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Developed Condition <br />Area to be developed into 9.0 acre of commercial area and 18.70 <br />acre of Residential area: <br />Runoff coeffiecient according to MN /DOT Manual: <br />Residential: C = 0.55 <br />Commercial: C = 0.75 <br />Drainage Areas: <br />Residential area = 18.70 Ac <br />Commercial area = 9.0 Ac <br />TOTAL = 27.70 Ac <br />C = 0.55 <br />C = 0.75 <br />100 year 24 hour Runoff Calculation <br />15Min. 30Min 60Min 2Hr 12Hr 24Hr <br />Duration <br />Precip ft. 0.15 0.19 0.25 0.29 0.43 0.49 <br />Residential <br />18.7 Ac 1.54 1.95 2.57 2.98 4.43 5.04 <br />Commercial <br />9.0 Ac 1.013 1.3 1.69 1.96 2.90 3.31 <br />Total Runoff <br />Ac /ft 2.55 3.25 4.26 4.94 7.33 8.35 <br />Discharge Ac 0.36 0.72 1.44 5.8 34.65 69.3 <br />Storage Required 2.19 2.53 2.82 - -- <br />Required Storage = 2.82 Ac /ft <br />= 3.0 Ac /ft <br />II. Ponding for the Commercial property only <br />Predeveloped: <br />Area = 9.0 Ac <br />Runoff length = 400' <br />Arg Slope = 0.01 ft /ft <br />N = 0.4 <br />: Tc = 26 Min <br />1100 = 4.8 in /hr <br />C = 0.3 <br />Qout = 0.3 (4.8) (9.0) = 12.96 CFS <br />= 25.71 Ac /ft 1 day <br />Page 27 <br />