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Job Number: 93-419-26 FIIB: F:\93\415�D005\PRED.W01 <br />Calculated by: T. Fisher Date: 04-Nov-93 <br />Checked by: Date: <br />Project: Everett Clinic <br />CALULATE THE WEIGHTED SCS CURVE NUMBERS FOR BASIN 'D' <br />PREDEVELOPED CONDITIONS AREA <br />-grass 0.326 <br />-pavement, buildings 0.005 <br />TOTAL = 0.333 Acres <br />WEIGHTED AVERAGE Cn VALUES: <br />PERVIOUS <br />-Predeveloped conditions 86.0 <br />'�Note: Hydroiogic soil group'C' was used as the SCS <br />soils map indicates Aidervvood (AgC) soils. <br />CALCULATE THE TIME OF CONCENTRATION <br />Cn• <br />86 <br />98 <br />IMPERVIOUS <br />98.0 <br />24 hour isoaiuvials: <br />2-yaar (P2) = 1.55 inches/day ref. KCSWDM 3.5.1-8 <br />Sheetllow: Tt= [0.42*(Ns•l.)^.6]/[(P2^0.5)`(So^0.4)] <br />Conc. t�ow: Tt = U[60"Ks"(So ^ 0.5)] <br />Predeveloped conditions <br />Segment Status Length Ns Ks So Tt <br />(ft) (%) (min) <br />D1 - D2 lawn 108 0.150 NA 6.0°k 9.6 <br />(sheet) <br />D2-D3 lawn <br />(sheet) <br />22 0.150 NA 2.5% 3.8 <br />Total = 13.5 min <br />SUMMARY OF INPUT DATA FOR KCSWDM'S ITYD PROGRAM <br />Predeveloped: <br />Aper Cn Aimp <br />(Ac) (Ac) <br />0.33 86.0 0.005 <br />Cn Tc P2 <br />(min) (in) <br />98.0 13.5 1.55 <br />