2011-09-26_PERMIT FILE - C1981012 (24)

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!. Quannrarive lmpaar oJ.Niting • Table 7. Extent of Drawdown of Piezometric Surface during Mining of the Golden Eagle Mine Vertical I.ealrance Extent of Drawdown from (B) Perimeter CASE (ft) (ft) lIB 2,137 11,322 IIIB 1,711 9,051 Conclusion The quantitative impacts from mining were evaluated during operations as well as following closure of the mine. The mining of the coal seam results in mine inflows which are pumped to maintain operational efficiency. These mine inflows appeaz to have little communication with the surface water flow regime at either the Golden Eagle and New Elk Mines. There is no correlation between mine inflow sites and surface drainage patterns and known sptmgs and seeps. The mine inflows appear to come from three sources at Golden Eagle: a fault neaz god Right, the roof, walls and floor of the coal seam and from the dewatering of overlying aquifers of limited extent through shafts and drill holes. Maximum predicted mine inflows are estimated at 218 gpm from the coal seam as well as any contn~bution associated with faulting. Subsidence induced by longwall mining has not materially increased the rate of mine inflows at Golden Eagle over historical observations in New Elk. Subsidence has not resulted in any visually observable changes in surface water geomorphology above the workings. Pumping has resulted in a cone of depression associated with dewatering. During the life of the mine, pumping has the potential to lower the elevation of the water table in the coal seam one foot 2.1 miles away, and decrease the water level immediately adjacent to the mine as much as 400 feet. Measure- ments of a water level in the New Elk mine suggests that flooding of the workings may exceed the rate of measured inflows, due to the sealing of old workings, and the initiation of their flooding prior to closure of the mine. 24