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Job Number: 93-419•26 <br />Calculated by� T. Fisher <br />Checked by: <br />Project: Everett Clinic <br />FI�O: F:\93\419�DOCS�POST.W01 <br />Date: 04-Nov-93 <br />Date: <br />CALULATE THE WEIC;HTED SCS CURVE NUMBERS - POST-DEVELOPED <br />POSTDEVELOPED CONDITIONS AREA <br />-grass 0.36 <br />-pavement, buildings 1.05 <br />TOTAL = 1.41 Acres <br />WEIGHTED AVERAGE Cn VALUES: PF_RVIOUS <br />-Postdeveloped conditions 86.0 <br />'Note: Hydrologic soil group'C' was used as the SCS <br />soils map indicates Aldervvood (AgC) soils. <br />CALCULATE THE TIME OF CONCENTRATION <br />Cn' <br />86 <br />98 <br />IMPERVIOUS <br />98.0 <br />24 hour isopluvials: <br />2-year (P2) = 1.55 inches/day ref. KCSWDM 3.5.1-8 <br />Sheetflow: Tt = [0.42"(Ns•L)^.8]I[(P2^0.5)•(So^0.4)] <br />Conc. ilow: Tt = U[60*Ks•(So ^ 0.5)] <br />Postdeveloped conditions Tt <br />Segmerrt Status Length Ns Ks �� � �min) <br />(/t) <br />A1 - A2 lawn 210 NA 11 0.5°/a 4.5 <br />A2-A3 <br />(conc.) <br />Pipe 80 NA 42 <br />(channel) <br />0.5°k 0.4 <br />Total = 4.9 min <br />SUMMARY OF INPUT DATA FOR KCSWDM'S ITYD PROGRAM <br />Postdeveloped: <br />Aper <br />(Ac) <br />0.36 <br />Cn <br />:. � <br />q�mp Cn Tc P2 <br />(Ac) (min) (in) <br />1.05 98.0 4.9 1.55 <br />