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Stormwater Plan - Preliminary.pdfq�G I�� v�,Eco J 8 ?p17 CpUNTE�F�C�S Preliminary Stormwater Site Plan for Port of Edmonds Marine Retail Shoreline Substantial Development Permit Owner: Port of Edmonds 336 Admiral Way Edmonds, WA 98020 August 2017 ReidMiddleton Preliminary Stormwater Site Plan Port of Edmonds Marine Retail 2017 The engineering material and data contained in this report were prepared under the supervision and direction of the undersigned, whose seal as a registered professional engineer is affixed below. �gEY D. J 1 A,b �A ti �G 41379 GI I' �;tiy��NA1. - . B/Bi►� Jeffrey D. Jenks, P.E. Project Engineer M 1 1 1 M rim U 728 134th Street SW, Suite 200 Everett, WA 98204 425-741-3800 File No. 222017.004 Preliminary Stormwater Site Plan Port of Edmonds Marine Retail Content Page No. PROJECTOVERVIEW.............................................................................................................................................1 METHODOLOGY......................................................................................................................................................1 MINIMUM REQUIREMENT #1 STORMWATER SITE PLANS........................................................................1 MINIMUMREQUIREMENT #2 SWPPP................................................................................................................2 ELEMENT #1: MARK CLEARING LIMITS.....................................................................................................................2 ELEMENT #2: ESTABLISH CONSTRUCTION ACCESS...................................................................................................2 ELEMENT #3: CONTROL FLow RATES.......................................................................................................................2 ELEMENT #4: INSTALL SEDIMENT CONTROLS...........................................................................................................3 ELEMENT#5: STABILIZE SOIL,s..................................................................................................................................3 ELEMENT#6: PROTECT SLOPES.................................................................................................................................3 ELEMENT#7: PROTECT DRAIN INLETS......................................................................................................................3 ELEMENT #8: STABILIZE CHANNELS AND OUTLETS..................................................................................................3 ELEMENT #9: CONTROL POLLUTANTS....................................................................................................................... 3 ELEMENT #10: CONTROL DE-WATERING..................................................................................................................3 ELEMENT#11: MAINTAIN BMPs...............................................................................................................................3 ELEMENT#12: MANAGE THE PROJECT......................................................................................................................3 MINIMUM REQUIREMENT #3 POLLUTION SOURCE CONTROL...............................................................4 MINIMUM REQUIREMENT #4 PRESERVATION OF NATURAL DRAINAGE............................................4 MINIMUM REQUIREMENT #5: ON -SITE STORMWATER MANAGEMENT..............................................4 MINIMUM REQUIREMENT #6: RUNOFF TREATMENT.................................................................................6 MINIMUM REQUIREMENT #7: FLOW CONTROL...........................................................................................6 MINIMUM REQUIREMENT #8: WETLANDS PROTECTION..........................................................................6 MINIMUM REQUIREMENT #9 BASIN PLANNING...........................................................................................6 MINIMUM REQUIREMENT #10: OPERATION AND MAINTENANCE.........................................................7 Appendices Appendix A — Drawings Appendix B — Calculations Appendix C — StormFilter® Operations and Maintenance Manual Appendix D — Maintenance Schedule & Agreement Preliminary Stormwater Site Plan i • . , , , Port of Edmonds Marine Retail PROJECT OVERVIEW This stormwater site plan report summarizes the storm drainage analysis and design for the proposed Port of Edmonds Marine Retail project. The project will construct a 6,650-square-foot retail building along Admiral Way. The existing site is a paved parking lot owned by the Port of Edmonds (Port). The project will include Low Impact Development features and water quality treatment. The project is in the planning stages and is under review for a Shoreline Substantial Development Permit. METHODOLOGY Drainage design for the project is based on Edmonds Development Code Chapter 18.30 and the Washington State Department of Ecology's (DOE) 2014 Stormwater Management Manual for Western Washington (SWMMWW). Western Washington Hydrology Model (WWHM 2012) is used for runoff calculations and stormwater management modelling. This project is a redevelopment project replacing more than 5,000 square feet of impervious area and is subject to Minimum Requirements 1-10 in the SWMMWW. The developed site will drain to the City of Edmonds' (City) storm sewer system in Admiral Way and discharge directly to salt water. MINIMUM REQUIREMENT #1 STORMWATER SITE PLANS Existing Conditions Summary The project site, 465 Admiral Way, is a 0.5-acre, Port -owned, existing parking lot on the east side of Admiral Way. The site is generally flat. A majority of the site drains by sheet flow to the parking lot recycling area to the south, and the west portion of the site drains by sheet flow to Admiral Way. The existing site is entirely hard surface, consisting of asphalt and gravel - over -asphalt areas. There is no existing storm drain infrastructure at the site. EXISTING SITE CHARACTERISTICS: Pavement/Gravel over Pavement: 0.5 acres EXSITING RUNOFF: Existing flow frequency rates from WWHM 2012: 2yr 0.16 cfs IOyr 0.26 cfs 50yr 0.37 cfs 100yr 0.42 cfs A map of existing conditions is included in Appendix A. Preliminary Stormwater Site Plan 1 • . , , , . Port of Edmonds Marine Retail Proposed Conditions Summary The project proposes to construct a 6,650-square-foot retail building with associated 20,880-square-foot parking lot and 2,700-square-foot outdoor retail display area. The site will be generally flat, sloping gently from west to east. Stormwater runoff will be collected in a traditional catch basin and pipe system. Water quality treatment for the vehicle parking lot will be provided by media filtration catch basins. The storm drain system will outfall to the City of Edmonds' storm drain system on Admiral Way. PROPOSED SITE CHARACTERISTICS: Pavement: 0.185 acres Roof: 0.27 acers Pasture (8" Topsoil Landscape): 0.045 acres Total: 0.5 acres 63 Zell 4 03 UIR[00 Proposed flow frequency rates from WWHM 2012: 2yr 0.15 cfs 10yr 0.20 cfs 50yr 0.34 cfs 100yr 0.38 cfs A proposed drainage plan is included in Appendix A. MINIMUM REQUIREMENT #2 SWPPP A Stormwater Pollution Prevention Plan (SWPPP) will be prepared for the project at a future date. The SWPPP will provide guidance for the construction contractor to meet the requirements of the DOE's Construction Stormwater General Permit. A summary of Best Management Practices (BMPs) likely to be used at this site is listed below. Element #1: Mark Clearing Limits Silt fence will be installed along the low side of the project limits. Project limits will be marked by temporary chain link fence or plastic orange protective fence. Element #2: Establish Construction Access A construction entrance will be provided from either Admiral Way or the adjacent Port -owned property and constructed according to BUT C 105 of the Stonnwater Manual. Element #3: Control Flow Rates Temporary sediment traps will be used as needed to control flow rates. Preliminary Stormwater Site Plan 2 • • , , , • , Port of Edmonds Marine Retail Element #4: Install Sediment Controls Sediment will be controlled using BMPs from the Stormwater Manual, including construction entrances and wheel washes, temporary seeding and mulching, dust control, storm drain structure inlet and outlet protection, silt fence, and sediment traps. Element #5: Stabilize Soils Exposed soils not being worked will be hydroseeded with an appropriate seed mix outlined in BMP C120. Alternately, mulch, blankets, or plastic sheeting will be used to stabilize soils as needed. Element #6: Protect Slopes There are no steep slopes at the project site. Element #7: Protect Drain Inlets Existing and proposed catch basins at or near the project site will be equipped with inlet protection. Element #8: Stabilize Channels and Outlets Outlets to ditches or vegetated areas will be protected with quarry spalls or erosion blankets. Element #9: Control Pollutants Demolition debris will be transported off site to an approved disposal site. Materials used on the project site will be properly stored and contained, and concrete will be handled per the guidelines in the Stormwater Manual. Element #10: Control De -Watering Dewatering will not likely be required at this site. Any dewatering will be handled the same as stormwater runoff. Element #11: Maintain BMPs Temporary and permanent erosion and sediment control best management practices (Buys) will be maintained and repaired as needed to ensure continued performance of their intended function. Maintenance and repair shall be conducted in accordance with BMP specifications. Element #12: Manage the Project Clearing and grading activities shall be permitted only if conducted pursuant to an approved site development plan that establishes permitted areas of grading, cutting, and filling. The contractor will be required to manage the project per the requirements of the Construction Stormwater General Permit. Preliminary Stormwater Site Plan 3 • Mr. , , I . , Port of Edmonds Marine Retail MINIMUM REQUIREMENT #3 POLLUTION SOURCE CONTROL Pollution Source Control BMPs will be implemented during construction to prevent pollution. Proposed BMPs will be per the requirements of the Stormwater Manual and will include but not be limited to the following: BMP C103, High Visibility Fence BMP C105, Construction Entrance BMP C106, Wheel Wash BMP C107, Construction Road/Parking Area Stabilization BMP C120, Temporary and Permanent Seeding BMP C121, Mulching BMP C123, Plastic Covering BMP C125, Topsoiling/Composting BMP C130, Surface Roughening BMP C140, Dust Control BMP C150, Materials on Hand BMP C151, Concrete Handling BMP C152, Sawcutting and Surfacing Pollution Prevention BMP C153, Material Delivery, Storage, and Containment BMP C154, Concrete Washout Area BMP C160, Certified Erosion and Sediment Control Lead (CESCL) BMP C200, Interceptor Dike and Swale BMP C201, Grass -Lined Channels BMP C207, Checkdams BMP C209, Outlet Protection BMP C220, Storm Inlet Protection BMP C233, Silt Fence BMP C241, Temporary Sediment Pond MINIMUM REQUIREMENT #4 PRESEIZVATION OF NATURAL DRAINAGE The project site is currently fully developed and contains no natural drainage elements. MINIMUM REQUIREMENT #5: ON -SITE STORMWATER MANAGEMENT This project is a redevelopment project that replaces more than 5,000 square feet of hard surfaces and will drain directly to salt water through the City's storm sewer system. Preliminary Stormwater Site Plan 4 • . , , , . , Port of Edmonds Marine Retail Per City Code 18.30.060, Paragraph D.S.b.iv, the project does not have to meet the Low Impact Development Performance Standard but does have to evaluate the following LID BMPs: BMP T5.13 Post Construction Soil Quality and Depth BMP T5.IOA Downspout Full Infiltration Systems BUT T5.1 OB Downspout Dispersion Systems BUT T5.1 OC Perforated Stub -out Connections BMP T5.11 Concentrated Flow Dispersion BMP T5.12 Sheet Flow Dispersion Evaluation of LID Features LID features are evaluated based on Infeasibility Criteria found in Appendix A of the City's Stormwater Management Code. BMP T5.13 Post Construction Soil Quality and Depth No slopes on the site exceed 33 percent, so Post Construction Soil Quality and Depth is feasible and will be used for landscape beds. BMP T5.10A Downspout Full Infiltration Systems Full downspout infiltration is infeasible, as the overflow could not be placed at least 1-foot below the pavement. The site is flat with a shallow outfall invert elevation in Admiral Way that prevents the storm drain system from being deep enough. BMP TS.IOB Downspout Full Dispersion Systems Full downspout dispersion is infeasible, as there is not a vegetation flow path available. BMP T5.10 C Perforated Stub -Out Connections Perforated stub -out connections are feasible and will be implemented. BMP T5.11 Concentrated Flow Dispersion Concentrated flow dispersion is not feasible, as there is not a vegetated flow path available. BMP T5.12 Sheet Flow Dispersion Sheet flow dispersion is not feasible, as there is not a vegetated flow path available. Preliminary Stormwater Site Plan 5 • . , , , . , Port of Edmonds Marine Retail Summary of LID Features The project will implement BUT T5.13 Post Construction Soil Quality and Depth for landscape beds. Building roof drains will be connected to the storm drain system with BUT T5.1 OC Perforated Stub -Out Connections. MINIMUM REQUIREMENT #6: RUNOFF TREATMENT This project includes more than 5,000 square feet of pollution -generating hard surface and requires stormwater quality treatment per Minimum Requirement #6. This site does not require oil control, as it does not cross the threshold of 100 vehicles per day per 1,000 square feet of building. Basic treatment is required, as this site discharges to salt water through the City's MS4. Proposed treatment will be provided by two StormFilter® Catch Basins in the parking lot. Filter #1 Water Quality Flow = 0.0117cfs = 6gpm Single Catch Basin StormFilter, with 7.5 gpm capacity ZPG Media Filter Cartridge. Filter #2 Water Quality Flow = 0.0111cfs = 5gpm Single Catch Basin StormFilter, with 7.5gpm capacity ZPG Media Filter Cartridge. MINIMUM REQUIREMENT #7: FLOW CONTROL This project discharges directly to salt water through the City's MS4 and is exempt from flow control. MINIMUM REQUIREMENT #8: WETLANDS PROTECTION This project does not drain to wetlands. MINIMUM REQUIREMENT #9 BASIN PLANNING No basin planning is required for this project beyond the Stormwater Manual. Preliminary Stormwater Site Plan 6 • , , , • , Port of Edmonds Marine Retail MINIMUM iZEQUIREMENT #10: OPERATION AND MAINTENANCE Operation and maintenance will be determined by the requirements of the Stormwater Manual and by the manufacturers of the selected water quality devices. Detail on specific maintenance and operations practices and procedures will be provided with the construction permit application. ehw\22sv\l7\004 poed; admiral way pricing lot topo\design\stormwater report\stormwater site plan report.docx\jdj Preliminary Stormwater Site Plan 7 • . , , , . , Port of Edmonds Marine Retail Appendix A Drawings Preliminary Stormwater Site Plan • - , , , • , Port of Edmonds Marine Retail K11m11O O sHRua r,y„� Lac CONFER TREE � � � � � � EDOE OF CWVEL 0 AP Nca+c a We Q DCoDEGanus TREE _x_ FENce p TELEPMxEJmWIY. __ ,A,o NxL TO TEl HONE PEDESTAL 111CObWlIAW1 W\'WAI Ni[ m GS VALVE RF1AR0 POWER USE ® - YETER OIERHFiWO POWER UNE to JL colt. WWx ® POWDE VAULT RECARDECAS UNE NWm YANHaE STORM DRNN UXE Q- slut rol£ �� *mm sm oxw uIC m POWER 1RANSFaWIER 1MWTMF 0P ul[ O "MOND WMWOIRT fO4 E— OILY ARCEIOR —. .,rt. IA[ WiRb (YYIw WM w RECORD vpTER UNE ❑ GTLX BASIN fARE N LINE — a1LVERf AS NOTED�� L CaWUNIC a UNE (nOER OPTIC) �w WATER VIMLT � � b1t�-� q FIRE E!!OR/tIf _ROVE OF ROM TM1FIt VALVE wKICAt WaWWWO IN WAIFA YEIFIi ® WMIOt D..Ql a 6 .c+r. IMUW WRNWIOx WEEK HOSE BIB SMx_ IRDWN WIEWWOU a BgLEldl b SIGN • W1 WxAWO WI♦'/AAIIIOIIi w GK . x MALL W/Wx.SHER i.� E.11K� �YJ� Yw`�►�\ 20 to D Ty AD SCALE IN FEET BURLINGTON NORTHERN SANTA FE RAILROAD SURVEY NOTES DATUMS: 1. THE UTILITIES SHOWN HEREON ME BASED ON aiSERVATION OF SURFACE FEATURES, AND RECORD UTILITY ELAPf. HELD LOCATIONS MUST BE VERIFIED M&WONEft Q rNmwW NAD mv., WA NORTIW PRIOR TO ANY CONSTRUCTION. 2 THIS SURVEY WAS MADE WITHOUT THE BENEFIT OF A TIRE REPORT AND DOES NOT PURPORT TO SHOW ANY EASELENTS OR OTHER TOMS OF RECORD. vvffWK DAiuw� NWYO ~ ROICWOIARt ]. BASIS OF BEARINGS: WASHINGTON STATE PLANE COORDINATES, NORTH ZONE, N-T, MET IW00. WRASS DISK YS��^e EEpNINpIK sa ON a tplp�7( 4. SURVEY MONUMENTS WERE FIELD MEASURED USING _FICA CS14 AND LEICA 12M CAPS RECEIVERS. MONUMENT POSITIONS THAT WERE NOT my V WILL or TLOWOI oTp0 14 W ORIN CW DIRECTLY OBSERVED USING CPS WERE TIED TD THOSE MNTS USING A LEIGA MSSO MULTI -STATION IN CONFORNPNCE WITH ACCEPTED SURVEY "O � s '�AINI UKIb PROCEDURES WHICH MEET OR EXCEED STATE STANDARDS SPECIFIED BY WAG 3I2-130 WITH REGARD TO LINEAR AND ANGULAR CLOSURES. S. THIS SURVEY WAS CONDUCTED WITHOUT THE BENEFIT OF A TIRE REPORT AND DOES NOT LL EASEMENTS TO DHOW AU_ OR OTHER ITEMS OF ELEVATION - 11W RECORp. TOPO & BOUNDARY SURVEY Y I � IN f CONCRETE \ O BURLINGTON NORTHERN SANTA FE RAILROAD EN RIM=11 6'FVC ENE IE-9.94 ce Y1s4a RPh1Ls1 s" CNC CN SW IE-9 12'CCNC NNE IE=9 .21 I 12'CINIC Sw IE-B 96 LEGEND -m- m,w uMnmF - CItlY R161 —Nf/— IGff OIYN PPE —rb— —a CMtlP qKj\OCO6� C d N d CO N C d W Q Ill O C 0 coa� PRELIMINARY GRADING & DRAINAGE PLAN C1.0 Appendix B Calculations Preliminary Stormwater Site Plan Port of Edmonds Marine Retail WWII! FLOW FREQUENCY FOR EXISTING AND PROPOSED CONDITIONS W Analysis 1.0 0.01 Cumulative Probability twtt t t 0.5 1 2 5 10 20 30 50 70 80 90 95 98 9999.5 Flow Frequency 1.0 Flow(crs) Predeveloped 2 Year 0.1602 5 Year - 0.2184 10 Year - 0.2613 25 Year - 0.3204 50 Year m 0.3683 100 Year - 0.4196 0.01 Stream Protection Duration I UD Dwation Flow Frequency I water Quality Hydrograph wetland Input Volumes UD Repat Recharge Duration Recharge FtedeveloW I Recharge Mitigated Analyze datasets Compact WDM Delete Selected All Datamta Flow Stege Precip Evap ' r U J Fhai Frerrrencl Meilwd Log Pearm Type III 17P r, w" r Curnane r Gringaten Mitigated 0.1460 0.1991 0.2302 0.2921 0.3358 0.3626 Annual Peaks 1949 0.1486 0.1355 1950 0 4B07 0.1833 1951 0.1709 0.1555 1952 0.1463 0.1332 1953 0.2000 0.1020 1954 0.2482 0.2274 1955 0.1864 0.1702 1956 0.0803 0.0805 1957 0.1500 0.1375 1958 0.3619 0.2294 1959 0.11542 0.1403 1960 0.1336 0.1217 1961 0.4059 0,4423 1962 0.1800 0.1646 1963 0.2160 0.1900 1964 0.114E 0.1040 1965 0.1146 0.1045 1966 0.1173 0.1068 1967 0.3336 0.3036 1968 0.1791 0.1630 1969 0.3105 0.2906 1970 0.1270 0.1156 1971 0.1056 0.1691 1972 0.2376 0.2163 1973 0.1902 0.1732 1974 0.2409 0.2192 1975 0.1020 0.1659 1976 0.1265 0.1151 A l I STORMFILTER #1 FLOW RATE Analysis i Run Analysis ....... ....... Water Quality 24 hour Volume (ac•ft) 0.0077 Standard Flow Rate (cfs) 0.0117 Standard Flow Rate (cfs) 0.0066 Stream Protection Duration LID Duration Flow Frequency Water Quality Hydrograph Wetland Input Volumes LID Report Recharge Duration Recharge Predeveloped Recharge Mitigated Analyze datasets Compact WDM J Delete Selected STORMFILTER #2 FLOW RATE Run Analysis Water Quality 24 hour Volume (acft) 0.0073 Standard Flow Rate (cls)0.0111 Standard Flow Rate (cfs)10.00li3 Sheam Protection DuratHnLID Duration Flow Frequency Water Quality Hydrograph Wetland Input VolumesReport I Recharge Duration I Recharge Predeveloped Recharge Mitigated Analyze datasets Compact WDM I Delete Selected Appendix C Department of Ecology TAPE Approval Preliminary Stormwater Site Plan I • Mr. I j, In , I . , Port of Edmonds Marine Retail WASHIN GT0N STATE EECA0 LE0 6 �Y April 2017 GENERAL USE LEVEL DESIGNATION FOR BASIC (TSS) TREATMENT For CONTECH Engineered Solutions Stormwater Management StormFilter' With ZPG Media at 1 gpm/sq ft media surface area Ecology's Decision: Based on the CONTECH Engineered Solutions' (CONTECH) application submissions, Ecology hereby issues a General Use Level Designation (GULD) for the Stormwater Management StormFilter® (StormFilter): 1. As a basic stormwater treatment practice for total suspended solids (TSS) removal, • Using ZPGTM media (zeolite/perlite/granular activated carbon), with the size distribution described below, • Sized at a hydraulic loading rate of 1 gpm/ft2 of media surface area, per Table 1, and • Internal bypassing needs to be consistent with the design guidelines in CONTECH's current product design manual. Table 1. StormFilter Design Flow Rates per Cartridge Effective Cartridge Height inches 12 18 27 Cartridge Flow Rate m/cartrid e 5 7.5 11.3 2. Ecology approves StormFilter systems containing ZPGTM media for treatment at the hydraulic loading rates shown in Table 1, and sized based on the water quality design flow rate for an off-line system. Contech designs their StormFilter systems to maintain treatment of the water quality design flow while routing excess flows around the treatment chamber during periods of peak bypass. The water quality design flow rates are calculated using the following procedures: • Western Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute now rate as calculated using the latest version of the Western Washington Hydrology Model or other Ecology -approved continuous runoff model. CONTECH - StormFilter® GULD Maintenance Update (November 2012) P age 11 • Eastern Washington: For treatment installed upstream of detention or retention, the water quality design flow rate is the peak 15-minute flow rate as calculated using one of the three methods described in Chapter 2.2.5 of the Stormwater Management Manual for Eastern Washington (SWMI%IEW) or local manual. • Entire State: For treatment installed downstream of detention, the water quality design flow rate is the full 2-year release rate of the detention facility. 3. This designation has no expiration date, but Ecology may amend or revoke it. Ecology's Conditions of Use: The StormFilter with ZPG media shall comply with the following conditions: 1. Design, install, operate, and maintain the StormFilter with ZPG media in accordance with applicable Contech Engineered Solutions manuals, documents, and the Ecology Decision. 2. Install StormFilter systems to bypass flows exceeding the water quality treatment rate. Additionally, high flows will not re -suspend captured sediments. Design StormFilter systems in accordance with the performance goals in Ecology's most recent Stormwater Manual and CONTECH's Product Design Manual Version 4. 1 (April 2006), or most current version, unless otherwise specified. 3. Owners must follow the design, pretreatment, land use application, and maintenance criteria in CONTECH's Design Manual. 4. Pretreatment of TSS and oil and grease may be necessary, and designers shall provide pre-treatment in accordance with the most current versions of the CONTECH's Product Design Manual (April 2006) or the applicable Ecology Stormwater Manual. Design pre-treatment using the performance criteria and pretreatment practices provided on Ecology's "Evaluation of Emerging Stormwater Treatment Technologies" website. 5. Maintenance: The required maintenance interval for stormwater treatment devices is often dependent upon the degree of pollutant loading from a particular drainage basin. Therefore, Ecology does not endorse or recommend a "one size fits all" maintenance cycle for a particular model/size of manufactured filter treatment device. • Typically, CONTECH designs StormFilter systems for a target filter media replacement interval of 12 months. Maintenance includes removing accumulated sediment from the vault, and replacing spent cartridges with recharged cartridges. CONTECH - StormFilter® GULD Maintenance Update (November 2012) Page 12 • Indications of the need for maintenance include effluent flow decreasing to below the design flow rate, as indicated by the scumline above the shoulder of the cartridge. Owners/operators must inspect StormFilter with ZPG media for a minimum of twelve months from the start of post -construction operation to determine site -specific maintenance schedules and requirements. You must conduct inspections monthly during the wet season, and every other month during the dry season. (According to the SVf AE%IWW, the wet season in western Washington is October 1 to April 30. According to SWMMEW, the wet season in eastern Washington is October 1 to June 30). After the first year of operation, owners/operators must conduct inspections based on the findings during the first year of inspections. • Conduct inspections by qualified personnel, follow manufacturer's guidelines, and use methods capable of determining either a decrease in treated effluent flowrate and/or a decrease in pollutant removal ability. • When inspections are performed, the following findings typically serve as maintenance triggers: • Accumulated vault sediment depths exceed an average of 2 inches, or • Accumulated sediment depths on the tops of the cartridges exceed an average of 0.5 inches, or • Standing water remains in the vault between rain events, or • Bypass occurs during storms smaller than the design storm. Note: If excessive floatables (trash and debris) are present, perform a minor maintenance consisting of gross solids removal, not cartridge replacement. 6. CONTECH shall maintain readily available reports listed under "Application Documents" (above) as public, as well as the documentation submitted with its previous conditional use designation application. CONTECH shall provide links to this information from its corporate website, and make this information available upon request, at no cost and in a timely manner. 7. ZPGTM media used shall conform with the following specifications: Each cartridge contains a total of approximately 2.6 cubic feet of media. The ZPGTM cartridge consists of an outer layer of perlite that is approximately 1.3 cubic feet in volume and an inner layer, consisting of a mixture of 90% zeolite and 10% granular activated carbon, which is approximately 1.3 cubic feet in volume. • Perlite Media: Perlite media shall be made of natural siliceous volcanic rock free of any debris or foreign matter. The expanded perlite shall CONTECH - StormFilter® GULD Maintenance Update (November 2012) P a g e 13 have a bulk density ranging from 6.5 to 8.5 lbs per cubic foot and particle sizes ranging from 0.09" (#8 mesh) to 0.38" (3/8" mesh). • Zeolite Media: Zeolite media shall be made of naturally occurring clinoptilolite. The zeolite media shall have a bulk density ranging from 44 to 50 lbs per cubic foot and particle sizes ranging from 0.13" (#6 mesh) to 0.19" (#4 mesh). Additionally, the cation exchange capacity (CEC) of zeolite shall range from approximately 1.0 to 2.2 meq/g. • Granular Activated Carbon: Granular activated carbon (GAC) shall be made of lignite coal that has been steam -activated. The GAC media shall have a bulk density ranging from 28 to 31 lbs per cubic foot and particle saes ranging from a 0.09" (#8 mesh) to 0.19" (#4 mesh). Approved Alternate Confieurations Peak Diversion StormFilter 1. The Peak Diversion StormFilter allows for off-line bypass within the StormFilter structure. Design capture flows and peak flows enter the inlet bay which contains an internal weir. The internal weir allows design flows to enter the cartridge bay through a transfer hole located at the bottom of the inlet bay while the unit routs higher flows around the cartridge bay. 2. To select the size of the Peak Diversion StormFilter unit, the designer must determine the number of cartridges required and size of the standard StormFilter using the site - specific water quality design flow and the StormFilter Design Flow Rates per Cartridge as described above. 3. New owners may not install the Peak Diversion StormFilter at an elevation or in a location where backwatering may occur. Applicant: Contech Engineered Solutions Applicant's Address: 11835 NE Glenn Widing Dr. Portland, OR 97220 Application Documents: The applicant's master report, titled, "The Stormwater Management StormFilter Basic Treatment Application for General Use Level Designation in Washington", Stormwater Management, Inc., November 1, 2004, includes the following reports: • (Public) Evaluation of the Stormwater Management StormFilter Treatment System: Data Validation Report and Summary of the Technical Evaluation Engineering Report (TEER) by Stormwater Management Inc., October 29, 2004 Ecology's technology assessment protocol requires the applicant to hire an independent consultant to complete the following work: CONTECH - StormFilter® GULD Maintenance Update (November 2012) Page 14 1. Complete the data validation report. 2. Prepare a TEER summary, including a testing summary and conclusions compared with the supplier's performance claims. 3. Provide a recommendation of the appropriate technology use level. 4. Work with Ecology to post recommend relevant information on Ecology's website. 5. Provide additional testing recommendations, if needed." 6. This report, authored by Dr. Gary Minton, Ph. D., P.E., Resource Planning Associates, satisfies the Ecology requirement. • (Public) "Performance of the Stormwater Management StormFilter Relative to the Washington State Department of Ecology Performance Goals for Basic Treatment," is a summary of StormFilter performance that strictly adheres to the criteria listed in the Guidance for Evaluating Emerging Stormwater Treatment Technologies, Technology Assessment Protocol — Ecology (TAPE). • "Heritage Marketplace Field Evaluation: Stormwater Management StormFilter with ZPGTM Media," is a report showing all of the information collected at Site A as stated in the SMI Quality Assurance Project Plan (QAPP). This document contains detailed information regarding each storm event collected at this site, and it provided a detailed overview of the data and project. • "Lake Stevens Field Evaluation: Stormwater Management StormFilter with ZPGTM Media," is a report that corresponds to Site E as stated in the SMI QAPP. This document contains detailed information regarding each storm collected at this site, and includes a detailed overview of the data and project. • (Public) "Evaluation of the Stormwater Management StormFilter for the removal of SIL-CO-SIL 106, a standardized silica product: ZPGTM at 7.5 GPM" is a report that describes laboratory testing at full design flow. • "Factors Other Than Treatment Performance." • 'State of Washington Installations." • "Peak Diversion StormFilter" is a technical document demonstrating the Peak Diversion StormFilter system complies with the Stormwater Management Manual for Western Washington Volume V Section 4.5.1. Above -listed documents noted as "public" are available by contacting CONTECH. Applicant's Use Level Request: That Ecology grant a General Use Level Designation for Basic Treatment for the StonnFilter using ZPGTM media (zeolite/perlite/granular activated carbon) at a hydraulic loading rate of 1 gpm/ft2 of media surface area in accordance with Ecology's 2011 Technical Guidance Manual for Evaluating Emerging Stormwater Treatment Technologies Technology Assessment Protocol —Ecology (TAPE). CONTECH - StormFilter® GULD Maintenance Update (November 2012) Page 15 Applicant's Performance Claim: The combined data from the two field sites reported in the TER (Heritage Marketplace and Lake Stevens) indicate that the performance of a StormFilter system configured for inline bypass with ZPGTM media and a hydraulic loading rate of 1 gpm/ft2 of media surface area meets Ecology performance goals for Basic Treatment. Ecology's Recommendations: Based on the weight of the evidence and using its best professional judgment, Ecology finds that: StormFilter, using ZPGTM media and operating at a hydraulic loading rate of no more than 1 gpm/ft of media surface area, is expected to provide effective stormwater treatment achieving Ecology's Basic Treatment (TSS removal) performance goals. Contech demonstrated this is through field and laboratory testing performed in accordance with the approved protocol. StormFilter is deemed satisfactory with respect to factors other than treatment performance (e.g., maintenance; see the protocol's Appendix B for complete list). Findings of Fact: • Influent TSS concentrations and particle size distributions were generally within the range of what Ecology considers "typical" for western Washington (silt -to -silt loam). • Contech sampled thirty-two (32) storm events at two sites for storms from April 2003 to March 2004, of which Contech deemed twenty-two (22) as "qualified" and were therefore included in the data analysis set. • Statistical analysis of these 22 storm events verifies the data set's adequacy. • Analyzing all 22 qualifying events, the average influent and effluent concentrations and aggregate pollutant load reduction are 114 mg/L, 25 mg/L, and 82%, respectively. • Analyzing all 22 qualifying events based on the estimated average flow rate during the event (versus the measured peak flow rate), and more heavily weighting those events near the design rate (versus events either far above or well below the design rate) does not significantly affect the reported results. • For the 7 qualifying events with influent TSS concentrations greater than 100 mg/L, the average influent and effluent concentrations and aggregate pollutant load reduction are 241 mg/L, 34 mg/L, and 89%, respectively. If we exclude the 2 of 7 events that exceed the maximum 300 mg/L specified in Ecology's guidelines, the average influent and effluent concentrations and aggregate pollutant load reduction are 158 mg/L, 35 mg/L, and 78%, respectively. • For the 15 qualifying events with influent TSS concentrations less than 100 mg/L, the average influent and effluent concentrations and aggregate pollutant load reduction are 55 mg/L, 20 mg/L, and 61 %, respectively. If the 6 of 15 events that fall below the minimum 33 mg/L TSS specified in Ecology's guidelines are excluded, the average CONTECH - StormFilter® GULD Maintenance Update (November 2012) P age 16 influent and effluent concentrations and aggregate pollutant load reduction are 78 mg/L, 26 mg/L, and 67%, respectively. • For the 8 qualifying events with peak discharge exceeding design flow (ranging from 120 to 257% of the design rate), results ranged from 52% to 96% TSS removal, with an average of 72%. • Due to the characteristics of the hydrographs, the field results generally reflect flows below (ranging between 20 and 60 percent of) the tested facilities' design rate. During these sub -design flow rate periods, some of the cartridges operate at or near their individual full design flow rate (generally between 4 and 7.5 GPM for an 18" cartridge effective height) because their float valves have opened. Float valves remain closed on the remaining cartridges, which operate at their base "trickle" rate of 1 to 1.5 GPM. • Laboratory testing using U.S. Silica's Sil-Co-Sil 106 fine silica product showed an average 87% TSS removal for testing at 7.5 GPM per cartridge (100% design flow rate). • Other relevant testing at I-5 Lake Union, Greenville Yards (New Jersey), and Ski Run Marina (Lake Tahoe) facilities shows consistent TSS removals in the 75 to 85% range. Note that the evaluators operated the I-5 Lake Union at 50%, 10001o, and 125% of design flow. • SMI's application included a satisfactory "Factors other than treatment performance" discussion. Note: Ecology's 80% TSS removal goal applies to 100 mg/l and greater influent TSS. Below 100 mg/L influent TSS, the goal is 20 mg/L effluent TSS. Technology Description: The Stormwater Management StormFilter® (StormFilter), a flow -through stormwater filtration system, improves the quality of stormwater runoff from the urban environment by removing pollutants. The StormFilter can treat runoff from a wide variety of sites including, but not limited to: retail and commercial development, residential streets, urban roadways, freeways, and industrial sites such as shipyards, foundries, etc. Operation: The StormFilter is typically comprised of a vault that houses rechargeable, media -filled, filter cartridges. Various media may be used, but this designation covers only the zeolite- perlite-granulated activated carbon (ZPGTM) medium. Stormwater from storm drains percolates through these media -filled cartridges, which trap particulates and may remove pollutants such as dissolved metals, nutrients, and hydrocarbons. During the filtering process, the StormFilter system also removes surface scum and floating oil and grease. Once filtered through the media, the treated stormwater is directed to a collection pipe or discharged to an open channel drainage way. This document includes a bypass schematic for flow rates exceeding the water quality design flow rate on page 8. CONTECH - StormFilter® GULD Maintenance Update (November 2012) Page 17 StormFilter Configurations: Contech offers the StormFilter in multiple configurations: precast, high flow, catch basin, curb inlet, linear, volume, corrugated metal pipe, drywell, and CON/Span form. Most configurations use pre -manufactured units to ease the design and installation process. Systems may be either uncovered or covered underground units. The typical precast StormFilter unit is composed of three sections: the energy dissipater, the filtration bay, and the outlet sump. As Stormwater enters the inlet of the StormFilter vault through the inlet pipe, piping directs stormwater through the energy dissipater into the filtration bay where treatment will take place. Once in the filtration bay, the stormwater ponds and percolates horizontally through the media contained in the StormFilter cartridges. After passing through the media, the treated water in each cartridge collects in the cartridge's center tube from where piping directs it into the outlet sump by a High Flow Conduit under -drain manifold. The treated water in the outlet sump discharges through the single outlet pipe to a collection pipe or to an open channel drainage way. In some applications where you anticipate heavy grit loads, pretreatment by settling may be necessary. CONTECH - StormFilter® GULD Maintenance Update (November 2012) Page 18 5TORMGATE ANHOLE, HIGH FLOW BYPA55 EFFECTIVE CARTRIDGE HEIGHT 1 2" 18" 27' CARTRIDGE FLOW RATE (af"cart) 5 7.5 1 1.31 RIDGE ELOW) STORMFILTER WITH STORMGATE ZSrORFAVYARM SCHEMATIC DETAIL 1 SOL S_ PLAN VIEW —1 mr�dfv��mn DAlE:11H1A0I SME:NONE I FU IW.IE:SOWI-mamoi..w-T DNAvrtt wn CnECI.l o; IpO( Figure 1. Stormwater Management StormFilter Configuration with Bypass CONTECH - StormFilter® GULD Maintenance Update (November 2012) Page 19 AIR LOCK CAD WITH CHECK VALVE � ., LIFTING TAB FLOAT VALVE J I • MESH HOOD FILTER MEDIA � I CENTER TUBE SCRUBBING REGULATOR UNFILTERED WATER UNFIUFRCO I'.•\J k FILTERED't..:;: UNDER -DRAIN MANIFOLD FILTEREUWATER UNDER -DRAIN':::. , •,.I CAST INTO VAULT BOOR Figure 2. The StormFilter Cartridge Cartridge Operation: As the water level in the filtration bay begins to rise, stormwater enters the StormFilter cartridge. Stormwater in the cartridge percolates horizontally through the filter media and passes into the cartridge's center tube, where the float in the cartridge is in a closed (downward) position. As the water level in the filtration bay continues to rise, more water passes through the filter media and into the cartridge's center tube. Water displaces the air in the cartridge and it purges from beneath the filter hood through the one-way check valve located in the cap. Once water fills the center tube, there is enough buoyant force on the float to open the float valve and allow the treated water to flow into the under -drain manifold. As the treated water drains, it tries to pull in air behind it. This causes the check valve to close, initiating a siphon that draws polluted water throughout the full surface area and volume of the filter. Thus, water filters through the entire filter cartridge throughout the duration of the storm, regardless of the water surface elevation in the filtration bay. This continues until the water surface elevation drops to the elevation of the scrubbing regulators. At this point, the siphon begins to break and air quickly flows beneath the hood through the scrubbing regulators, causing energetic bubbling between the inner surface of the hood and the outer surface of the filter. This bubbling agitates and cleans the surface of the filter, releasing accumulated sediments on the surface, flushing them from beneath the hood, and allowing them to settle to the vault floor. Adjustable cartridge flow rate: Inherent to the design of the StormFilter is the ability to control the individual cartridge flow rate with an orifice -control disc placed at the base of the cartridge. Depending on the treatment requirements and on the pollutant characteristics of the influent stream as CONTECH - StormFilter® GULD Maintenance Update (November 2012) P age 110 specified in the CONTECH Product Design Manual, operators may adjust the flow rate through the filter cartridges. By decreasing the flow rate through the filter cartridges, the influent contact time with the media is increased and the water velocity through the system is decreased, thus increasing both the level of treatment and the solids removal efficiencies of the filters, respectively (de Ridder, 2002). Recommended research and development: Ecology encourages CONTECH to pursue continuous improvements to the StormFilter. To that end, CONTECH recommends the following actions: Determine, through laboratory testing, the relationship between accumulated solids and flow rate through the cartridge containing the ZPGTM media. Completed 11/05. Determine the system's capabilities to meet Ecology's enhanced, phosphorus, and oil treatment goals. Develop easy -to -implement methods of determining that a StormFilter facility requires maintenance (cleaning and filter replacement). Contact Information: Applicant Contact: Jeremiah Lehman Contech Engineered Solutions 11835 NE Glenn Widing Drive Portland, OR, 97220 503-258-3136 j lehman(a),conteches. com Applicant Web link http://www.conteches.com/ CONTECH - StormFilter® GULD Maintenance Update (November 2012) Page 111 Ecology web link: http://www.ecy.wa.gov_/pr•og►•arcs/wq/stormwater/newtech/index html Ecology Contact: Douglas C. Howie, P.E. Department of Ecology Water Quality Program (360) 407-6444 douglas.howie(c),ecy.wa.gov Revision History Date Revision Jan 2005 Original Use Level Designation Dec 2007 Revision May 2012 Maintenance requirements updated November 2012 Design Storm and Maintenance requirements updated January 2013 Updated format to match Ecology standard format September 2014 Added Peak Diversion StormFilter Alternate Configuration November 2016 Revised Contech contact information April 2017 Revised sizing language to note sizing based on Off-line calculations CONTECH - StormFilter® GULD Maintenance Update (November 2012) Page 112 Appendix D Maintenance Schedule &Agreement (TO BE PROVIDED WITH BUILDING PERMIT APPLICATION) Preliminary Stormwater Site Plan Port of Edmonds Marine Retail