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III. Environmental Setting, Impacts,and Mitigations <br /> K. Hydrology, Geohydrology,and Water Quality <br /> TABLE III.K.3: PEAK RUNOFF FROM THE COMPLETED PROJECT <br /> Hydrologic Area <br /> Area (acres) Proposed Land Use Runoff Curve Number <br /> A 257 capped landfill 98 (impervious) <br /> B 10 stormwater pond and floodplain? 0(does not contribute) <br /> C 3 buffer 80(open space;75% grass cover) <br /> Peak discharge to pond 185 cfs <br /> Pond Maximum Storage Volume at design water surface <br /> elevation 13 acre-feet <br /> Peak Discharge to Little Johns Creek at downstream <br /> boundary 100 cfs <br /> NOTE: cfs=cubic feet per second. <br /> /a/ The Runoff Curve Number represents the average percent impervious surface and includes <br /> consideration for the hydrologic properties of the soil. <br /> Assumptions: Time of concentration for post development, 1.5 hours. Assumed SCS Type 1 <br /> rainfall distribution; Average 2 antecedent moisture conditions; 100-year 24-hour <br /> storm of 3.2 inches. <br /> SOURCE: R.W. Beck and Associates, March 1992. <br /> Mitigation Measure K3. <br /> Proposed as Part of the Project <br /> (a) The surface water conveyance system,including the detention pond would be designed to <br /> handle the 100-year storm. <br /> (b) Stormwater runoff from the working face would be collected at the edges of the landfill and <br /> a perimeter drainage system would route the water to the perimeter leachate collection <br /> trenches to prevent overtopping of the perimeter berm. <br /> Implementation of these measures would reduce the impact to below significance. <br /> III.K.14 <br />