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Goldfinch Brothers <br /> Drainage Study <br /> August 27,2008 <br /> 5. WATER QUALITY DESIGN CRITERIA (cont.) <br /> TESC SEDIMENT TRAP DESIGN FOR CONSTRUCTION AREA <br /> Sediment Traps are sized per the Everett Stormwater Manual for small sites of less than <br /> three acres. <br /> • Trap Surface Area, As= 1.2 Q2/Vsed <br /> • Qc=2-year design inflow for cleared site=0.096 CFS- 0.1 CFS <br /> • Vsed=velocity of medium 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 * 0.331/0.00096 fps= 413.75 SF <br /> _ <br /> Minimum Depth 2.5' <br /> From Waterworks: 6-Month Developed flow rate= 0.192 CFS <br /> I <br /> I <br /> I <br /> I <br /> I <br /> I <br /> 1 9 <br />