Peak flow reduction facilities will consist of ultimate facilities identified in the Comprehensive Plan and Master Plan and interim facilities which will accommodate development before the Comprehensive Plan and Master Plan facilities are in place. Peak flow reduction facilities may include retention basins, flow-by or flow through detention basins, and flow through retarding basins. Retarding basins will be designed for detention and retention in combination.
Where the upstream watershed is undeveloped, the basins will be sized to handle undeveloped condition flows from the upstream tributary area and developed condition flows from the development itself.
Where the upstream watershed is developed, the method of handling the flows from the upstream tributary area will be determined based on the existing conditions with consideration of the future master plan and Comprehensive Plan facilities.
1. Retention Basins - Retention basins may be used if the results of percolation tests, performed and signed by a Soils Engineer or an engineering geologist show that the basin can percolate dry (no water in the basin) within seven (7) days.
In determining the required retention basin volume, Figure V-9 shall be used with an additional 1.35 multiplier in the K-Zone, 1.25 multiplier in the J-Zone and 1.1 multiplier in the I-Zone. Hydrologic soil classifications to be used with Figure V-9
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