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-36- <br /> Probable Hydrologic Consequences - Ground Water <br /> The impacts incurred by ground water resources as a result of the proposed <br /> mining operations are expected to be insignificant. However, several slight <br /> changes in the hydrologic system are expected: First, the coal seams and <br /> their immediately adjacent strata will be dewatered during mining; second, the <br /> ground water quality of alluvial ground water located adjacent to the coal <br /> processing waste and tunnel rock piles will become slightly degraded; and <br /> third, slight mixing of ground waters from previously unconnected aquifers may <br /> occur as a result of the proposed rock tunnel . None of these potential <br /> impacts are expected to cause material damage to ground waters in the Coal <br /> Basin area. Each is discussed in greater detail below. <br /> As a part of normal operating procedures, the applicant must handle water that <br /> develops in the mine workings. Mine inflow waters are: <br /> 1 . consumed in the mining operation, and <br /> 2. pumped from the mine at a rate of 40 to 300 gpm. <br /> The amount of mine inflows produced by the mines is estimated from records of <br /> water pumped from the mines. Based on mine pumpage records (see Table III-E-2 <br /> of the permit application) , the amount of water pumped from the mine workings <br /> increases during the spring and significantly decreases during the late fall <br /> and winter. <br /> The mine dewatering process should lower water levels in the two coal seams <br /> being mined, the Rollins and Middle sandstones, and the lenticular and <br /> discontinuous sandstones of the Mesaverde Formation. The applicant predicts <br /> that the total mine inflow to all 5 mines will be low. This prediction is <br /> based on the estimated low permeabilities of the effected strata, and the <br /> proximity of the mine workings to the under saturated recharge areas of the <br /> aquifers. The applicant also predicts that the drawndown of water levels in <br /> the effected aquifers will not extend beyond one mile from the outer extent of <br /> the mine workings. <br /> The present measured mine discharge rates vary seasonally between 40 and 300 <br /> gallons per minute (gpm) . These inflow rates may increase significantly as <br /> the mines move farther down the dip of the strata. At lower elevations the <br /> hydraulic pressures within the aquifers will be greater, as will be the <br /> pressure differential between the mine workings (atmospheric pressure) and the <br /> aquifers. This will increase the rate of flow towards the mine workings. <br /> There are no known users of ground water from the Mesaverde Formation aquifers <br /> within a two-mile radius from the edge of the mine. Therefore, no impacts to <br /> ground water use should result from the dewatering of the mine workings. When <br /> mining is completed in Coal Basin, the water levels in the aquifers should <br /> showly rise to a level which approximates the pre-mining ground levels in the <br /> aquifers. <br />