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<br />Infiltration of this runoff, based on an estimated 16.6 acres of refuse <br />being present, suggests that a mean flow of 0.001 cfs could issue from <br />the pile. Amass balance calculation using a Q7-10 low flow value of 1.6 <br />cfs for the Middle Purgatoire and a total TDS value of 204 indicates TDS <br />values in the river would only increase about 2.0 mq/1 as a result of <br />this seepage. Calculation of SAR values for the Middle Purgatoire once <br />this seepage is included also show no appreciable increase. Use of the <br />water for either drinking or irrigation purposes is therefore, not likely <br />to be affected. <br />After the cessation of mining operations, mine water from the New Elk <br />Mine would no longer be discharged, and the abandoned workings would fill <br />with water, a process taking up to 80 years. The piezometric surface <br />would partially recover. Because the underground workings lie 400 to 800 <br />feet below the surface, the piezometric surface of the coal aquifer would <br />not be expected to rise to a level where it would intersect the ground <br />surface and thus cause discharge. A permanent depression in the <br />piezometric surface would exist in the vicinity of the flooded mine <br />workings, Given the assumption that the Allen seam is hydrologically <br />similar to the Maxwell seam, the depression mdy extend to a distance of 2 <br />to 3 miles from the edge of the mine workings. <br />When pumping of water from the workings is discontinued, the water that <br />accumulates is expected to be of lower quality than that currently pooped <br />due to increased residence time (Exhibit 6, Table 5). The quality of the <br />stagnant mine water should be similar to the quality measured below the <br />New Elk waste piles (Exhibit 6, Table 13 ). Total dissolved solids may be <br />equal to or exceed 2600 mg/1. This mine water would spread as a plume of <br />degraded quality ground water down gradient fran the mine. Based on the <br />structural contours of the coal seam, water passing through the flooded <br />workings would move in a northeasterly direction. It mdy spread to <br />approximateiy 2 to 3 miles from the edge of the mine workings. It is <br />anticipated that soluble materials would be readily flushed from the mine <br />cavity, but flow would be very slow away from the mine due to the low <br />permeabilities of the coal, causing the flushing action to persist over <br />an extended period of time. Since the coal seam aquifer contains poor <br />quality water, 806 to 1100 mg/1, and is not used as a water supply in the <br />general area, mining within this aquifer will not materially damage the <br />quality of ground water used off site. <br />Post-mining effects of the New Elk Mine on the water quality in the <br />stream-alluvial aquifer system would be expected to be less than during <br />operations, because mine water would no longer be discharged from the <br />underground workings. Therefore, seepage from the refuse piles would be <br />the only source of pollutant and this, as indicated earlier, is neglible. <br />-25- <br />