm maximum for all other geotextile types (#50 sieve). 0.15 mm minimum for all fabric types (#100 sieve). Water Permittivity (ASTM D4491) 0.02 sec-1 minimum Grab Tensile Strength (ASTM D4632) 180 lbs. Minimum for extra strength fabric. 100 lbs minimum for standard strength fabric. Grab Tensile Strength (ASTM D4632) 30% maximum Ultraviolet Resistance (ASTM D4355) 70% minimum Table II-3.11: Geotextile Fabric Standards for Silt Fence l Support standard strength geotextiles with wire mesh, chicken wire, 2-inch x 2-inch wire, safety fence, or jute mesh to increase the strength of the geotextile. Silt fence materials are available that have synthetic mesh backing attached. l Silt fence material shall contain ultraviolet ray inhibitors and stabilizers to provide a minimum of six months of expected usable construction life at a temperature range of 0°F to 120°F. l One-hundred percent biodegradable silt fence is available that is strong, long lasting, and can be left in place after the project is completed, if permitted by the local jurisdiction. l Refer to Figure II-3.22: Silt Fence for standard silt fence details. Include the following Stand- ard Notes for silt fence on construction plans and specifications: 1. The Contractor shall install and maintain temporary silt fences at the locations shown in the Plans. 2. Construct silt fences in areas of clearing, grading, or drainage prior to starting those activities. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 372 3. The silt fence shall have a 2-feet min. and a 2½-feet max. height above the original ground surface. 4. The geotextile fabric shall be sewn together at the point of manufacture to form fabric lengths as required. Locate all sewn seams at support posts. Alternatively, two sections of silt fence can be overlapped, provided that the overlap is long enough and that the adjacent silt fence sections are close enough together to prevent silt laden water from escaping through the fence at the overlap. 5. Attach the geotextile fabric on the up-slope side of the posts and secure with staples, wire, or in accordance with the manufacturer's recommendations. Attach the geotextile fabric to the posts in a manner that reduces the potential for tearing. 6. Support the geotextile fabric with wire or plastic mesh, dependent on the properties of the geotextile selected for use. If wire or plastic mesh is used, fasten the mesh securely to the up-slope side of the posts with the geotextile fabric up-slope of the mesh. 7. Mesh support, if used, shall consist of steel wire with a maximum mesh spacing of 2- inches, or a prefabricated polymeric mesh. The strength of the wire or polymeric mesh shall be equivalent to or greater than 180 lbs. grab tensile strength. The polymeric mesh must be as resistant to the same level of ultraviolet radiation as the geotextile fabric it supports. 8. Bury the bottom of the geotextile fabric 4-inches min. below the ground surface. Backfill and tamp soil in place over the buried portion of the geotextile fabric, so that no flow can pass beneath the silt fence and scouring cannot occur. When wire or polymeric back-up support mesh is used, the wire or polymeric mesh shall extend into the ground 3-inches min. 9. Drive or place the silt fence posts into the ground 18-inches min. A 12–inch min. depth is allowed if topsoil or other soft subgrade soil is not present and 18-inches cannot be reached. Increase fence post min. depths by 6 inches if the fence is located on slopes of 3H:1V or steeper and the slope is perpendicular to the fence. If required post depths cannot be obtained, the posts shall be adequately secured by bracing or guying to pre- vent overturning of the fence due to sediment loading. 10. Use wood, steel or equivalent posts. The spacing of the support posts shall be a max- imum of 6-feet. Posts shall consist of either: l Wood with minimum dimensions of 2 inches by 2 inches by 3 feet. Wood shall be free of defects such as knots, splits, or gouges. l No. 6 steel rebar or larger. l ASTM A 120 steel pipe with a minimum diameter of 1-inch. l U, T, L, or C shape steel posts with a minimum weight of 1.35 lbs./ft. l Other steel posts having equivalent strength and bending resistance to the post sizes listed above. 11. Locate silt fences on contour as much as possible, except at the ends of the fence, 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 373 where the fence shall be turned uphill such that the silt fence captures the runoff water and prevents water from flowing around the end of the fence. 12. If the fence must cross contours, with the exception of the ends of the fence, place check dams perpendicular to the back of the fence to minimize concentrated flow and erosion. The slope of the fence line where contours must be crossed shall not be steeper than 3H:1V. l Check dams shall be approximately 1-foot deep at the back of the fence. Check dams shall be continued perpendicular to the fence at the same elevation until the top of the check dam intercepts the ground surface behind the fence. l Check dams shall consist of crushed surfacing base course, gravel backfill for walls, or shoulder ballast. Check dams shall be located every 10 feet along the fence where the fence must cross contours. l Refer to Figure II-3.23: Silt Fence Installation by Slicing Method for slicing method details. The following are specifications for silt fence installation using the slicing method: 1. The base of both end posts must be at least 2- to 4-inches above the top of the geo- textile fabric on the middle posts for ditch checks to drain properly. Use a hand level or string level, if necessary, to mark base points before installation. 2. Install posts 3- to 4-feet apart in critical retention areas and 6- to 7-feet apart in standard applications. 3. Install posts 24-inches deep on the downstream side of the silt fence, and as close as possible to the geotextile fabric, enabling posts to support the geotextile fabric from upstream water pressure. 4. Install posts with the nipples facing away from the geotextile fabric. 5. Attach the geotextile fabric to each post with three ties, all spaced within the top 8- inches of the fabric. Attach each tie diagonally 45 degrees through the fabric, with each puncture at least 1-inch vertically apart. Each tie should be positioned to hang on a post nipple when tightening to prevent sagging. 6. Wrap approximately 6-inches of the geotextile fabric around the end posts and secure with 3 ties. 7. No more than 24-inches of a 36-inch geotextile fabric is allowed above ground level. 8. Compact the soil immediately next to the geotextile fabric with the front wheel of the tractor, skid steer, or roller exerting at least 60 pounds per square inch. Compact the upstream side first and then each side twice for a total of four trips. Check and correct the silt fence installation for any deviation before compaction. Use a flat-bladed shovel to tuck the fabric deeper into the ground if necessary. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 374 Figure II-3.23: Silt Fence Installation by Slicing Method 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 375 Maintenance Standards l Repair any damage immediately. l Intercept and convey all evident concentrated flows uphill of the silt fence to a sediment trap- ping BMP. l Check the uphill side of the silt fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence and remove the trapped sediment. l Remove sediment deposits when the deposit reaches approximately one-third the height of the silt fence, or install a second silt fence. l Replace geotextile fabric that has deteriorated due to ultraviolet breakdown. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 376 treatment pond prior to decanting. Compliance with the water quality standards is determined in the receiving water. Operator Training Each project site using chemical treatment must have a trained operator who is certified for oper- ation of an Enhanced Chemical Treatment system. The operator must be trained and certified by an organization approved by Ecology. Organizations approved for operator training are found at the fol- lowing website: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-permittee- guidance-resources/Contaminated-water-on-construction-sites Sediment Removal and Disposal l Sediment shall be removed from the untreated stormwater storage pond and treatment cells as necessary. Typically, sediment removal is required at least once during a wet season and at the decommissioning of the chemical treatment system. Sediment remaining in the cells between batches may enhance the settling process and reduce the required chemical dosage. l Sediment that is known to be non-toxic may be incorporated into the site away from drain- ages. BMP C251: Construction Stormwater Filtration Purpose Filtration removes sediment from runoff originating from disturbed areas of the site. Conditions of Use Traditional Construction Stormwater BMPs used to control soil erosion and sediment loss from con- struction sites may not be adequate to ensure compliance with the water quality standard for tur- bidity in the receiving water. Filtration may be used in conjunction with gravity settling to remove sediment as small as fine silt (0.5 µm). The reduction in turbidity will be dependent on the particle size distribution of the sediment in the stormwater. In some circumstances, sedimentation and fil- tration may achieve compliance with the water quality standard for turbidity. The use of construction stormwater filtration does not require approval from Ecology as long as treat- ment chemicals are not used. Filtration in conjunction with BMP C250: Construction Stormwater Chemical Treatment requires testing under the Chemical Technology Assessment Protocol – Eco- logy (CTAPE) before it can be initiated. Approval from Ecology must be obtained at each site where chemical use is proposed prior to use. See https://- fortress.wa.gov/ecy/publications/SummaryPages/ecy070258.html for a copy of the Request for Chemical Treatment form. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 404 Design and Installation Specifications Two types of filtration systems may be applied to construction stormwater treatment: rapid and slow. Rapid filtration systems are the typical system used for water and wastewater treatment. They can achieve relatively high hydraulic flow rates, on the order of 2 to 20 gpm/sf, because they have auto- matic backwash systems to remove accumulated solids. Slow filtration systems have very low hydraulic rates, on the order of 0.02 gpm/sf, because they do not have backwash systems. Slow filtration systems have generally been used as post construction BMPs to treat stormwater (see V-6 Filtration BMPs). Slow filtration is mechanically simple in com- parison to rapid filtration, but requires a much larger filter area. Filter Types and Efficiencies Sand media filters are available with automatic backwashing features that can filter to 50 µm particle size. Screen or bag filters can filter down to 5 µm. Fiber wound filters can remove particles down to 0.5 µm. Filters should be sequenced from the largest to the smallest pore opening. Sediment removal efficiency will be related to particle size distribution in the stormwater. Treatment Process and Description Stormwater is collected at interception point(s) on the site and diverted to an untreated stormwater sediment pond or tank for removal of large sediment, and storage of the stormwater before it is treated by the filtration system. In a rapid filtration system, the untreated stormwater is pumped from the pond or tank through the filtration media. Slow filtration systems are designed using gravity to convey water from the pond or tank to and through the filtration media. Sizing Filtration treatment systems must be designed to control the velocity and peak volumetric flow rate that is discharged from the system and consequently the project site. See Element 3: Control Flow Rates for further details on this requirement. The untreated stormwater storage pond or tank should be sized to hold 1.5 times the volume of run- off generated from the site during the 10-year, 24-hour storm event, minus the filtration treatment system flowrate for an 8-hour period. For a chitosan-enhanced sand filtration system, the filtration treatment system flowrate should be sized using a hydraulic loading rate between 6-8 gpm/ft2. Other hydraulic loading rates may be more appropriate for other systems. Bypass should be provided around the filtration treatment system to accommodate extreme storm events. Runoff volume shall be calculated using the methods presented in III-2.3 Single Event Hydrograph Method. Worst-case land cover conditions (i.e., producing the most runoff) should be used for analyses (in most cases, this would be the land cover conditions just prior to final landscaping). If the filtration treatment system design does not allow you to discharge at the rates as required by Element 3: Control Flow Rates, and if the site has a permanent Flow Control BMP that will serve the planned development, the discharge from the filtration treatment system may be directed to the per- manent Flow Control BMP to comply with Element 3: Control Flow Rates. In this case, all discharge (including water passing through the treatment system and stormwater bypassing the treatment 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 405 system) will be directed into the permanent Flow Control BMP. If site constraints make locating the untreated stormwater storage pond difficult, the permanent Flow Control BMP may be divided to serve as the untreated stormwater storage pond and the post-treatment temporary flow control pond. A berm or barrier must be used in this case so the untreated water does not mix with the treated water. Both untreated stormwater storage requirements, and adequate post-treatment flow control must be achieved. The designer must document in the Construction SWPPP how the per- manent Flow Control BMP is able to attenuate the discharge from the site to meet the requirements of Element 3: Control Flow Rates. If the design of the permanent Flow Control BMP was modified for temporary construction flow control purposes, the construction of the permanent Flow Control BMP must be finalized, as designed for its permanent function, at project completion. Maintenance Standards l Rapid sand filters typically have automatic backwash systems that are triggered by a pre-set pressure drop across the filter. If the backwash water volume is not large or substantially more turbid than the untreated stormwater stored in the holding pond or tank, backwash return to the untreated stormwater pond or tank may be appropriate. However, other means of treat- ment and disposal may be necessary. l Screen, bag, and fiber filters must be cleaned and/or replaced when they become clogged. l Sediment shall be removed from the storage and/or treatment ponds as necessary. Typically, sediment removal is required once or twice during a wet season and at the decommissioning of the ponds. l Disposal of filtration equipment must comply with applicable local, state, and federal reg- ulations. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 406 P a g e | 29 C. Correspondence Please see the following for any pertinent correspondence regarding this project. P a g e | 30 D. Site Inspection Form Please see the following pages for the site inspection form. Construction Stormwater Site Inspection Form Page 1 Project Name Permit # Inspection 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 Page 2 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? Construction Stormwater Site Inspection Form Page 3 Element #Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 5 Stabilize Soils Cont. 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? 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? Construction Stormwater Site Inspection Form Page 4 Element #Inspection BMPs Inspected BMP needs maintenance BMP failed Action required (describe in section F) yes no n/a 9 Cont. 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? 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? 13 Protect LID Is all Bioretention and Rain Garden Facilities protected from sedimentation with appropriate BMPs? Is the Bioretention and Rain Garden protected against over compaction of construction equipment and foot traffic to retain its infiltration capabilities? Permeable pavements are clean and free of sediment and sediment laden- water runoff. Muddy construction equipment has not been on the base material or pavement. Have soiled permeable pavements been cleaned of sediments and pass infiltration test as required by stormwater manual methodology? Heavy equipment has been kept off existing soils under LID facilities to retain infiltration rate. E. Check all areas that have been inspected. All in place BMPs All disturbed soils All concrete wash out area All material storage areas All discharge locations All equipment storage areas All construction entrances/exits Construction Stormwater Site Inspection Form Page 5 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)Date: Title/Qualification of Inspector: P a g e | 31 E. Construction Stormwater General Permit (CSWGP) Please see the following attachment for the CSWGP Issuance Date: November 18, 2020 Effective Date: January 1, 2021 Expiration Date: December 31, 2025 CONSTRUCTION STORMWATER 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. __________________________________ Vincent McGowan, P.E. Water Quality Program Manager Washington State Department of Ecology Construction Stormwater General Permit Page i TABLE OF CONTENTS LIST OF TABLES .................................................................................................................................. ii SUMMARY OF PERMIT REPORT SUBMITTALS ...................................................................................... 1 SPECIAL CONDITIONS ......................................................................................................................... 3 S1. Permit Coverage .............................................................................................................................. 3 S2. Application Requirements ............................................................................................................... 7 S3. Compliance with Standards ............................................................................................................. 9 S4. Monitoring Requirements, Benchmarks, and Reporting Triggers ................................................. 10 S5. Reporting and Recordkeeping Requirements ................................................................................ 17 S6. Permit Fees .................................................................................................................................... 20 S7. Solid and Liquid Waste Disposal .................................................................................................... 20 S8. Discharges to 303(D) or TMDL Waterbodies ................................................................................. 20 S9. Stormwater Pollution Prevention Plan .......................................................................................... 23 S10. Notice Of Termination ................................................................................................................... 32 GENERAL CONDITIONS ..................................................................................................................... 34 G1. Discharge Violations....................................................................................................................... 34 G2. Signatory Requirements ................................................................................................................ 34 G3. Right of Inspection and Entry ......................................................................................................... 35 G4. General Permit Modification and Revocation ............................................................................... 35 G5. Revocation of Coverage Under tPermit ......................................................................................... 35 G6. Reporting a Cause for Modification ............................................................................................... 36 G7. Compliance with Other Laws and Statutes .................................................................................... 36 G8. Duty to Reapply.............................................................................................................................. 36 G9. Removed Substance ....................................................................................................................... 36 G10. Duty to Provide Information .......................................................................................................... 36 G11. Other Requirements of 40 CFR ...................................................................................................... 37 G12. Additional Monitoring .................................................................................................................... 37 G13. Penalties for Violating Permit Conditions ...................................................................................... 37 G14. Upset .............................................................................................................................................. 37 G15. Property Rights .............................................................................................................................. 37 G16. Duty to Comply .............................................................................................................................. 37 G17. Toxic Pollutants .............................................................................................................................. 38 G18. Penalties for Tampering ................................................................................................................. 38 G19. Reporting Planned Changes ........................................................................................................... 38 G20. Reporting Other Information ......................................................................................................... 38 G21. Reporting Anticipated Non-Compliance ........................................................................................ 38 Construction Stormwater General Permit Page ii G22. Requests to Be Excluded From Coverage Under the Permit ......................................................... 39 G23. Appeals........................................................................................................................................... 39 G24. Severability..................................................................................................................................... 39 G25. Bypass Prohibited .......................................................................................................................... 39 APPENDIX A – DEFINITIONS .............................................................................................................. 42 APPENDIX B – ACRONYMS ................................................................................................................ 50 LIST OF TABLES Table 1 Summary of Required Submittals ................................................................................................ 1 Table 2 Summary of Required On-site Documentation ........................................................................... 2 Table 3 Summary of Primary Monitoring Requirements ....................................................................... 12 Table 4 Monitoring and Reporting Requirements ................................................................................. 14 Table 5 Turbidity, Fine Sediment & Phosphorus Sampling and Limits for 303(d)-Listed Waters ................................................................................................................ 22 Table 6 pH Sampling and Limits for 303(d)-Listed Waters ..................................................................... 22 Construction Stormwater General Permit Page 1 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.D Request for Chemical Treatment Form As necessary Written approval from Ecology is required prior to using chemical treatment (with the exception of dry ice, CO2 or food grade vinegar 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 S2.A Notice of Permit Transfer As necessary G19 Notice of Planned Changes As necessary G21 Reporting Anticipated Non-compliance As necessary 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. Construction Stormwater General Permit Page 2 Table 2 Summary of Required On-site Documentation Document Title Permit Conditions Permit Coverage Letter See Conditions S2, S5 Construction Stormwater General Permit (CSWGP) See Conditions S2, S5 Site Log Book See Conditions S4, S5 Stormwater Pollution Prevention Plan (SWPPP) See Conditions S5, S9 Site Map See Conditions S5, S9 Construction Stormwater General Permit Page 3 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 and 4. 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 related to construction-support activity as 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 category 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 groundwater, 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 S1.F). c. Routine maintenance that is performed to maintain the original line and grade, hydraulic capacity, or original purpose of a facility. 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 Construction Stormwater General Permit Page 4 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 groundwater 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. 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 groundwater, are prohibited: Construction Stormwater General Permit Page 5 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. 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. Construction Stormwater General Permit Page 6 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. F. 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 five (5) acres and the site is not a portion of a common plan of development or sale that will disturb five (5) acres or greater. 2. Calculation of Erosivity “R” Factor and Regional Timeframe: a. The project’s calculated rainfall erosivity factor (“R” Factor) must be less than five (5) during the period of construction activity, (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 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/resourcesguida nce.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 Construction Stormwater General Permit Page 7 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. 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 S1.F.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. S2. APPLICATION REQUIREMENTS A. Permit Application Forms 1. Notice of Intent Form 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://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 c. The operator must submit the NOI at least 60 days before discharging stormwater from construction activities and must submit it prior to 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, coverage under the general permit will automatically commence on the 31st 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). See S8.B for Limits on Coverage for New Discharges to TMDL or 303(d)-Listed Waters. 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, the applicant must provide notice of the Construction Stormwater General Permit Page 8 selection of an equivalent BMP to Ecology at least 60 days before intended use of the equivalent BMP. e. 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. Related portions of the Stormwater Pollution Prevention Plan (SWPPP) that address the management of contaminated and potentially contaminated construction stormwater and dewatering water, iv. Dewatering plan and/or dewatering contingency plan. 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: i. The Permittee submits a complete Transfer of Coverage Form to Ecology, signed by the current and new discharger and containing a specific date for transfer of permit responsibility, coverage and liability (including any Administrative Orders associated with the permit); and ii. Ecology does not notify the current discharger and new discharger of 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 indicate the remaining permitted acreage after the transfer. Transfers do not require public notice. 3. Modification of Coverage Form Permittees must notify Ecology regarding any changes to the information provided on the NOI by submitting an Update/Modification of Permit Coverage form in accordance with General Conditions G6 and G19. 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. Construction Stormwater General Permit Page 9 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 be run after the NOI has been submitted and 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 total number of acres to be disturbed over the lifetime of the project. 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 and the receiving water(s) the system discharges to. 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. S3. COMPLIANCE WITH STANDARDS A. Discharges must not cause or contribute to a violation of surface water quality standards (Chapter 173-201A WAC), groundwater quality standards (Chapter 173-200 WAC), sediment management standards (Chapter 173-204 WAC), and human health-based criteria in the Federal water quality criteria applicable to Washington. (40 CFR Part 131.45) Discharges that are not in compliance with these standards are prohibited. 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: Construction Stormwater General Permit Page 10 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 management 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 groundwater, the groundwater discharges must also meet the terms and conditions of this CSWGP. Permittees who discharge to groundwater through an injection well must also comply with any applicable requirements of the Underground Injection Control (UIC) regulations, Chapter 173-218 WAC. 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 Construction sites one (1) acre or larger that discharge stormwater to surface waters of the State must have site inspections conducted by a Certified Erosion and Sediment Control Lead (CESCL). Sites less than one (1) acre may have a person without CESCL certification conduct inspections. (See Special Conditions S4.B.3 and B.4, below, for detailed requirements of the Permittee’s CESCL.) Site inspections must include all areas disturbed by construction activities, all BMPs, and all stormwater discharge points under the Permittee’s operational control. 1. 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. The SWPPP must identify the CESCL or inspector, who must be present on site or on-call at all times. The CESCL (sites one (1) acre or more) 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.) 2. The CESCL or inspector must examine stormwater visually for the presence of suspended sediment, turbidity, discoloration, and oil sheen. BMP effectiveness must be evaluated to Construction Stormwater General Permit Page 11 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, 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. 3. The CESCL or inspector 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 (1) day do not require daily inspections. For example, if a stormwater pond discharges continuously over the course of a week, only one (1) inspection is required that week.) Inspection frequency may be reduced to once every calendar month for inactive sites that are temporarily stabilized. 4. 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. c. The general conditions during inspection. d. The approximate amount of precipitation since the last inspection. e. The approximate amount of precipitation within the last 24 hours. f. A summary or list of all implemented BMPs, including observations of all erosion/sediment control structures or practices. g. A description of: i. BMPs inspected (including location). ii. BMPs that need maintenance and why. iii. BMPs that failed to operate as designed or intended, and iv. Where additional or different BMPs are needed, and why. h. A description of stormwater discharged from the site. The Permittee must note the presence of suspended sediment, turbidity, discoloration, and oil sheen, as applicable. Construction Stormwater General Permit Page 12 i. Any water quality monitoring performed during inspection. j. General comments and notes, including a brief description of any BMP repairs, maintenance, or installations made following the inspection. k. An implementation schedule for 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. l. A summary report of the inspection. m. 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 concrete or recycled concrete placed or poured 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.a or b. 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.4.a. Construction Stormwater General Permit Page 13 C. Turbidity/Transparency Sampling Requirements 1. Sampling Methods a. If construction activity involves the disturbance of five (5) acres or more, the Permittee must conduct turbidity sampling per Special Condition S4.C.4.a, below. b. If construction activity involves one (1) acre or more but fewer than five (5) acres of soil disturbance, the Permittee must conduct either transparency sampling or turbidity sampling per Special Condition S4.C.4.a or b, below. 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) in the SWPPP and on the 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. 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. Construction Stormwater General Permit Page 14 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 Turbidity NTU SM2130 Weekly, if discharging 25 NTUs Transparency Cm Manufacturer instructions, or Ecology guidance Weekly, if discharging 33 cm 5. Turbidity/Transparency Benchmark Values and Reporting Triggers The benchmark value for turbidity is 25 NTUs. 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 and follow S5.F – Noncompliance Notification for reporting requirements applicable to discharges which exceed the numeric effluent limit for turbidity. a. Turbidity 26 – 249 NTUs, or Transparency 32 – 7 cm: If the discharge turbidity is 26 to 249 NTUs; or if discharge transparency is 32 to 7 cm, the Permittee must: i. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs, and no later than 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. 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. 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 Construction Stormwater General Permit Page 15 management process described below. For discharges which are subject to a numeric effluent limit for turbidity, see S5.F – Noncompliance Notification. i. Within 24 hours, 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), 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 These numbers and a link to the ERTS reporting page are also listed at the following website: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.html. 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. iii. Sample discharges daily until: a) Turbidity is 25 NTUs (or lower); or b) Transparency is 33 cm (or greater); or c) The Permittee has demonstrated compliance with the water quality standard 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 *Note: background turbidity in the receiving water must be measured immediately upstream (upgradient) or outside of the area of influence of the discharge. d) The discharge stops or is eliminated. iv. Review the SWPPP for compliance with Special Condition S9 and make appropriate revisions within seven (7) days of the date the discharge exceeded the benchmark. Construction Stormwater General Permit Page 16 v. Document BMP implementation and maintenance in the site log book. Compliance with these requirements does not relieve the Permittee from responsibility to maintain continuous compliance with permit benchmarks. 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 placed or 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. 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. 2. During the applicable pH monitoring period defined below, the Permittee must obtain a representative sample of stormwater and conduct pH analysis at least once per week. a. For sites with significant concrete work, the Permittee must begin the pH sampling period when the concrete is first placed or poured and exposed to precipitation, and continue weekly throughout and after the concrete placement, pour and curing period, until stormwater pH is in the range of 6.5 to 8.5 (su). b. 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). c. 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. 3. 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. 4. The benchmark value for pH is 8.5 standard units. Anytime sampling indicates that pH is 8.5 or greater, the Permittee must either: a. Prevent the high pH water (8.5 or above) from entering storm sewer systems or surface waters of the state; 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, dry ice or food grade vinegar. The Permittee must obtain written approval from Ecology before using any form of chemical treatment other than CO2 sparging, dry ice or food grade vinegar. Construction Stormwater General Permit Page 17 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 notify Ecology within 24 hours of analysis either by calling the applicable Ecology Region’s Environmental Report Tracking System (ERTS) number by phone or by submitting an electronic ERTS report (through Ecology’s Water Quality Permitting Portal (WQWebPortal) – Permit Submittals when the form is available). See the CSWGP website 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 G12 (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. 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, WA 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 must 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 the first full month following the effective date of permit coverage up until Ecology has approved termination of the coverage). For more information, contact Ecology staff using information provided at the following website: 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 five (5) 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 Construction Stormwater General Permit Page 18 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 samples or monitors any pollutant more frequently than required by this permit using test procedures specified by Special Condition S4 of this permit, the sampling results for 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 or fuels or other materials, catastrophic pond or slope failure, and discharges that violate water quality standards), or exceed 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 go to https://ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue to find contact information for the regional offices.) 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 (See S5.F.3, below, for details on submitting results in a report). 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. Construction Stormwater General Permit Page 19 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 e. Erosivity Waiver (if applicable) 2. The Permittee must address written requests for plans and records listed above (Special Condition S5.G.1) as follows: 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 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. Construction Stormwater General Permit Page 20 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 Water Bodies 1. Permittees who discharge to segments of water bodies 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, 2021, 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 Construction sites that discharge to a TMDL or 303(d)-listed waterbody are not eligible for coverage under this permit unless the operator: Construction Stormwater General Permit Page 21 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 only after Ecology makes an affirmative determination that the discharge will not cause or contribute to the existing impairment or exceed the TMDL. 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. 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 must sample discharges daily until the violation is corrected and comply with the non-compliance notification requirements in Special Condition S5.F. Construction Stormwater General Permit Page 22 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) 1 Permittees 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). 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 su 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 must 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 Construction Stormwater General Permit Page 23 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, unless 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. iii. 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, 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. 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 identify best management practices (BMPs) which prevent erosion and sedimentation, and to reduce, eliminate or prevent stormwater contamination and water pollution from construction activity. 2. To prevent violations of surface water quality, groundwater quality, or sediment management standards. 3. To control peak volumetric flow rates and velocities of stormwater discharges. Construction Stormwater General Permit Page 24 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. 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 Construction Stormwater General Permit Page 25 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 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. f. Control street wash wastewater by pumping back on site or otherwise preventing it from discharging into systems tributary to waters of the State. Construction Stormwater General Permit Page 26 3. Control Flow Rates a. Protect properties and waterways downstream of construction sites from erosion and the associated discharge of turbid waters due to increases in the 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 infiltration or detention BMPs as one of the first steps in grading. Assure that detention BMPs 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 sedimentation 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: 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 Construction Stormwater General Permit Page 27 control fabrics and matting, soil application of polyacrylamide (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). b. The Permittee must divert off-site stormwater (run-on) or groundwater 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. Construction Stormwater General Permit Page 28 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 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. Construction Stormwater General Permit Page 29 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. Minimize storage of hazardous materials on-site. Safety Data Sheets (SDS) should be supplied for all materials stored. Chemicals should be kept in their original labeled containers. 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 of 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 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 onto the ground, or into storm drains, open ditches, streets, or streams. Washout of small concrete handling equipment may be disposed of in a formed area awaiting concrete where it will not contaminate surface or groundwater. 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 Construction Stormwater General Permit Page 30 prohibited. At no time shall concrete be washed off into the footprint of an area where an infiltration BMP will be installed. i. Obtain written approval from Ecology before using any chemical treatment, with the exception of CO2, dry ice or food grade vinegar, 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, in conjunction with BMPs to reduce sedimentation before discharge to a sediment trap or sediment pond. b. Permittees may discharge clean, non-turbid dewatering water, such as well-point groundwater, 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. 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. Construction Stormwater General Permit Page 31 12. Manage the Project a. Phase development projects to the maximum degree practicable and take into account seasonal work limitations. b. 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. 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 on-site LID Stormwater Management is to reduce the disruption of the natural site hydrology through infiltration. LID BMPs are permanent facilities. a. Permittees must protect all LID BMPs (including, but not limited to, 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 BMPs 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. b. Permittees must maintain the infiltration capabilities of LID BMPs 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 or base materials. 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 BMPs 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. Construction Stormwater General Permit Page 32 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. 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 Partial terminations of permit coverage are not authorized. 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 Special Condition S2.A), 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, WA 98504-7696 Construction Stormwater General Permit Page 33 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 31st calendar day following the date Ecology receives a complete NOT form, unless Ecology notifies the Permittee that 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 34 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. 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 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. Construction Stormwater General Permit Page 35 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. 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. Construction Stormwater General Permit Page 36 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, WA 98504-7696 G9. REMOVED SUBSTANCE 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. G10. 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)]. Construction Stormwater General Permit Page 37 G11. OTHER REQUIREMENTS OF 40 CFR All other requirements of 40 CFR 122.41 and 122.42 are incorporated in this permit by reference. G12. ADDITIONAL MONITORING Ecology may establish specific monitoring requirements in addition to those contained in this permit by administrative order or permit modification. G13. 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. 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. G14. 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. G15. PROPERTY RIGHTS This permit does not convey any property rights of any sort, or any exclusive privilege. G16. 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. Construction Stormwater General Permit Page 38 G17. 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. G18. 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. G19. 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: 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. G20. 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. G21. 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 unavoidable interruption of Construction Stormwater General Permit Page 39 operation and degradation of effluent quality, must be scheduled during non-critical water quality periods and carried out in a manner approved by Ecology. G22. 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. G23. 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. G24. 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. G25. 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 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. Construction Stormwater General Permit Page 40 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. 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 Construction Stormwater General Permit Page 41 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 42 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, 2021, or before the date the operator’s complete permit application is received by Ecology, whichever is later. TMDLs completed after a 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. 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 43 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 groundwater. Construction Activity means land disturbing operations including clearing, grading or excavation which disturbs the surface of the land (including off-site disturbance acreage related to construction-support activity). 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. Construction Support Activity means off-site acreage that will be disturbed as a direct result of the construction project and will discharge stormwater. For example, off-site equipment staging yards, material storage areas, borrow areas, and parking areas. 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 soil means soil which contains contaminants, pollutants, or hazardous substances that do not occur naturally or occur at levels greater than natural background. Contaminated groundwater means groundwater 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. 2. The pollutant removal performance expected from the BMPs selected. Construction Stormwater General Permit Page 44 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 groundwater 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 groundwater 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 groundwater 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 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 completion of all soil disturbing activities at the site and the establishment of permanent vegetative cover, or equivalent permanent stabilization measures (such as pavement, riprap, gabions, or geotextiles) which will prevent erosion. See the applicable Stormwater Management Manual for more information on vegetative cover expectations and equivalent permanent stabilization measures. Construction Stormwater General Permit Page 45 Groundwater 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 sub-stance as defined in RCW 70.105.010(14) 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, 42U.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 • 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. Construction Stormwater General Permit Page 46 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 the 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 non-stormwater 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 groundwater drainage, redirecting stream natural flows, or for conveyance of irrigation water/return flows that coincidentally convey stormwater are considered the receiving water. 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. Construction Stormwater General Permit Page 47 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 groundwater quality or sediment management standards. Significant Concrete Work means greater than 1000 cubic yards placed or 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 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. Construction Stormwater General Permit Page 48 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. Transfer of Coverage (TOC) means a request for transfer of coverage under this general permit as specified by Special Condition S2.A 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. 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. 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 Construction Stormwater General Permit Page 49 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 50 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 CPD Common Plan of Development 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 P a g e | 32 F. 303(d) List Waterbodies / TMDL Waterbodies Information An unnamed creek (tributary to Lake Washington) is the ultimate tributary waterbody for the project. The creek is listed on the Washington State Department of Ecology’s 303(d) list for impaired waterbodies and is classified as Category 5. P a g e | 33 G. Contaminated Site Information There are no known contaminants onsite. P a g e | 34 H. Engineering Calculations N/A Appendix D – Operation & Maintenance Manual LUA24-000081 January 7, 2025 SHOPHIE JO SHORT PLAT Stormwater Facility Maintenance Program PROPERTY ADDRESS S 21st Street, Renton, WA 98055 PREPARED FOR Schneider Homes, Inc. 6510 Southcenter Blvd, Suite100 Tukwila, WA 98188 PREPARED BY ESM Consulting Engineers, LLC 33400 8th Avenue S, Suite 205 Federal Way, WA 98003 Email: brandon.loucks@esmcivil.com 253.838.6113 tel 253.838.7104 fax Sophie Jo Short Plat - Stormwater Facility Maintenance Program TABLE OF CONTENTS Vicinity Map Site map Maintenance and Source Control Manual SECTION 1 – Project Description SECTION 2 – Maintenance Importance and Intent SECTION 3 – Responsible Parties SECTION 4 – Facilities Requiring Maintenance SECTION 5 – Maintenance Instructions SECTION 6 – Vegetation Maintenance SECTION 7 – Pollution Source Control Measures SECTION 8 – Annual Cost of Maintenance Appendices APPENDIX I - Drainage System Maintenance Guide Forms APPENDIX II - Manufacturer Maintenance Guide Forms Sophie Jo Short Plat - Stormwater Facility Maintenance Program Sophie Jo Short Plat - Stormwater Facility Maintenance Program 1. INTRODUCTION This manual is prepared in conjunction with the Drainage Control Report (DCR) for the site improvements. This Storm Water Facility Maintenance (SWFM) Manual shall reside in the Facility Manager’s office within the main building on the site. The SWFM Manual shall be updated annually with the inspection reports as part of regular storm drainage system maintenance activities. The SWFM Manual shall be made available to City personnel for inspection at any time. Project Description Sophie Jo Short Plat is located at the southeast corner of the intersection between S 21st Street and Smithers Ave S in the City of Renton. The development includes 3 single family lots, a joint use driveway tract used for a shared access between lots 2 and 3, and a stormwater detention vault. The drainage control management system consists of multiple collection basins, conveyance pipes, and below ground detention vault. All of these systems are designed to control surface runoff from the site to reduce impacts on the environment downstream of the site. “Drainage control” can be quality or quantity control and each system requires consistent maintenance for proper operation. Descriptions of each of the features and how they operate are provided below. Refer to the site map for the site configuration and locations of storm drainage control systems. Site Ownership Schneider Homes, Inc. 6510 Southcenter Blvd, Suite100 Tukwila, WA 98188 Permanent Stormwater Control System Description The on-site stormwater control systems for quality and/or quantity control exist all around the site. A site plan showing the location of the drainage systems for the site is provided on the following page. Per Ecology TAPE approval, the owner shall have the system inspected for a minimum of 12 months from start of post construction operation. Monthly inspection is required Sophie Jo Short Plat - Stormwater Facility Maintenance Program in wet season from Oct - April 30 and every other month during the remaining dry season. The inspection results shall be used to identify the initial min. maintenance regiment required from site loading. 2. DRAINAGE FACILITIES MAINTENANCE The importance of maintenance for the proper functioning of stormwater control facilities cannot be over-emphasized. A substantial portion of failures (clogging of filters, resuspension of sediments, loss of storage capacity, etc.) are due to inadequate maintenance. Stormwater BMP maintenance is essential to ensure that BMPs function as intended throughout their full life cycle. The fundamental goals of maintenance activities are to ensure the entire flow regime and treatment train designed for this site continue to fully function. For this site these include: • Maintain designed stormwater detention capacity. • Maintain ability of storm facility to attenuate flow rates. • Maintain ability to safely convey design stormwater flows. • Maintain ability to treat stormwater runoff quality. • Preserve soil and plant health, as well as stormwater flow contact with plant and soil systems. • Clearly identify systems so they can be protected. • Keep maintenance costs low. • Prevent large-scale or expensive stormwater system failures. • Prevent water quality violations or damage to downstream properties. The intent of this section and manual is to pass on to the responsible parties all the information critical to understand the design of the system, risks and considerations for proper use, suggestions for maintenance frequencies, and cost so that realistic budgets can be established. The overall drainage control systems will require the same maintenance on a regular, annual basis in order to assure satisfactory performance throughout the year. Most maintenance should be performed during the early summer to identify existing or potential problems and allow repairs to be completed in time for the winter season. At the conclusion of the maintenance, an Inspection Report should be completed and stored with this Operation Manual as a record of maintenance activities. 3. RESPONSIBLE PARTIES The parties responsible for maintenance will be the property ownership as listed above. Sophie Jo Short Plat - Stormwater Facility Maintenance Program 4. FACILITIES REQUIRING MAINTENANCE Annual inspection of treatment and flow control system to be performed by a qualifying/certified 3rd party trained in proper inspection and maintenance of these systems. Annual inspection and maintenance reports to be provided to the City of Renton to review and confirm compliance. Specific instructions for particular drainage system feature maintenance is provided in Appendix I. The following drainage system features are included: Area Drains and Catch Basins – Area drains and catch basins serve two purposes on this site, collect surface runoff in special locations, and allow pipes to connect and change direction. Generally, they are low maintenance devices, but some minor attention to them is necessary. Conveyance Systems (Pipes, Ditches, Swales) - Conveyance systems are those features that allow collected water to move reliably and safely around the site. For this project, pipes are the main conveyance system. It should be obvious that any significant blockage can and will present problems. Though easy to do, period inspection and cleaning is necessary to keep water going to where it was intended on this site. Detention System - The detention system for this site consists of a below ground detention facility located under the parking lot. If there are any questions or additional information is desired, please contact the City of Renton. City of Renton Public Works 1055 South Grady Way Renton, Washington 98057 (206) 445-5924 5. MAINTENANCE INSTRUCTIONS The parties responsible for maintenance must review and apply the maintenance requirements contained herein. These maintenance instructions outline conditions for determining if maintenance actions are required, as identified through inspection. However, they are not intended to be a measure of the facility’s required condition between inspections. Exceedance of these conditions at any time between inspections or maintenance activity does not automatically constitute a violation of these standards. However, based upon inspection observations, the inspection and maintenance presented in the checklists shall be adjusted to minimize the length of time that a facility is in a condition that requires a maintenance action. For facilities not owned and maintained by the city, a Sophie Jo Short Plat - Stormwater Facility Maintenance Program log of maintenance activity that indicates what actions were taken must be kept on site and be available for inspection by the city. A brief discussion for each stormwater facility and BMP is provided below. Example Maintenance checklists for all stormwater facilities and BMPs are provided in Appendix I and II. Underground Detention (Checklist #1 & Appendix II) Catch Basins (Checklist #2) See Checklist #6 6. VEGETATION MAINTENANCE Vegetation shall be maintained at a minimum to prevent debris and material from entering the storm system. 7. POLLUTION SOURCE CONTROL MEASURES and MAINTENANCE GUIDANCE Pollution source controls are actions taken by a person or business to reduce the amount of pollution reaching surface and ground waters. Controls, also called “best management practices” (BMP’s), include: Altering the activity (e.g., substitute non-toxic products or recycle used oil) Enclosing or covering the activity (e.g., building a roof) Segregating the activity (e.g., diverting runoff away from an area that is contaminated) Routing runoff from the activity to a treatment alternative as allowed by the City (e.g., to a wastewater treatment facility, sanitary sewer, or stormwater treatment area). Pollution source controls are needed because of the contamination found in the runoff from commercial areas and the effects of this contamination on aquatic life and human health. Research on urban runoff in the Puget Sound area and elsewhere has found oil and grease, nutrients, organic substances, toxic metals, bacteria, viruses, and sediments at unacceptable levels. 8. ANNUAL COST OF MAINTENANCE It is estimated that annual maintenance of the storm drainage control systems around the site will be approximately $1,000 per year. Sophie Jo Short Plat - Stormwater Facility Maintenance Program APPENDIX I DRAINAGE SYSTEM MAINTENANCE GUIDE FORMS APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-6 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site 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 City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City 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. Excessive growth of grass/groundcover Grass or groundcover exceeds 18 inches in height. Grass or groundcover mowed to a height no greater than 6 inches. Tank or Vault Storage Area Trash and debris Any trash and debris accumulated in vault or tank (includes floatables and non- floatables). No trash or debris in vault. 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. Tank Structure 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. 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. Inlet/Outlet Pipes 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. Damaged inlet/outlet pipes 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. Access Manhole Cover/lid not in place Cover/lid is missing or only partially in place. Any open manhole requires immediate maintenance. Manhole access covered. CHECKLIST #1 APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-7 NO. 3 – DETENTION TANKS AND VAULTS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Access Manhole (cont.) 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. Ladder rungs unsafe Missing rungs, misalignment, rust, or cracks. Ladder meets design standards. Allows maintenance person safe access. Large access doors/plate 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 be opened as designed. Gaps, doesn't cover completely Large access doors not flat and/or access opening not completely covered. Doors close flat; 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. APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-8 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Trash and debris 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 1/3 the depth from the bottom of basin to invert the lowest pipe into or out of the basin. No trash or debris in the structure. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Sediment accumulation 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. Damage to frame and/or top slab 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. 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 in walls or bottom 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 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. 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. FROP-T Section Damaged FROP-T 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. CHECKLIST #2 APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-9 NO. 4 – CONTROL STRUCTURE/FLOW RESTRICTOR MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED FROP-T Section (cont.) Damaged FROP-T (cont.) 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. Any holes—other than designed holes—in the structure. Structure has no holes other than designed holes. Cleanout Gate Damaged or missing cleanout gate Cleanout gate is missing. Replace cleanout gate. 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. Orifice Plate Damaged or missing orifice plate Control device is not working properly due to missing, out of place, or bent orifice plate. Plate is in place and works as designed. Obstructions to orifice plate Any trash, debris, sediment, or vegetation blocking the plate. Plate is free of all obstructions and works as designed. Overflow Pipe Obstructions to overflow pipe Any trash or debris blocking (or having the potential of blocking) the overflow pipe. Pipe is free of all obstructions and works as designed. Deformed or damaged lip of overflow pipe Lip of overflow pipe is bent or deformed. Overflow pipe does not allow overflow at an elevation lower than design Inlet/Outlet Pipe 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. Damaged inlet/outlet pipe 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. Metal Grates (If applicable) 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. Damaged or missing grate Grate missing or broken member(s) of the grate. Grate is in place and meets design standards. Manhole Cover/Lid 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. 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 STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-10 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Structure Sediment accumulation 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 and debris 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. Deposits of garbage exceeding 1 cubic foot in volume. No condition present which would attract or support the breeding of insects or rodents. Damage to frame and/or top slab 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. 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 in walls or bottom 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 is structurally sound. 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. 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. Inlet/Outlet Pipe 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. CHECKLIST #3 APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-11 NO. 5 – CATCH BASINS AND MANHOLES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Inlet/Outlet Pipe (cont.) Damaged inlet/outlet pipe 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. Metal Grates (Catch Basins) 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. Damaged or missing grate Grate missing or broken member(s) of the grate. Any open structure requires urgent maintenance. Grate is in place and meets design standards. Manhole Cover/Lid 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. 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 STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-12 NO. 6 – CONVEYANCE PIPES AND DITCHES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Pipes Sediment & debris accumulation Accumulated sediment or debris that exceeds 20% of the diameter of the pipe. Water flows freely through pipes. Vegetation/root growth in pipe 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. Damaged pipes 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. Ditches 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 City personnel or the public. Noxious and nuisance vegetation removed according to applicable regulations. No danger of noxious vegetation where City 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. Excessive vegetation growth 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. 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. CHECKLIST #4 APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-18 NO. 12 – ACCESS ROADS MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITION WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Site Trash and debris 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. 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. Blocked roadway Any obstruction which reduces clearance above road surface to less than 14 feet. Roadway overhead clear to 14 feet high. 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. Road Surface Erosion, settlement, potholes, soft spots, ruts Any surface defect which hinders or prevents maintenance access. Road drivable by maintenance vehicles. Vegetation on road surface Trees or other vegetation prevent access to facility by maintenance vehicles. Maintenance vehicles can access facility. Shoulders and Ditches 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. 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. Modular Grid Pavement 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. Damaged or missing blocks/grids Access surface compacted because of broken on missing modular block. Access road surface restored so road infiltrates. CHECKLIST #5 APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 2022 City of Renton Surface Water Design Manual 6/22/2022 A-47 NO. 38 – SOIL AMENDMENT BMP MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Soil Media Unhealthy vegetation Vegetation not fully covering ground surface or vegetation health is poor. Yellowing: possible Nitrogen (N) deficiency. Poor growth: possible Phosphorous (P) deficiency. Poor flowering, spotting or curled leaves, or weak roots or stems: possible Potassium (K) deficiency. Plants are healthy and appropriate for site conditions Inadequate soil nutrients and structure In the fall, return leaf fall and shredded woody materials from the landscape to the site when possible Soil providing plant nutrients and structure Excessive vegetation growth Grass becomes excessively tall (greater than 10 inches); nuisance weeds and other vegetation start to take over. Healthy turf- “grasscycle” (mulch-mow or leave the clippings) to build turf health Weeds Preventive maintenance Avoid use of pesticides (bug and weed killers), like “weed & feed,” which damage the soil Fertilizer needed Where fertilization is needed (mainly turf and annual flower beds), a moderate fertilization program should be used which relies on compost, natural fertilizers or slow-release synthetic balanced fertilizers Integrated Pest Management (IPM) protocols for fertilization followed Bare spots Bare spots on soil No bare spots, area covered with vegetation or mulch mixed into the underlying soil. Compaction Poor infiltration due to soil compaction  To remediate compaction, aerate soil, till to at least 8-inch depth, or further amend soil with compost and re-till  If areas are turf, aerate compacted areas and top dress them with 1/4 to 1/2 inch of compost to renovate them  If drainage is still slow, consider investigating alternative causes (e.g., high wet season groundwater levels, low permeability soils)  Also consider site use and protection from compacting activities No soil compaction Poor infiltration Soils become waterlogged, do not appear to be infiltrating. Facility infiltrating properly Erosion/Scouring Erosion Areas of potential erosion are visible Causes of erosion (e.g., concentrate flow entering area, channelization of runoff) identified and damaged area stabilized (regrade, rock, vegetation, erosion control matting).For deep channels or cuts (over 3 inches in ponding depth), temporary erosion control measures in place until permanent repairs can be made Grass/Vegetation Unhealthy vegetation Less than 75% of planted vegetation is healthy with a generally good appearance. Healthy vegetation. Unhealthy plants removed/replaced. Appropriate vegetation planted in terms of exposure, soil and soil moisture. Noxious Weeds Noxious weeds Listed noxious vegetation is present (refer to current County noxious weed list). No noxious weeds present. CHECKLIST #6 APPENDIX A MAINTENANCE REQUIREMENTS FOR STORMWATER FACILITIES AND ON-SITE BMPS 6/22/2022 2022 City of Renton Surface Water Design Manual A-48 NO. 39 – RETAINED TREES MAINTENANCE COMPONENT DEFECT OR PROBLEM CONDITIONS WHEN MAINTENANCE IS NEEDED RESULTS EXPECTED WHEN MAINTENANCE IS PERFORMED Tree Dead or declining Dead, damaged, or declining Tree replaced per planting plan or acceptable substitute CHECKLIST #7 Sophie Jo Short Plat - Stormwater Facility Maintenance Program APPENDIX II MANUFACTURER MAINTENANCE GUIDE FORMS www.wavin.usOverview of Maintenance1 Overview of Maintenance Wavin AquaCell www.wavin.usOverview of Maintenance2 for AquaCell SystemOverview of Maintenance The Wavin AquaCell is an innovative stormwater management system designed for the efficient collection, retention, and infiltration of rainwater. It consists of modular cells that can be configured to meet various project requirements, providing a flexible and sustainable solution for managing stormwater runoff. Maintenance of the Wavin AquaCell is essential to ensure its efficient and reliable operation. Regular maintenance involves cleaning the system to remove debris, sediment, and other obstructions that can cause blockages and reduce the system’s capacity. This process helps prevent flooding, minimizes environmental impact, and extends the lifespan of the infrastructure. By conducting routine inspections and cleaning, potential issues can be identified and addressed before they escalate into major problems, ensuring the Wavin AquaCell system continues to protect communities and properties from stormwater-related damage. A. Preparation & Planning 1. Inspect the AQUACELL system a. Conduct a preliminary inspection to identify areas that require cleaning and assess the condition of the system. 2. Gather Necessary Equipment a. Ensure you have all the necessary equipment, including a high-pressure water jet, vacuum truck, personal protective equipment (PPE), gas detector, and communication devices. 3. Safety Protocols a. Establish safety protocols, including confined space entry procedures, traffic control measures, and emergency response plans. B. Safety Measures 1. PPE a. Equip all workers with appropriate PPE, including hard hats, gloves, safety goggles, respirators, and protective clothing. 2. Gas Detection a. Use gas detectors to check for hazardous gases like methane, hydrogen sulfide, and carbon monoxide in the system before entry. 3. Ventilation a. Ensure proper ventilation to prevent the accumulation of hazardous gases. 4. Confined Space Entry a. Follow confined space entry procedures, including having a trained attendant and using a harness and lifeline for the worker entering the space. C. System Isolation 1. Isolate the Area 2. Block off the section of the stormwater system being cleaned to prevent water from entering during the cleaning process. 3. Notify Relevant Parties a. Inform local authorities, businesses, and residents about the cleaning operation and potential disruptions. www.wavin.usOverview of Maintenance3 D. Debris Removal 1. Access the AQUACELL through 10” Ø ventilation / inspection ports located directly above the system. 2. Initial Debris Removal a. Use manual tools or mechanical equipment to remove large debris and objects that may obstruct the cleaning process. 3. High-Pressure Water Jetting a. Use a high-pressure water jet to dislodge sediment, silt, and smaller debris from the walls and floor of the system. E. Vacuum Extraction 1. Vacuum Truck a. Use a vacuum truck to suck out the dislodged debris and water from the system. Ensure the vacuum hose reaches all areas of the section being cleaned. 2. Repeat Process a. Repeat the jetting and vacuuming process until the section is thoroughly cleaned. F. Inspection and Verification 1. Inspect Cleaned Sections a. Conduct a post-cleaning inspection to verify that all debris has been removed and the system is functioning properly. 2. CCTV Inspection a. Use a CCTV camera to inspect the interior of the system for any remaining debris, blockages, or structural issues. G. Final Steps 1. Dispose of Waste a. Properly dispose of the collected debris and wastewater according to local regulations and environmental guidelines. 2. Document the Process a. Record the cleaning process, including areas cleaned, equipment used, and any issues encountered. 3. Reopen System a. Remove isolation measures and restore the AQUACELL system to normal operation. H. Regular Maintenance 1. Schedule Regular Cleanings a. Establish a regular maintenance schedule based on the system’s usage and local conditions to prevent future blockages and ensure efficient operation. 2. Monitor System Performance a. Continuously monitor the system’s performance and address any issues promptly to maintain its effectiveness. www.wavin.usOverview of Maintenance4 D1 E1 4.4 in 4.4 in 4.4 in 4.4 in 4.4 in4.4 in 4.4 in 4.4 in 4.4 in 0.7 in 0.7 in 0.7 in 0.7 in 0.7 in 0.7 in 0.7 in 0.7 in9.4 in 5.8 in 9.4" open entry through top adapter and 5.8" width of inner channelsbetween columns allow for clear access into interior of AQUACELL tank 16.7 in 12.1 in Wavin 950 Winter Street, South Entrance 1st Floor, Waltham, MA 02451 (US) | 5700 Côte de Liesse, Montréal, QC H4T 1B1 (CAN) © 2024 Wavin Wavin reserves the right to make alterations without prior notice. Due to continuous product development, changes in technical specifications may change. Installation & maintenance must comply with the installation. Wavin operates a program of continuous product development, and therefore reserves the right to modify or amend the specification of their products without notice. All information in this publication is given in good faith and believed to be correct at the time of going to press. However, no responsibility can be accepted for any errors, omissions, or incorrect assumptions.