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concentrations of trace elements are far below both the reliability of <br />• the computation method and the ability to detect the changes. <br />Surface runoff from the refuse pile is expected to be in the range <br />of 7.6 to 12.7 acre-ft in the year of maximum surface area. Runoff will <br />be routed through a sediment pond that will result in concentrations of <br />suspended and settleable solids in compliance with effluent limitations. <br />Concentrations of iron and manganese in the discharge are estimated at <br />0.3 mg/1 and 0.03 mg/1, respectively. These values are well below the <br />corresponding limitations of 3.5 and 2.0 mg/1 for average daily <br />conditions. The concentration of dissolved solids in the sediment pond <br />discharge is estimated at about 1000 mg/1. It is estimated that this <br />will increase the average in-stream TDS concentration in the range of 0.3 <br />to 0.5 mg/1 at the Madrid gaging station. The increase will be on the <br />order of 1 mg/1 immediately downstream from the New Elk Mine. <br />Subsurface seepage through the refuse pile is expected to occur <br />as the result of abnormally wet years, only. Average precipitation <br />conditions should result in no leachate production. The maximum annual <br />• volume of seepage resulting from an abnormally wet year is estimated at <br />3.6 acre-ft and is expected to contain about 4200 mg/1 dissolved solids. <br />Such a discharge would increase the average in-stream TD.S by 0.5 mg/1 at <br />Madrid and by about 1 mg/1 at the New Elk Mine. Calculated changes in <br />the in-stream concentrations of all trace elements are far below the <br />level at which change can be measured. The calculations on which these <br />statements are based were made for conditions substantially worse than <br />expected to occur on the average. <br />In summary, the construction of the refuse pile will have no <br />effect on the quantity of water yielded by the watershed. Under <br />reasonable worst case conditions, the combined effect on in-stream water <br />quality (Purgatoire River) will be to increase the average TDS <br />concentration in the vicinity of the mine by about 2 mg/1. Changes in <br />the in-stream concentrations of trace elements will be well below the <br />level at which such changes can be measured. Concentrations of iron and <br />manganese should be on the order of 20 percent or less of applicable <br />effluent limitations. <br />• <br />2.05-82 <br />(Revised OS/l 1194) <br />