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I� <br />Ic <br />I( <br />Ir <br />I( <br />Ic <br />Bill Mima�•-Drai�o@e Sddy <br />TES[' SEDIMENT TRAP DESIGN <br />Sediment Traps are sized per the Everett Stormwater Manual for small sites of less then <br />three acres. <br />• Trap Surface Area, As = 1.2 Q2/ Vsed <br />• Qc = 2-year design inflow for cieared site = 0.02 CFS <br />• VseJ = velocity of inedium silt particle = 0.00096 fps <br />. Minimum storage depth shall be 1.5 feet. <br />• Outlet shall be a CMP riser with washed gravel filter cone. <br />• Length to width ratio is > 3:1. <br />As = 1.2 Q2/ Vsed = 1.2' 0.02/ 0.00096 fps = 25 sf <br />Minimum Depth = 1.5' <br />Paved driving and parking area = 0.14 Acrcc <br />6-Month Rainfall = 0.99 Inches <br />Tc = 10.0 Min. <br />From Waterworks: 6-Month Developed tlow rate = 0.025 cfs <br />100-Year Conveyance Flow = 0.09 cfs <br />IWftiTh:NN ENGINI?IiRS, INC. PROJF.CT:01-lI l-A <br />i <br />�U <br />