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4.4 Waste Rock Pile Drainage <br />Where needed, seepage interceptor trenches have been and will be constructed to drain seeps that are <br />encountered in the foundation zone of the waste rock pile. Seepage interceptor trenches will drain to <br />the thalweg underdrain. The seepage interceptor trenches will also intercept and drain water that has <br />infiltrated through the waste rock pile. <br />As the constructed waste rock pile increases in elevation, buried waste rock pile drains will be <br />constructed along the west edge of the working pad to drain water that may infiltrate through the <br />waste rock pile. The buried waste rock pile drains will be initially constructed as temporary <br />sediment ditches to enhance the drainage of water away from the working pad and away from the <br />underdrain to the sediment ditch on the west side of the RPEE. At intervals of 25 to 50 feet in <br />elevation as the waste rock pile is developed up the gulch, the sediment ditches will be filled with a <br />granular drainage material before they are covered with subsequent lifts of refuse to create buried <br />drains that will intercept and divert water that might infiltrate through the refuse. Water captured by <br />the buried waste rock pile drains will drain to the sediment ditch on the west side of the RPEE. <br />4.5 Compaction <br />Refuse will be compacted to 90 percent (or greater) of the maximum standard Proctor dry density in <br />lifts of no greater than 24 inches in thickness. <br />4.6 Cover <br />The RPEE waste rock pile will be contemporaneously reclaimed with an average thickness of 18 to <br />24 inches of soil cover obtained from the uppermost soil horizon(s) of colluvial soils stripped from <br />the RPEE waste rock pile foundation area, and revegetated with MCC's permanent seed mixture <br />found in Table 37 of MCC's permit. As the coal refuse material and soils characteristics are similar <br />to that of the existing LRP and RPE coal refuse piles, the variance from four -feet of soil cover that <br />was approved by the CDRMS for both the LRP and RPE construction was also approved for the <br />RPEE construction. Contemporaneous reclamation will occur after the refuse slopes of the waste <br />rock pile have been finished to design grades, assuming weather and ground conditions allow for safe <br />access and for suitable soil handling and placement. <br />22 <br />P:\Mpls\06 CO\26\06261003 MCC Refuse Pile Site Review & Permit\WorkFiles\Permit Application\2014 Revision\Exhibit 82 2014-05- <br />29.docx <br />