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2020.0266.SP0002 RPT SWPPP Tahoma Terra 09-01-2020 PRELIMINARY Stormwater Pollution Prevention Plan (SWPPP) TAHOMA TERRA PHASE II, DIVISION III Project # 10182000024 September 1, 2020 Prepared by: Ben Enfield, PE Frances Constantino Consulting Engineers 612 Woodland Square Loop SE, Suite 100 Lacey, WA 98503 (360) 292-7230 (360) 292-7231 FAX Construction Stormwater General Permit (CSWGP) Stormwater Pollution Prevention Plan (SWPPP) for Tahoma Terra Phase II, Division III Prepared for: Department of Ecology Northwest Regional Office Permittee / Owner Developer Operator / Contractor Tahoma Terra Holding, LLC Tahoma Terra Holding, LLC TBD Certified Erosion and Sediment Control Lead (CESCL) Name Organization Contact Phone Number TBD - - SWPPP Prepared By Name Organization Contact Phone Number Frances Constantino KPFF Consulting Engineers (360) 292-7230 SWPPP Preparation Date 9/1/2020 Project Construction Dates Activity / Phase Start Date End Date Site Improvements TBD TBD TABLE OF CONTENTS Project Information __________________________________________________ 1 Existing Conditions __________________________________________________ 1 Proposed Construction Activities _______________________________________ 2 Construction Stormwater Best Management Practices (BMPs) ______________ 3 The 13 Elements ____________________________________________________ 3 Element 1: Preserve Vegetation/Mark Clearing Limits _____________________ 3 Element 2: Establish Construction Access ______________________________ 4 Element 3: Control Flow Rates ______________________________________ 5 Element 4: Install Sediment Controls __________________________________ 6 Element 5: Stabilize Soils ___________________________________________ 7 Element 6: Protect Slopes __________________________________________ 8 Element 7: Protect Drain Inlets ______________________________________ 9 Element 8: Stabilize Channels and Outlets ____________________________ 10 Element 9: Control Pollutants _______________________________________ 11 Element 10: Control Dewatering ____________________________________ 14 Element 11: Maintain BMPs ________________________________________ 15 Element 12: Manage the Project ____________________________________ 16 Element 13: Protect Low Impact Development _________________________ 19 Pollution Prevention Team ___________________________________________ 20 Monitoring and Sampling Requirements ________________________________ 21 Site Inspection ____________________________________________________ 21 Stormwater Quality Sampling _________________________________________ 21 Turbidity Sampling _______________________________________________ 21 pH Sampling ____________________________________________________ 23 Discharges to 303 (d) or Total Maximum Daily Load (TMDL) Waterbodies_____ 24 303 (d) Listed Waterbodies __________________________________________ 24 TMDL Waterbodies ________________________________________________ 24 Reporting and Record Keeping ________________________________________ 25 Record Keeping ___________________________________________________ 25 Site Log Book ___________________________________________________ 25 Records Retention _______________________________________________ 25 Updating the SWPPP _____________________________________________ 25 Reporting ________________________________________________________ 26 Discharge Monitoring Reports ______________________________________ 26 Notification of Noncompliance ______________________________________ 26 List of Tables Table 1 _____________________________________________________________ 1 Table 2 ____________________________________________________________ 11 Table 3 ____________________________________________________________ 12 Table 4 ____________________________________________________________ 14 Table 5 ____________________________________________________________ 16 Table 6 ____________________________________________________________ 17 Table 7 ____________________________________________________________ 20 Table 8 ____________________________________________________________ 21 Table 9 ____________________________________________________________ 23 List of Appendices A. Site Map B. BMP Details C. Correspondence D. Site Inspection Form E. Construction Stormwater General Permit (CSWGP) 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 1 Project Information (1.0) Project/Site Name: Tahoma Terra - Phase II, Division III Street/Location: Tahoma Blvd. SE City: Yelm State: WA Zip code: 98597 Subdivision: n/a Receiving waterbody: Groundwater Existing Conditions (1.1) Total acreage: 46.6 acres Disturbed acreage: 46.6 acres Existing structures: Existing Storm Drainage Pipe Land cover: The project site mainly consists of natural vegetation with two existing infiltration ponds in the center of the site. There are no existing impervious surfaces on site. Landscape topography: The project site generally slopes from six to sixty-six percent. The highest point of the site is located approximately 50 ft. east of nearest existing pond at an elevation of 406 feet. The lowest existing elevation on the property is located on the east property line at approximately 329 feet. Drainage patterns: An existing storm pipe system was installed in a previous development in which the main pipes run along Tahoma Boulevard and heads south into nearest existing pond. The majority of stormwater runoff follows the existing topography and generally sheet flows into the existing infiltration ponds located in the center of site. Runoff currently infiltrates on-site and sheet flows off-site along the south and east property lines of the project site. Existing Vegetation: The site was cleared in 2007. Current vegetation consists of bushes, grass, and small trees throughout project site. Critical Areas (wetlands, streams, flood zone and high erosion risk): The site lies within a critical aquifer recharge area and a portion of the site is located within a wellhead protection area. There are also nearby streams, wetland areas, and floodplain adjacent to the site per FEMA Flood Zone A as shown on FIRM Panel 53067C0335E. Table 1 includes a list of suspected and/or known contaminants associated with the construction activity. Table 1 – Summary of Site Pollutant Constituents Constituent (Pollutant) Location Depth Concentration None - - - 2 Proposed Construction Activities (1.2) Description of site development: The proposed project will be a residential development with 234 lots and 4 apartment buildings. Description of construction activities: TESC installation, site grading, trenching & installation for underground utilities (sanitary sewer, water, stormwater, underground vaults), building construction. Description of site drainage including flow from and onto adjacent properties. Must be consistent with Site Map in Appendix A: Proposed grading of the project site consists of creating a relatively flat developable site. Infiltration ponds and wetponds will treat and infiltrate more than half of the on-site stormwater runoff. Runoff from the proposed parking lot, driveway, and roof areas will be conveyed to nearest pond via pipes. Runoff not infiltrated into the soil will be conveyed into the proposed main storm system. Description of final stabilization: Final stabilization will consist of landscaping and paving. Contaminated Site Information: Proposed activities regarding contaminated soils or groundwater (example: on-site treatment system, authorized sanitary sewer discharge): None known or suspected. 3 Construction Stormwater Best Management Practices (BMPs) (2.0) 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. The 13 Elements (2.1) Element 1: Preserve Vegetation / Mark Clearing Limits (2.1.1) To protect adjacent properties and to reduce the area of soil exposed to construction, the limits of construction will be clearly marked before land-disturbing activities begin. Trees that are to be preserved, as well as sensitive areas and their buffers, shall be clearly delineated, both in the field and on the plans. In general, natural vegetation and native topsoil shall be retained in an undisturbed state to the maximum extent possible. List and describe BMPs: BMP C101: Preserving Natural Vegetation BMP C102: Buffer Zones BMP C233: Silt Fence Installation Schedules: Prior to land disturbing activities and as needed. Inspection and Maintenance plan: Per BMP Maintenance Standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed prior to land disturbing activities. Once installed, the CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. The CESCL may also suggest the installation of additional BMPs not listed above. Responsible Staff: Contractor provided CESCL. 4 Element 2: Establish Construction Access (2.1.2) Two stabilized construction entrances will be provided off Tahoma Boulevard SE. Construction access or activities occurring on unpaved areas shall be minimized, yet where necessary, access points shall be stabilized to minimize the tracking of sediment onto public roads, and wheel washing, street sweeping, and street cleaning shall be employed to prevent sediment from entering State waters. All wash wastewater shall be controlled on-site. List and describe BMPs: BMP C105: Stabilized Construction Access BMP C106: Wheel Wash BMP C107: Construction Road/Parking Area Stabilization Construction road/parking area stabilization shall be implemented to keep the existing on-site roads clean. Installation Schedules: Prior to land disturbing activities. Inspection and Maintenance plan: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed prior to land disturbing activities. Once installed, the CESCL must inspect the construction entrance for silt and soil build up and also look for any soil washout on to hard surfaces. If soil washout is present, the CESCL must take appropriate actions to alleviate the problem. Responsible Staff: Contractor provided CESCL. 5 Element 3: Control Flow Rates (2.1.3) In order to protect the properties and waterways downstream of the project site, stormwater from the site will be controlled by two existing infiltration ponds on site. V-ditches with rock check dams will be installed to direct stormwater flow towards the infiltration ponds. Silt fence will also be installed around the downstream project perimeter to prevent sediment laden runoff from leaving the project site. 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: BMP C241: Sediment Pond (Temporary) BMP C207: Check Dams Installation Schedules: Prior to land disturbing activities and as needed. Inspection and Maintenance Plan: Per BMP maintenance standards sediment levels shall be monitored and sediment shall be removed to ensure proper performance of the check dams and sediment ponds. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed prior to land disturbing activities. Once installed, the CESCL must inspect the construction entrance for silt and soil build up and also look for any soil washout on to hard surfaces. If the above listed BMPs are inadequate at controlling flowrates, the CESCL must take appropriate actions to alleviate the problem Responsible Staff: Contractor provided CESCL 6 Element 4: Install Sediment Controls (2.1.4) All stormwater runoff from disturbed areas shall pass through an appropriate sediment removal BMP before leaving the construction site, or prior to being discharged to an infiltration facility. In addition, sediment will be removed from paved areas, in and adjacent to construction work areas manually or using mechanical sweepers, as needed, to minimize tracking of sediments on vehicle tires away from the site and to minimize wash off of sediments from adjacent streets in runoff. List and describe BMPs: BMP C220: Storm Drain Inlet Protection BMP C233: Silt Fence Installation Schedules: Prior to land disturbing activities and as needed. Inspection and Maintenance Plan: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed. Once installed, the CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. The CESCL may also suggest the installation of additional BMPs not listed above. Responsible Staff: Contractor provided CESCL 7 Element 5: Stabilize Soils (2.1.5) Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. All stockpiled soils shall be stabilized from erosion, protected with sediment trapping measures, and where possible, be located away from storm drain inlets, waterways, and drainage channels. West of the Cascade Mountains Crest Season Dates Number of Days Soils Can be Left Exposed During the Dry Season May 1 – September 30 7 days During the Wet Season October 1 – April 30 2 days Soils must be stabilized at the end of the shift before a holiday or weekend if needed based on the weather forecast. Anticipated project dates: Start date: Spring 2021 End date: Summer 2024 Will you construct during the wet season? ☒Yes ☐No Exposed and unworked soils shall be stabilized with the application of effective BMPs to prevent erosion throughout the life of the project. List and describe BMPs: BMP C140: Dust Control BMP C120: Temporary and Permanent Seeding Installation Schedules: As needed. Inspection and Maintenance Plan: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed. Once installed, the CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. The CESCL may also suggest the installation of additional BMPs not listed above. Responsible Staff: Contractor provided CESCL 8 Element 6: Protect Slopes (2.1.6) All cut and fill slopes will be designed, constructed, and protected in a manner than minimizes erosion. Scouring will be reduced by using v-ditches with rock check dams to convey stormwater to the sediment pond on-site. Will steep slopes be present at the site during construction? ☒Yes ☐No BMP C207: Check Dams Installation Schedules: Prior to grading that directs runoff toward slopes. Inspection and Maintenance Plan: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed. Once installed, the CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. The CESCL may also suggest the installation of additional BMPs not listed above. Responsible Staff: Contractor provided CESCL 9 Element 7: Protect Drain Inlets (2.1.7) All storm drain inlets and culverts made operable during construction shall be protected to prevent unfiltered or untreated water from entering the drainage conveyance system. However, the first priority is to keep all access roads clean of sediment, and keep street wash water separate from entering storm drains until treatment can be provided. Storm Drain Inlet Protection (BMP C220) will be implemented for all drainage inlets and culverts that could potentially be impacted by sediment-laden runoff on and near the project site. List and describe BMPs: BMP C220: Storm Drain Inlet Protection Installation Schedules: Prior to land disturbing activities. Inspection and Maintenance Plan: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed. Once installed, the CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. Storm drain inlet protection should be regularly emptied and cleans to maximize effectiveness. Responsible Staff: Contractor provided CESCL 10 Element 8: Stabilize Channels and Outlets (2.1.8) For construction stormwater conveyance, v-ditches with rock check dams will be installed to stabilize channels. 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. Where site runoff is to be conveyed in channels, or discharged to a stream or some other natural drainage point, efforts will be taken to prevent downstream erosion List and describe BMPs: BMP C207: Check Dams Installation Schedules: Prior to grading that directs runoff toward slopes. Inspection and Maintenance Plan: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed. Once installed, the CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. The CESCL may also suggest the installation of additional BMPs not listed above. Responsible Staff: Contractor provided CESCL 11 Element 9: Control Pollutants (2.1.9) The following pollutants are anticipated to be present on-site: Table 2 – Pollutants Pollutant (and source, if applicable) Petroleum products for construction equipment Asphalt and concrete for site improvements etc. All pollutants, including waste materials and demolition debris, that occur on-site 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. List and describe BMPs: BMP C151: Concrete Handling BMP C153: Material Delivery, Storage and Containment BMPC154: Concrete Washout Area BMP C251: Construction Stormwater Filtration Volume IV – Source Control BMPs S407 BMPs for Dust Control at Disturbed Land Areas and Unpaved Roadways and Parking Lots S411 BMPs for Landscaping and Lawn/Vegetation Management S412 BMPs for Loading and Unloading Areas for Liquid and Solid Material S414 BMPs for Maintenance and Repair of Vehicles and Equipment S417 BMPs for Maintenance of Stormwater Drainage and Treatment Systems S419 BMPs for Mobile Fueling of Vehicles and Heavy Equipment S421 BMPs for Parking and Storage of Vehicles and Equipment S426 BMPs for Spills of Oil and Hazardous Materials Installation Schedules: As needed. Inspection and Maintenance Plan: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed. Once installed, the CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. The CESCL may also suggest the installation of additional BMPs not listed above. Responsible Staff: Contractor provided CESCL. 12 Will maintenance, fueling, and/or repair of heavy equipment and vehicles occur on-site? ☒Yes ☐No List and describe BMPs: S412 BMPs for Loading and Unloading Areas for Liquid and Solid Material S414 BMPs for Maintenance and Repair of Vehicles and Equipment S419 BMPs for Mobile Fueling of Vehicles and Heavy Equipment S426 BMPs for Spills of Oil and Hazardous Materials Installation Schedules: As needed. Inspection and Maintenance Plan: As needed Responsible Staff: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed. Once installed, the CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. The CESCL may also suggest the installation of additional BMPs not listed above. 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 X 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 X Concrete pumping and mixer washout waters Recycled concrete Other (i.e. calcium lignosulfate) [please describe] List and describe BMPs: BMP C252: Treating and Disposing of High pH Water Installation Schedules: Inspection and Maintenance Plan: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed. Once installed, the 13 CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. The CESCL may also suggest the installation of additional BMPs not listed above. Responsible Staff: Contractor provided 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. 14 Element 10: Control Dewatering (2.1.10) Dewatering could potentially be necessary depending on field conditions. Groundwater was not encountered during geotechnical site explorations. It is not anticipated that any contaminants will be encountered during excavation or possible dewatering. Possible dewatering is to be discharged on-site via BMP C240: Temporary Sediment Trap or any CESCL approved on-site dispersion. Table 4 – Dewatering BMPs X 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: Installation Schedules: Prior to land disturbing activities and as needed. Inspection and Maintenance Plan: Per BMP maintenance standards. It is the CESCL’s responsibility to ensure that all necessary BMPs are adequately installed. Once installed, the CESCL must perform periodic inspections to ensure that all BMPs are functioning properly. The CESCL may also suggest the installation of additional BMPs not listed above. Responsible Staff: Contractor provided CESCL 15 Element 11: Maintain BMPs (2.1.11) 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. 16 Element 12: Manage the Project (2.1.12) 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 X Design the project to fit the existing topography, soils, and drainage patterns X Emphasize erosion control rather than sediment control X Minimize the extent and duration of the area exposed X Keep runoff velocities low X Retain sediment on-site X Thoroughly monitor site and maintain all ESC measures X Schedule major earthwork during the dry season Other (please describe) 17 Table 6 – BMP Implementation Schedule Phase of Construction Project Stormwater BMPs Date Wet/Dry Season TBD TBD TBD TBD 18 Phase of Construction Project Stormwater BMPs Date Wet/Dry Season TBD TBD TBD TBD 19 Element 13: Protect Low Impact Development (LID) BMPs (2.1.13). Infiltration ponds are proposed and amended soils will be utilized for landscape areas. Care should be taken to ensure heavy machinery does not compact areas for future infiltration in order to maintain the infiltration capacity of existing soils. Sediment should be removed from the bottom of the existing infiltration pond at the end of construction. 20 Pollution Prevention Team (3.0) Table 7 – Team Information Title Name(s) Phone Number Certified Erosion and Sediment Control Lead (CESCL) TBD Resident Engineer Ben Enfield (360) 292-7230 Emergency Ecology Contact Northwest Regional Office (425) 649-7000 Emergency Permittee/ Owner Contact TBD Non-Emergency Owner Contact TBD Monitoring Personnel TBD Ecology Regional Office Northwest Regional Office (425) 649-7000 21 Monitoring and Sampling Requirements (4.0) 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 Create your own Site Inspection Form or use the Construction Stormwater Site Inspection Form found on Ecology’s website. https://www.ecology.wa.gov/Regulations-Permits/Permits- certifications/Stormwater-general-permits/Construction-stormwater-permit Blank form under Appendix D. The site log book must be maintained on-site within reasonable access to the site and be made available upon request to Ecology or the local jurisdiction. Numeric effluent limits may be required for certain discharges to 303(d) listed waterbodies. See CSWGP Special Condition S8 and Section 5 of this template. Site Inspection (4.1) 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) are indicated on the Site Map (see Appendix A) and in accordance with the applicable requirements of the CSWGP. Stormwater Quality Sampling (4.2) Turbidity Sampling (4.2.1) Requirements include calibrated turbidity meter or transparency tube to sample site discharges for compliance with the CSWGP. Sampling will be conducted at all discharge points at least once per calendar week. Method for sampling turbidity: Table 8 – Turbidity Sampling Method X Turbidity Meter/Turbidimeter (required for disturbances 5 acres or greater in size) Transparency Tube (option for disturbances less than 1 acre and up to 5 acres in size) The benchmark for turbidity value is 25 nephelometric turbidity units (NTU) and a transparency less than 33 centimeters. If the discharge’s turbidity is 26 to 249 NTU or the transparency is less than 33 cm but equal to or greater than 6 cm, the following steps will be conducted: 22 1. Review the SWPPP for compliance with Special Condition S9. Make appropriate revisions within 7 days of the date the discharge exceeded the benchmark. 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period. 3. Document BMP implementation and maintenance in the site log book. If the turbidity exceeds 250 NTU or the transparency is 6 cm or less at any time, the following steps will be conducted: 1. Telephone or submit an electronic report to the applicable Ecology Region’s Environmental Report Tracking System (ERTS) within 24 hours. https://www.ecology.wa.gov/About-us/Get-involved/Report-an-environmental-issue · Northwest Region (King, Kitsap, Island, San Juan, Skagit, Snohomish, Whatcom): (425) 649-7000 2. Immediately begin the process to fully implement and maintain appropriate source control and/or treatment BMPs as soon as possible. Address the problems within 10 days of the date the discharge exceeded the benchmark. If installation of necessary treatment BMPs is not feasible within 10 days, Ecology may approve additional time when the Permittee requests an extension within the initial 10-day response period 3. Document BMP implementation and maintenance in the site log book. 4. Continue to sample discharges daily until one of the following is true: · Turbidity is 25 NTU (or lower). · Transparency is 33 cm (or greater). · Compliance with the water quality limit for turbidity is achieved. o 1 - 5 NTU over background turbidity, if background is less than 50 NTU o 1% - 10% over background turbidity, if background is 50 NTU or greater · The discharge stops or is eliminated. 23 pH Sampling (4.2.2) pH monitoring is required for “Significant concrete work” (i.e. greater than 1000 cubic yards poured concrete or recycled concrete over the life of the project).The use of engineered soils (soil amendments including but not limited to Portland cement-treated base [CTB], cement kiln dust [CKD] or fly ash) also requires pH monitoring. For significant concrete work, pH sampling will start the first day concrete is poured and continue until it is cured, typically three (3) weeks after the last pour. For engineered soils and recycled concrete, pH sampling begins when engineered soils or recycled concrete are first exposed to precipitation and continues until the area is fully stabilized. If the measured pH is 8.5 or greater, the following measures will be taken: 1. Prevent high pH water from entering storm sewer systems or surface water. 2. Adjust or neutralize the high pH water to the range of 6.5 to 8.5 su using appropriate technology such as carbon dioxide (CO2) sparging (liquid or dry ice). 3. Written approval will be obtained from Ecology prior to the use of chemical treatment other than CO2 sparging or dry ice. Method for sampling pH: Table 9 – pH Sampling Method pH meter X pH test kit Wide range pH indicator paper 24 Discharges to 303(d) or Total Maximum Daily Load (TMDL) Waterbodies (5.0) 303(d) Listed Waterbodies (5.1) Is the receiving water 303(d) (Category 5) listed for turbidity, fine sediment, phosphorus, or pH? ☐Yes ☒No TMDL Waterbodies (5.2) Waste Load Allocation for CWSGP discharges: N/A Discharges to TMDL receiving waterbodies will meet in-stream water quality criteria at the point of discharge. 25 Reporting and Record Keeping (6.0) Record Keeping (6.1) Site Log Book (6.1.1) 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 Records Retention (6.1.2) Records will be retained during the life of the project and for a minimum of three (3) years following the termination of permit coverage in accordance with Special Condition S5.C of the CSWGP. Permit documentation to be retained on-site: · CSWGP · Permit Coverage Letter · SWPPP · Site Log Book Permit documentation will be provided within 14 days of receipt of a written request from Ecology. A copy of the SWPPP or access to the SWPPP will be provided to the public when requested in writing in accordance with Special Condition S5.G.2.b of the CSWGP. Updating the SWPPP (6.1.3) 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. 26 Reporting (6.2) Discharge Monitoring Reports (6.2.1) 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. To sign up for WQWebDMR go to: https://www.ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Water-quality- permits-guidance/WQWebPortal-guidance Notification of Noncompliance (6.2.2) 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 numbers listed below). 2. Immediate action will be taken to prevent the discharge/pollution or otherwise stop or correct the noncompliance. If applicable, sampling and analysis of any noncompliance will be repeated immediately and the results submitted to Ecology within five (5) days of becoming aware of the violation. 3. A detailed written report describing the noncompliance will be submitted to Ecology within five (5) days, unless requested earlier by Ecology. Specific information to be included in the noncompliance report is found in Special Condition S5.F.3 of the CSWGP. 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. · Northwest Region at (425) 649-7000 for Island, King, Kitsap, San Juan, Skagit, Snohomish, or Whatcom County 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. APPENDIX A Site Map CALL UNDERGROUND LOCATE TWO (2) WORKING DAYS BEFORE YOU DIG 811 SECTION 23, TOWNSHIP 17 NORTH, RANGE 1 EAST, W.M.THURSTON COUNTY, WASHINGTONTAHOMA TERRA PHASE III 612 Woodland Square Loop, Suite 100 Lacey, WA 98503 360.292.7230 www.kpff.com LEGENDTAHOMA BOULEVARDSWPPP SITE PLAN1NOTE:ABWETLANDCLEGAL DESCRIPTION:FINE SANDY LOAMEVERETT VERYGRAVELLY SANDY LOAMTISCH SILT LOAMFEMA FLOOD ZONEBOUNDARYD CALL UNDERGROUND LOCATE TWO (2) WORKING DAYS BEFORE YOU DIG 811 SECTION 23, TOWNSHIP 17 NORTH, RANGE 1 EAST, W.M.THURSTON COUNTY, WASHINGTONTAHOMA TERRA PHASE III 612 Woodland Square Loop, Suite 100 Lacey, WA 98503 360.292.7230 www.kpff.com STANDARD EROSION CONTROL NOTES:SILT FENCES:SIDE VIEWFRONT VIEWSILT FENCEANOTES:INLET SEDIMENT PROTECTIONBSITE MAP NOTES & DETAILS2 CONSTRUCTION ENTRANCECCONSTRUCTION ENTRANCE NOTES:SPACING BETWEEN CHECK DAMSSECTION A - ANOTE:AAVIEW LOOKING UPSTREAMDROCK CHECK DAMMAINTENANCE STANDARDS: APPENDIX B BMP Detail BMP C101: Preserving Natural Vegetation Purpose The purpose of preserving natural vegetation is to reduce erosion wherever practicable. Limiting site  disturbance is the single most effective method for reducing erosion. For example, conifers can hold  up to about 50 percent of all rain that falls during a storm. Up to 20-30 percent of this rain may never  reach the ground but is taken up by the tree or evaporates. Another benefit is that the rain held in the  tree can be released slowly to the ground after the storm. Conditions of Use Natural vegetation should be preserved on steep slopes, near perennial and intermittent water- courses or swales, and on building sites in wooded areas.  l As required by local governments.  l Phase construction to preserve natural vegetation on the project site for as long as possible  during the construction period. Design and Installation Specifications Natural vegetation can be preserved in natural clumps or as individual trees, shrubs and vines. The preservation of individual plants is more difficult because heavy equipment is generally used to  remove unwanted vegetation. The points to remember when attempting to save individual plants  are:  l Is the plant worth saving? Consider the location, species, size, age, vigor, and the work  involved. Local governments may also have ordinances to save natural vegetation and trees.  l Fence or clearly mark areas around trees that are to be saved. It is preferable to keep ground  disturbance away from the trees at least as far out as the dripline. Plants need protection from three kinds of injuries:  l Construction Equipment - This injury can be above or below the ground level. Damage results  from scarring, cutting of roots, and compaction of the soil. Placing a fenced buffer zone around  plants to be saved prior to construction can prevent construction equipment injuries.  l Grade Changes - Changing the natural ground level will alter grades, which affects the plant's  ability to obtain the necessary air, water, and minerals. Minor fills usually do not cause prob- lems although sensitivity between species does vary and should be checked. Trees can typ- ically tolerate fill of 6 inches or less. For shrubs and other plants, the fill should be less. When there are major changes in grade, it may become necessary to supply air to the roots of  plants. This can be done by placing a layer of gravel and a tile system over the roots before the  fill is made. The tile system should be laid out on the original grade leading from a dry well  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 271 around the tree trunk. The system should then be covered with small stones to allow  air to cir- culate over the root area. Lowering the natural ground level can seriously damage trees and shrubs. The highest per- centage of the plant roots are in the upper 12 inches of the soil and cuts of only 2-3 inches can  cause serious injury. To protect the roots it may be necessary to terrace the immediate area  around the plants to be saved. If roots are exposed, construction of retaining walls may be  needed to keep the soil in place. Plants can also be preserved by leaving them on an undis- turbed, gently sloping mound. To increase the chances for survival, it is best to limit grade  changes and other soil disturbances to areas outside the dripline of the plant.  l Excavations - Protect trees and other plants when excavating for drainfields, power, water,  and sewer lines. Where possible, the trenches should be routed around trees and large  shrubs. When this is not possible, it is best to tunnel under them. This can be done with hand  tools or with power augers. If it is not possible to route the trench around plants to be saved,  then the following should be observed:  o Cut as few roots as possible. When you have to cut, cut clean. Paint cut root ends with a  wood dressing like asphalt base paint if roots will be exposed for more than 24-hours.  o Backfill the trench as soon as possible.  o Tunnel beneath root systems as close to the center of the main trunk to preserve most  of the important feeder roots. Some problems that can be encountered with a few  specific trees are:  l Maple, Dogwood, Red alder, Western hemlock, Western red cedar, and Douglas fir do not  readily adjust to changes in environment and special care should be taken to protect these  trees.  l The windthrow hazard of Pacific silver fir and madrona is high, while that of Western hemlock  is moderate. The danger of windthrow increases where dense stands have been thinned.  Other species (unless they are on shallow, wet soils less than 20 inches deep) have a low   windthrow hazard.  l Cottonwoods, maples, and willows have water-seeking roots. These can cause trouble in  sewer lines and infiltration fields. On the other hand, they thrive in high moisture conditions  that other trees would not.  l Thinning operations in pure or mixed stands of Grand fir, Pacific silver fir, Noble fir, Sitka  spruce, Western red cedar, Western hemlock, Pacific dogwood, and Red alder can cause ser- ious disease problems. Disease can become established through damaged limbs, trunks,  roots, and freshly cut stumps. Diseased and weakened trees are also susceptible to insect  attack. Maintenance Standards Inspect flagged and/or fenced areas regularly to make sure flagging or fencing has not been  removed or damaged. If the flagging or fencing has been damaged or visibility reduced, it shall be  repaired or replaced immediately and visibility restored. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 272 If tree roots have been exposed or injured, “prune” cleanly with an appropriate pruning saw or lop- pers directly above the damaged roots and recover with native soils. Treatment of sap flowing trees  (fir, hemlock, pine, soft maples) is not advised as sap forms a natural healing barrier. BMP C102: Buffer Zones Purpose Creation of an undisturbed area or strip of natural vegetation or an established suitable planting that  will provide a living filter to reduce soil erosion and stormwater runoff velocities. Conditions of Use Buffer zones are used along streams, wetlands and other bodies of water that need protection from  erosion and sedimentation. Contractors can use vegetative buffer zone BMPs to protect natural  swales and they can incorporate them into the natural landscaping of an area. Do not use critical-areas buffer zones as sediment treatment areas. These areas shall remain com- pletely undisturbed. The local permitting authority may expand the buffer widths temporarily to allow  the use of the expanded area for removal of sediment. The types of buffer zones can change the level of protection required as shown below: Designated Critical Area Buffers - buffers that protect Critical Areas, as defined by the Washington  State Growth Management Act, and are established and managed by the local permitting authority.  These should not be disturbed and must protected with sediment control BMPs to prevent impacts.  The local permitting authority may expand the buffer widths temporarily to allow the use of the expan- ded area for removal of sediment. Vegetative Buffer Zones - areas that may be identified in undisturbed vegetation areas or managed  vegetation areas that are outside any Designated Critical Area Buffer. They may be utilized to  provide an additional sediment control area and/or reduce runoff velocities. If being used for pre- servation of natural vegetation, they should be arranged in clumps or strips. They can be used to pro- tect natural swales and incorporated into the natural landscaping area. Design and Installation Specifications  l Preserving natural vegetation or plantings in clumps, blocks, or strips is generally the easiest  and most successful method.  l Leave all unstable steep slopes in natural vegetation.  l Mark clearing limits and keep all equipment and construction debris out of the natural areas  and buffer zones. Steel construction fencing is the most effective method to protect sensitive  areas and buffers. Alternatively, wire-backed silt fence on steel posts is marginally effective.  Flagging alone is typically not effective.  l Keep all excavations outside the dripline of trees and shrubs.  l Do not push debris or extra soil into the buffer zone area because it will cause damage by  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 273 burying and smothering vegetation.  l Vegetative buffer zones for streams, lakes or other waterways shall be established by the  local permitting authority or other state or federal permits or approvals. Maintenance Standards Inspect the area frequently to make sure flagging remains in place and the area remains undis- turbed. Replace all damaged flagging immediately. Remove all materials located in the buffer area  that may impede the ability of the vegetation to act as a filter. BMP C103: High-Visibility Fence Purpose High-visibility fencing is intended to:  l Restrict clearing to approved limits.  l Prevent disturbance of sensitive areas, their buffers, and other areas required to be left undis- turbed.  l Limit construction traffic to designated construction entrances, exits, or internal roads.  l Protect areas where marking with survey tape may not provide adequate protection. Conditions of Use To establish clearing limits plastic, fabric, or metal fence may be used:  l At the boundary of sensitive areas, their buffers, and other areas required to be left uncleared.  l As necessary to control vehicle access to and on the site. Design and Installation Specifications High-visibility plastic fence shall be composed of a high-density polyethylene material and shall be at  least four feet in height. Posts for the fencing shall be steel or wood and placed every 6 feet on center  (maximum) or as needed to ensure rigidity. The fencing shall be fastened to the post every six inches  with a polyethylene tie. On long continuous lengths of fencing, a tension wire or rope shall be used as  a top stringer to prevent sagging between posts. The fence color shall be high-visibility orange. The  fence tensile strength shall be 360 lbs/ft using the ASTM D4595 testing method. If appropriate install fabric silt fence in accordance with BMP C233:  Silt Fence to act as high-visibility  fence. Silt fence shall be at least 3 feet high and must be highly visible to meet the requirements of  this BMP. Metal fences shall be designed and installed according to the manufacturer's specifications. Metal fences shall be at least 3 feet high and must be highly visible. Fences shall not be wired or stapled to trees. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 274 Maintenance Standards If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and  visibility restored. 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 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 C207: Check Dams Purpose Construction of check dams across a swale or ditch reduces the velocity of concentrated flow and dis- sipates energy at the check dam. Conditions of Use Use check dams where temporary or permanent channels are not yet vegetated, channel lining is  infeasible, and/or velocity checks are required.  l Check dams may not be placed in streams unless approved by the State Department of Fish  and Wildlife.   l Check dams may not be placed in wetlands without approval from a permitting agency.  l Do not place check dams below the expected backwater from any salmonid bearing water  between October 1 and May 31 to ensure that there is no loss of high flow refuge habitat for  overwintering juvenile salmonids and emergent salmonid fry. Design and Installation Specifications  l Construct rock check dams from appropriately sized rock. The rock used must be large  enough to stay in place given the expected design flow  through the channel. The rock must be  placed by hand or by mechanical means (do not dump the rock to form the dam) to achieve  complete coverage of the ditch or swale and to ensure that the center of the dam is lower than  the edges.  l Check dams may also be constructed of either rock or pea-gravel filled bags. Numerous new  products are also available for this purpose. They tend to be re-usable, quick and easy to  install, effective, and cost efficient.  l Place check dams perpendicular to the flow of water.  l The check dam should form a triangle when viewed from the side. This prevents undercutting  as water flows over the face of the check dam rather than falling directly onto the ditch bottom.  l Before installing check dams, impound and bypass upstream water flow away from the work  area. Options for bypassing include pumps, siphons, or temporary channels.  l Check dams combined with sumps work more effectively at slowing flow  and retaining sed- iment than a check dam alone. A deep sump should be provided immediately upstream of the  check dam.  l In some cases, if carefully located and designed, check dams can remain as permanent install- ations with very minor regrading. They may be left as either spillways, in which case accu- mulated sediment would be graded and seeded, or as check dams to prevent further  sediment from leaving the site.  l The maximum spacing between check dams shall be such that the downstream toe of the  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 351 upstream dam is at the same elevation as the top of the downstream dam.  l Keep the maximum height at 2 feet at the center of the check dam.  l Keep the center of the check dam at least 12 inches lower than the outer edges at natural  ground elevation.  l Keep the side slopes of the check dam at 2H:1V or flatter.  l Key the stone into the ditch banks and extend it beyond the abutments a minimum of 18  inches to avoid washouts from overflow around the dam.  l Use filter fabric foundation under a rock or sand bag check dam. If a blanket ditch liner is used,  filter fabric is not necessary. A piece of organic or synthetic blanket cut to fit will also work for  this purpose.  l In the case of grass-lined ditches and swales, all check dams and accumulated sediment shall  be removed when the grass has matured sufficiently to protect the ditch or swale - unless the  slope of the swale is greater than 4 percent. The area beneath the check dams shall be  seeded and mulched immediately after dam removal.  l Ensure that channel appurtenances, such as culvert entrances below check dams, are not  subject to damage or blockage from displaced stones.   l See Figure II-3.16: Rock Check Dam. Maintenance Standards Check dams shall be monitored for performance and sediment accumulation during and after each  rainfall that produces runoff. Sediment shall be removed when it reaches one half the sump depth.  l Anticipate submergence and deposition above the check dam and erosion from high flows  around the edges of the dam.  l If significant erosion occurs between dams, install a protective riprap liner in that portion of the  channel. See BMP C202:  Riprap Channel Lining. 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 352 Figure II-3.16: Rock Check Dam 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 353 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 BMP C231: Brush Barrier Purpose The purpose of brush barriers is to reduce 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  l Brush barriers may be used downslope of disturbed areas that are less than one-quarter acre.  l Brush barriers are not intended to treat concentrated flows, nor are they intended to treat sub- stantial amounts of overland flow. Any concentrated flows must be directed to a sediment trap- ping BMP. The only circumstance in which overland flow can be treated solely by a brush  barrier, rather than by a sediment trapping BMP, is when the area draining to the barrier is  small.  l Brush barriers should only be installed on contours. Design and Installation Specifications  l Height: 2 feet (minimum) to 5 feet (maximum).  l Width: 5 feet at base (minimum) to 15 feet (maximum).  l Filter fabric (geotextile) may be anchored over the brush berm to enhance the filtration ability  of the barrier. Ten-ounce burlap is an adequate alternative to filter fabric. 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. BMP C234: Vegetated Strip Purpose Vegetated strips reduce the transport of coarse sediment from a construction site by providing a  physical barrier to sediment and reducing the runoff velocities of overland flow. Conditions of Use  l Vegetated strips may be used downslope of all disturbed areas.  l Vegetated strips are not intended to treat concentrated flows, nor are they intended to treat  substantial amounts of overland flow. Any concentrated flows must be conveyed through the  drainage system to BMP C241:  Sediment Pond (Temporary) or other sediment trapping  BMP. The only circumstance in which overland flow  can be treated solely by a vegetated strip,  rather than by a sediment trapping BMP, is when the following criteria are met (see Table II- 3.12: Contributing Drainage Area for Vegetated Strips): Average Contributing Area Slope Average Contributing Area Per- cent Slope Max Contributing area Flowpath Length 1.5H : 1V or flatter 67% or flatter 100 feet 2H : 1V or  flatter 50% or flatter 115 feet 4H : 1V or  flatter 25% or flatter 150  feet 6H : 1V or  flatter 16.7% or flatter 200  feet 10H  : 1V or  flatter 10% or flatter 250  feet Table II-3.12: Contributing Drainage Area for Vegetated Strips 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 376 BMP C241: Sediment Pond (Temporary) Purpose Sediment ponds are temporary ponds used during construction to remove sediment from runoff ori- ginating from disturbed areas of the project site. Sediment ponds are typically designed to remove  sediment no smaller than medium silt (0.02 mm). Consequently, they usually reduce turbidity only  slightly. Conditions of Use  l Use a sediment pond where the contributing drainage area to the pond is 3 acres or more.  Ponds must be used in conjunction with other Construction Stormwater BMPs to reduce the  amount of sediment flowing into the pond.  l Do not install sediment ponds on sites where failure of the BMP would result in loss of life,  damage to homes or buildings, or interruption of use or service of public roads or utilities. Also,  sediment ponds are attractive to children and can be dangerous. Compliance with local ordin- ances regarding health and safety must be addressed. If fencing of the pond is required, show  the type of fence and its location on the drawings in the Construction SWPPP.  l Sediment ponds that can impound 10 acre-ft (435,600 cu-ft, or 3.26 million gallons) or more,  or have an embankment of more than 6 feet, are subject to the Washington Dam Safety Regu- lations (Chapter 173-175 WAC). See BMP D.1: Detention Ponds for more information regard- ing dam safety considerations for detention ponds.  l Projects that are constructing permanent Flow  Control BMPs or Runoff Treatment BMPs that  use ponding for treatment may use the rough-graded or final-graded permanent BMP foot- print for the temporary sediment pond. When permanent BMP footprints are used as tem- porary sediment ponds, the surface area requirement of the temporary sediment pond must  be met. If the surface area requirement of the sediment pond is larger than the surface area of  the permanent BMP, then the sediment pond shall be enlarged beyond the permanent BMP  footprint to comply with the surface area requirement. The permanent control structure must be temporarily replaced with a control structure that  only allows water to leave the temporary sediment pond from the surface or by pumping.  Alternatively, the permanent control structure may used if it is temporarily modified by plug- ging any outlet holes below  the riser. The permanent control structure must be installed as  part of the permanent BMP after the site is fully stabilized. Design and Installation Specifications General  l See Figure II-3.28: Sediment Pond Plan View, Figure II-3.29: Sediment Pond Cross Section,  and Figure II-3.30: Sediment Pond Riser Detail for details.  l Use of permanent infiltration BMP footprints for temporary sediment ponds during  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 388 construction tends to clog the soils and reduce their capacity to infiltrate. If permanent infilt- ration BMP footprints are used, the sides and bottom of the temporary sediment pond must  only be rough excavated to a minimum of 2 feet above final grade of the permanent infiltration  BMP. Final grading of the permanent infiltration BMP shall occur only when all contributing  drainage areas are fully stabilized. Any proposed permanent pretreatment BMP prior to the  infiltration BMP should be fully constructed and used with the temporary sediment pond to  help prevent clogging of the soils. See Element 13: Protect Low  Impact Development BMPs  for more information about protecting permanent infiltration BMPs.  l The pond shall be divided into two roughly equal volume cells by a permeable divider that will  reduce turbulence while allowing movement of water between the cells. The divider shall be at  least one-half the height of the riser, and at least one foot below  the top of the riser. Wire- backed, 2- to 3-foot high, high strength geotextile fabric supported by treated 4"x4"s can be  used as a divider. Alternatively, staked straw bales wrapped with geotextile fabric may be  used. If the pond is more than 6 feet deep, a different divider design must be proposed. A  riprap embankment is one acceptable method of separation for deeper ponds. Other designs  that satisfy the intent of this provision are allowed as long as the divider is permeable, struc- turally sound, and designed to prevent erosion under and around the divider.  l The most common structural failure of sediment ponds is caused by piping. Piping refers to  two phenomena:  (1) water seeping through fine-grained soil, eroding the soil grain by grain  and forming pipes or tunnels; and, (2) water under pressure flowing upward through a gran- ular soil with a head of sufficient magnitude to cause soil grains to lose contact and capability  for support. The most critical construction practices to prevent piping are:  o Tight connections between the riser and outlet pipe, and other pipe connections.  o Adequate anchoring of the riser.  o Proper soil compaction of the embankment and riser footing.  o Proper construction of anti-seep devices. Sediment Pond Geometry To determine the sediment pond geometry, first calculate the design surface area (SA) of the pond,  measured at the top of the riser pipe. Use the following equation: SA  = 2 x Q2/0.00096  or 2080 square feet per cfs of inflow See BMP C240:  Sediment Trap for more information on the above equation. The basic geometry of the pond can now be determined using the following design criteria:  l Required surface area SA (from the equation above) at the top of the riser.  l Minimum 3.5-foot depth from the top of the riser to the bottom of the pond. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 389  l Maximum 3H:1V interior side slopes and maximum 2H:1V exterior slopes. The interior slopes  can be increased to a maximum of 2H:1V if fencing is provided at or above the maximum  water surface.  l One foot of freeboard between the top of the riser and the crest of the emergency spillway.  l Flat bottom.  l Minimum 1-foot deep spillway.  l Length-to-width ratio between 3:1 and 6:1. Sediment Pond Discharge The outlet for the pond consists of a combination of principal and emergency spillways. These out- lets must pass the peak runoff expected from the contributing drainage area for a 100-year storm. If,  due to site conditions and basin geometry, a separate emergency spillway is not feasible, the prin- cipal spillway must pass the entire peak runoff expected from the 100-year storm. However, an  attempt to provide a separate emergency spillway should always be made. Base the runoff cal- culations on the site conditions during construction. The flow through the dewatering orifice cannot  be utilized when calculating the 100-year storm elevation because of its potential to become  clogged; therefore, available spillway storage must begin at the principal spillway riser crest. The principal spillway designed by the procedures described below  will result in some reduction in  the peak rate of runoff. However, the design will not control the discharge flow rates to the extent  required to comply with I-3.4.7 MR7: Flow Control. The size of the contributing basin, the expected  life of the construction project, the anticipated downstream effects, and the anticipated weather con- ditions during construction should be considered to determine the need for additional discharge con- trol. Principal Spillway: Determine the required diameter for the principal spillway (riser pipe). The dia- meter shall be the minimum necessary to pass the peak volumetric flow  rate using a 15-minute time  step from a Type 1A, 10-year, 24-hour frequency storm for the developed condition. Use Figure II- 3.31: Riser Inflow Curves to determine the riser diameter. To aid in determining sediment depth, one-foot intervals shall be prominently marked on the riser. Emergency Overflow Spillway: Size the emergency overflow spillway for the peak volumetric flow  rate using a 10-minute time step from a Type 1A, 100-year, 24-hour frequency storm for the  developed condition. See BMP D.1: Detention Ponds for additional guidance for Emergency Over- flow  Spillway design Dewatering Orifice: Size of the dewatering orifice(s) (minimum 1-inch diameter) using a modified  version of the discharge equation for a vertical orifice and a basic equation for the area of a circular  orifice. Determine the required area of the orifice with the following equation: where  Ao = orifice area (square feet) 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 390 AS = pond surface area (square feet) h = head of water above orifice (height of riser in feet) T = dewatering time (24 hours) g = acceleration of gravity (32.2 feet/second2) Convert the orifice area (in square feet) to the orifice diameter D (in inches): The vertical, perforated tubing connected to the dewatering orifice must be at least 2 inches larger in  diameter than the orifice to improve flow  characteristics. The size and number of perforations in the  tubing should be large enough so that the tubing does not restrict flow. The orifice should control the  flow  rate.   2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 391 Figure II-3.28: Sediment Pond Plan View 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 392 Figure II-3.29: Sediment Pond Cross Section 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 393 Figure II-3.30: Sediment Pond Riser Detail 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 394 Figure II-3.31: Riser Inflow Curves 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 395 Maintenance Standards  l Remove sediment from the pond when it reaches 1 foot in depth.  l Repair any damage to the pond embankments or slopes. BMP C250: Construction Stormwater Chemical Treatment Purpose This BMP applies when using chemicals to treat turbidity in stormwater by either  batch or flow- through chemical treatment. Turbidity is difficult to control once fine particles are suspended in stormwater runoff from a con- struction site. BMP C241:  Sediment Pond (Temporary) is effective at removing larger particulate  matter by gravity settling, but is ineffective at removing smaller particulates such as clay and fine silt.  Traditional Construction Stormwater BMPs may not be adequate to ensure compliance with the  water quality standards for turbidity in the receiving water. Chemical treatment can reliably provide exceptional reductions of turbidity and associated pol- lutants. Chemical treatment may be required to meet turbidity stormwater discharge requirements,  especially when construction proceeds through the wet season. Conditions of Use Formal written approval from Ecology is required for the use of chemical treatment, regardless of  site size. See https://fortress.wa.gov/ecy/publications/SummaryPages/ecy070258.html for a copy of  the Request for Chemical Treatment form. The Local Permitting Authority may also require review   and approval. When authorized, the chemical treatment systems must be included in the Con- struction Stormwater Pollution Prevention Plan (SWPPP). Chemically treated stormwater discharged from construction sites must be nontoxic to aquatic organ- isms. The Chemical Technology Assessment Protocol - Ecology (CTAPE) must be used to evaluate  chemicals proposed for stormwater treatment. Only chemicals approved by Ecology under the  CTAPE may be used for stormwater treatment. The approved chemicals, their allowable application  techniques (batch treatment or flow-through treatment), allowable application rates, and conditions  of use can be found at the Department of Ecology Emerging Technologies website: https://ecology.wa.gov/Regulations-Permits/Guidance-technical-assistance/Stormwater-permittee- guidance-resources/Emerging-stormwater-treatment-technologies Background on Chemical Treatment Systems Coagulation and flocculation have been used for over a century to treat water. The use of coagu- lation and flocculation to treat stormwater is a very recent application. Experience with the treatment  of water and wastewater has resulted in a basic understanding of the process, in particular factors  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 396 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. BMP C252: Treating and Disposing of High pH Water Purpose When pH levels in stormwater rise above 8.5, it is necessary to lower the pH levels to the acceptable  range of 6.5 to 8.5 prior to discharge to surface or ground water. A pH level range of 6.5 to 8.5 is typ- ical for most natural watercourses, and this neutral pH range is required for the survival of aquatic  organisms. Should the pH rise or drop out of this range, fish and other aquatic organisms may  become stressed and may die. Conditions of Use  l The water quality standard for pH  in Washington State is in the range of 6.5 to 8.5. Storm- water with pH levels exceeding water quality standards may be either neutralized on site or  disposed of  to a sanitary sewer or concrete batch plant with pH neutralization capabilities.  l Neutralized stormwater may be discharged to surface waters under the Construction Storm- water General permit.  l Neutralized process water such as concrete truck wash-out, hydro-demolition, or saw-cutting  slurry must be managed to prevent discharge to surface waters. Any stormwater  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 406 contaminated during concrete work is considered process wastewater and must not be dis- charged to waters of the State or stormwater collection systems.  l The process used for neutralizing and/or disposing of high pH stormwater from the site must  be documented in the Construction Stormwater Pollution Prevention Plan. Causes of High pH High pH at construction sites is most commonly caused by the contact of stormwater with poured or  recycled concrete, cement, mortars, and other Portland cement or lime containing construction  materials. (See BMP C151: Concrete Handling for more information on concrete handling pro- cedures). The principal caustic agent in cement is calcium hydroxide (free lime). Calcium hardness can contribute to high pH  values and cause toxicity that is associated with high pH  conditions. A high level of calcium hardness in waters of the state is not allowed. Ground water stand- ard for calcium and other dissolved solids in Washington State is less than 500 mg/l. Treating High pH Stormwater by Carbon Dioxide Sparging Advantages of Carbon Dioxide Sparging  l Rapidly neutralizes high pH water.  l Cost effective and safer to handle than acid compounds.  l CO2 is self-buffering. It is difficult to overdose and create harmfully low pH levels.  l Material is readily available. The Chemical Process of Carbon Dioxide Sparging When carbon dioxide (CO2) is added to water (H 2O), carbonic acid (H2CO3) is formed which can  further dissociate into a proton (H+) and a bicarbonate anion (HCO3-) as shown below: CO2 + H 2O ↔ H2CO3 ↔ H+ + HCO3- The free proton is a weak acid that can lower the pH. Water temperature has an effect on the reac- tion as well. The colder the water temperature is, the slower the reaction occurs. The warmer the  water temperature is, the quicker the reaction occurs. Most construction applications in Washington  State have water temperatures in the 50°F or higher range so the reaction is almost simultaneous. The Treatment Process of Carbon Dioxide Sparging High pH water may be treated using continuous treatment, continuous discharge systems. These  manufactured systems continuously monitor influent and effluent pH to ensure that pH values are  within an acceptable range before being discharged. All systems must have fail safe automatic shut  off switches in the event that pH is not within the acceptable discharge range. Only trained operators  may operate manufactured systems. System manufacturers often provide trained operators or train- ing on their devices. The following procedure may be used when not using a continuous discharge system: 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 407  1. Prior to treatment, the appropriate jurisdiction should be notified in accordance with the reg- ulations set by the jurisdiction.  2. Every effort should be made to isolate the potential high pH water in order to treat it separately  from other stormwater on-site.  3. Water should be stored in an acceptable storage facility, detention pond, or containment cell  prior to pH  treatment.  4. Transfer water to be treated for pH  to the pH treatment structure. Ensure that the pH treat- ment structure size is sufficient to hold the amount of water that is to be treated. Do not fill the  pH treatment structure completely, allow at least 2 feet of freeboard.  5. The operator samples the water within the pH treatment structure for pH  and notes the clarity  of the water. As a rule of thumb, less CO2 is necessary for clearer water. The results of the  samples and water clarity observations should be recorded.  6. In the pH  treatment structure, add CO2 until the pH falls into the range of 6.9-7.1. Adjusting  pH to within 0.2 pH units of receiving water (background pH) is recommended. It is unlikely  that pH can be adjusted to within 0.2 pH units using dry ice. Compressed carbon dioxide gas  should be introduced to the water using a carbon dioxide diffuser located near the bottom of  the pH  treatment structure, this will allow carbon dioxide to bubble up through the water and  diffuse more evenly.  7. Slowly discharge the water, making sure water does not get stirred up in the process. Release  about 80% of the water from the pH treatment structure leaving any sludge behind. If turbidity  remains above the maximum allowable, consider adding filtration to the treatment train. See  BMP C251:  Construction Stormwater Filtration.  8. Discharge treated water through a pond or drainage system.  9. Excess sludge needs to be disposed of properly as concrete waste. If several batches of  water are undergoing pH treatment, sludge can be left in the treatment structure for the next  batch treatment. Dispose of sludge when it fills 50% of the treatment structure volume.  10. Disposal must comply with applicable local, state, and federal regulations. Treating High pH Stormwater by Food Grade Vinegar Food grade vinegar that meets FDA standards may be used to neutralize high pH  water. Food  grade vinegar is only 4% to 18% acetic acid with the remainder being water.  Food grade vinegar  may be used if dosed just enough to lower pH sufficiently. Use a treatment process as described  above for CO2 sparging, but add food grade vinegar instead of CO2. This treatment option for high pH stormwater does not apply to anything but food grade vinegar.  Acetic acid does not equal vinegar. Any other product or waste containing acetic acid must go  through the evaluation process in Appendix G of Whole Effluent Toxicity Testing Guidance and Test Review Criteria (Marshall, 2016).  2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 408 Disposal of High pH Stormwater Sanitary Sewer Disposal Local sewer authority approval is required prior to disposal via the sanitary sewer. Concrete Batch Plant Disposal  l Only permitted facilities may accept high pH water.  l Contact the facility to ensure they can accept the high pH  water. Maintenance Standards Safety and materials handling:  l All equipment should be handled in accordance with OSHA rules and regulations.  l Follow  manufacturer guidelines for materials handling. Each operator should provide:  l A diagram of the monitoring and treatment equipment.  l A description of the pumping rates and capacity the treatment equipment is capable of treat- ing. Each operator should keep a written record of the following:  l Client name and phone number.  l Date of treatment.  l Weather conditions.  l Project name and location.  l Volume of water treated.  l pH of untreated water.  l Amount of CO2 or food grade vinegar needed to adjust water to a pH range of 6.9-7.1.  l pH of treated water.  l Discharge point location and description. A copy of this record should be given to the client/contractor who should retain the record for three  years. 2019 Stormwater Management Manual for Western Washington Volume II -Chapter 3 -Page 409 APPENDIX C Correspondence (Correspondence to be added to the appendix as received) APPENDIX D Site Inspection Form 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 APPENDIX E Construction Stormwater General Permit (CSWGP) Download the CSWGP: http://www.ecy.wa.gov/programs/wq/stormwater/construction/index.htm