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Infiltration Trench (continued) <br /> Trench length required(ft) =Roof area (ft2) *minimum trench length(ft) <br /> 1,000 ft2 <br /> ■ Roof area requiring mitigation(ft2): <br /> ■ USDA Soil Type per soils report: <br /> ■ Trench length required (ft): <br /> (Trench length cannot exceed 100 feet. If length exceeds 100 feet, multiple trenches will be required.) <br /> ■ Number of trenches: <br /> ■ Length of each trench (ft): <br /> ❑ Include the following on the Stormwater Site Plan: infiltration trench length and width; <br /> roof area (including ft2 draining to each infiltration trench) <br /> ❑ Attach Soils Report <br /> Infiltration Dry Wells <br /> The minimum rock volume and dry well rock layer depth depend on soil type.The soils report <br /> will provide the USDA Soil Type.The following table provides the volume of washed rock and <br /> depth of washed rock required. <br /> 'W Volume of washed rock Drywell rock layer depth at <br /> SDA Soil Type (ftl)per 1,000ft2 of 1,000 <br /> impervious area ft'of impervious area <br /> "Coarse sand" (more than 50%of 60 4'9" <br /> sand fraction remains on#4 sieve) <br /> "Medium sand" (more than 50%of 90 7,2„ <br /> sand fraction remains on#40 sieve) <br /> ■ Roof area requiring mitigation(ft2): <br /> ■ USDA Soil Type per soils report: <br /> ■ Rock layer depth required (ft): <br /> ■ Volume of washed rock required (ft'): <br /> Volume of Washed Rock Required =Tributary Impervious Area (ft') * Standard Volume (ft') <br /> 1,000 ft2 <br /> ❑ Include the following on the Stormwater Site Plan: infiltration dry well location and depth; <br /> roof area (including ft2 draining to each infiltration dry well) <br /> ❑ Attach Soils Report <br /> Note:Stormwater facilities that infiltrate stormwater by means of an underground facility such as <br /> an infiltration trench or dry well may need to be registered as an underground injection well(UIC). <br /> For more information, visit everettwa.gov/1985/Stormwater-Technical-Resources <br /> City of Everett Public Works <br /> Small Project Stormwater Site Plan/Report—Sept.2023 Page 34 of 40 <br />