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La Plata No. 1 <br />Pond Dewatering Calculation <br />10 year, 24 hour storm runoff volume = 0.63 ac ft <br />Pond Volume Pond Stage <br />(acre-feet) (feet) <br />2.43 8.7 Peak Stage <br />1.8 7.3 Permanent Pool Elevation <br />Maximum Head Difference = 0.8 ft <br />Average Head = 0.4 ft =- <br />Average Discharge Reouired <br />24 hour detention = 1/2 storm volume detained 24 hours <br />(0.43 ac. ft/2) = 9365 cubic feet <br />24 hours 86,400 sec = 0.11 cfs <br />Orifice Size Reouired <br />Q = CA (gh)0'S Where: C = loss coefficient = 0.6 <br />A = orifice area (ft2) <br />A = Q/C (gh)0'S g = force of gravity = 32.2 ft/sec <br />= 0.71 ft3/sec, h = head difference (feet) <br />(0.6)[(32.2)(0.4)]0.5 <br />= 0.05 ft2 <br />= 6.7 in2 <br />= square 2.6 in on a side <br />= circle with diameter of 3.0 inches <br />