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• Section 816.46 (b) Continued. All sedimentation ponds have been designed to store 0.1 acre-foot of dead storage for each acre of disturbed land within the tribu- tary watershed. The acreage of disturbed land was calculated based on the maximum amount of planned disturbance at any time during the mining and reclamation period. (c} Detention time. Sedimentation ponds shall provide the required theoretical detention time for the water inflow or runoff entering the pond from a 10-year, 24-hour precipitation event (design event). Theore- tical detention time is defined as the average time that the design flow is detained in the pond; and is further defined as the time difference between the centroid of the inflow hydrograph and the centroid of the outflow hydrograph for the design event. Runoff diverted under Sections 816.43 and 816.44, away from the disturbed drainage areas and not passed • through the sedimentation pond need not be considered in sedimentation pond design. In determining the runoff volume, the characteristics of the mine site, reclamation procedures, and onsite sediment control practices shall be considered. Sedimentation ponds shall provide a theoretical detention time of not less than twenty-four hours, or any higher amount required by the regulatory authority, except as provided under subparagraphs (1), (2), or (3) of this paragraph. (1) The regulatory authority may approve a theoretical detention time of not less than 10 hours, when the person who conducts the surface mining activities demonstrates that-- (i) The improvement in sediment removal efficiency is equlvalenL to the reduction in detention time as a result of pond design. Improvements in pond design may include, but are not limited to pond configuration, in-flow and out-flow facility locations, baffles to decrease in-flow • velocity and short-circuiting, and surface areas; and 816-49