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Emereencv Overllow Soillwav <br />The emergency overAow spillway was designed to convey the 100 year, 24 hour <br />undetained devcloped flow of 12.78 cfs. The bottom of the spillway has an elevation of <br />511.00 which corcesponds to the hydraulic grade line elevation used to size the overflow <br />riser (please reference the overflow riser calculations on the previous page). The length of <br />the spillway was calculated assuming a flow depth equal to 4 inches. Please note that the <br />top of the bertn was adjusted so that there is a minimum of six inches of freeboard <br />between the spillway design flow depth and the top of the berm. A summary of the <br />spillway calculation are provided below. <br />L = Length of spillway <br />Q�oo = 100 year undetained flow for entire site <br />H = Depth of flow <br />L = Q�oo/(3.21 •H'R)-2.4*H <br />L = 12.78 / (3.21 • Q.333'� ) -2.4' 0.333 <br />L = 19.91 ft <br />Therefore, the spillway was designed to be 20 feet in length with 4 inches of flow <br />depth starting at elevation 511.00. <br />Water Oualitv <br />Water quality enhancement for the site wilt be provided through the use of dead storage. <br />The volume of dead storage required is based on DOE standards which state the volume <br />equal to the developed condition hydrograph with a rainfall equal to 64% of the 2-year, <br />24-hour precipitation. <br />(0.64)(PZ�t) _ (0.64)(1.55 in) = 0.99 in <br />Please refer to the developed condition hydrograph summaries for the water quality <br />hydrograph. As stated previously, the volume of the water quality hydrograph is 52,489 <br />cubic-feet. The volume of dead s�orage required is 52,793 cubic-f'eeG Tke vo/ume of <br />Idead storage provided is 70,047 cubic feet <br />Srorni Drainnge Repor7 For King Extrusion - Page 11 <br />I <br />