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SEDIMENT TRAP DESIGN <br /> Project Name: RITEAID#5231 By: P.A.D. <br /> Project Number: 08028 Date: 10/24/2008 <br /> DRAINAGE CRITERIA: CITY OF EVERETT <br /> RAINFALL METHOD: Rational Method <br /> METHOD OF ANALYSIS: <br /> Step 1) Required Sediment Trap Surface Area <br /> Tributary area= 2.15 ac <br /> Q2= 0.45 cfs <br /> Q100= 1.24 cfs <br /> H=Storage depth= 2 ft <br /> Z=Sideslope= 3 ft/ft <br /> T=Dewatering time= 24 hr <br /> G=Gravity= 32.2 ft/s^2 <br /> As=Req'd surface area=Q2*2080 sf/cfs= 936 sf <br /> Step 2)Provided Sediment Trap Surface Area <br /> Provided trap dimensions: width(ft) length (ft) <br /> bottom = 8 52 <br /> water surface= 20 64 AREA= 1280 sf, OK! <br /> top= 26 70 <br /> Step 3) Emergency Overflow Spillway <br /> ho=Overflow depth= 0.25 ft <br /> Lo=Bottom width= (Q100/(3.21*ho^1.5))-2.4*ho <br /> 2.5 ft, USE 2.0 FT <br /> Provide:6"min.freeboard;2.0'min. bottom width <br /> 08028-STMCLC.xls,SEDIMENT TRAP `Z <br />