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Quality of Surface Water <br />The primary impact of Yoast mining operations on surface water quality will <br />be an increase in total dissolved solids concentration resulting from the <br />occurrence of spoil springs after backfilled spoil in the mine pits has become <br />saturated. Using conservative assumptions regarding the amount of inflows <br />to the reclaimed pits, and the quality of spoil spring water, and information <br />gathered from the nearby Seneca II Mine in recent years, Seneca Coa] <br />Company has estimated the changes in surface water quality which may be <br />caused by the proposed Yoast Mine. The projected impacts on each of the <br />affected drainages neaz the permit area aze summazized below. <br />Armand Draw <br />Following the occurrence of spoil springs at the Yoast Mine, the total <br />dissolved solid (TDS) content of surface water in Armand Draw is projected <br />to increase from 950 to 3938 mg/1. These values, and all TDS values <br />discussed below aze mean TDS values during the irrigation season, which <br />was considered to last from June 1 through September 30. <br />No use is presently made ofthis water before it flows into Grassy Creek. Due <br />to the minimal flows in Armand Draw, it is reasonable to assume that no <br />future use of this water will be made, other than livestock watering. <br />Therefore, this increase in salinity will not result in material damage. <br />Grassy Creek <br />An evaluation of the water quality impacts of the Yoast Mine on Grassy <br />Creek in the permit application projects no increase in TDS in Grassy Creek <br />downstream from the mine. This conclusion is drawn by estimating the <br />quality of Grassy Creek water after salt loading from Yoast Mine spoil <br />springs, and comparing that projected water quality to current water quality in <br />Grassy Creek downstream from the Yoast permit azea. Water in lower Grassy <br />Creek currently has an average TDS of 2584 mg/1, partially due to the <br />influence of spoil spring dischazges from the Seneca II Mine. Seneca Coal <br />Company predicts that lower Grassy Creek TDS will be 2177 mg/1 after <br />addition of Yoast spoil springs. Thus, Seneca Coal Company concludes that <br />TDS in Grassy Creek will not increase as a result of Yoast Mine operations. <br />Using Seneca Coal Company's assumptions about spoil spring development <br />at the Yoast mine, and the existing baseline water quality data for lower <br />Grassy Creek, the Division estimated the TDS of lower Grassy Creek after <br />establishment of Yoast spoil springs will increase by approximately five <br />percent. Because the quantity and quality of Grassy Creek water is mazginal <br />or unsuitable for use as domestic or irrigation water, this projected increase in <br />Yoast Mine 30 February 28, 2006 <br />