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seepage is expected to approximate 4200 mg/1. The dissolved solids load <br />added to the Purgatoire River as the result of wet year seepage could be as <br />much as 20 tons, therefore. This is about 0.2 percent of the average salt <br />load as measured at the Madrid gaging station. An input of 20 tons of <br />additional dissolved solids will increase the average concentration for an <br />average year by 0.5 mg/1. The calculated changes in the in-stream <br />concentrations of trace elements are far below both the reliability of the <br />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 be <br />routed through a sediment pond that will result in concentrations of <br />suspended and settleable solids in cort~liance with effluent limitations. <br />Concentrations of iron and manganese in the discharge are estimated at 0.3 <br />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 conditions. <br />The concentration of dissolved solids in the sediment pond discharge is <br />' estimated at about 1000 mg/1. It i5 estimated that this will increase the <br />average in-stream TDS croncentration in the range of 0.3 to 0.5 r5/1 at the <br />Madrid gaging station. The increase will be on the order of 1 mg/1 <br />imemdiately downstream from the New Elk Mine. <br />Subsurface seepage through the refuse pile is expected to occur as <br />the result of abnormally wet years, only. Average precipitation conditions <br />should result in no leachate production. The maximum annual volume of <br />seepage resulting from an abnormally wet year is estimated at 3.6 acre-ft <br />and is expected to contain about 4200 mg/1 dissolved solids. such a <br />discharge could increase the average in-stream TDS by 0.5 mg/1 at Madrid <br />and by about 1 m9/1 at the New Elk Mine. Calculated changes in the in- <br />stream concentrations of all trace elements are far below the level at <br />which changes can be measured. The calculations on which these statements <br />are based were made for conditions substantially worse than expected to <br />occur on the average. <br />2.05-89 <br />