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• <br />0 <br />Worksheet 3 <br />DISPERSON BMPS <br />BMP Sizing Worksheets <br />BMP T5.11 Concentrated Flow Dispersion <br />Concentrated flow dispersion BMPs shall be designed in accordance with the SWMMWW. Clearly show the <br />vegetated flowpath on the site plan. A maximum of 700 ft2 of roof area can drain to each dispersion BMP. <br />■ Hard surface area requiring mitigation: <br />■ Hard surface draining to dispersion BMP: <br />■ # of dispersion BMPs: Total Hard Surface = _ <br />700 ft2 <br />■ Dispersion trench required? ❑ Yes ❑ No <br />(must be included if flow path is 25 to 50 ft) <br />BMP T5.12 Sheet Flow Dispersion <br />Sheet flow dispersion BMPs shall be designed in accordance with the SWMMWW. <br />■ Hard surface area requiring mitigation: <br />■ Width of paved surface discharging into sheet flow dispersion BMP: <br />■ Minimum required width of vegetated buffer: <br />(10 ft for every 20 ft of paved/hard surface, or fraction there of) <br />BMP T5.30 Full Dispersion <br />Full dispersion BMPs shall be designed in accordance with the SWMMWW. <br />■ Residential (impervious surfaces). All calculations are for areas with a single Threshold Discharge <br />Area (TDA). If multiple TDAs exist, provide a calculation for each. <br />Total Impervious (ft2)*100% = °k (must be less than 10% to use BMP) <br />Total Area (ft2) <br />■ Required Dispersion Area (ft2) = Total Impervious Area (ft2)* 6.5 <br />Required Dispersion Area (ft2)* 6.5 = <br />ft2 <br />■ Dispersion area provided: <br />(Note. Dispersion area must be preserved as forest or native vegetation.) <br />City of Everett Public Works <br />Small Project Stormwater Site Plan Report -Dec 2019 37 <br />