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Jim Herron -3- March 17, 1982 <br /> Probable Hydrologic Consequences <br /> The impacts imposed upon ground water resources as a result of the proposed mining <br /> operations are expected to be insignificant. However, several slight changes <br /> in the hydrologic system are expected. First, the coal seams and immediately <br /> adjacent strata will be dewatered in the vicinity of the mining operations. <br /> Second, the water quality of alluvial ground water located adjacent to the several <br /> mine-wastes piles may become slightly degraded. Third, slight mixing of ground <br /> waters from previously unconnected aquifers may occur as a result of the proposed <br /> rock tunnel. None of these potential impacts are expected to cause material <br /> damage to ground waters in the Coal Basin area. Each is discussed in greater <br /> detail below. <br /> As part of normal operating procedures, the applicant must handle water that <br /> develops in the mine workings. This water is handled in one of the following <br /> ways: <br /> 1) used during the mining process, <br /> 2) allowed to migrate downdip either in the coal or the underlying sandstone <br /> units, or <br /> 3) Pumped from the mine at a rate of 40 to 300 gpm. <br /> Based on mine pump records (see Table III-E-2 of the permit application) , the amount <br /> of pumped water increases during the spring and significantly decreases during <br /> the late fall and winter. This mine dewatering process should lower water levels <br /> in the two coal seams being mined and the Rollins and Middle Sandstones. Based <br /> on the expected low transmissivities, it is unlikely that the drawdowns would <br /> extend more than a mile from the edge of the mine workings. Since the mine is <br /> located near an outcrop area, it is unlikely that these strata are fully saturated <br /> anyway. The low pumping rates required to dewater the mine workings is evidence <br /> of this. Also, the fact that the pumping rates dramatically increase during <br /> the spring season indicates variable degrees of aquifer saturation throughout <br /> a given year. There are no known users of ground water from these strata within <br /> at least a two-mile radius from the edge of the mine. Therefore, no impacts <br /> should result from the dewatering of the mine workings. When mining is completed <br /> in Coal Basin, the water levels in the aquifers should slowly return to original, <br /> pre-mining elevations. <br /> The disposal of mine and processing waste materials at the mine have the potential <br /> to degrade the quality of the alluvial ground water of Coal Creek. A geochemical <br /> analysis of the roof and floor rock and coal (see p. III-D-37 of the permit appli- <br /> cation) failed to undover any toxic or hazardous materials. In addition, seven <br /> years of ground and surface water monitoring, while similar wastes were being <br /> disposed of, indicate no adverse affects to date. Therefore, it is concluded <br /> that this potential impact is insignificant. If an impact were to occur, the <br /> existing monitoring system, with the stipulations discussed later, is adequate <br /> for early detection. <br />