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<br />2. In addition to the construction of the diversion channel, <br />• Cotter Corporation will regrade the waste dump to less than <br />the angle of repose. The final slope of the waste dump will <br />be no steeper than a horizontal to vertical ratio of 1:1. <br />This slope is generally equivalent to the contours of the <br />terrain adjacent to the dump, although some slopes of the <br />existing terrain are on the order of 1.2:1. Upon completion <br />of regrading operations, the top of the waste dump will be <br />covered with a 6 inch clay cover, compacted to 95% maximum <br />then covered with four to six inches of topsoil and revegetated <br />with an appropriate seed mixture. <br />The effect of the diversion channel, clay cover .and topsoil horizon, <br />and vegetative cover will be to significantly reduce the total volume of <br />runoff over the waste dump and will reduce the erosion potential to belo~.~ <br />• hazardous levels. <br />Additionally, infiltration of precipitation into the waste rock zone <br />will be reduced significantly. Estimates from the ASCE Planual of Engin- <br />eering Practice, No. 28 and from the Soil Conservation Service indicate <br />that infiltration into loam topsoil horizons can be expected to be on the <br />order of 0.3 inches per hour and infiltration into a compacted clay will <br />be at a rate of approximately .0002 inches per hour. Therefore, the re- <br />duced infiltration through the topsoil horizon combined with the semi- <br />impermeable characteristics of a compacted clay cover and the effects <br />of depression storage and evapotranspiration will preclude tF~e develop- <br />ment of saturated conditions in the waste rock zone. <br />Referring to Exhibit C, all adits and ventilation boreholes will <br />. be sealed upon completion of mining operations. <br />E-5 <br />