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calculating a daily coal pile leachate volume; and 4) calculating the chemical load and <br />chemical concentration increases when leachate is mixed with the alluvial aquifer. The <br />alluvial width uas measured from [he alluvial deposits map a[ a point opposite the loadout <br />and was estimated to 6e approximately 900 feet. The alluvial thickness uas estimated from <br />thicknesses measured at alluvial wells in several portions of the Dry Lreek drainage. The <br />average thickness determined uas approximately 45 feet. The deeper paleochannel width of <br />the alluvium was assumed equal to the meander amplitudes, which were determined [o be 400 <br />feet. Because the edges of the alluvium are usually intermixed ui th col luvium and <br />unsaturated, 100 feet on either side of the alluvial cross section was subtracted when <br />Constructing [he trapezoidal cross sectional representation. The depth to the water table <br />at alluvial 4ell HGDAL3 is approximately six feet. Thus, [he saturated alluvial cross <br />section is approximately 2 triangles having side lengths of 150 by 39 feet and a central <br />rectangle having side lengths of 400 by 39 feet. This configuration yields a saturated <br />cross sectional area of 21,450 ft2. <br />the alluvial aquifer ua ter table gradient was assumed to parallel the surface alluvia! <br />gradient. The alluvial aquifer gradient adjacent to the loadout was determined from a <br />topographic map to be 0. 0056 ft/ft. <br />the daily coal stockpile leachate volume was calculated as previously described in the <br />surface eater quality section. The mixing calculations were performed using the equations <br />from Ferreira (1984) and the results are as follows. <br />Coal leachate L = 0.0066 x 300 x 0.0027 = 0.0053 tons/day <br />Alluvi of aquifer L = 0.0063 x 2222 x 0.0027 = 0.0378 tons/day <br />= lowest TDS value measured at a Dry Creek alluvial well <br />historically <br />DSC (leachate/alluvium) = 0.0053 + 0.0378 = .0437 = 1231 mg/l <br />1.984 x 0.0129 x 0.00136 .000035 <br />The coal leachate will have no impact on the Dry Creek alluvial aquifer quality. The <br />leachate would actually dilute the TDS concentration of [he alluvial aquifer. <br />the loadout operation also includes a septic leach field. Leachate from this leach field <br />could possibly discharge [o the Dry Creek alluvium and/or streamflou. A limited number of <br />shower facilities are required by XSHA, but are no[ used by the mine employees. The only <br />8 Revised OG/i8/94 <br />