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Section 780.21(b) Continued. <br />no private wel)s are completed in the coal aquifer within the <br />adjacent area, no adverse effects will occur as a result of <br />dewatering the pits. <br />The ground water inflow to the mine pit will collect in a sump at the <br />lowest elevation of the excavation. This water will be used <br />primarily for dust suppression on haul roads. The excess inflow will <br />be handled by pumping the water over the highwall and then into <br />sedimentation ponds downstream from the pit. Detention of water in <br />the ponds is necessary to meet effluent limitations for total <br />suspended solids content. For the purpose of analyzing detention <br />time, the entire amount of inflow to the excavation is assumed to be <br />pumped into sedimentation ponds, even though consumptive use for dust <br />suppression and evaporation will make the actual amount of discharge <br />somewhat less. <br />The theoretical detention time for the water to be pumped from the <br />mine is analyzed as follows: the highest rate of inflow to the pit is <br />given in Figure 22, Kerr North Area Mine Discharge, as 2.42 x 10° <br />cubic feet per day into Pit #2. If all of this water was to be <br />pumped out of the mine pit, the average rate of discharge would be <br />0.28 cubic feet per second. The smaller of the two sedimentation <br />ponds which will serve Pit #2, Pond H, is designed to handle a ]0- <br />year, 24-hour inflow of 53 cubic feet per second with a detention <br />time of 37.3 hours, which is more than the required 24 hours (see <br />Exhibit 42, Drainage and Sediment Control Plan). The amount of <br />inflow from the pit -would- be only one-half _of one. percent of the <br />inflow that Pond H is designed for. Even if pumping was conducted <br />during a 10-year, 24-hour runoff event, the amount of additional <br />inflow to the pond (0.28 cfs) would be insignificant as related to <br />the inflow generated by the storm event (53 cfs), and theoretical <br />detention time would not be measurably affected by pumping from the <br />-~; pit. furthermore, since the highest rate of <br />780-107 aaR <br />Revised - January, 1991 <br />