Question

Trenuevey 4. Mechanicsville has obtained a grant from the state government to build a condominium complex for the retired. The total land set aside is 74,010 m². of this area 15,831 m² will be used for Swiss chalet condominiums with slate roofs (C = 0.75). Public streets and drives (C =0.70) will occupy 18,886 m². The remainder will be lawns. The area is flat and has a sandy soil (C = 0.05). Find the peak discharge from the development for a 2-year storm. Assume an overland flow distance of 272 m and the time of concentration of 18 minutes. Figure - IDE Curves for Mechanicsville

Answer 1

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By Rational Formula Qp = CIA where ce runoff factor i rainfall intensity (from IDE graph) A Area For 2 From year graph storm and time of concentration 18 min. i = 75 mm/hour (approx) -0.075 ml hour (1) (2) Swiss chalet condominiums with slated roof. c=0.75, A= 15831 m² Q1 = CiA = 0.75 X 0.075 X 15831 mlhr = 8go.5 m/hr. Public streets & drives C=0.7, A: 18 886 Q2 = CiA = 0.7% 0.075 X 18 886 m3/hu - 991.51 m3/hr. Lawens, C = 0.05, A = 74010- (1583)+18886) m? - 39 293 m? Gz = CiA = 0.05x0.075839298 in - 147.35 m² lhe Total Op: Q+Q₂ + Q 890.5 + 99151+ 147.35 mln Qp - 2029.36 m3/how (3)