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8/11/87 <br />l� <br />Y <br />DRAINAGE COMPUTATIONS <br />FINE ASSOCIATES VENTURE ADDITION <br />x= <br />1. Runoff to Snelling Avenue <br />Existing Area = 1.20 Ac. S <br />= 1.8% <br />C = 0.35 L <br />= 100 <br />n <br />= 0.30 <br />tc <br />= 9.5 <br />minutes <br />i100 <br />= 8.4 <br />in/hr <br />Q = C A = 0.35 ,'8.4)(1.2) = 3.5 cfs <br />Proposed - Pavement 0.04 Ac <br />Roof 0.40 Ac <br />Green Area 0.20 Ac <br />„a <br />Total 0.64 Ac <br />'' <br />C (0 04)(.85) + (0.04)(G.90) + (0.25)(0.30) = 0.72 <br />0.64 <br />S = 0.50 tc = 12 <br />L = 160 il'p`,1 = 7.7 in/hr <br />n = 0.15 <br />Q = CiA = (0.72)(7.7)(0.64) = 3.5cfs (same as existing) <br />2. Pond Capacity Requirements - Reconveyed MnDOT <br />Property <br />Undeveloped Site <br />A = 4.90 Ac L = 570 <br />S = 1.4% <br />tc = <br />i100 <br />17.5 min <br />= 6.62 in/hr <br />C = 0.35 <br />n = 0.15 <br />Q100 (.35)(6.62)(4.90) = 11.4cfs. <br />Developed Site - Pavement 2.52 Ac <br />Roof •0.82 Ac <br />Green Area 1.56 Ac <br />Total 4.90 Ac <br />C = (0 25)(1.56) + (0.85)(2.52) + (0.90)(.82) = 0.67 <br />4.90 <br />n 0.13 tc = 19 min <br />L = 550 LF i100 = 6.20 in/hr <br />S = 0..70% <br />*Q100 = (0.67)(6.2)(4.90) = 20.4 cfs <br />STORAGE REQUIRED <br />Soil Type n <br />(CN) = (1.56)(61) + (2.52)(98) + (.82)(98) = 86 <br />- <br />4.90 <br />