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Note: If using BMP T5.10A: Downspout Full Infiltration, the project must meet the <br /> specified design criteria for the BMP (e.g., separate trenches for each pipe <br /> length at the specified spacing and dimensions). If modeling is used to size <br /> an infiltration trench,the design must meet the requirements for BMP T7.20: <br /> Infiltration Trenches. BMP T7.20 sizing requires a site-specific infiltration <br /> rate,typically determined from pilot infiltration testing. BMP T5.10A and <br /> BMP T7.20 have difference separation to groundwater requirements. <br /> Stating that soils have low infiltration rates is inadequate to demonstrate <br /> that an LID BMP is infeasible. Appropriate infiltration test data must be <br /> provided to demonstrate that infiltration rates are below the infeasibility <br /> threshold for the BMP. <br /> BMPs using compost are not allowed if the project drains to Silver Lake. <br /> MINIMUM REQUIREMENT #6 <br /> • Indicate the required level of treatment for each TDA and describe the Runoff <br /> Treatment BMPs that will be used. <br /> • Verify that design criteria are met per requirements in the Manual and DCSS. Verify <br /> that the selected treatment BMP is allowed by the DCSS. <br /> • Attach modeling results, sizing calculations, and site-specific plans (including <br /> those for proprietary BMPs). <br /> • Attach traffic studies or similar documentation, where appropriate,to determine if <br /> oil control is required for commercial, industrial, and roadway-related projects. <br /> • If using a proprietary treatment technology, include the Ecology General Use Level <br /> Designation (GULD) letter, and provide documentation that is required by Ecology. <br /> This may include a certification letter from the manufacturer. <br /> Note: Phosphorus treatment is not presently required in the City of Everett. <br /> BMPs using compost are not allowed if the project drains to Silver Lake. <br /> Frontage improvements are considered to be part of the project hard <br /> surfaces, and MR #6 requirements should be addressed for frontage PGIS. <br /> Runoff draining to UIC wells requires a different water quality treatment <br /> BMP selection process than MR #6. <br /> Minimum Requirement#1-9 Supplemental Guidance City of Everett <br /> Page 16 Aug 2022 <br />