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Future Site Conditian <br />Prorated future runoff coefficient <br />Building and concrete area = 0.23 Ac. @ 0.90 <br />Asphalt Area = 0.34 Ac. @ 0.90 <br />Planter Area = 0.06 Ac. @ 0,20 <br />(0.23)(0.9) + (0.34)(0.9) i� (0.06)(0.2? = 0.73 Cf <br />0.67 <br />Qo = allowable = 0.56 = 1.14 c.f,s,/Ac <br />Area futC 0.63 0. <br />Assume orifice conditions exist (7.5 year design storm) <br />T,= -25 + 2706 =-25 + 2706 = 23,72 min. {25 yr, storm Everett) <br />Qa � <br />Vs = 4329T - 40 QoT =�324(23.72) - 40(1.14)(23.72) = 21f�7.63 = 1026.00ft3/AcC <br />T+25 23.72 +25 (25 yr. Ererett) <br />V total = Vs(Ac)fut C= 1026.00(0.53)0.7� = 504.17 ft.� <br />Sizina the Detention System <br />Required volume of detention = 504,17 ft.3 <br />4' Dia. Type 2 MH = 12.57 `t.3/v.f. <br />V.F. = vertical feet above flow line of outlet <br />CB Type 1-C = 3.97 ft,3/v.f. <br />CB MH No. 1 Type II = 12.57 f't.3/V.F. X 3.82 V.F. _ <br />CB MH No. 2 Type II = 12.57 ft.3/V,F. X 3.19 V.F. _ <br />CB MH No. 3 Type 1-C = 3,97 ft.3/V.F. X 2.61 V.F. _ <br />CB MH No. 4 lype 1-C = 3.97 ft,3/V,F. X 1.96 V.F. _ <br />18" culv. _ ',.767 ft.3/l,f. <br />12" culv. = 0.7854 ft.3/l.f. <br />Install 125 L.f. 18" @ 1.767 ft3/L.F. _ <br />48.01 ft3 <br />40,10 ft� <br />10.36 ft3 <br />7,86 ft3 <br />220.87 ft3 <br />