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SWPPP (3)
Civil Engineers ● Structural Engineers ● Landscape Architects ● Community Planners ● Land Surveyors Construction Stormwater Pollution Prevention Plan PREPARED FOR: Mill Pond Development, LLC. Fircrest, WA 98466 PROJECT: The Meadows at Mill Pond Yelm, Washington 2210152.10 PREPARED BY: J. Matthew Weber, PE Principal DATE July 2021 Construction Stormwater Pollution Prevention Plan PREPARED FOR: Mill Pond Development, LLC. Fircrest, WA 98466 PROJECT: The Meadows at Mill Pond Yelm, Washington 2210152.10 PREPARED BY: J. Matthew Weber, PE. Principal DATE: July 2021 I hereby state that this Construction Stormwater Pollution Prevention Plan for The Meadows at Mill Pond project has been prepared by me or under my supervision, and meets the standard of care and expertise that is usual and customary in this community for professional engineers. I understand that City of Yelm does not and will not assume liability for the sufficiency, suitability, or performance of drainage facilities prepared by me. 07/26/2021 Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2210152.10 Table of Contents Section Page 1.0 Introduction .................................................................................................................................... 1 2.0 Project Description ........................................................................................................................ 2 3.0 Existing Site Conditions ................................................................................................................ 2 4.0 Adjacent Areas and Drainage ....................................................................................................... 2 5.0 Critical Areas .................................................................................................................................. 2 6.0 Soils ................................................................................................................................................. 2 7.0 Potential Erosion Problems .......................................................................................................... 2 8.0 Construction Stormwater Pollution Prevention Elements ......................................................... 2 8.1 Mark Clearing Limits ........................................................................................................... 2 8.2 Establish Construction Access ............................................................................................ 3 8.3 Control Flow Rates.............................................................................................................. 3 8.4 Install Sediment Controls .................................................................................................... 3 8.5 Stabilize Soils ...................................................................................................................... 3 8.6 Protect Slopes ..................................................................................................................... 3 8.7 Protect Drain Inlets.............................................................................................................. 3 8.8 Stabilize Channels and Outlets ........................................................................................... 3 8.9 Control Pollutants ................................................................................................................ 4 8.10 Control Dewatering ............................................................................................................. 5 8.11 Maintain BMPs .................................................................................................................... 5 8.12 Manage the Project ............................................................................................................. 6 8.13 Protect Low Impact Development BMPs ............................................................................ 6 9.0 Construction Sequence and Phasing .......................................................................................... 6 9.1 Construction Sequence ....................................................................................................... 6 9.2 Construction Phasing .......................................................................................................... 7 10.0 Construction Schedule .................................................................................................................. 8 11.0 Financial/Ownership Responsibilities ......................................................................................... 8 12.0 Certified Erosion and Sediment Control Lead (CESCL) ............................................................ 8 Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2210152.10 Exhibits Exhibit 1 NRCS Soils Map Exhibit 2 TESC Calculations Exhibit 3 Inspection Logs Exhibit 4 Selected Best Management Practices (BMPs) Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 1 2210152.10 1.0 Introduction In 1972, Congress passed the Federal Water Pollution Control Act (FWPCA), also known as the Clean Water Act (CWA), to restore and maintain the quality of the nation's waterways. The ultimate goal was to make sure that rivers and streams were fishable, swimmable, and drinkable. In 1987, the Water Quality Act (WQA) added provisions to the CWA that allowed the Environmental Protection Agency (EPA) to govern stormwater discharges from construction sites. The National Pollutant Discharge Elimination System (NPDES) General Permit includes provisions for development of a Stormwater Pollution Prevention Plan (SWPPP) to maximize the potential benefits of pollution prevention and sediment and erosion control measures at construction sites. The proposed project will disturb more than 1 acre of area, and therefore is required to obtain an NPDES General Permit for Stormwater Associated with Construction Activities. The 2014 Department of Ecology Stormwater Management Manual for Western Washington (SMMWW), as adopted by the City of Yelm, requires a Construction Stormwater Pollution Prevention Plan (CSWPPP) for projects that add or replace more than 2,000 square feet of impervious surface. The proposed project will exceed this threshold; therefore, a CSWPPP is required. Development, implementation, and maintenance of the CSWPPP will provide the selected General Contractor with the framework for reducing soil erosion and minimizing pollutants in stormwater during construction. The CSWPPP will: • Define the characteristics of the site and the type of construction that will occur. • Describe the practices that will be implemented to control erosion and the release of pollutants in stormwater. • Create an implementation schedule to ensure that the practices described in this CSWPPP are in fact implemented, and to evaluate the plan's effectiveness in reducing erosion, sediment, and pollutant levels in stormwater discharged from the site. • Describe the final stabilization/termination design to minimize erosion and prevent stormwater impacts after construction is complete. This CSWPPP: • Identifies the CSWPPP Coordinator with a description of this person's duties. • Identifies the Stormwater Pollution Prevention Team (SWPP Team) that will assist in implementation of the CSWPPP during construction. • Describes the existing site conditions, including existing land use, soil types at the site, and the location of surface waters that are located on or next to the site. • Identifies the body or bodies of water that will receive runoff from the construction site, including the ultimate body of water that receives the stormwater. • Identifies the drainage areas and potential stormwater contaminants. • Describes the stormwater management controls and various Best Management Practices (BMPs) necessary to reduce erosion, sediment, and pollutants in stormwater discharge. • Describes the facility monitoring plan and how controls will be coordinated with construction activities. • Describes the implementation schedule and provisions for amendment of the plan. Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2 2210152.10 2.0 Project Description This CSWPPP accompanies the civil engineering plans submitted for a site development permit for the proposed project, The Meadows at Mill Pond. Proposed improvements are for a 21-lot development. The project site is currently vacant land and is 4.88 acres in size (5.03 acres to centerline), located on Parcel 22730220600. The project site is located in Section 30, Township 17 North, Range 01 East of the Willamette Meridian, in the City of Yelm, Thurston County, Washington. 3.0 Existing Site Conditions The site is presently covered with grass and evergreen trees, with slopes ranging from 0 to 5 percent. Presently, the site infiltrates directly into the ground with no offsite runoff. 4.0 Adjacent Areas and Drainage Review of available GIS topographic information indicates that there is minimal potential of runoff from adjacent properties. The minor offsite contribution would be from primarily perviou s surfaces. Runoff from a portion of the existing fronting Mill Road SE will be collected and managed in the proposed stormwater facilities The site is currently bounded to the north by Cochrane Memorial Park, to the south and east by single family residences and Mill Road SE to the west. The site is currently zoned as R-4. 5.0 Critical Areas The project site is within an aquifer recharge area. To our knowledge, no environmentally sensitive areas, including creeks, lakes, ponds, wetlands, ravines, gullies, steep slopes, or springs, are located on or down gradient of the property. 6.0 Soils Site soils are identified by the NRCS Web Soil Survey (A-4) as Spanaway gravelly sandy loam and Spanaway stony sandy loam, Type A soils. These soils are characterized as very deep, somewhat excessively drained. 7.0 Potential Erosion Problems There are no known historical erosion problems on the site. There are no known potential erosion problems that will be created onsite. 8.0 Construction Stormwater Pollution Prevention Elements The purpose of this section is to describe how each of the 1 3 Construction Stormwater Pollution Prevention elements has been addressed and to identify the type and location of BMPs used to satisfy the required element. If an element is not applicable to the project, a reason is provided. 8.1 Mark Clearing Limits Prior to beginning land-disturbing activities, clearing limits will be marked with high visibility plastic or metal fence (BMP C103). Significant vegetation to remain will be marked and protected by fencing. Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 3 2210152.10 8.2 Establish Construction Access A formal quarry spall construction entrance (BMP C105) is proposed off Mill Road SE. If sediment tracking should occur, the Contractor will be required to sweep the impacted roadways. Dump trucks hauling material to and from the site will be covered by a tarp. 8.3 Control Flow Rates Two sediment traps (BMP C240) will utilize infiltration to control flows during construction. The proposed sediment traps will infiltrate 100-percent of construction phase runoff with a maximum design water depth of less than 6-inches. Sizing of the facility is found in Exhibit 2. 8.4 Install Sediment Controls As part of the initial construction activities, BMPs will be installed to trap sediment onsite. The identified BMPs include sediment trap (BMP C240) and silt fencing (BMP C233). 8.5 Stabilize Soils To protect soil from the erosive forces of raindrops, flowing water, and wind, the following BMPs will be implemented: • All disturbed areas that will remain unworked will be stabilized with temporary hydroseed (BMP C120) or mulch (BMP C121) within 2 days (October 1 - April 30) or 7 days (May 1 - September 30). • After fertilizing, all areas that will not be impacted by construction will be seeded (BMP C120). • Topsoil stockpiles will be stabilized with plastic coverings (BMP C123). • Dust control (BMP C140) will be provided by sprinkling the site with water. • Permanent erosion control measures will include site paving and seeding of exposed soils. 8.6 Protect Slopes Slopes on the site will be protected to minimize erosion. Temporary and permanent seeding (BMP C120) will be used to reduce erosion of exposed soils on slopes. Runoff collection methods include temporary interceptor swales (BMP C200). 8.7 Protect Drain Inlets Proposed drain inlets shall be protected until final site stabilization. Any storm drain inlets downstream shall be protected so that surface water runoff does not enter the conveyance system without first being filtered. Inlets shall be inspected weekly, at a minimum, and daily during storm events. Storm Drain Inlet Protection (BMP C220) will be provided. 8.8 Stabilize Channels and Outlets Interceptor swales are proposed for the project to divert stormwater away from the construction area and direct it to the sediment traps. Stabilized channels will not be necessary for the project based on small slopes. Outlets to the sediment traps will be stabilized to prevent erosion and check dams (BMP C207) will be provided. Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 4 2210152.10 8.9 Control Pollutants All waste materials will be collected and stored in a securely closed metal dumpster. All trash and construction debris from the site will be deposited in the dumpster. The dumpster will be emptied a minimum of once per week, and the trash will be hauled to the local landfill. No construction materials will be buried onsite. All personnel will be instructed regarding the correct procedure for waste disposal. All sanitary waste will be collected from the portable units a minimum of three times per week. Good housekeeping and spill control practices will be followed during construction to minimize stormwater contamination from petroleum products, fertilizers, and concrete. Table 1 below lists several pollutants that are commonly found on construction sites that have the potential to contaminate storm runoff. These pollutants will be present, mainly in areas of building and pavement construction. The Contractor and the CSWPPP/TESC coordinator will be responsible for identifying areas where these pollutants are being used and monitor runoff coming from these areas. Pollutant sources will be covered with plastic if contaminated runoff is observed from these areas. If contaminated runoff is found in the sediment trap or soils, the Certified Erosion and Sedimentation Control Lead (CESCL) will direct the Contractor to remove the polluted water/soil and dispose of it in an approved area offsite. Table 1 – Potential Construction Site Stormwater Pollutants Trade Name Material Chemical/Physical Description(1) Stormwater Pollutants(1) Pesticides (insecticides, fungicides, herbicide, rodenticides) Various colored to colorless liquid, powder, pellets, or grains Chlorinated hydrocarbons, organophosphates, carbamates, arsenic Fertilizer Liquid or solid grains Nitrogen, phosphorous Plaster White granules or powder Calcium sulphate, calcium carbonate, sulfuric acid Cleaning solvents Colorless, blue, or yellow-green liquid Perchloroethylene, methylene chloride, trichloroethylene, petroleum distillates Asphalt Black solid Oil, petroleum distillates Concrete White solid Limestone, sand Glue, adhesives White or yellow liquid Polymers, epoxies Paints Various colored liquid Metal oxides, Stoddard solvent, talc, calcium carbonate, arsenic Curing compounds Creamy white liquid Naphtha Wastewater from construction equipment washing Water Soil, oil & grease, solids Wood preservatives Clear amber or dark brown liquid Stoddard solvent, petroleum distillates, arsenic, copper, chromium Hydraulic oil/fluids Brown oily petroleum hydrocarbon Mineral oil Gasoline Colorless, pale brown or pink petroleum hydrocarbon Benzene, ethyl benzene, toluene, xylene, MTBE Diesel fuel Clear, blue-green to yellow liquid Petroleum distillate, oil & grease, naphthalene, xylenes Kerosene Pale yellow liquid petroleum hydrocarbon Coal oil, petroleum distillates Antifreeze/coolant Clear green/yellow liquid Ethylene glycol, propylene glycol, heavy metals (copper, lead, zinc) Erosion Solid Particles Soil, Sediment (1) Data obtained from MSDS when available Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 5 2210152.10 8.9.1 Required BMPs The following BMPs or equivalent measures are required of all businesses and agencies during concrete pouring and asphalt application at temporary sites: • Employees must be educated on the pollution hazards of concrete and asphalt application and cutting. • Loose aggregate chunks and dust must be swept or shoveled and collected (not hosed down a storm drain) for recycling or proper disposal at the end of each work day, especially at work sites such as streets, driveways, parking lots, sidewalks, curbs, and gutters where rain can readily pick up the loose material and carry it to the nearest stormwater conveyance. Small amounts of excess concrete, grout, and mortar can be disposed of in the trash. • Storm drain covers or similarly effective containment devices must be placed over all nearby drains at the beginning of each day. Shovel or vacuum slurry and remove from the site. All accumulated runoff and solids must be collected and properly d isposed at the end of each workday, or more often if necessary. • Exposed aggregate washing, where the top layer of unhardened concrete is hosed or scraped off to leave a rough finish, must be done with a mechanism for containment and collection of the discarded concrete slurry (such as the storm drain covers mentioned above). The easiest way to contain the wash water will be to direct the washings to a hole in the ground where the water can percolate into the ground and the solids later covered with soil. • If directed to a drain, a catch basin filter insert must be used to remove the solids. This is especially useful if the activity must proceed on rainy days. • Cleaning of concrete application and mixing equipment or concrete vehicles on the work site must be done in a designated area where the rinse water is controlled . The rinse water must either be collected for proper disposal or put into a hole in the ground where the water can percolate away and the solids later covered with soil or recovered and disposed or recycled. The use of any treatment BMP must not result in the violation of groundwater, surface water, or drinking water quality standards. 8.10 Control Dewatering Dewatering is not anticipated for the project. 8.11 Maintain BMPs Temporary and permanent erosion and sediment control BMPs shall be maintained and repaired as needed to assure performance of their intended functions. Sediment control BMPs such as silt fencing, slope blankets, and drain inlet protection shall be inspected weekly or after a runoff-producing event. Temporary erosion and sediment control BMPs will be removed within 30 days after final site stabilization is achieved. The following inspection and maintenance practices will be used to maintain erosion and sediment controls: • Built-up sediment will be removed from silt fencing when it has reached one-third the height of the fence. Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 6 2210152.10 • Silt fences will be inspected for depth of sediment, tears in the fabric, and attachment to the fence posts, and to determine that fence posts are firmly in the ground. Accumulated sediment will be removed from behind the fence. • Check dams will be inspected for depth of sediment. Accumulated sediment will be removed when it reaches 6 inches in depth. • Temporary and permanent seeding will be inspected for bare spots, washouts, and healthy growth. • The Contractor Certified Erosion and Sedimentation Control Lead (CESCL) (BMP C160) will provide erosion control inspection services and stormwater disposal monitoring through construction. The City Inspector will be notified of daily construction activities and scheduled meetings between the Erosion Control Inspector and the Contractor. The maintenance inspection report will be made after each inspection. Copies of the report forms to be completed by the CSWPPP coordinator are attached as Exhibit 3 of this CSWPPP. Completed forms will be provided to the City Inspector and will also be maintained onsite during the entire construction project. If construction activities or design modifications are made to the site plan that could impact stormwater, or if AHBL determines that the measures are not adequate to prevent erosion and the discharge of sediment from the site (based on turbidity measurements), this CSWPPP will be amended appropriately. The amended CSWPPP will have a description of the new activities that contribute to the increased pollutant loading and the planned source control activities. 8.12 Manage the Project The following practices will be required during construction to properly manage activities: • Comply with seasonal work limitations. • Inspect, maintain, and repair BMPs. • Identify a CESCL (BMP C160). • Maintain the CSWPPP onsite at all times, including narrative and plans. 8.13 Protect Low Impact Development BMPs • Proposed infiltration location will be protected from construction vehicles and equipment to the maximum extent practical. • Proposed sediment traps designed to not impact infiltration interface of future infiltration facility. • All Low Impact Development (LID) BMPs should be kept clean of sediment and equipment to the maximum extent practical. 9.0 Construction Sequence and Phasing 9.1 Construction Sequence The construction sequence is described below: 1. Stake/flag clearing and construction limits. 2. Arrange and attend a pre-construction meeting with City of Yelm. Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 7 2210152.10 3. Install construction entrance. 4. Provide demolition as required to install all temporary erosion control BMPs according to the TESC plan. Install inlet sediment protection in existing catch basins. 5. Provide all perimeter erosion control and site barrier fencing including filter fabric fence prior to start of any clearing or grading activities. 6. Excavate temporary TESC ponds (protect subgrades from compaction – used for infiltration). 7. Demolish remainder of existing site features as designated for demolition on the plans. 8. Maintain erosion control measures as site development progresses. 9. Rough grade site and provide erosion control BMPs to stabilize the site and direct all surface runoff to the TESC plans. 10. Apply erosion control mulch and seeding, straw mulch or equal to areas that will not be brought to final grade or permanently vegetated within 7 days of exposure, during the dry season and 2 days of exposure during the wet season (October 1 – Aril 30). 11. Relocate erosion control measures or install new measures so that as the site conditions change, the erosion and sediment control is always in accordance with the SWPPP minimum requirements. 12. Construct storm system and misc. utilities and install inlet sediment protectio n to new catch basins. 13. Fine grade asphalt paved areas, place curb and gutters, and pave. 14. After site is stabilized, complete bio-retention construction: 14.1. Scarify bio-retention sub-grade (do not compact bio-retention bottoms). Schedule geotechnical engineer for infiltration testing to ensure bio-retention functions per design. Provide infiltration testing to include a minimum of 2 tests per bio-retention system. 14.2. Upon approval of infiltration testing results, provide bio-retention treatment soil mix per plans. Bio-retention soil mix placement and bio-retention excavation shall not be conducted during wet or saturated conditions. 15. Provide landscape plantings and final bio-retention stabilization per landscape design. 16. Remove remaining temporary erosion control items once site has been stabilized and upon approval from the city. 17. Perform final close-out items as required by city and owner. 9.2 Construction Phasing No phasing is proposed. The proposed construction will be done as one project. Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 8 2210152.10 10.0 Construction Schedule Construction is anticipated to begin in Fall 2021 and be completed in Winter 2021/2022. Based on the construction schedule, construction may be ongoing during the wet season. During construction, measures will be taken to prevent the transportation of sediment from the site to receiving waters. These measures include the use of, but are not limited to, the BMPs listed in Exhibit 4. 11.0 Financial/Ownership Responsibilities The Developer is the party responsible for initiation of bonds and other financial securities. The project must comply with City of Yelm financial liability requirements. 12.0 Certified Erosion and Sediment Control Lead (CESCL) The General Contractor shall be required to provide a CESCL prior to permit issuance. The CESCL can be identified at the preconstruction meeting. Once this individual is identified, the City Inspector will be notified. The contractor will designate their CESCL here: Name: _____________________________________________ Address: _____________________________________________ Phone: _____________________________________________ Fax Number: _____________________________________________ The CESCL is required to meet Washington State Department of Ecology certification requirements. The City Inspector will be provided with CESCL information. The duties of the CESCL include: • Implementing the CSWPPP/TESC plan with the aid of the SWPP Team. • Overseeing maintenance practices identified as BMPs in the CSWPPP. • Conducting or providing for inspection and monitoring activities. • Sampling stormwater for turbidity using a turbidity meter. • Identifying other potential pollutant sources and ensuring they are added to the plan. • Identifying any deficiencies in the CSWPPP and ensuring they are corrected. • Ensuring that any changes in construction plans are addressed in the CSWPPP. To aid in the implementation of the CSWPPP, the members of the SWPP Team include the following: General Contractor, CESCL, City of Yelm Inspector, the geotechnical engineering consultant, and AHBL. The General Contractor will ensure that all housekeeping and monitoring procedures are implemented, while the CESCL will ensure the integrity of the structural BMPs. The SWPP Team will observe construction and erosion control practices and recommend revisions or additions to the CSWPPP and drawings. Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 9 2210152.10 This analysis is based on data and records either supplied to or obtained by AHB L, Inc. These documents are referenced within the text of the analysis. The analysis has been prepared utilizing procedures and practices within the standard accepted practices of the industry. We conclude that this project, as proposed, will not create any new problems within the existing downstream drainage system. This project will not noticeably aggravate any existing downstream problems due to either water quality or quantity. AHBL, Inc. J. Matthew Weber, PE Principal JW July 2021 Q:\2021\2210152\10_CIV\NON_CAD\REPORTS\20210421 Rpt (SWPPP_Meadows) 2210152.10.docx Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2210152.10 Exhibit 1 NRCS Soils Map 2215 North 30th Street, Suite 300, Tacoma, WA 98403 253.383.2422 TEL 253.383.2572 FAX THE MEADOWS AT MILL POND PLAT NRCS SOIL MAP A-4 PROJECT SITE Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2210152.10 Exhibit 2 TESC Calculations WWHM2012 PROJECT REPORT 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 2 General Model Information Project Name:2210152_Meadow(TESC) Site Name:Meadows Site Address:104th City:Yelm Report Date:7/26/2021 Gage:Lake Lawrence Data Start:1955/10/01 Data End:2008/09/30 Timestep:15 Minute Precip Scale:0.857 Version Date:2019/09/13 Version:4.2.17 POC Thresholds Low Flow Threshold for POC1:50 Percent of the 2 Year High Flow Threshold for POC1:50 Year Low Flow Threshold for POC2:50 Percent of the 2 Year High Flow Threshold for POC2:50 Year 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 3 Landuse Basin Data Predeveloped Land Use 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 4 Mitigated Land Use N TESC Basin Bypass:No GroundWater:No Pervious Land Use acre A B, Lawn, Flat 1.679 Pervious Total 1.679 Impervious Land Use acre ROADS FLAT 0.077 SIDEWALKS FLAT 0.019 Impervious Total 0.096 Basin Total 1.775 Element Flows To: Surface Interflow Groundwater Sediment Trap 1 Sediment Trap 1 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 5 S TESC Basin Bypass:No GroundWater:No Pervious Land Use acre A B, Lawn, Flat 2.28 Pervious Total 2.28 Impervious Land Use acre ROADS FLAT 0.576 DRIVEWAYS FLAT 0.287 SIDEWALKS FLAT 0.091 Impervious Total 0.954 Basin Total 3.234 Element Flows To: Surface Interflow Groundwater Sediment Trap 2 Sediment Trap 2 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 6 Routing Elements Predeveloped Routing 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 7 Mitigated Routing Sediment Trap 1 Bottom Length:45.00 ft. Bottom Width:30.00 ft. Depth:2 ft. Volume at riser head:0.0172 acre-feet. Infiltration On Infiltration rate:20 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):22.558 Total Volume Through Riser (ac-ft.):0 Total Volume Through Facility (ac-ft.):22.558 Percent Infiltrated:100 Total Precip Applied to Facility:4.651 Total Evap From Facility:0.366 Side slope 1:3 To 1 Side slope 2:3 To 1 Side slope 3:3 To 1 Side slope 4:3 To 1 Discharge Structure Riser Height:0.5 ft. Riser Diameter:12 in. Element Flows To: Outlet 1 Outlet 2 Pond Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.031 0.000 0.000 0.000 0.0222 0.031 0.000 0.000 0.629 0.0444 0.031 0.001 0.000 0.634 0.0667 0.031 0.002 0.000 0.639 0.0889 0.031 0.002 0.000 0.643 0.1111 0.032 0.003 0.000 0.648 0.1333 0.032 0.004 0.000 0.653 0.1556 0.032 0.004 0.000 0.657 0.1778 0.032 0.005 0.000 0.662 0.2000 0.033 0.006 0.000 0.667 0.2222 0.033 0.007 0.000 0.672 0.2444 0.033 0.007 0.000 0.676 0.2667 0.033 0.008 0.000 0.681 0.2889 0.034 0.009 0.000 0.686 0.3111 0.034 0.010 0.000 0.691 0.3333 0.034 0.010 0.000 0.696 0.3556 0.034 0.011 0.000 0.701 0.3778 0.035 0.012 0.000 0.706 0.4000 0.035 0.013 0.000 0.711 0.4222 0.035 0.014 0.000 0.715 0.4444 0.035 0.014 0.000 0.720 0.4667 0.036 0.015 0.000 0.725 0.4889 0.036 0.016 0.000 0.730 0.5111 0.036 0.017 0.012 0.735 0.5333 0.036 0.018 0.064 0.740 0.5556 0.037 0.018 0.138 0.745 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 8 0.5778 0.037 0.019 0.229 0.750 0.6000 0.037 0.020 0.333 0.756 0.6222 0.037 0.021 0.448 0.761 0.6444 0.038 0.022 0.572 0.766 0.6667 0.038 0.023 0.703 0.771 0.6889 0.038 0.023 0.838 0.776 0.7111 0.038 0.024 0.976 0.781 0.7333 0.039 0.025 1.115 0.786 0.7556 0.039 0.026 1.251 0.791 0.7778 0.039 0.027 1.383 0.797 0.8000 0.039 0.028 1.509 0.802 0.8222 0.040 0.029 1.627 0.807 0.8444 0.040 0.030 1.736 0.812 0.8667 0.040 0.030 1.834 0.818 0.8889 0.040 0.031 1.921 0.823 0.9111 0.041 0.032 1.996 0.828 0.9333 0.041 0.033 2.060 0.834 0.9556 0.041 0.034 2.114 0.839 0.9778 0.041 0.035 2.160 0.844 1.0000 0.042 0.036 2.227 0.850 1.0222 0.042 0.037 2.276 0.855 1.0444 0.042 0.038 2.324 0.860 1.0667 0.043 0.039 2.371 0.866 1.0889 0.043 0.040 2.417 0.871 1.1111 0.043 0.041 2.462 0.877 1.1333 0.043 0.042 2.506 0.882 1.1556 0.044 0.043 2.550 0.888 1.1778 0.044 0.044 2.593 0.893 1.2000 0.044 0.045 2.635 0.899 1.2222 0.044 0.046 2.676 0.904 1.2444 0.045 0.047 2.717 0.910 1.2667 0.045 0.048 2.757 0.915 1.2889 0.045 0.049 2.797 0.921 1.3111 0.046 0.050 2.836 0.926 1.3333 0.046 0.051 2.875 0.932 1.3556 0.046 0.052 2.913 0.938 1.3778 0.046 0.053 2.950 0.943 1.4000 0.047 0.054 2.988 0.949 1.4222 0.047 0.055 3.024 0.955 1.4444 0.047 0.056 3.060 0.960 1.4667 0.047 0.057 3.096 0.966 1.4889 0.048 0.058 3.132 0.972 1.5111 0.048 0.059 3.167 0.977 1.5333 0.048 0.060 3.201 0.983 1.5556 0.049 0.061 3.235 0.989 1.5778 0.049 0.062 3.269 0.995 1.6000 0.049 0.063 3.303 1.001 1.6222 0.049 0.065 3.336 1.006 1.6444 0.050 0.066 3.369 1.012 1.6667 0.050 0.067 3.402 1.018 1.6889 0.050 0.068 3.434 1.024 1.7111 0.051 0.069 3.466 1.030 1.7333 0.051 0.070 3.497 1.036 1.7556 0.051 0.071 3.529 1.042 1.7778 0.052 0.073 3.560 1.048 1.8000 0.052 0.074 3.591 1.054 1.8222 0.052 0.075 3.621 1.060 1.8444 0.052 0.076 3.652 1.066 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 9 1.8667 0.053 0.077 3.682 1.072 1.8889 0.053 0.078 3.711 1.078 1.9111 0.053 0.080 3.741 1.084 1.9333 0.054 0.081 3.770 1.090 1.9556 0.054 0.082 3.799 1.096 1.9778 0.054 0.083 3.828 1.102 2.0000 0.055 0.084 3.857 1.108 2.0222 0.055 0.086 3.886 1.114 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 10 Sediment Trap 2 Bottom Length:83.00 ft. Bottom Width:24.00 ft. Depth:2 ft. Volume at riser head:0.0253 acre-feet. Infiltration On Infiltration rate:20 Infiltration safety factor:1 Wetted surface area On Total Volume Infiltrated (ac-ft.):169.298 Total Volume Through Riser (ac-ft.):0.006 Total Volume Through Facility (ac-ft.):169.304 Percent Infiltrated:100 Total Precip Applied to Facility:0 Total Evap From Facility:0 Side slope 1:3 To 1 Side slope 2:3 To 1 Side slope 3:3 To 1 Side slope 4:3 To 1 Discharge Structure Riser Height:0.5 ft. Riser Diameter:12 in. Element Flows To: Outlet 1 Outlet 2 Pond Hydraulic Table Stage(feet)Area(ac.)Volume(ac-ft.)Discharge(cfs)Infilt(cfs) 0.0000 0.045 0.000 0.000 0.000 0.0222 0.046 0.001 0.000 0.928 0.0444 0.046 0.002 0.000 0.935 0.0667 0.046 0.003 0.000 0.942 0.0889 0.047 0.004 0.000 0.948 0.1111 0.047 0.005 0.000 0.955 0.1333 0.047 0.006 0.000 0.962 0.1556 0.048 0.007 0.000 0.968 0.1778 0.048 0.008 0.000 0.975 0.2000 0.048 0.009 0.000 0.982 0.2222 0.049 0.010 0.000 0.989 0.2444 0.049 0.011 0.000 0.995 0.2667 0.049 0.012 0.000 1.002 0.2889 0.050 0.013 0.000 1.009 0.3111 0.050 0.014 0.000 1.016 0.3333 0.050 0.016 0.000 1.023 0.3556 0.051 0.017 0.000 1.030 0.3778 0.051 0.018 0.000 1.036 0.4000 0.051 0.019 0.000 1.043 0.4222 0.052 0.020 0.000 1.050 0.4444 0.052 0.021 0.000 1.057 0.4667 0.052 0.023 0.000 1.064 0.4889 0.053 0.024 0.000 1.071 0.5111 0.053 0.025 0.012 1.078 0.5333 0.053 0.026 0.064 1.085 0.5556 0.054 0.027 0.138 1.092 0.5778 0.054 0.028 0.229 1.099 0.6000 0.054 0.030 0.333 1.106 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 11 0.6222 0.055 0.031 0.448 1.113 0.6444 0.055 0.032 0.572 1.120 0.6667 0.055 0.033 0.703 1.127 0.6889 0.056 0.035 0.838 1.134 0.7111 0.056 0.036 0.976 1.142 0.7333 0.057 0.037 1.115 1.149 0.7556 0.057 0.038 1.251 1.156 0.7778 0.057 0.040 1.383 1.163 0.8000 0.058 0.041 1.509 1.170 0.8222 0.058 0.042 1.627 1.177 0.8444 0.058 0.044 1.736 1.185 0.8667 0.059 0.045 1.834 1.192 0.8889 0.059 0.046 1.921 1.199 0.9111 0.059 0.048 1.996 1.206 0.9333 0.060 0.049 2.060 1.214 0.9556 0.060 0.050 2.114 1.221 0.9778 0.060 0.052 2.160 1.228 1.0000 0.061 0.053 2.227 1.236 1.0222 0.061 0.054 2.276 1.243 1.0444 0.062 0.056 2.324 1.250 1.0667 0.062 0.057 2.371 1.258 1.0889 0.062 0.058 2.417 1.265 1.1111 0.063 0.060 2.462 1.273 1.1333 0.063 0.061 2.506 1.280 1.1556 0.063 0.063 2.550 1.287 1.1778 0.064 0.064 2.593 1.295 1.2000 0.064 0.066 2.635 1.302 1.2222 0.065 0.067 2.676 1.310 1.2444 0.065 0.068 2.717 1.317 1.2667 0.065 0.070 2.757 1.325 1.2889 0.066 0.071 2.797 1.333 1.3111 0.066 0.073 2.836 1.340 1.3333 0.066 0.074 2.875 1.348 1.3556 0.067 0.076 2.913 1.355 1.3778 0.067 0.077 2.950 1.363 1.4000 0.068 0.079 2.988 1.371 1.4222 0.068 0.080 3.024 1.378 1.4444 0.068 0.082 3.060 1.386 1.4667 0.069 0.083 3.096 1.394 1.4889 0.069 0.085 3.132 1.401 1.5111 0.069 0.086 3.167 1.409 1.5333 0.070 0.088 3.201 1.417 1.5556 0.070 0.090 3.235 1.424 1.5778 0.071 0.091 3.269 1.432 1.6000 0.071 0.093 3.303 1.440 1.6222 0.071 0.094 3.336 1.448 1.6444 0.072 0.096 3.369 1.456 1.6667 0.072 0.098 3.402 1.463 1.6889 0.073 0.099 3.434 1.471 1.7111 0.073 0.101 3.466 1.479 1.7333 0.073 0.102 3.497 1.487 1.7556 0.074 0.104 3.529 1.495 1.7778 0.074 0.106 3.560 1.503 1.8000 0.074 0.107 3.591 1.511 1.8222 0.075 0.109 3.621 1.519 1.8444 0.075 0.111 3.652 1.527 1.8667 0.076 0.112 3.682 1.535 1.8889 0.076 0.114 3.711 1.543 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 12 1.9111 0.076 0.116 3.741 1.551 1.9333 0.077 0.117 3.770 1.559 1.9556 0.077 0.119 3.799 1.567 1.9778 0.078 0.121 3.828 1.575 2.0000 0.078 0.123 3.857 1.583 2.0222 0.078 0.124 3.886 1.591 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 13 Analysis Results POC 1 POC #1 was not reported because POC must exist in both scenarios and both scenarios must have been run. 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 14 POC 2 POC #2 was not reported because POC must exist in both scenarios and both scenarios must have been run. 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 15 Model Default Modifications Total of 0 changes have been made. PERLND Changes No PERLND changes have been made. IMPLND Changes No IMPLND changes have been made. 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 16 Appendix Predeveloped Schematic 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 17 Mitigated Schematic 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 18 Predeveloped UCI File 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 19 Mitigated UCI File RUN GLOBAL WWHM4 model simulation START 1955 10 01 END 2008 09 30 RUN INTERP OUTPUT LEVEL 3 0 RESUME 0 RUN 1 UNIT SYSTEM 1 END GLOBAL FILES <File> <Un#> <-----------File Name------------------------------>*** <-ID-> *** WDM 26 2210152_Meadow(TESC).wdm MESSU 25 Mit2210152_Meadow(TESC).MES 27 Mit2210152_Meadow(TESC).L61 28 Mit2210152_Meadow(TESC).L62 30 POC2210152_Meadow(TESC)1.dat 31 POC2210152_Meadow(TESC)2.dat END FILES OPN SEQUENCE INGRP INDELT 00:15 PERLND 7 IMPLND 1 IMPLND 8 IMPLND 5 RCHRES 1 RCHRES 2 COPY 1 COPY 501 COPY 2 COPY 502 DISPLY 1 DISPLY 2 END INGRP END OPN SEQUENCE DISPLY DISPLY-INFO1 # - #<----------Title----------->***TRAN PIVL DIG1 FIL1 PYR DIG2 FIL2 YRND 1 Sediment Trap 1 MAX 1 2 30 9 2 Sediment Trap 2 MAX 1 2 31 9 END DISPLY-INFO1 END DISPLY COPY TIMESERIES # - # NPT NMN *** 1 1 1 501 1 1 2 1 1 502 1 1 END TIMESERIES END COPY GENER OPCODE # # OPCD *** END OPCODE PARM # # K *** END PARM END GENER PERLND GEN-INFO <PLS ><-------Name------->NBLKS Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 7 A/B, Lawn, Flat 1 1 1 1 27 0 END GEN-INFO *** Section PWATER*** 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 20 ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC *** 7 0 0 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ***************************** PIVL PYR # - # ATMP SNOW PWAT SED PST PWG PQAL MSTL PEST NITR PHOS TRAC ********* 7 0 0 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO PWAT-PARM1 <PLS > PWATER variable monthly parameter value flags *** # - # CSNO RTOP UZFG VCS VUZ VNN VIFW VIRC VLE INFC HWT *** 7 0 0 0 0 0 0 0 0 0 0 0 END PWAT-PARM1 PWAT-PARM2 <PLS > PWATER input info: Part 2 *** # - # ***FOREST LZSN INFILT LSUR SLSUR KVARY AGWRC 7 0 5 0.8 400 0.05 0.3 0.996 END PWAT-PARM2 PWAT-PARM3 <PLS > PWATER input info: Part 3 *** # - # ***PETMAX PETMIN INFEXP INFILD DEEPFR BASETP AGWETP 7 0 0 2 2 0 0 0 END PWAT-PARM3 PWAT-PARM4 <PLS > PWATER input info: Part 4 *** # - # CEPSC UZSN NSUR INTFW IRC LZETP *** 7 0.1 0.5 0.25 0 0.7 0.25 END PWAT-PARM4 PWAT-STATE1 <PLS > *** Initial conditions at start of simulation ran from 1990 to end of 1992 (pat 1-11-95) RUN 21 *** # - # *** CEPS SURS UZS IFWS LZS AGWS GWVS 7 0 0 0 0 3 1 0 END PWAT-STATE1 END PERLND IMPLND GEN-INFO <PLS ><-------Name-------> Unit-systems Printer *** # - # User t-series Engl Metr *** in out *** 1 ROADS/FLAT 1 1 1 27 0 8 SIDEWALKS/FLAT 1 1 1 27 0 5 DRIVEWAYS/FLAT 1 1 1 27 0 END GEN-INFO *** Section IWATER*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # ATMP SNOW IWAT SLD IWG IQAL *** 1 0 0 1 0 0 0 8 0 0 1 0 0 0 5 0 0 1 0 0 0 END ACTIVITY PRINT-INFO <ILS > ******** Print-flags ******** PIVL PYR # - # ATMP SNOW IWAT SLD IWG IQAL ********* 1 0 0 4 0 0 0 1 9 8 0 0 4 0 0 0 1 9 5 0 0 4 0 0 0 1 9 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 21 END PRINT-INFO IWAT-PARM1 <PLS > IWATER variable monthly parameter value flags *** # - # CSNO RTOP VRS VNN RTLI *** 1 0 0 0 0 0 8 0 0 0 0 0 5 0 0 0 0 0 END IWAT-PARM1 IWAT-PARM2 <PLS > IWATER input info: Part 2 *** # - # *** LSUR SLSUR NSUR RETSC 1 400 0.01 0.1 0.1 8 400 0.01 0.1 0.1 5 400 0.01 0.1 0.1 END IWAT-PARM2 IWAT-PARM3 <PLS > IWATER input info: Part 3 *** # - # ***PETMAX PETMIN 1 0 0 8 0 0 5 0 0 END IWAT-PARM3 IWAT-STATE1 <PLS > *** Initial conditions at start of simulation # - # *** RETS SURS 1 0 0 8 0 0 5 0 0 END IWAT-STATE1 END IMPLND SCHEMATIC <-Source-> <--Area--> <-Target-> MBLK *** <Name> # <-factor-> <Name> # Tbl# *** N TESC Basin*** PERLND 7 1.679 RCHRES 1 2 PERLND 7 1.679 RCHRES 1 3 IMPLND 1 0.077 RCHRES 1 5 IMPLND 8 0.019 RCHRES 1 5 S TESC Basin*** PERLND 7 2.28 RCHRES 2 2 PERLND 7 2.28 RCHRES 2 3 IMPLND 1 0.576 RCHRES 2 5 IMPLND 5 0.287 RCHRES 2 5 IMPLND 8 0.091 RCHRES 2 5 ******Routing****** PERLND 7 1.679 COPY 1 12 IMPLND 1 0.077 COPY 1 15 IMPLND 8 0.019 COPY 1 15 PERLND 7 1.679 COPY 1 13 PERLND 7 2.28 COPY 2 12 IMPLND 1 0.576 COPY 2 15 IMPLND 5 0.287 COPY 2 15 IMPLND 8 0.091 COPY 2 15 PERLND 7 2.28 COPY 2 13 RCHRES 1 1 COPY 501 17 RCHRES 2 1 COPY 502 17 END SCHEMATIC NETWORK <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** COPY 501 OUTPUT MEAN 1 1 48.4 DISPLY 1 INPUT TIMSER 1 COPY 502 OUTPUT MEAN 1 1 48.4 DISPLY 2 INPUT TIMSER 1 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 22 <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # #<-factor->strg <Name> # # <Name> # # *** END NETWORK RCHRES GEN-INFO RCHRES Name Nexits Unit Systems Printer *** # - #<------------------><---> User T-series Engl Metr LKFG *** in out *** 1 Sediment Trap 1 2 1 1 1 28 0 1 2 Sediment Trap 2 2 1 1 1 28 0 1 END GEN-INFO *** Section RCHRES*** ACTIVITY <PLS > ************* Active Sections ***************************** # - # HYFG ADFG CNFG HTFG SDFG GQFG OXFG NUFG PKFG PHFG *** 1 1 0 0 0 0 0 0 0 0 0 2 1 0 0 0 0 0 0 0 0 0 END ACTIVITY PRINT-INFO <PLS > ***************** Print-flags ******************* PIVL PYR # - # HYDR ADCA CONS HEAT SED GQL OXRX NUTR PLNK PHCB PIVL PYR ********* 1 4 0 0 0 0 0 0 0 0 0 1 9 2 4 0 0 0 0 0 0 0 0 0 1 9 END PRINT-INFO HYDR-PARM1 RCHRES Flags for each HYDR Section *** # - # VC A1 A2 A3 ODFVFG for each *** ODGTFG for each FUNCT for each FG FG FG FG possible exit *** possible exit possible exit * * * * * * * * * * * * * * *** 1 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 2 0 1 0 0 4 5 0 0 0 0 0 0 0 0 2 2 2 2 2 END HYDR-PARM1 HYDR-PARM2 # - # FTABNO LEN DELTH STCOR KS DB50 *** <------><--------><--------><--------><--------><--------><--------> *** 1 1 0.01 0.0 0.0 0.5 0.0 2 2 0.02 0.0 0.0 0.5 0.0 END HYDR-PARM2 HYDR-INIT RCHRES Initial conditions for each HYDR section *** # - # *** VOL Initial value of COLIND Initial value of OUTDGT *** ac-ft for each possible exit for each possible exit <------><--------> <---><---><---><---><---> *** <---><---><---><---><---> 1 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 2 0 4.0 5.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 END HYDR-INIT END RCHRES SPEC-ACTIONS END SPEC-ACTIONS FTABLES FTABLE 1 91 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.030992 0.000000 0.000000 0.000000 0.022222 0.031222 0.000691 0.000000 0.629638 0.044444 0.031453 0.001388 0.000000 0.634292 0.066667 0.031684 0.002089 0.000000 0.638963 0.088889 0.031917 0.002796 0.000000 0.643650 0.111111 0.032150 0.003508 0.000000 0.648354 0.133333 0.032384 0.004225 0.000000 0.653074 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 23 0.155556 0.032619 0.004947 0.000000 0.657811 0.177778 0.032854 0.005674 0.000000 0.662564 0.200000 0.033091 0.006407 0.000000 0.667333 0.222222 0.033328 0.007145 0.000000 0.672119 0.244444 0.033566 0.007888 0.000000 0.676922 0.266667 0.033805 0.008637 0.000000 0.681741 0.288889 0.034045 0.009391 0.000000 0.686576 0.311111 0.034286 0.010150 0.000000 0.691428 0.333333 0.034527 0.010915 0.000000 0.696296 0.355556 0.034769 0.011685 0.000000 0.701181 0.377778 0.035012 0.012460 0.000000 0.706082 0.400000 0.035256 0.013241 0.000000 0.711000 0.422222 0.035501 0.014027 0.000000 0.715934 0.444444 0.035746 0.014819 0.000000 0.720885 0.466667 0.035993 0.015616 0.000000 0.725852 0.488889 0.036240 0.016418 0.000000 0.730835 0.511111 0.036488 0.017226 0.012432 0.735835 0.533333 0.036736 0.018040 0.064540 0.740852 0.555556 0.036986 0.018859 0.138729 0.745885 0.577778 0.037236 0.019684 0.229424 0.750934 0.600000 0.037488 0.020514 0.333520 0.756000 0.622222 0.037740 0.021350 0.448641 0.761082 0.644444 0.037992 0.022191 0.572643 0.766181 0.666667 0.038246 0.023039 0.703432 0.771296 0.688889 0.038501 0.023891 0.838881 0.776428 0.711111 0.038756 0.024750 0.976818 0.781576 0.733333 0.039012 0.025614 1.115035 0.786741 0.755556 0.039269 0.026484 1.251329 0.791922 0.777778 0.039527 0.027359 1.383552 0.797119 0.800000 0.039785 0.028240 1.509672 0.802333 0.822222 0.040044 0.029127 1.627854 0.807564 0.844444 0.040305 0.030020 1.736538 0.812811 0.866667 0.040566 0.030919 1.834531 0.818074 0.888889 0.040827 0.031823 1.921105 0.823354 0.911111 0.041090 0.032733 1.996100 0.828650 0.933333 0.041354 0.033649 2.060036 0.833963 0.955556 0.041618 0.034571 2.114227 0.839292 0.977778 0.041883 0.035499 2.160903 0.844638 1.000000 0.042149 0.036433 2.227125 0.850000 1.022222 0.042415 0.037372 2.276078 0.855379 1.044444 0.042683 0.038318 2.324001 0.860774 1.066667 0.042951 0.039269 2.370955 0.866185 1.088889 0.043220 0.040227 2.416998 0.871613 1.111111 0.043490 0.041190 2.462179 0.877058 1.133333 0.043761 0.042160 2.506546 0.882519 1.155556 0.044033 0.043135 2.550142 0.887996 1.177778 0.044305 0.044117 2.593004 0.893490 1.200000 0.044579 0.045104 2.635170 0.899000 1.222222 0.044853 0.046098 2.676671 0.904527 1.244444 0.045127 0.047098 2.717538 0.910070 1.266667 0.045403 0.048104 2.757800 0.915630 1.288889 0.045680 0.049116 2.797483 0.921206 1.311111 0.045957 0.050134 2.836611 0.926798 1.333333 0.046235 0.051158 2.875206 0.932407 1.355556 0.046514 0.052189 2.913290 0.938033 1.377778 0.046794 0.053225 2.950882 0.943675 1.400000 0.047074 0.054268 2.988001 0.949333 1.422222 0.047356 0.055318 3.024665 0.955008 1.444444 0.047638 0.056373 3.060890 0.960700 1.466667 0.047921 0.057435 3.096691 0.966407 1.488889 0.048205 0.058503 3.132083 0.972132 1.511111 0.048490 0.059577 3.167080 0.977872 1.533333 0.048775 0.060658 3.201694 0.983630 1.555556 0.049061 0.061745 3.235937 0.989403 1.577778 0.049348 0.062839 3.269822 0.995193 1.600000 0.049636 0.063938 3.303360 1.001000 1.622222 0.049925 0.065045 3.336560 1.006823 1.644444 0.050215 0.066157 3.369434 1.012663 1.666667 0.050505 0.067276 3.401989 1.018519 1.688889 0.050796 0.068402 3.434236 1.024391 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 24 1.711111 0.051088 0.069534 3.466183 1.030280 1.733333 0.051381 0.070673 3.497839 1.036185 1.755556 0.051675 0.071818 3.529210 1.042107 1.777778 0.051969 0.072969 3.560305 1.048045 1.800000 0.052264 0.074127 3.591131 1.054000 1.822222 0.052561 0.075292 3.621694 1.059971 1.844444 0.052857 0.076463 3.652002 1.065959 1.866667 0.053155 0.077641 3.682060 1.071963 1.888889 0.053454 0.078826 3.711875 1.077984 1.911111 0.053753 0.080017 3.741452 1.084021 1.933333 0.054053 0.081215 3.770797 1.090074 1.955556 0.054354 0.082419 3.799915 1.096144 1.977778 0.054656 0.083631 3.828813 1.102230 2.000000 0.054959 0.084849 3.857493 1.108333 END FTABLE 1 FTABLE 2 91 5 Depth Area Volume Outflow1 Outflow2 Velocity Travel Time*** (ft) (acres) (acre-ft) (cfs) (cfs) (ft/sec) (Minutes)*** 0.000000 0.045730 0.000000 0.000000 0.000000 0.022222 0.046058 0.001020 0.000000 0.928835 0.044444 0.046387 0.002047 0.000000 0.935465 0.066667 0.046716 0.003082 0.000000 0.942111 0.088889 0.047047 0.004123 0.000000 0.948774 0.111111 0.047378 0.005172 0.000000 0.955453 0.133333 0.047710 0.006229 0.000000 0.962148 0.155556 0.048043 0.007293 0.000000 0.968860 0.177778 0.048376 0.008364 0.000000 0.975588 0.200000 0.048711 0.009443 0.000000 0.982333 0.222222 0.049046 0.010529 0.000000 0.989095 0.244444 0.049382 0.011623 0.000000 0.995872 0.266667 0.049719 0.012724 0.000000 1.002667 0.288889 0.050057 0.013833 0.000000 1.009477 0.311111 0.050395 0.014949 0.000000 1.016305 0.333333 0.050735 0.016072 0.000000 1.023148 0.355556 0.051075 0.017204 0.000000 1.030008 0.377778 0.051416 0.018342 0.000000 1.036885 0.400000 0.051758 0.019489 0.000000 1.043778 0.422222 0.052100 0.020643 0.000000 1.050687 0.444444 0.052444 0.021804 0.000000 1.057613 0.466667 0.052788 0.022974 0.000000 1.064556 0.488889 0.053133 0.024150 0.000000 1.071514 0.511111 0.053479 0.025335 0.012432 1.078490 0.533333 0.053826 0.026527 0.064540 1.085481 0.555556 0.054173 0.027727 0.138729 1.092490 0.577778 0.054521 0.028935 0.229424 1.099514 0.600000 0.054871 0.030150 0.333520 1.106556 0.622222 0.055220 0.031374 0.448641 1.113613 0.644444 0.055571 0.032605 0.572643 1.120687 0.666667 0.055923 0.033844 0.703432 1.127778 0.688889 0.056275 0.035090 0.838881 1.134885 0.711111 0.056629 0.036345 0.976818 1.142008 0.733333 0.056983 0.037607 1.115035 1.149148 0.755556 0.057337 0.038877 1.251329 1.156305 0.777778 0.057693 0.040155 1.383552 1.163477 0.800000 0.058050 0.041441 1.509672 1.170667 0.822222 0.058407 0.042735 1.627854 1.177872 0.844444 0.058765 0.044037 1.736538 1.185095 0.866667 0.059124 0.045347 1.834531 1.192333 0.888889 0.059484 0.046665 1.921105 1.199588 0.911111 0.059844 0.047991 1.996100 1.206860 0.933333 0.060206 0.049325 2.060036 1.214148 0.955556 0.060568 0.050667 2.114227 1.221453 0.977778 0.060931 0.052017 2.160903 1.228774 1.000000 0.061295 0.053375 2.227125 1.236111 1.022222 0.061659 0.054741 2.276078 1.243465 1.044444 0.062025 0.056115 2.324001 1.250835 1.066667 0.062391 0.057498 2.370955 1.258222 1.088889 0.062758 0.058888 2.416998 1.265626 1.111111 0.063126 0.060287 2.462179 1.273045 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 25 1.133333 0.063495 0.061694 2.506546 1.280481 1.155556 0.063865 0.063109 2.550142 1.287934 1.177778 0.064235 0.064532 2.593004 1.295403 1.200000 0.064606 0.065964 2.635170 1.302889 1.222222 0.064978 0.067404 2.676671 1.310391 1.244444 0.065351 0.068852 2.717538 1.317909 1.266667 0.065725 0.070308 2.757800 1.325444 1.288889 0.066099 0.071773 2.797483 1.332996 1.311111 0.066474 0.073246 2.836611 1.340564 1.333333 0.066850 0.074727 2.875206 1.348148 1.355556 0.067227 0.076217 2.913290 1.355749 1.377778 0.067605 0.077715 2.950882 1.363366 1.400000 0.067983 0.079222 2.988001 1.371000 1.422222 0.068363 0.080737 3.024665 1.378650 1.444444 0.068743 0.082260 3.060890 1.386317 1.466667 0.069124 0.083792 3.096691 1.394000 1.488889 0.069506 0.085332 3.132083 1.401700 1.511111 0.069888 0.086881 3.167080 1.409416 1.533333 0.070272 0.088438 3.201694 1.417148 1.555556 0.070656 0.090004 3.235937 1.424897 1.577778 0.071041 0.091579 3.269822 1.432663 1.600000 0.071427 0.093162 3.303360 1.440444 1.622222 0.071814 0.094753 3.336560 1.448243 1.644444 0.072201 0.096353 3.369434 1.456058 1.666667 0.072590 0.097962 3.401989 1.463889 1.688889 0.072979 0.099579 3.434236 1.471737 1.711111 0.073369 0.101206 3.466183 1.479601 1.733333 0.073759 0.102840 3.497839 1.487481 1.755556 0.074151 0.104484 3.529210 1.495379 1.777778 0.074543 0.106136 3.560305 1.503292 1.800000 0.074937 0.107797 3.591131 1.511222 1.822222 0.075331 0.109466 3.621694 1.519169 1.844444 0.075726 0.111145 3.652002 1.527132 1.866667 0.076121 0.112832 3.682060 1.535111 1.888889 0.076518 0.114528 3.711875 1.543107 1.911111 0.076915 0.116233 3.741452 1.551119 1.933333 0.077313 0.117946 3.770797 1.559148 1.955556 0.077712 0.119669 3.799915 1.567193 1.977778 0.078112 0.121400 3.828813 1.575255 2.000000 0.078512 0.123141 3.857493 1.583333 END FTABLE 2 END FTABLES EXT SOURCES <-Volume-> <Member> SsysSgap<--Mult-->Tran <-Target vols> <-Grp> <-Member-> *** <Name> # <Name> # tem strg<-factor->strg <Name> # # <Name> # # *** WDM 2 PREC ENGL 0.857 PERLND 1 999 EXTNL PREC WDM 2 PREC ENGL 0.857 IMPLND 1 999 EXTNL PREC WDM 1 EVAP ENGL 0.76 PERLND 1 999 EXTNL PETINP WDM 1 EVAP ENGL 0.76 IMPLND 1 999 EXTNL PETINP WDM 2 PREC ENGL 0.857 RCHRES 1 EXTNL PREC WDM 1 EVAP ENGL 0.76 RCHRES 1 EXTNL POTEV END EXT SOURCES EXT TARGETS <-Volume-> <-Grp> <-Member-><--Mult-->Tran <-Volume-> <Member> Tsys Tgap Amd *** <Name> # <Name> # #<-factor->strg <Name> # <Name> tem strg strg*** RCHRES 1 HYDR RO 1 1 1 WDM 1000 FLOW ENGL REPL RCHRES 1 HYDR O 1 1 1 WDM 1001 FLOW ENGL REPL RCHRES 1 HYDR O 2 1 1 WDM 1002 FLOW ENGL REPL RCHRES 1 HYDR STAGE 1 1 1 WDM 1003 STAG ENGL REPL COPY 1 OUTPUT MEAN 1 1 48.4 WDM 701 FLOW ENGL REPL COPY 501 OUTPUT MEAN 1 1 48.4 WDM 801 FLOW ENGL REPL RCHRES 2 HYDR RO 1 1 1 WDM 1004 FLOW ENGL REPL RCHRES 2 HYDR O 1 1 1 WDM 1005 FLOW ENGL REPL RCHRES 2 HYDR O 2 1 1 WDM 1006 FLOW ENGL REPL RCHRES 2 HYDR STAGE 1 1 1 WDM 1007 STAG ENGL REPL COPY 2 OUTPUT MEAN 1 1 48.4 WDM 702 FLOW ENGL REPL COPY 502 OUTPUT MEAN 1 1 48.4 WDM 802 FLOW ENGL REPL 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 26 END EXT TARGETS MASS-LINK <Volume> <-Grp> <-Member-><--Mult--> <Target> <-Grp> <-Member->*** <Name> <Name> # #<-factor-> <Name> <Name> # #*** MASS-LINK 2 PERLND PWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 2 MASS-LINK 3 PERLND PWATER IFWO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 3 MASS-LINK 5 IMPLND IWATER SURO 0.083333 RCHRES INFLOW IVOL END MASS-LINK 5 MASS-LINK 12 PERLND PWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 12 MASS-LINK 13 PERLND PWATER IFWO 0.083333 COPY INPUT MEAN END MASS-LINK 13 MASS-LINK 15 IMPLND IWATER SURO 0.083333 COPY INPUT MEAN END MASS-LINK 15 MASS-LINK 17 RCHRES OFLOW OVOL 1 COPY INPUT MEAN END MASS-LINK 17 END MASS-LINK END RUN 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 27 Predeveloped HSPF Message File 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 28 Mitigated HSPF Message File 2210152_Meadow(TESC)7/26/2021 2:29:36 PM Page 29 Disclaimer Legal Notice This program and accompanying documentation are provided 'as-is' without warranty of any kind. The entire risk regarding the performance and results of this program is assumed by End User. Clear Creek Solutions Inc. and the governmental licensee or sublicensees disclaim all warranties, either expressed or implied, including but not limited to implied warranties of program and accompanying documentation. In no event shall Clear Creek Solutions Inc. be liable for any damages whatsoever (including without limitation to damages for loss of business profits, loss of business information, business interruption, and the like) arising out of the use of, or inability to use this program even if Clear Creek Solutions Inc. or their authorized representatives have been advised of the possibility of such damages. Software Copyright © by : Clear Creek Solutions, Inc. 2005-2021; All Rights Reserved. Clear Creek Solutions, Inc. 6200 Capitol Blvd. Ste F Olympia, WA. 98501 Toll Free 1(866)943-0304 Local (360)943-0304 www.clearcreeksolutions.com Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2210152.10 Exhibit 3 Inspection Logs Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2210152.10 The Meadows at Mill Pond Construction Stormwater Pollution Prevention Plan Inspection and Maintenance Report Form To be completed every 7 days and within 24 hours of a rainfall event of 0.5 inches or more Inspector: Date: Inspector's Qualifications: Days since last rainfall: Amount of last rainfall: inches Stabilization Measures Drainage Area Date Since Last Disturbance Date of Disturbance Stabilized (yes/No) Stabilized With Condition Stabilization required: To be performed by: On or before: Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2210152.10 The Meadows at Mill Pond Construction Stormwater Pollution Prevention Plan Inspection and Maintenance Report Form Perimeter Structural Controls: Date: Silt Fence Drainage Area Perimeter Has Silt Reached 1/3 of Fence Height? Is Fence Properly Secured? Is There Evidence of Washout or Overtopping? Maintenance required for silt fence and straw bales: To be performed by: On or before: Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2210152.10 The Meadows at Mill Pond Construction Stormwater Pollution Prevention Plan Inspection and Maintenance Report Form Changes required to the pollution prevention plan: Reasons for changes: I certify under penalty of law that this document and all attachments were prepared under my direction or supervision in accordance with a system designed to assure that qualified personnel properly gathered and evaluated the information submitted. Based on my inquiry of the person or persons who manage the system, or those persons directly responsible for gathering the information, the information submitted is, to the best of my knowledge and belief, true, accurate, and complete. I am aware that there are significant penalties for submitting false information, including the possibility of fine and imprisonment for knowing violations. Signature: Date: ____________________ Construction Stormwater Pollution Prevention Plan The Meadows at Mill Pond 2210152.10 Exhibit 4 Selected Best Management Practices (BMPs) • High Visibility Fence (BMP C103) • Stabilized Construction Entrance (BMP C105) • Temporary and Permanent Seeding (BMP C120) • Mulching (BMP C121) • Nets and Blankets (BMP C122) • Plastic Covering (BMP C123) • Dust Control (BMP C140) • Materials on Hand (BMP C150) • Concrete Handling (BMP C151) • Sawcutting and Surfacing Pollution Prevention (BMP C152) • Material Delivery, Storage, and Containment (BMP C153) • Concrete Washout Area (BMP C154) • Certified Erosion and Sediment Control Lead (BMP C160) • Scheduling (BMP C162) • Interceptor Dike and Swale (BMP C200) • Check Dams (BMP C207) • Outlet Protection (BMP C209) • Storm Drain Inlet Protection (BMP C220) • Silt Fence (BMP C233) • Sediment Trap (BMP C240) BMP C103: High Visibility Fence Purpose Fencing is intended to: 1. Restrict clearing to approved limits. 2. Prevent disturbance of sensitive areas, their buffers, and other areas required to be left undisturbed. 3. Limit construction traffic to designated construction entrances, exits, or internal roads. 4. Protect areas where marking with survey tape may not provide adequate pro- tection. 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 sag- ging 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 (p.367)to act as high visibility fence. Silt fence shall be at least 3 feet high and must be highly vis- ible to meet the requirements of this BMP. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 269 Metal fences shall be designed and installed according to the manufacturer's spe- cifications. Metal fences shall be at least 3 feet high and must be highly visible. Fences shall not be wired or stapled to trees. Maintenance Standards If the fence has been damaged or visibility reduced, it shall be repaired or replaced immediately and visibility restored. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 270 BMP C105: Stabilized Construction Entrance / Exit Purpose Stabilized Construction entrances are established to reduce the amount of sediment transported onto paved roads by vehicles or equipment. This is done by constructing a stabilized pad of quarry spalls at entrances and exits for construction sites. Conditions of Use Construction entrances 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 construction provide stabilized construction entrances for each residence, rather than only at the main subdivision entrance. Stabilized surfaces shall be of suf- ficient length/width to provide vehicle access/parking, based on lot size/configuration. On large commercial, highway, and road projects, the designer should include enough extra materials in the contract to allow for additional stabilized entrances 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-4.1.1 Stabilized Construction Entrance (p.273)for details. Note: the 100’ minimum length of the entrance 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 entrances 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 concrete, cement, or calcium chloride for construction entrance sta- bilization because these products raise pH levels in stormwater and concrete discharge to surface waters of the State is prohibited. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 270 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 following standards: Grab Tensile Strength (ASTM D4751)200 psi min. 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) l Consider early installation of the first lift of asphalt in areas that will paved;this can be used as a stabilized entrance.Also consider the installation of excess concrete as a stabilized entrance.During large concrete pours,excess concrete is often available for this purpose. l Fencing (see BMP C103:High Visibility Fence (p.269))shall be installed as neces- sary to restrict traffic to the construction entrance. l Whenever possible,the entrance shall be constructed on a firm,compacted sub- grade.This can substantially increase the effectiveness of the pad and reduce the need for maintenance. l Construction entrances should avoid crossing existing sidewalks and back of walk drains if at all possible.If a construction entrance 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. Maintenance Standards Quarry spalls shall be added if the pad is no longer in accordance with the spe- cifications. l If the entrance 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 replacement/cleaning of the existing quarry spalls,street sweeping,an increase in the dimensions of the entrance,or the installation of a wheel wash. l Any sediment that is tracked onto pavement shall be removed by shoveling or street sweeping.The sediment collected by sweeping shall be removed or sta- bilized on site.The pavement shall not be cleaned by washing down the street, except when high efficiency sweeping is ineffective and there is a threat to public safety.If it is necessary to wash the streets,the construction of a small sump to con- tain 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 efficiency mechanical sweeper because this creates dust and throws soils into storm systems or conveyance ditches. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 271 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 entrance(s),fencing (see BMP C103)shall be installed to control traffic. l Upon project completion and site stabilization,all construction accesses intended as permanent access for maintenance shall be permanently stabilized. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 272 Figure II-4.1.1 Stabilized Construction Entrance D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.1.1 Stabilized Construction Entrance Revised June 2015 NOT TO SCALE Existin g R o a d Notes: 1. Driveway shall meet the requirements of the permitting agency. 2. It is recommended that the entrance be crowned so that runoff drains off the pad. Install driveway culvert if there is a roadside ditch present 4" - 8" quarry spalls Geotextile 12" minimum thickness 15' min. 100' min. Provide full width of ingress/egress area 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 273 Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C105:Stab- ilized Construction Entrance /Exit. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to con- sideration for local use. The products are available for review on Ecology’s website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 274 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 with straw 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 protection. l Mulch is required at all times for seeding because it protects seeds from heat, mois- ture loss, and transport due to runoff. Mulch can be applied on top of the seed or simultaneously by hydroseeding. See BMP C121:Mulching (p.284)for spe- cifications. l Seed and mulch, all disturbed areas not otherwise vegetated at final site sta- bilization. Final stabilization means the completion of all soil disturbing activities at the site and the establishment of a permanent vegetative cover, or equivalent per- 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 278 manent stabilization measures (such as pavement,riprap,gabions,or geotextiles) which will prevent erosion. Design and Installation Specifications Seed retention/detention ponds as required. 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 hydroseed.Before allowing water to flow in vegetated channels,establish 75 percent vegetation cover.If vegetated channels cannot be estab- lished by seed before water flow;install sod in the channel bottom—over hydromulch and erosion control 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 percent tackifier.See BMP C121:Mulching (p.284)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. l When installing seed via hydroseeding operations,only about 1/3 of the seed actu- ally 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: 1.Phase 1-Install all seed and fertilizer with 25-30 percent mulch and tackifier onto soil in the first lift. 2.Phase 2-Install the rest of the mulch and tackifier over the first lift. Or,enhance vegetation by: 1.Installing the mulch,seed,fertilizer,and tackifier in one lift. 2.Spread or blow straw over the top of the hydromulch at a rate of 800-1000 pounds per acre. 3.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: 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 279 l Irrigation. l Reapplication of mulch. l Repair of failed slope surfaces. This technique works with standard hydromulch (1,500 pounds per acre minimum) and BFM/MBFMs (3,000 pounds per acre minimum). l Seed may be installed by hand if: l Temporary and covered by straw,mulch,or topsoil. l Permanent in small areas (usually less than 1 acre)and covered with mulch, topsoil,or erosion blankets. l The seed mixes listed in the tables below include recommended mixes for both temporary and permanent seeding. l Apply these mixes,with the exception of the wetland mix,at a rate of 120 pounds per acre.This rate can be reduced if soil amendments or slow- release fertilizers are used. l Consult the local suppliers or the local conservation district for their recom- mendations because the appropriate mix depends on a variety of factors, including location,exposure,soil type,slope,and expected foot traffic.Altern- ative seed mixes approved by the local authority may be used. l Other mixes may be appropriate,depending on the soil type and hydrology of the area. l Table II-4.1.2 Temporary Erosion Control Seed Mix (p.280)lists the standard mix for areas requiring a temporary vegetative cover. %Weight %Purity %Germination 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 Table II-4.1.2 Temporary Erosion Control Seed Mix l Table II-4.1.3 Landscaping Seed Mix (p.281)lists a recommended mix for land- scaping seed. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 280 %Weight %Purity %Germination Perennial rye blend Lolium perenne 70 98 90 Chewings and red fescue blend Festuca rubra var.commutata or Festuca rubra 30 98 90 Table II-4.1.3 Landscaping Seed Mix l Table II-4.1.4 Low-Growing Turf Seed Mix (p.281)lists a turf seed mix for dry situ- ations where there is no need for watering.This mix requires very little main- tenance. %Weight %Purity %Germination Dwarf tall fescue (several varieties) Festuca arundinacea 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 Table II-4.1.4 Low-Growing Turf Seed Mix l Table II-4.1.5 Bioswale Seed Mix*(p.281)lists a mix for bioswales and other inter- mittently wet areas. %Weight %Purity %Germination Tall or meadow fescue Festuca arundinacea or Festuca ela- tior 75-80 98 90 Seaside/Creeping bentgrass Agrostis palustris 10-15 92 85 Redtop bentgrass Agrostis alba or Agrostis gigantea 5-10 90 80 *Modified Briargreen,Inc.Hydroseeding Guide Wetlands Seed Mix Table II-4.1.5 Bioswale Seed Mix* l Table II-4.1.6 Wet Area Seed Mix*(p.282)lists a low-growing,relatively non-invas- ive seed mix appropriate for very wet areas that are not regulated wetlands.Apply 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 281 this mixture at a rate of 60 pounds per acre.Consult Hydraulic Permit Authority (HPA)for seed mixes if applicable. %Weight %Purity %Germination Tall or meadow fescue Festuca arundinacea or Festuca ela- tior 60-70 98 90 Seaside/Creeping bentgrass Agrostis palustris 10-15 98 85 Meadow foxtail Alepocurus pratensis 10-15 90 80 Alsike clover Trifolium hybridum 1-6 98 90 Redtop bentgrass Agrostis alba 1-6 92 85 *Modified Briargreen,Inc.Hydroseeding Guide Wetlands Seed Mix Table II-4.1.6 Wet Area Seed Mix* l Table II-4.1.7 Meadow Seed Mix (p.282)lists a recommended meadow seed mix for infrequently maintained areas or non-maintained areas where colonization by native plants is desirable.Likely applications include rural road and utility right-of- way.Seeding should take place in September or very early October in order to obtain adequate establishment prior to the winter months.Consider the appro- priateness of clover,a fairly invasive species,in the mix.Amending the soil can reduce the need for clover. %Weight %Purity %Germination Redtop or Oregon bentgrass Agrostis alba or Agrostis oregonensis 20 92 85 Red fescue Festuca rubra 70 98 90 White dutch clover Trifolium repens 10 98 90 Table II-4.1.7 Meadow Seed Mix l 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 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 282 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 prac- tical,initially rip the subgrade to improve long-term permeability,infiltration, and water inflow qualities.At a minimum,permanent areas shall use soil amendments to achieve organic matter and permeability performance 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. l 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 (including 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 fer- tilizer to the hydromulch machine,or agitate,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 fer- tilizers.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. l 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 of mulch with approximately 10 percent tackifier. Achieve a minimum of 95 percent soil coverage during application.Numer- ous products are available commercially.Installed products per man- ufacturer’s instructions.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. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 283 l BFMs and MBFMs provide good alternatives to blankets in most areas requir- ing vegetation establishment. Advantages over blankets include: l BFM and MBFMs do not require surface preparation. l Helicopters can assist in installing BFM and MBFMs in remote areas. l On slopes steeper than 2.5H:1V, blanket installers may require ropes and harnesses for safety. l Installing BFM and MBFMs can save at least $1,000 per acre com- pared to blankets. Maintenance Standards Reseed any seeded areas that fail to establish at least 80 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, or nets/blankets. If winter weather pre- vents adequate grass growth, this time limit may be relaxed at the discretion of the local authority when sensitive areas would otherwise be protected. 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 runoff. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C120:Tem- porary and Permanent Seeding. The products did not pass through the Technology Assessment Protocol – Ecology (TAPE) process. Local jurisdictions may choose not to accept this product approved as equivalent, or may require additional testing prior to con- sideration for local use. The products are available for review on Ecology’s website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 284 BMP C121: Mulching Purpose Mulching soils provides immediate temporary protection from erosion. Mulch also enhances plant establishment by conserving moisture, holding fertilizer, seed, and top- soil in place, and moderating soil temperatures. There is an enormous 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: 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 284 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 ver- tical relief. Mulch may be applied at any time of the year and must be refreshed periodically. l For seeded areas mulch may be made up of 100 percent:cottonseed meal;fibers made of wood,recycled cellulose,hemp,kenaf;compost;or blends of these.Tack- ifier shall be plant-based,such as guar or alpha plantago,or chemical-based such as polyacrylamide or polymers.Any mulch or tackifier product used shall be installed per manufacturer’s instructions.Generally,mulches come in 40-50 pound bags.Seed and fertilizer are added at time of application. Design and Installation Specifications For mulch materials,application rates,and specifications,see Table II-4.1.8 Mulch Standards and Guidelines (p.286).Always use a 2-inch minimum mulch thickness; increase the thickness until the ground is 95%covered (i.e.not visible under the mulch layer).Note:Thickness may be increased for disturbed areas in or near sensitive areas or other areas highly susceptible to erosion. Where the option of “Compost”is selected,it should be a coarse compost that meets the following size gradations when tested in accordance with the U.S.Composting Council “Test Methods for the Examination of Compost and Composting”(TMECC)Test Method 02.02-B. Coarse Compost Minimum Percent passing 3”sieve openings 100% Minimum Percent passing 1”sieve openings 90% Minimum Percent passing ¾”sieve openings 70% Minimum Percent passing ¼”sieve openings 40% Mulch used within the ordinary high-water mark of surface waters should be selected to minimize potential flotation of organic matter.Composted organic materials have higher specific gravities (densities)than straw,wood,or chipped material.Consult Hydraulic Permit Authority (HPA)for mulch mixes if applicable. Maintenance Standards l The thickness of the cover must be maintained. l Any areas that experience erosion shall be remulched and/or protected with a net 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 285 or blanket.If the erosion problem is drainage related,then the problem shall be fixed and the eroded area remulched. Mulch Material Quality Standards Application Rates Remarks Straw Air-dried; free from undesirable seed and coarse material. 2"-3"thick; 5 bales per 1,000 sf or 2-3 tons per acre Cost-effective protection when applied with adequate thickness.Hand-application generally requires greater thickness than blown straw.The thickness of straw may be reduced by half when used in conjunction with seeding.In windy areas straw must be held in place by crimping,using a tackifier,or covering with netting.Blown straw always has to be held in place with a tackifier as even light winds will blow it away.Straw,how- ever,has several deficiencies that should be con- sidered when selecting mulch materials.It often introduces and/or encourages the propagation of weed species and it has no significant long-term benefits It should also not be used within the ordinary high-water elevation of surface waters (due to flotation). Hydromulch No growth inhibiting factors. Approx.25- 30 lbs per 1,000 sf or 1,500 - 2,000 lbs per acre Shall be applied with hydromulcher.Shall not be used without seed and tackifier unless the applic- ation rate is at least doubled.Fibers longer than about 3/4 -1 inch clog hydromulch equipment. Fibers should be kept to less than 3/4 inch. Compost No visible water or dust during handling. Must be pro- duced per WAC 173- 350,Solid Waste Handling Standards, but may have up to 35% 2"thick min.; approx.100 tons per acre (approx. 800 lbs per yard) More effective control can be obtained by increas- ing thickness to 3".Excellent mulch for protecting final grades until landscaping because it can be directly seeded or tilled into soil as an amend- ment.Compost used for mulch has a coarser size gradation than compost used for BMP C125:Top- soiling /Composting (p.297)or BMP T5.13:Post- Construction Soil Quality and Depth (p.911).It is more stable and practical to use in wet areas and during rainy weather conditions.Do not use near wetlands or near phosphorous impaired water bodies. Table II-4.1.8 Mulch Standards and Guidelines 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 286 Mulch Material Quality Standards Application Rates Remarks biosolids. Chipped Site Veget- ation Average size shall be several inches. Gradations from fines to 6 inches in length for texture, vari- ation, and interlocking properties. 2" thick min.; This is a cost-effective way to dispose of debris from clearing and grubbing, and it eliminates the problems associated with burning. Generally, it should not be used on slopes above approx. 10% because of its tendency to be transported by run- off. It is not recommended within 200 feet of sur- face waters. If seeding is expected shortly after mulch, the decomposition of the chipped veget- ation may tie up nutrients important to grass estab- lishment. Wood- based Mulch or Wood Straw No visible water or dust during handling. Must be pur- chased from a sup- plier with a Solid Waste Handling Permit or one exempt from solid waste reg- ulations. 2" thick min.; approx. 100 tons per acre (approx. 800 lbs. per cubic yard) This material is often called "hog or hogged fuel". The use of mulch ultimately improves the organic matter in the soil. Special caution is advised regarding the source and composition of wood- based mulches. Its preparation typically does not provide any weed seed control, so evidence of residual vegetation in its composition or known inclusion of weed plants or seeds should be mon- itored and prevented (or minimized). Wood Strand Mulch A blend of loose, long, thin wood pieces derived from native conifer or deciduous trees with 2" thick min. Cost-effective protection when applied with adequate thickness. A minimum of 95-percent of the wood strand shall have lengths between 2 and 10-inches, with a width and thickness between 1/16 and 3/8-inches. The mulch shall not contain resin, tannin, or other compounds in quantities that would be detrimental to plant life. Sawdust or wood shavings shall not be used as mulch. (WSDOT specification (9-14.4(4)) Table II-4.1.8 Mulch Standards and Guidelines (continued) 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 287 Mulch Material Quality Standards Application Rates Remarks high length- to-width ratio. Table II-4.1.8 Mulch Standards and Guidelines (continued) 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 288 BMP C122: Nets and Blankets Purpose Erosion control nets and blankets are intended to prevent erosion and hold seed and mulch in place on steep slopes and in channels so that vegetation can become well established. In addition, some nets and blankets can be used to permanently reinforce turf to protect drainage ways during high flows. Nets (commonly called matting) are strands of material woven into an open, but high-tensile strength net (for example, coconut fiber matting). Blankets are strands of material that are not tightly woven, but instead form a layer of interlocking fibers, typically held together by a biodegradable or photodegradable netting (for example, excelsior or straw blankets). They generally have lower tensile strength than nets, but cover the ground more completely. Coir (coconut fiber) fabric comes as both nets and blankets. Conditions of Use Erosion control nets and blankets should be used: l To aid permanent vegetated stabilization of slopes 2H:1V or greater and with more than 10 feet of vertical relief. l For drainage ditches and swales (highly recommended). The application of appro- priate netting or blanket to drainage ditches and swales can protect bare soil from channelized runoff while vegetation is established. Nets and blankets also can cap- ture a great deal of sediment due to their open, porous structure. Nets and blankets can be used to permanently stabilize channels and may provide a cost-effective, environmentally preferable alternative to riprap. 100 percent synthetic blankets manufactured for use in ditches may be easily reused as temporary ditch liners. Disadvantages of blankets include: l Surface preparation required. l On slopes steeper than 2.5H:1V, blanket installers may need to be roped and har- nessed for safety. l They cost at least $4,000-6,000 per acre installed. Advantages of blankets include: 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 288 l Installation without mobilizing special equipment. l Installation by anyone with minimal training l Installation in stages or phases as the project progresses. l Installers can hand place seed and fertilizer as they progress down the slope. l Installation in any weather. l There are numerous types of blankets that can be designed with various para- meters in mind.Those parameters include:fiber blend,mesh strength,longevity, biodegradability,cost,and availability. Design and Installation Specifications l See Figure II-4.1.3 Channel Installation (p.292)and Figure II-4.1.4 Slope Install- ation (p.293)for typical orientation and installation of blankets used in channels and as slope protection.Note:these are typical only;all blankets must be installed per manufacturer’s installation instructions. l Installation is critical to the effectiveness of these products.If good ground contact is not achieved,runoff can concentrate under the product,resulting in significant erosion. l Installation of Blankets on Slopes: 1.Complete final grade and track walk up and down the slope. 2.Install hydromulch with seed and fertilizer. 3.Dig a small trench,approximately 12 inches wide by 6 inches deep along the top of the slope. 4.Install the leading edge of the blanket into the small trench and staple approx- imately every 18 inches.NOTE:Staples are metal,“U”-shaped,and a min- imum of 6 inches long.Longer staples are used in sandy soils. Biodegradable stakes are also available. 5.Roll the blanket slowly down the slope as installer walks backwards.NOTE: The blanket rests against the installer’s legs.Staples are installed as the blanket is unrolled.It is critical that the proper staple pattern is used for the blanket being installed.The blanket is not to be allowed to roll down the slope on its own as this stretches the blanket making it impossible to main- tain soil contact.In addition,no one is allowed to walk on the blanket after it is in place. 6.If the blanket is not long enough to cover the entire slope length,the trailing edge of the upper blanket should overlap the leading edge of the lower 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 289 blanket and be stapled.On steeper slopes,this overlap should be installed in a small trench,stapled,and covered with soil. l With the variety of products available,it is impossible to cover all the details of appropriate use and installation.Therefore,it is critical that the design engineer consult the manufacturer's information and that a site visit takes place in order to ensure that the product specified is appropriate.Information is also available at the following web sites: 1.WSDOT (Section 3.2.4): http://www.wsdot.wa.gov/NR/rdonlyres/3B41E087-FA86-4717-932D- D7A8556CCD57/0/ErosionTrainingManual.pdf 2.Texas Transportation Institute: http://www.txdot.gov/business/doing_business/product_evaluation/erosion_ control.htm l Use jute matting in conjunction with mulch (BMP C121:Mulching (p.284)).Excel- sior,woven straw blankets and coir (coconut fiber)blankets may be installed without mulch.There are many other types of erosion control nets and blankets on the market that may be appropriate in certain circumstances. l In general,most nets (e.g.,jute matting)require mulch in order to prevent erosion because they have a fairly open structure.Blankets typically do not require mulch because they usually provide complete protection of the surface. l Extremely steep,unstable,wet,or rocky slopes are often appropriate candidates for use of synthetic blankets,as are riverbanks,beaches and other high-energy environments.If synthetic blankets are used,the soil should be hydromulched first. l 100-percent biodegradable blankets are available for use in sensitive areas. These organic blankets are usually held together with a paper or fiber mesh and stitching which may last up to a year. l Most netting used with blankets is photodegradable,meaning they break down under sunlight (not UV stabilized).However,this process can take months or years even under bright sun.Once vegetation is established,sunlight does not reach the mesh.It is not uncommon to find non-degraded netting still in place several years after installation.This can be a problem if maintenance requires the use of mowers or ditch cleaning equipment.In addition,birds and small animals can become trapped in the netting. Maintenance Standards l Maintain good contact with the ground.Erosion must not occur beneath the net or blanket. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 290 l Repair and staple any areas of the net or blanket that are damaged or not in close contact with the ground. l Fix and protect eroded areas if erosion occurs due to poorly controlled drainage. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 291 Figure II-4.1.3 Channel Installation D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.1.3 Channel Installation Revised June 2015 NOT TO SCALE Source: Clackamas County 2009 Erosion Prevention Planning and Design Manual Notes: 1. Check slots to be constructed per manufacturers specifications. 2. Staking or stapling layout per manufacturers specifications. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 292 Figure II-4.1.4 Slope Installation D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.1.4 Slope Installation Revised June 2015 NOT TO SCALE Notes: 1. Slope surface shall be smooth before placement for proper soil contact. 2. Stapling pattern as per manufacturer's recommendations. 3. Do not stretch blankets/mattings tight - allow the rolls to mold to any irregularities. 4. For slopes less than 3H:1V, rolls may be placed in horizontal strips. 5. If there is a berm at the top of the slope, anchor upslope of the berm. 6. Lime, fertilize, and seed before installation. Planting of shrubs, trees, etc. should occur after installation. Min. 2" overlap Anchor in 6" x 6" min. trench and staple at 12" intervals Min. 6" overlap Staple overlaps max. 5" spacing Bring material down to a level area, turn the end under 4" and staple at 12" intervals 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 293 BMP C123:Plastic Covering Purpose Plastic covering provides immediate,short-term erosion protection to slopes and dis- turbed areas. Conditions of Use Plastic covering may be used on disturbed areas that require cover measures for less than 30 days,except as stated below. l Plastic is particularly useful for protecting cut and fill slopes and stockpiles.Note: The relatively rapid breakdown of most polyethylene sheeting makes it unsuitable for long-term (greater than six months)applications. l Due to rapid runoff caused by plastic covering,do not use this method upslope of areas that might be adversely impacted by concentrated runoff.Such areas include steep and/or unstable slopes. l Plastic sheeting may result in increased runoff volumes and velocities,requiring additional on-site measures to counteract the increases.Creating a trough with wattles or other material can convey clean water away from these areas. l To prevent undercutting,trench and backfill rolled plastic covering products. l While plastic is inexpensive to purchase,the added cost of installation,main- tenance,removal,and disposal make this an expensive material,up to $1.50-2.00 per square yard. l Whenever plastic is used to protect slopes install water collection measures at the base of the slope.These measures include plastic-covered berms,channels,and pipes used to covey clean rainwater away from bare soil and disturbed areas.Do not mix clean runoff from a plastic covered slope with dirty runoff from a project. l Other uses for plastic include: 1.Temporary ditch liner. 2.Pond liner in temporary sediment pond. 3.Liner for bermed temporary fuel storage area if plastic is not reactive to the type of fuel being stored. 4.Emergency slope protection during heavy rains. 5.Temporary drainpipe (“elephant trunk”)used to direct water. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 294 Design and Installation Specifications l Plastic slope cover must be installed as follows: 1.Run plastic up and down slope,not across slope. 2.Plastic may be installed perpendicular to a slope if the slope length is less than 10 feet. 3.Minimum of 8-inch overlap at seams. 4.On long or wide slopes,or slopes subject to wind,tape all seams. 5.Place plastic into a small (12-inch wide by 6-inch deep)slot trench at the top of the slope and backfill with soil to keep water from flowing underneath. 6.Place sand filled burlap or geotextile bags every 3 to 6 feet along seams and tie them together with twine to hold them in place. 7.Inspect plastic for rips,tears,and open seams regularly and repair imme- diately.This prevents high velocity runoff from contacting bare soil which causes extreme erosion. 8.Sandbags may be lowered into place tied to ropes.However,all sandbags must be staked in place. l Plastic sheeting shall have a minimum thickness of 0.06 millimeters. l If erosion at the toe of a slope is likely,a gravel berm,riprap,or other suitable pro- tection shall be installed at the toe of the slope in order to reduce the velocity of run- off. Maintenance Standards l Torn sheets must be replaced and open seams repaired. l Completely remove and replace the plastic if it begins to deteriorate due to ultra- violet radiation. l Completely remove plastic when no longer needed. l Dispose of old tires used to weight down plastic sheeting appropriately. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C123:Plastic Covering.The products did not pass through the Technology Assessment Protocol – Ecology (TAPE)process.Local jurisdictions may choose not to accept this product approved as equivalent,or may require additional testing prior to consideration for local use.The products are available for review on Ecology’s website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 295 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 l In areas (including roadways)subject to surface and air movement of dust where on-site and 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 plant- ing,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 ori- ginal ground cover as long as practical. l Construct natural or artificial windbreaks or windscreens.These may be designed as enclosures for small dust sources. l Sprinkle the site with water until surface is wet.Repeat as needed.To prevent carryout of mud onto street,refer to BMP C105:Stabilized Construction Entrance / Exit (p.270). 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 pro- hibited from use as a dust suppressant.Local governments may approve other dust palliatives such as calcium chloride or PAM. l PAM (BMP C126:Polyacrylamide (PAM)for Soil Erosion Protection (p.300)) added to water at a rate of 0.5 lbs.per 1,000 gallons of water per acre and applied from a water truck is more effective than water alone.This is due to increased infilt- ration of water into the soil and reduced evaporation.In addition,small soil particles are bonded together and are not as easily transported by wind.Adding PAM may actually reduce the quantity of water needed for dust control.Use of PAM could be a cost-effective dust control method. Techniques that can be used for unpaved roads and lots include: 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 310 l Lower speed limits. High vehicle speed increases the amount of dust stirred up from unpaved roads and lots. l Upgrade the road surface strength by improving particle size, shape, and mineral types that make up the surface and base materials. l 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. l Use geotextile fabrics to increase the strength of new roads or roads undergoing reconstruction. l Encourage the use of alternate, paved routes, if available. l Restrict use of paved roadways by tracked vehicles and heavy trucks to prevent damage to road surface and base. l 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. l Pave unpaved permanent roads and other trafficked areas. l Use vacuum street sweepers. l Remove mud and other dirt promptly so it does not dry and then turn into dust. l Limit dust-causing work on windy days. l Contact your local Air Pollution Control Authority for guidance and training on other dust control measures. Compliance with the local Air Pollution Control Authority constitutes compliance with this BMP. Maintenance Standards Respray area as necessary to keep dust to a minimum. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 311 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 unex- pected heavy summer rains. Having these materials on-site reduces the time needed to implement BMPs when inspections indicate that existing BMPs are not meeting the Con- struction SWPPP requirements. In addition, contractors can save money by buying some materials in bulk and storing them at their office or yard. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 311 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 pipe, sandbags, geotextile fab- ric and steel “T” posts. l Materials are stockpiled and readily available before any site clearing, grubbing, or earthwork begins. A large contractor or developer could keep a stockpile of mater- ials 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: Material Clear Plastic, 6 mil Drainpipe, 6 or 8 inch diameter Sandbags, filled Straw Bales for mulching, Quarry Spalls Washed Gravel Geotextile Fabric Catch Basin Inserts Steel "T" Posts Silt fence material 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 used as needed. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 312 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 discharge to surface waters of the State is prohibited.Use this BMP to minimize and eliminate concrete,concrete process water,and concrete slurry from entering waters of the state. Conditions of Use Any time concrete is used,utilize these management practices.Concrete construction projects include,but are not limited to,the following: l Curbs l Sidewalks l Roads l Bridges l Foundations l Floors l Runways Design and Installation Specifications l Assure that washout of concrete trucks,chutes,pumps,and internals is performed at an approved off-site location or in designated concrete washout areas.Do not wash out concrete trucks onto the ground,or into storm drains,open ditches, streets,or streams.Refer to BMP C154:Concrete Washout Area (p.317)for inform- ation on concrete washout areas. l 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 con- crete washout areas. l Wash off hand tools including,but not limited to,screeds,shovels,rakes,floats, and trowels into formed areas only. l Wash equipment difficult to move,such as concrete pavers in areas that do not dir- ectly drain to natural or constructed stormwater conveyances. l Do not allow washdown from areas,such as concrete aggregate driveways,to drain directly to natural or constructed stormwater conveyances. l Contain washwater and leftover product in a lined container when no formed areas 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 313 are available. Dispose of contained concrete in a manner that does not violate ground water or surface water quality standards. l Always use forms or solid barriers for concrete pours, such as pilings, within 15- feet of surface waters. l Refer to BMP C252:High pH Neutralization Using CO2 (p.409)and BMP C253: pH Control for High pH Water (p.412)for pH adjustment requirements. l Refer to the Construction Stormwater General Permit for pH monitoring require- ments if the project involves one of the following activities: l Significant concrete work (greater than 1,000 cubic yards poured concrete or recycled concrete used over the life of a project). l The use of engineered soils amended with (but not limited to) Portland cement-treated base, cement kiln dust or fly ash. l Discharging stormwater to segments of water bodies on the 303(d) list (Cat- egory 5) for high pH. Maintenance Standards Check containers for holes in the liner daily during concrete pours and repair the same day. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 314 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 surface waters of the State is prohibited. Use this BMP to minimize and eliminate process water and slurry created through sawcutting or surfacing from entering waters of the State. Conditions of Use Utilize these management practices anytime sawcutting or surfacing operations take place. Sawcutting and surfacing operations include, but are not limited to, the following: l Sawing l Coring l Grinding l Roughening 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 314 l Hydro-demolition l Bridge and road surfacing 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 con- veyance including 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 surface water quality standards. l Do not allow process water generated during hydro-demolition, surface rough- ening or similar operations to drain to any natural or constructed drainage con- veyance including stormwater systems. Dispose process water in a manner that does not violate ground water or surface water quality standards. l Handle and dispose 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 stand- ards could occur, stop operations and immediately implement preventive measures such as berms, barriers, secondary containment, and vacuum trucks. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 315 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 materials in a designated area, and install secondary con- tainment. Conditions of Use These procedures are suitable for use at all construction sites with delivery and storage of the following materials: 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 315 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 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 The following steps should be taken to minimize risk: l Temporary storage area should be located away from vehicular traffic,near the con- struction entrance(s),and away from waterways or storm drains. l Material Safety Data Sheets (MSDS)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 earthen dike,horse trough,or even a children’s wading pool for non-reactive materials such as deter- gents,oil,grease,and paints.Small amounts of material may be secondarily con- tained in “bus boy”trays or concrete mixing trays. l Do not store chemicals,drums,or bagged materials directly on the ground.Place these items on a pallet and,when possible,and within secondary containment. 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. Material Storage Areas and Secondary Containment Practices: 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 facil- ities. l Temporary secondary containment facilities shall provide for a spill containment 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 316 volume able to contain 10% of the total enclosed container volume of all con- tainers, or 110% of the capacity of the largest container within its boundary, whichever is greater. l Secondary containment facilities shall be impervious to the materials stored therein for a minimum contact time of 72 hours. l Secondary containment facilities shall be maintained free of accumulated rain- water 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 haz- ardous waste unless testing determines them to be non-hazardous. 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 appropriate spill clean-up material (spill kit). l The spill kit should include, at a minimum: 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 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 317 BMP C154: Concrete Washout Area Purpose Prevent or reduce the discharge of pollutants to stormwater from concrete waste by con- ducting washout off-site, or performing on-site washout in a designated area to prevent pollutants from entering surface waters or ground water. Conditions of Use Concrete washout area best management practices are implemented on construction projects where: 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 317 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 trucks,pumpers,or other concrete coated equipment are washed on-site. l Note:If less than 10 concrete trucks or pumpers need to be washed out on-site,the washwater may be disposed of in a formed area awaiting concrete or an upland disposal site where it will not contaminate surface or ground water.The upland dis- posal site shall be at least 50 feet from sensitive areas such as storm drains,open ditches,or water bodies,including wetlands. Design and Installation Specifications Implementation The following steps will help reduce stormwater pollution from concrete wastes: l Perform washout of concrete trucks at an approved off-site location or in des- ignated concrete washout areas only. l Do not wash out concrete trucks onto the ground,or into storm drains,open ditches,streets,or streams. l Do not allow excess concrete to be dumped on-site,except in designated concrete washout areas. 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 pre- ferred 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 prac- tical. Education l Discuss the concrete management techniques described in this BMP with the ready-mix concrete supplier before any deliveries are made. l Educate employees and subcontractors on the concrete waste management tech- niques described in this BMP. l Arrange for contractor’s superintendent or Certified Erosion and Sediment Control 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 318 Lead (CESCL)to oversee and enforce concrete waste management procedures. l A sign should be installed adjacent to each temporary concrete washout facility to inform concrete equipment operators to utilize the proper facilities. Contracts Incorporate requirements for concrete waste management into concrete supplier and sub- contractor agreements. Location and Placement l Locate washout area at least 50 feet from sensitive areas such as storm drains, open ditches,or water bodies,including wetlands. l Allow convenient access for concrete trucks,preferably near the area where the concrete is being poured. l If trucks need to leave a paved area to access washout,prevent track-out with a pad of rock or quarry spalls (see BMP C105:Stabilized Construction Entrance / Exit (p.270)).These areas should be far enough away from other construction traffic to reduce the likelihood of accidental damage and spills. l The number of facilities you install should depend on the expected demand for stor- age capacity. l On large sites with extensive concrete work,washouts should be placed in mul - tiple locations for ease of use by concrete truck drivers. On-site Temporary Concrete Washout Facility,Transit Truck Washout Procedures: l Temporary concrete washout facilities shall be located a minimum of 50 ft from sensitive areas including storm drain inlets,open drainage facilities,and water- courses.See Figure II-4.1.7a Concrete Washout Area (p.322),Figure II-4.1.7b Con- crete Washout Area (p.323),and Figure II-4.1.8 Prefabricated Concrete Washout Container w/Ramp (p.324). l Concrete washout facilities shall be constructed and maintained in sufficient quant- ity and size to contain all liquid and concrete waste generated by washout oper- ations. l Washout of concrete trucks shall be performed in designated areas only. l Concrete washout from concrete pumper bins can be washed into concrete pumper trucks and discharged into designated washout area or properly disposed of off-site. l Once concrete wastes are washed into the designated area and allowed to 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 319 harden,the concrete should be broken up,removed,and disposed of per applic- able solid waste regulations.Dispose of hardened concrete on a regular basis. l Temporary Above-Grade Concrete Washout Facility l Temporary concrete washout facility (type above grade)should be con- structed as shown on the details below,with a recommended 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 imper- meability of the material. l Temporary Below-Grade Concrete Washout Facility l Temporary concrete washout facilities (type below grade)should be con- structed as shown on the details below,with a recommended minimum length and minimum width of 10 ft.The quantity and volume should be suf- ficient to contain all liquid and concrete waste generated by washout oper- ations. l Lath and flagging should be commercial type. l Plastic lining material shall be a minimum of 10 mil polyethylene sheeting and should be free of holes,tears,or other defects that compromise the imper- meability of the material. l Liner seams shall be installed in accordance with manufacturers’recom- mendations. 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 BMPs are in place prior to the com- mencement of concrete work. l During periods of concrete work,inspect daily to verify continued performance. l Check overall condition and performance. l Check remaining capacity (%full). l If using self-installed washout facilities,verify plastic liners are intact and side- walls are not damaged. l If using prefabricated containers,check for leaks. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 320 l Washout facilities shall be maintained to provide adequate holding capacity with a minimum freeboard of 12 inches. l Washout facilities must be cleaned,or new facilities must be constructed and ready for use once the washout is 75%full. l If the washout 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 use sanitary sewer without local approval. l Place a secure,non-collapsing,non-water collecting cover over the concrete washout facility prior to predicted wet weather to prevent accumulation and overflow of precipitation. l Remove and dispose of hardened concrete and return the structure to a func- tional condition.Concrete may be reused on-site or hauled away for disposal or recycling. l When you remove materials from the self-installed concrete washout,build a new structure;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 Temporary Concrete Washout Facilities l When temporary concrete washout facilities are no longer required for the work, the hardened concrete,slurries and liquids shall be removed and properly dis- posed of. l Materials used to construct temporary concrete washout facilities 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 tem- porary concrete washout facilities shall be backfilled,repaired,and stabilized to prevent erosion. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 321 Figure II-4.1.7a Concrete Washout Area D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.1.7a Concrete Washout Area Revised June 2015 NOT TO SCALE Sandbag Berm 10 mil plastic lining 1 m Section A-A Plan Type "Below Grade" Lath and flagging on 3 sides 3m Minimum Varies Sandbag Berm 10 mil plastic lining Type "Above Grade" with Wood Planks Section B-B Plan 3m Minimum Stake (typ.) AA 10 mil plastic lining Varies Two-stacked 2x12 rough wood frame BB 10 mil plastic lining Wood frame securely fastened around entire perimeter with two stakes Notes: 1. Actual layout determined in the field. 2. A concrete washout sign shall be installed within 10 m of the temporary concrete washout facility. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 322 Figure II-4.1.7b Concrete Washout Area D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.1.7b Concrete Washout Area Revised June 2015 NOT TO SCALE Type "Above Grade" with Straw Bales Plan Section B-B Concrete Washout Sign Detail (or equivalent) Staple Detail Wood or metal stakes (2 per bale) Staples (2 per bale) Straw bale 10 mil plastic lining Native material (optional) Binding wire CONCRETE WASHOUT 915 mm 915 mm Plywood 1200 mm x 610 mm painted white Black letters 150 mm height Lag screws (12.5 mm) Wood post (89 mm x 89 mm x 2.4 m) 50 mm 200 mm 3.05 mm dia. steel wire 3m Minimum Varies 10 mil plastic lining Stake (typ) Straw bale (typ.) BB Notes: 1. Actual layout determined in the field. 2. The concrete washout sign shall be installed within 10 m of the temporary concrete washout facility. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 323 Figure II-4.1.8 Prefabricated Concrete Washout Container w/Ramp D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.1.8 Prefabricated Concrete Washout Container w/Ramp Revised June 2015 NOT TO SCALE 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 324 BMP C160:Certified Erosion and Sediment Control Lead Purpose The project proponent designates at least one person as the responsible representative in charge of erosion and sediment control (ESC),and water quality protection.The des- ignated person shall be the Certified Erosion and Sediment Control Lead (CESCL)who is responsible for ensuring compliance with all local,state,and federal erosion and sed- iment control and water quality requirements. Conditions of Use A CESCL shall be made available on projects one acre or larger that discharge storm- water to surface waters of the state.Sites less than one acre may have a person without CESCL certification conduct inspections;sampling is not required on sites that disturb less than an acre. l The CESCL shall: l Have a current certificate proving attendance in an erosion and sediment con- trol training course that meets the minimum ESC training and certification requirements established by Ecology (see details below). Ecology will maintain a list of ESC training and certification providers at: http://www.ecy.wa.gov/programs/wq/stormwater/cescl.html OR l Be a Certified Professional in Erosion and Sediment Control (CPESC);for additional information go to:http://www.envirocertintl.org/cpesc/ Specifications l Certification shall remain valid for three years. l The CESCL shall have authority to act on behalf of the contractor or developer and shall be available,or on-call,24 hours per day throughout the period of con- struction. l The Construction SWPPP shall include the name,telephone number,fax number, and address of the designated CESCL. l A CESCL may provide inspection and compliance services for multiple con- struction projects in the same geographic region. Duties and responsibilities of the CESCL shall include,but are not limited to the fol- lowing: 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 325 l Maintaining permit file on site at all times which includes the Construction SWPPP and any associated permits and plans. l Directing BMP installation, inspection, maintenance, modification, and removal. l Updating all project drawings and the Construction SWPPP with changes made. l Completing any sampling requirements including reporting results using WebDMR. l Keeping daily logs, and inspection reports. Inspection reports should include: l Inspection date/time. l Weather information; general conditions during inspection and approximate amount of precipitation since the last inspection. l A summary or list of all BMPs implemented, including observations of all erosion/sediment control structures or practices. The following shall be noted: 1. Locations of BMPs inspected. 2. Locations of BMPs that need maintenance. 3. Locations of BMPs that failed to operate as designed or intended. 4. Locations of where additional or different BMPs are required. l Visual monitoring results, including a description of discharged stormwater. The presence of suspended sediment, turbid water, discoloration, and oil sheen shall be noted, as applicable. l Any water quality monitoring performed during inspection. l General comments and notes, including a brief description of any BMP repairs, maintenance or installations made as a result of the inspection. l Facilitate, participate in, and take corrective actions resulting from inspections per- formed by outside agencies or the owner. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 326 BMP C162: Scheduling Purpose Sequencing a construction project reduces the amount and duration of soil exposed to erosion by wind, rain, runoff, and vehicle tracking. Conditions of Use The construction sequence schedule is an orderly listing of all major land-disturbing activities together with the necessary erosion and sedimentation control measures 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 326 planned for the project.This type of schedule guides the contractor on work to be done before other work is started so that serious erosion and sedimentation problems can be avoided. Following a specified work schedule that coordinates the timing of land-disturbing activ- ities and the installation of control measures is perhaps the most cost-effective way of controlling erosion during construction.The removal of surface ground cover leaves a site vulnerable to accelerated erosion.Construction procedures that limit land clearing provide timely installation of erosion and sedimentation controls,and restore protective cover quickly can significantly reduce the erosion potential of a site. Design Considerations l Minimize construction during rainy periods. l Schedule projects to disturb only small portions of the site at any one time.Com- plete grading as soon as possible.Immediately stabilize the disturbed portion before grading the next portion.Practice staged seeding in order to revegetate cut and fill slopes as the work progresses. II-4.2 Runoff Conveyance and Treatment BMPs This section contains the standards and specifications for Runoff Conveyance and Treat- ment BMPs.Table II-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Ele- ment (p.327),below,shows the relationship of the BMPs in II-4.2 Runoff Conveyance and Treatment BMPs to the Construction Stormwater Pollution Prevention Plan (SWPPP)Elements described in II-3.3.3 Step 3 -Construction SWPPP Development and Implementation (p.236). BMP or Ele- ment Name Ele- ment #3 Con- trol Flow Rates Element #4 Install Sed- iment Con- trols Ele- ment #6 Pro- tect Slopes Ele- ment #7 Pro- tect Drain Inlets Element #8 Stab- ilize Chan- nels and Out- lets Element #9 Con- trol Pol- lutants Ele- ment #10 Control De- Water- ing Element #13 Protect Low Impact Devel- opment BMP C200: Interceptor Dike and Swale (p.331) ü ü Table II-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Element 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 327 BMP or Ele- ment Name Ele- ment #3 Con- trol Flow Rates Element #4 Install Sed- iment Con- trols Ele- ment #6 Pro- tect Slopes Ele- ment #7 Pro- tect Drain Inlets Element #8 Stab- ilize Chan- nels and Out- lets Element #9 Con- trol Pol- lutants Ele- ment #10 Control De- Water- ing Element #13 Protect Low Impact Devel- opment BMP C201: Grass- Lined Chan- nels (p.333) ü ü BMP C202: Channel Lining (p.338) ü BMP C203: Water Bars (p.339) ü ü ü BMP C204: Pipe Slope Drains (p.342) ü BMP C205: Subsurface Drains (p.346) ü BMP C206: Level Spreader (p.348) ü ü BMP C207: Check Dams (p.352) ü ü ü ü BMP C208: Triangular Silt Dike (TSD)(Geo- ü ü Table II-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Element (continued) 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 328 BMP or Ele- ment Name Ele- ment #3 Con- trol Flow Rates Element #4 Install Sed- iment Con- trols Ele- ment #6 Pro- tect Slopes Ele- ment #7 Pro- tect Drain Inlets Element #8 Stab- ilize Chan- nels and Out- lets Element #9 Con- trol Pol- lutants Ele- ment #10 Control De- Water- ing Element #13 Protect Low Impact Devel- opment textile- Encased Check Dam) (p.355) BMP C209: Outlet Pro- tection (p.356) ü ü BMP C220: Storm Drain Inlet Pro- tection (p.357) ü BMP C231: Brush Bar- rier (p.365) ü ü BMP C232: Gravel Filter Berm (p.367) ü BMP C233: Silt Fence (p.367) ü ü BMP C234: Vegetated Strip (p.375) ü ü BMP C235: Wattles (p.376) ü ü BMP C236:ü Table II-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Element (continued) 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 329 BMP or Ele- ment Name Ele- ment #3 Con- trol Flow Rates Element #4 Install Sed- iment Con- trols Ele- ment #6 Pro- tect Slopes Ele- ment #7 Pro- tect Drain Inlets Element #8 Stab- ilize Chan- nels and Out- lets Element #9 Con- trol Pol- lutants Ele- ment #10 Control De- Water- ing Element #13 Protect Low Impact Devel- opment Vegetative Filtration (p.379) BMP C240: Sediment Trap (p.383) ü ü BMP C241: Temporary Sediment Pond (p.388) ü ü BMP C250: Con- struction Stormwater Chemical Treatment (p.396) ü ü BMP C251: Con- struction Stormwater Filtration (p.404) ü ü BMP C252: High pH Neut- ralization Using CO2 (p.409) ü BMP C253: pH Control ü Table II-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Element (continued) 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 330 BMP or Ele- ment Name Ele- ment #3 Con- trol Flow Rates Element #4 Install Sed- iment Con- trols Ele- ment #6 Pro- tect Slopes Ele- ment #7 Pro- tect Drain Inlets Element #8 Stab- ilize Chan- nels and Out- lets Element #9 Con- trol Pol- lutants Ele- ment #10 Control De- Water- ing Element #13 Protect Low Impact Devel- opment for High pH Water (p.412) Table II-4.2.1 Runoff Conveyance and Treatment BMPs by SWPPP Element (continued) 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 331 BMP C200: Interceptor Dike and Swale Purpose Provide a ridge of compacted soil, or a ridge with an upslope swale, at the top or base of a disturbed slope or along the perimeter of a disturbed construction area to convey storm- water. Use the dike and/or swale to intercept the runoff from unprotected areas and direct it to areas where erosion can be controlled. This can prevent storm runoff from entering the work area or sediment-laden runoff from leaving the construction site. Conditions of Use Where the runoff from an exposed site or disturbed slope must be conveyed to an erosion control facility which can safely convey the stormwater. l Locate upslope of a construction site to prevent runoff from entering disturbed area. l When placed horizontally across a disturbed slope, it reduces the amount and velo- city of runoff flowing down the slope. l Locate downslope to collect runoff from a disturbed area and direct water to a sed- iment basin. Design and Installation Specifications l Dike and/or swale and channel must be stabilized with temporary or permanent vegetation or other channel protection during construction. l Channel requires a positive grade for drainage; steeper grades require channel protection and check dams. l Review construction for areas where overtopping may occur. l Can be used at top of new fill before vegetation is established. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 331 l May be used as a permanent diversion channel to carry the runoff. l Sub-basin tributary area should be one acre or less. l Design capacity for the peak volumetric flow rate calculated using a 10-minute time step from a 10-year,24-hour storm,assuming a Type 1A rainfall distribution,for temporary facilities.Alternatively,use 1.6 times the 10-year,1-hour flow indicated by an approved continuous runoff model.For facilities that will also serve on a per- manent basis,consult the local government’s drainage requirements. Interceptor dikes shall meet the following criteria: l Top Width:2 feet minimum. l Height:1.5 feet minimum on berm. l Side Slope:2H:1V or flatter. l Grade:Depends on topography,however,dike system minimum is 0.5%,and max- imum is 1%. l Compaction:Minimum of 90 percent ASTM D698 standard proctor. l Horizontal Spacing of Interceptor Dikes: Average Slope Slope Percent Flowpath Length 20H:1V or less 3-5%300 feet (10 to 20)H:1V 5-10%200 feet (4 to 10)H:1V 10-25%100 feet (2 to 4)H:1V 25-50%50 feet l Stabilization:depends on velocity and reach l Slopes <5%:Seed and mulch applied within 5 days of dike construction (see BMP C121:Mulching (p.284)). l Slopes 5 -40%:Dependent on runoff velocities and dike materials.Stabilization should be done immediately using either sod or riprap or other measures to avoid erosion. l The upslope side of the dike shall provide positive drainage to the dike outlet.No erosion shall occur at the outlet.Provide energy dissipation measures as neces- sary.Sediment-laden runoff must be released through a sediment trapping facility. l Minimize construction traffic over temporary dikes.Use temporary cross culverts for channel crossing. Interceptor swales shall meet the following criteria: l Bottom Width:2 feet minimum;the cross-section bottom shall be level. l Depth:1-foot minimum. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 332 l Side Slope: 2H:1V or flatter. l Grade: Maximum 5 percent, with positive drainage to a suitable outlet (such as a sediment pond). l Stabilization: Seed as per BMP C120:Temporary and Permanent Seeding (p.278), or BMP C202:Channel Lining (p.338), 12 inches thick riprap pressed into the bank and extending at least 8 inches vertical from the bottom. Inspect diversion dikes and interceptor swales once a week and after every rainfall. Immediately remove sediment from the flow area. Damage caused by construction traffic or other activity must be repaired before the end of each working day. Check outlets and make timely repairs as needed to avoid gully formation. When the area below the temporary diversion dike is permanently stabilized, remove the dike and fill and stabilize the channel to blend with the natural surface. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 333 BMP C207:Check Dams Purpose Construction of small dams across a swale or ditch reduces the velocity of concentrated flow and dissipates energy at the check dam. Conditions of Use Where temporary channels 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 Depart- ment of Fish and Wildlife.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 bear- ing 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. 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 (no dumping of rock to form 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 dam should form a triangle when viewed from the side.This prevents under- cutting as water flows over the face of the 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 chan- nels. l Check dams in association with sumps work more effectively at slowing flow and retaining sediment than just 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 per- manent installations with very minor regrading.They may be left as either spill- ways,in which case accumulated sediment would be graded and seeded,or as 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 352 check dams to prevent further sediment from leaving the site. l The maximum spacing between the dams shall be such that the toe of the 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 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.Figure II-4.2.7 Rock Check Dam (p.354)depicts a typical rock check dam. Maintenance Standards Check dams shall be monitored for performance and sediment accumulation during and after each runoff producing rainfall.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. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C207:Check Dams.The products did not pass through the Technology Assessment Protocol –Eco- logy (TAPE)process.Local jurisdictions may choose not to accept this product approved as equivalent,or may require additional testing prior to consideration for local use.The products are available for review on Ecology’s website at http://www.ecy.wa.gov- /programs/wq/stormwater/newtech/equivalent.html 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 353 Figure II-4.2.7 Rock Check Dam D E P A R T M E N T O F E C O L O G Y S t a t e o f W a s h i n g t o n Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.2.7 Rock Check Dam Revised July 2015 NOT TO SCALE View Looking Upstream Section A-A Spacing Between Check Dams Note: Key stone into channel banks and extend it beyond the abutments a minimum of 18" (0.5m) to prevent flow around dam. A A 12" (150mm) 18" (0.5m) 24" (0.6m) Flow 24" (0.6m) 8' (2.4m) Point 'A'Point 'B' 'L' 'L' = the distance such that points 'A' and 'B' are of equal elevation. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 354 BMP C209: Outlet Protection Purpose Outlet protection prevents scour at conveyance outlets and minimizes the potential for downstream erosion by reducing the velocity of concentrated stormwater flows. Conditions of Use Outlet protection is required at the outlets of all ponds, pipes, ditches, or other con- veyances, and where runoff is conveyed to a natural or manmade drainage feature such as a stream, wetland, lake, or ditch. Design and Installation Specifications The receiving channel at the outlet of a culvert shall be protected from erosion by rock lin- ing a minimum of 6 feet downstream and extending up the channel sides a minimum of 1–foot above the maximum tailwater elevation or 1-foot above the crown, whichever is higher. For large pipes (more than 18 inches in diameter), the outlet protection lining of the channel is lengthened to four times the diameter of the culvert. l Standard wingwalls, and tapered outlets and paved channels should also be con- sidered when appropriate for permanent culvert outlet protection. (See WSDOT Hydraulic Manual, available through WSDOT Engineering Publications). l Organic or synthetic erosion blankets, with or without vegetation, are usually more effective than rock, cheaper, and easier to install. Materials can be chosen using manufacturer product specifications. ASTM test results are available for most products and the designer can choose the correct material for the expected flow. l With low flows, vegetation (including sod) can be effective. l The following guidelines shall be used for riprap outlet protection: 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 356 1. If the discharge velocity at the outlet is less than 5 fps (pipe slope less than 1 percent), use 2-inch to 8-inch riprap. Minimum thickness is 1-foot. 2. For 5 to 10 fps discharge velocity at the outlet (pipe slope less than 3 per- cent), use 24-inch to 48-inch riprap. Minimum thickness is 2 feet. 3. For outlets at the base of steep slope pipes (pipe slope greater than 10 per- cent), an engineered energy dissipater shall be used. l Filter fabric or erosion control blankets should always be used under riprap to pre- vent scour and channel erosion. l New pipe outfalls can provide an opportunity for low-cost fish habitat improve- ments. For example, an alcove of low-velocity water can be created by con- structing the pipe outfall and associated energy dissipater back from the stream edge and digging a channel, over-widened to the upstream side, from the outfall. Overwintering juvenile and migrating adult salmonids may use the alcove as shel- ter during high flows. Bank stabilization, bioengineering, and habitat features may be required for disturbed areas. This work may require a HPA. See Volume V (p.765)for more information on outfall system design. Maintenance Standards l Inspect and repair as needed. l Add rock as needed to maintain the intended function. l Clean energy dissipater if sediment builds up. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 357 BMP C220: Storm Drain Inlet Protection Purpose Storm drain inlet protection prevents coarse sediment from entering drainage systems prior to permanent stabilization of the disturbed area. Conditions of Use Use storm drain inlet protection at inlets that are operational before permanent sta- bilization of the disturbed drainage area. Provide protection for all storm drain inlets downslope and within 500 feet of a disturbed or construction area, unless conveying run- off entering catch basins to a sediment pond or trap. Also consider inlet protection for lawn and yard drains on new home construction. These small and numerous drains coupled with lack of gutters in new home construction 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 pre- 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 357 vent sediment from entering the system until completion of landscaping.Provide 18- inches of sod around each finished lawn and yard drain. Table II-4.2.2 Storm Drain Inlet Protection (p.358)lists several options for inlet protection. All of the methods for storm drain inlet protection tend to plug and require a high fre- quency of maintenance.Limit drainage areas to one acre or less.Possibly provide emer- gency overflows with additional end-of-pipe treatment where stormwater ponding would cause a hazard. Type of Inlet Protection Emergency Overflow Applicable for Paved/Earthen Surfaces Conditions of Use Drop Inlet Protection Excavated drop inlet protection Yes,tem- porary flood- ing will occur Earthen Applicable for heavy flows.Easy to maintain.Large area Require- ment:30'x30'/acre Block and gravel drop inlet protection Yes Paved or Earthen Applicable for heavy concentrated flows.Will not pond. Gravel and wire drop inlet pro- tection No Applicable for heavy concentrated flows.Will pond.Can withstand traffic. Catch basin fil- ters 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 installation. Block and gravel curb inlet protection Yes Paved Sturdy,but limited filtration. Culvert Inlet Protection Culvert inlet Sed- iment trap 18 month expected life. Table II-4.2.2 Storm Drain Inlet Protection Design and Installation Specifications Excavated Drop Inlet Protection -An excavated impoundment around the storm drain. Sediment settles out of the stormwater prior to entering the storm drain. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 358 l Provide a depth of 1-2 ft as measured from the crest of the inlet structure. l Slope sides of excavation no steeper than 2H:1V. l Minimum volume of excavation 35 cubic yards. l Shape basin to fit site with longest dimension oriented toward the longest inflow area. l Install provisions for draining to prevent standing water problems. l Clear the area of all debris. 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 pre- vent bypass flow. Block and Gravel Filter -A barrier formed around the storm drain inlet with standard con- crete blocks and gravel.See Figure II-4.2.8 Block and Gravel Filter (p.360). l Provide a height of 1 to 2 feet above inlet. l Recess the first row 2-inches into the ground for stability. l Support subsequent courses by placing a 2x4 through the block opening. l Do not use mortar. l Lay some blocks in the bottom row on their side for dewatering the pool. l Place hardware cloth or comparable wire mesh with ½-inch openings over all block openings. l Place gravel just below the top of blocks on slopes of 2H:1V or flatter. l An alternative design is a gravel donut. l Provide an inlet slope of 3H:1V. l Provide an outlet slope of 2H:1V. l Provide a1-foot wide level stone area between the structure and the inlet. l Use inlet slope stones 3 inches in diameter or larger. l Use gravel ½-to ¾-inch at a minimum thickness of 1-foot for the outlet slope. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 359 Figure II-4.2.8 Block and Gravel Filter D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.2.8 Block and Gravel Filter Revised August 2015 NOT TO SCALE Plan View A A Section A-A Drain grate Concrete block Gravel backfill Less than5% slope Gravel backfill Concrete block Water Overflow water Drop inlet Ponding height Wire screen or filter fabric Notes: 1. Drop inlet sediment barriers are to be used for small, nearly level drainage areas. (less than 5%) 2. Excavate a basin of sufficient size adjacent to the drop inlet. 3. The top of the structure (ponding height) must be well below the ground elevation downslope to prevent runoff from bypassing the inlet. A temporary dike may be necessary on the downslope side of the structure. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 360 Gravel and Wire Mesh Filter -A gravel barrier placed over the top of the inlet.This struc- ture does not provide an overflow. l Use a hardware cloth or comparable wire mesh with ½-inch openings. l Use coarse aggregate. l Provide a height 1-foot or more,18-inches wider than inlet on all sides. l Place wire mesh over the drop inlet so that the wire extends a minimum of 1-foot beyond each side of the inlet structure. l Overlap the strips if more than one strip of mesh is necessary. l Place coarse aggregate over the wire mesh. l Provide at least a 12-inch depth of gravel over the entire inlet opening and extend at least 18-inches on all sides. Catchbasin Filters –Use inserts designed by manufacturers for construction sites.The limited sediment storage capacity increases the amount of inspection and maintenance required,which may be daily for heavy sediment loads.To reduce maintenance require- ments combine a catchbasin 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. 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 catchbasin filter in the catchbasin just below the grating. Curb Inlet Protection with Wooden Weir –Barrier formed around a curb inlet with a wooden frame and gravel. 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 wire/fabric. l Place weight on frame anchors. Block and Gravel Curb Inlet Protection –Barrier formed around a curb inlet with concrete blocks and gravel.See Figure II-4.2.9 Block and Gravel Curb Inlet Protection (p.363). 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 361 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. Curb and Gutter Sediment Barrier –Sandbag or rock berm (riprap and aggregate)3 feet high and 3 feet wide in a horseshoe shape.See Figure II-4.2.10 Curb and Gutter Barrier (p.364). 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 outside of the berm sized to sediment trap standards for protecting a culvert inlet. Maintenance Standards l Inspect catch basin filters frequently,especially after storm events.Clean and replace clogged inserts.For systems with clogged stone filters:pull away the stones from the inlet and clean or replace.An alternative approach would be to use the clogged stone as fill and put fresh stone around the inlet. 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 appro- priate. Approved as Equivalent Ecology has approved products as able to meet the requirements of BMP C220:Storm Drain Inlet Protection.The products did not pass through the Technology Assessment Protocol –Ecology (TAPE)process.Local jurisdictions may choose not to accept this product approved as equivalent,or may require additional testing prior to consideration for local use.The products are available for review on Ecology’s website at http://www.ecy.wa.gov/programs/wq/stormwater/newtech/equivalent.html 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 362 Figure II-4.2.9 Block and Gravel Curb Inlet Protection D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.2.9 Block and Gravel Curb Inlet Protection Revised August 2015 NOT TO SCALE Plan View A A Section A-A Notes: 1. Use block and gravel type sediment barrier when curb inlet is located in gently sloping street segment, where water can pond and allow sediment to separate from runoff. 2. Barrier shall allow for overflow from severe storm event. 3. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately. Back of sidewalk Catch basin Back of curb Curb inlet Concrete block 2x4 Wood stud Concrete block34 inch (20 mm) Drain gravel Wire screen or filter fabric 3 4 inch (20 mm) Drain gravel Wire screen or filter fabric Ponding height Overflow 2x4 Wood stud (100x50 Timber stud) Concrete block Curb inlet Catch basin 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 363 Figure II-4.2.10 Curb and Gutter Barrier D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.2.10 Curb and Gutter Barrier Revised September 2015 NOT TO SCALE Plan View Back of sidewalk Runoff Runoff Spillway Burlap sacks to overlap onto curb Gravel filled sandbags stacked tightly Curb inlet Catch basin Back of curb Notes: 1. Place curb type sediment barriers on gently sloping street segments, where water can pond and allow sediment to separate from runoff. 2. Sandbags of either burlap or woven 'geotextile' fabric, are filled with gravel, layered and packed tightly. 3. Leave a one sandbag gap in the top row to provide a spillway for overflow. 4. Inspect barriers and remove sediment after each storm event. Sediment and gravel must be removed from the traveled way immediately. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 364 BMP C233: Silt Fence Purpose Use of a 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. See Figure II-4.2.12 Silt Fence (p.369)for details on silt fence con- struction. Conditions of Use Silt fence may be used downslope of all disturbed areas. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 367 l Silt fence shall prevent soil carried by runoff water 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 sub- stantial amounts of overland flow.Convey any concentrated flows through the drainage system to a sediment pond. 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. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 368 Figure II-4.2.12 Silt Fence D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.2.12 Silt Fence Revised October 2014 NOT TO SCALE Joints in filter fabric shall be spliced at posts. Use staples, wire rings or equivalent to attach fabric to posts 6' max Post spacing may be increased to 8' if wire backing is used 2"x2" by 14 Ga. wire or equivalent, if standard strength fabric used Minimum 4"x4" trench 2"x2" wood posts, steel fence posts, or equivalent 12" min 2' min 2"x2" by 14 Ga. wire or equivalent, if standard strength fabric used Filter fabric Minimum 4"x4" trench 2"x2" wood posts, steel fence posts, or equivalent Backfill trench with native soil or 3 4" - 1.5" washed gravel 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 369 Design and Installation Specifications l Use in combination with sediment basins or other BMPs. l Maximum slope steepness (normal (perpendicular)to fence line)1H:1V. l Maximum sheet or overland flow path length to the fence of 100 feet. l Do not allow flows greater than 0.5 cfs. l The geotextile used shall meet the following standards.All geotextile properties lis- ted 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-4.2.3 Geotextile Stand- ards (p.370)): 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-4.2.3 Geotextile Standards l Support standard strength fabrics with wire mesh,chicken wire,2-inch x 2-inch wire,safety fence,or jute mesh to increase the strength of the fabric.Silt fence materials are available that have synthetic mesh backing attached. l Filter fabric 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 last- ing,and can be left in place after the project is completed,if permitted by local reg- ulations. l Refer to Figure II-4.2.12 Silt Fence (p.369)for standard silt fence details.Include the following standard Notes for silt fence on construction plans and specifications: 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 370 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. 3.The silt fence shall have a 2-feet min.and a 2½-feet max.height above the original ground surface. 4.The filter fabric shall be sewn together at the point of manufacture to form fil- ter fabric lengths as required.Locate all sewn seams at support posts.Altern- atively,two sections of silt fence can be overlapped,provided the Contractor can demonstrate,to the satisfaction of the Engineer,that the overlap is long enough and that the adjacent fence sections are close enough together to prevent silt laden water from escaping through the fence at the overlap. 5.Attach the filter fabric on the up-slope side of the posts and secure with staples,wire,or in accordance with the manufacturer's recommendations. Attach the filter fabric to the posts in a manner that reduces the potential for tearing. 6.Support the filter 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 filter fabric up-slope of the mesh. 7.Mesh support,if used,shall consist of steel wire with a maximum mesh spa- cing 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 ultra- violet radiation as the filter fabric it supports. 8.Bury the bottom of the filter fabric 4-inches min.below the ground surface. Backfill and tamp soil in place over the buried portion of the filter fabric,so that no flow can pass beneath the 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 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 prevent overturning of the fence due to sediment loading. 10.Use wood,steel or equivalent posts.The spacing of the support posts shall 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 371 be a maximum of 6-feet.Posts shall consist of either: l Wood with dimensions of 2-inches by 2-inches wide min.and a 3-feet min.length.Wood posts 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,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 gravel 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 Gravel check dams shall be approximately 1-foot deep at the back of the fence.Gravel 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 Gravel check dams shall consist of crushed surfacing base course, gravel backfill for walls,or shoulder ballast.Gravel check dams shall be located every 10 feet along the fence where the fence must cross con- tours. l Refer to Figure II-4.2.13 Silt Fence Installation by Slicing Method (p.374)for slicing method details.Silt fence installation using the slicing method specifications: 1.The base of both end posts must be at least 2-to 4-inches above the top of the filter 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 install - ation. 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 filter fabric,enabling posts to support the filter fabric from upstream water pressure. 4.Install posts with the nipples facing away from the filter fabric. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 372 5.Attach the filter fabric to each post with three ties,all spaced within the top 8- inches of the filter fabric.Attach each tie diagonally 45 degrees through the fil- ter 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 fabric around the end posts and secure with 3 ties. 7.No more than 24-inches of a 36-inch filter fabric is allowed above ground level. Compact the soil immediately next to the filter 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 fabric deeper into the ground if necessary. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 373 Figure II-4.2.13 Silt Fence Installation by Slicing Method D EPARTMENT OF ECOLOGY State of Washington Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.2.13 Silt Fence Installation by Slicing Method Revised November 2015 NOT TO SCALE Completed Installation Silt Fence Post installed after compaction Vibratory plow is not acceptable because of horizontal compaction Slicing blade (18 mm width) Horizontal chisel point (76 mm width) Fabric above ground 200 - 300mm Roll of silt fenceOperation No more than 24" of a 36" fabric is allowed above groundSteel support post100% compaction 100% compaction FLOW Drive over each side of silt fence 2 to 4 times with device exerting 60 p.s.i. or greater Attach fabric to upstream side of post Ponding height max. 24" POST SPACING: 7' max. on open runs 4' max. on pooling areas POST DEPTH: As much below ground as fabric above ground Top of Fabric Belt top 8" Diagonal attachment doubles strength Attachment Details: x Gather fabric at posts, if needed. x Utilize three ties per post, all within top 8" of fabric. x Position each tie diagonally, puncturing holes vertically a minimum of 1" apart. x Hang each tie on a post nipple and tighten securely. Use cable ties (50 lbs) or soft wire. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 374 Maintenance Standards l Repair any damage immediately. l Intercept and convey all evident concentrated flows uphill of the silt fence to a sed- iment pond. l Check the uphill side of the fence for signs of the fence clogging and acting as a barrier to flow and then causing channelization of flows parallel to the fence. If this occurs, replace the fence or remove the trapped sediment. 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 filter fabric that has deteriorated due to ultraviolet breakdown. 2014 Stormwater Management Manual for Western Washington Volume II - Chapter 4 - Page 375 BMP C240:Sediment Trap Purpose A sediment trap is a small temporary ponding area with a gravel outlet used to collect and store sediment from sites cleared and/or graded during construction.Sediment traps,along with other perimeter controls,shall be installed before any land disturbance takes place in the drainage area. Conditions of Use Prior to leaving a construction site,stormwater runoff must pass through a sediment pond or trap or other appropriate sediment removal best management practice.Non- engineered sediment traps may be used on-site prior to an engineered sediment trap or sediment pond to provide additional sediment removal capacity. It is intended for use on sites where the tributary drainage area is less than 3 acres,with no unusual drainage features,and a projected build-out time of six months or less.The sediment trap is a temporary measure (with a design life of approximately 6 months)and shall be maintained until the site area is permanently protected against erosion by veget- ation and/or structures. Sediment traps and ponds are only effective in removing sediment down to about the medium silt size fraction.Runoff with sediment of finer grades (fine silt and clay)will pass through untreated,emphasizing the need to control erosion to the maximum extent first. Whenever possible,sediment-laden water shall be discharged into on-site,relatively level,vegetated areas (see BMP C234:Vegetated Strip (p.375)).This is the only way to effectively remove fine particles from runoff unless chemical treatment or filtration is used.This can be particularly useful after initial treatment in a sediment trap or pond. The areas of release must be evaluated on a site-by-site basis in order to determine appropriate locations for and methods of releasing runoff.Vegetated wetlands shall not be used for this purpose.Frequently,it may be possible to pump water from the col- lection point at the downhill end of the site to an upslope vegetated area.Pumping shall only augment the treatment system,not replace it,because of the possibility of pump fail - ure or runoff volume in excess of pump capacity. All projects that are constructing permanent facilities for runoff quantity control should use the rough-graded or final-graded permanent facilities for traps and ponds.This includes combined facilities and infiltration facilities.When permanent facilities are used as temporary sedimentation facilities,the surface area requirement of a sediment trap or pond must be met.If the surface area requirements are larger than the surface area of the permanent facility,then the trap or pond shall be enlarged to comply with the surface 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 383 area requirement.The permanent pond shall also be divided into two cells as required for sediment ponds. Either a permanent control structure or the temporary control structure (described in BMP C241:Temporary Sediment Pond (p.388))can be used.If a permanent control structure is used,it may be advisable to partially restrict the lower orifice with gravel to increase residence time while still allowing dewatering of the pond.A shut-off valve may be added to the control structure to allow complete retention of stormwater in emergency situations.In this case,an emergency overflow weir must be added. A skimmer may be used for the sediment trap outlet if approved by the Local Permitting Authority. Design and Installation Specifications l See Figure II-4.2.16 Cross Section of Sediment Trap (p.386)and Figure II-4.2.17 Sediment Trap Outlet (p.387)for details. l If permanent runoff control facilities are part of the project,they should be used for sediment retention. l To determine the sediment trap geometry,first calculate the design surface area (SA)of the trap,measured at the invert of the weir.Use the following equation: SA =FS(Q2/Vs) where Q2 =Design inflow based on the peak discharge from the developed 2-year runoff event from the contributing drainage area as computed in the hydrologic analysis.The 10-year peak flow shall be used if the project size,expected timing and duration of construction, or downstream conditions warrant a higher level of protection.If no hydrologic analysis is required,the Rational Method may be used. Vs =The settling velocity of the soil particle of interest.The 0.02 mm (medium silt) particle with an assumed density of 2.65 g/cm3 has been selected as the particle of interest and has a settling velocity (Vs)of 0.00096 ft/sec. FS =A safety factor of 2 to account for non-ideal settling. Therefore,the equation for computing surface area becomes: SA =2 x Q2/0.00096 or 2080 square feet per cfs of inflow 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 384 Note:Even if permanent facilities are used,they must still have a surface area that is at least as large as that derived from the above formula.If they do not,the pond must be enlarged. l To aid in determining sediment depth,all sediment traps shall have a staff gauge with a prominent mark 1-foot above the bottom of the trap. l Sediment traps may not be feasible on utility projects due to the limited work space or the short-term nature of the work.Portable tanks may be used in place of sed- iment traps for utility projects. Maintenance Standards l Sediment shall be removed from the trap when it reaches 1-foot in depth. l Any damage to the pond embankments or slopes shall be repaired. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 385 Figure II-4.2.16 Cross Section of Sediment Trap D E P A R T M E N T O F E C O L O G Y S t a t e o f W a s h i n g t o n Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.2.16 Cross Section of Sediment Trap Revised November 2015 NOT TO SCALE 3H : 1 V M a x . 3.5' - 5' Flat Bottom 1.5' Min. 1' Min. Surface area determined at top of weir 3 4" - 1.5" Washed gravel Geotextile 2" - 4" Rock Rip Rap Discharge to stabilized conveyance, outlet, or level spreader 4' Min. 1' Min. 1' Min. Overflow Note: Trap may be formed by berm or by partial or complete excavation. 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 386 Figure II-4.2.17 Sediment Trap Outlet D E P A R T M E N T O F E C O L O G Y S t a t e o f W a s h i n g t o n Please see http://www.ecy.wa.gov/copyright.html for copyright notice including permissions, limitation of liability, and disclaimer. Figure II-4.2.17 Sediment Trap Outlet Revised November 2015 NOT TO SCALE 6' Min. 1' Min. depth overflow spillway Native soil or compacted backfill Geotextile Min. 1' depth 2" - 4" rock Min. 1' depth 3 4" - 1.5" washed gravel 2014 Stormwater Management Manual for Western Washington Volume II -Chapter 4 -Page 387