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Labco Auto Body Repair Facility <br />Drainage Report, February 21, 1993 <br />Page 8 <br />A2. Detention Volume Calculations <br />Required Detention Volume: 1121 cf <br />North MH 631.99 - 628.09 = 3.90 f' <br />South Central MH 631.99 - 628.30 = 3.69 ft <br />South West MH 631.99 - 628.64 = 3.35 ft <br />South East MH 631.99 - 628.51 = 3.48 ft <br />Total Depth = 14.42 ft <br />Detention Volume From Manholes = (T7xd2xD)/4 <br />d = 4.5 feet <br />D = total depth (ft) <br />Detention Volume From Manholes <br />Detention Volume From 36" pipe <br />Detention Volume From 12" pipe <br />Detention Volume From 18" pipe <br />Total Detention Volume Provided <br />A3. Orifice Sizing <br />Orifice #1, 2 year return frequency storm: <br />= 3.1415 x 5.06 x 14.42 = 229 cf <br />= 3.1415 x 7.06 x 116 =820cf <br />= 3.1415 x 0.25 x 30 = 24cf <br />= 3.1415 x 0.56 x 42 = 74cf <br />= 1,147 cf > 1121 cf Q}, <br />Peak discharge (Q) = 0.07 (Lawns & landscaping) x 0.58 = 0.0406 cfs <br />Elev. 626.09 <br />IE out 628.09 <br />Overflow 631.99 <br />Height (H)= 631.99 - 628.09 = 3.9 ft <br />Q = 0.62a(2GH)12 <br />a = (TTxd2xdodrice)/4 <br />a = cross -sectional orifice area <br />G = gravitational constant <br />doHfkx= orifice diameter (feet) <br />Orifice #1, dodfice = 0.28 ft or 3.4 inches <br />nRIEMP WPS <br />