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0 <br />Worksheet 3 BMP Sizing Worksheets <br />DISPERSON BMPS <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 ft' of roof area can drain to each dispersion BMP. <br />■ Hard surface area requiring mitigation: N/A______ <br />■ Hard surface draining to dispersion BMP: N/A___ <br />■ # of dispersion BMPs: Total Hard Surface = N/A <br />700 ft' <br />■ Dispersion trench required? ❑ Yes 0 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 />■ 751 (493 for SFR driveway, 258 for DADU driveway <br />Hard surface area requiring mitigation: ______________ <br />■ 23.5' for SFR and 11' for DADI <br />Width of paved surface discharging into sheet flow dispersion BMP: <br />■ Minimum required width of vegetated buffer: 11 75' for SFR and 5.5' for DADL <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°io = 7_07 ____% (must be less than 10% to use BMP) <br />Total Area (ft') (For SFR Driveway) <br />3.70% (For DADU Driveway) <br />■ Required Dispersion Area (ft') = Total Impervious Area (ftz)* 6.5 <br />Required Dispersion Area (ft2)* 6.5 = 45.96 ftz (24 ft^2 for DADU driveway) <br />(I"o r-SR17riveway) <br />■ Dispersion area provided: 70 ft^2 total -------------- <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 />