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Collection System Collaborative Benchmarking Group <br />Best Practices for Sanitary Sewer Overflow (SSO) Prevention and <br />Response Plan <br />The formula used to develop Table C is Q=CcVA, where Q is equal to the <br />quantity of the flow in gallons per minute, Cc is equal to the coefficient of <br />contraction (.63), V is equal to the velocity of the overflow, and A is equal to the <br />area of the pick hole.2 If all units are in feet, the quantity will be calculated in <br />cubic feet per second, which when multiplied by 448.8 will give the answer in <br />gallons per minute. (One cubic foot per second is equal to 448.8 gallons per <br />minute, hence this conversion method). <br />Example Overflow Estimation: <br />The maintenance hole cover is in place and the height of water coming out of the <br />pick hole seven -eighths of an inch in diameter (7/8") is 3 inches (3" ). This will <br />produce an SSO flow of approximately 4.7 gallons per minute. <br />FLOW OUT OF VENT OR PICK HOLE (TABLE " <br />Height to be meas <br />This sanitary sewer overflow drawing was developed by Debbie Myers, Principal <br />Engineering Technician, for Ed Euyen, Civil Engineer, P.E. No. 33955, California, <br />of County Sanitation District 1. <br />Velocity for the purposes of this formula is calculated by using the formula h = v squared / 2G, where h is <br />equal to the height of the overflow, v is equal to velocity, and G is equal to the acceleration of gravity. <br />19F-98 <br />