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the HELP model results and site hydrology combined with Clearwater diversions). Additional cross <br />sectional area (28 square feet) is provided by the design (see permit drawings) to provide a factor of <br />safety of over 2. The horizontal alignment of the underdrain beneath the refuse pile will follow the <br />thalweg of the gulch and may also be adjusted based on the type of material encountered in the area <br />of the underdrain and the ability to excavate the drain without hardship. <br />4.5 Compaction <br />Refuse will be compacted to 90 percent (or greater) of the maximum standard Proctor dry density and <br />lifts will be no greater than 24 inches in thickness, as required by Rule 4.10.4 (3). <br />4.6 Cover <br />The refuse pile will be contemporaneously reclaimed with an average of 18 to 24 inches of soil <br />cover obtained from the uppermost soil horizon(s) of colluvial soils stripped from the refuse pile <br />foundation area and revegetated with MCC's permanent seed mixture found in Table 37 of the <br />Permit document. As the coal refuse material and soils characteristics are similar to (but <br />expected to be more coarse - grained than) that of the existing LRP and RPE refuse piles, the <br />variance from four -feet of soil cover that was approved by the CDRMS for both the LRP and <br />RPE construction has been applied to the RPE East construction. Contemporaneous reclamation <br />will begin once the lowest part of the refuse pile has reached design grades after construction of <br />Phase 3 of the rock buttress. <br />4.7 Haul Roads (Rule 2.05.3(3)(c) & 4.03.1) <br />Haul roads needed to support the RPE East refuse pile operations are shown on the permit drawings <br />in Appendix D. Provided in these drawings are haul road alignments, profiles, and typical sections. <br />Haul roads were designed to conform to requirements in Rule 4.03.1. Additional description of haul <br />road design is provided below. <br />4.7.1 Haul Road Horizontal and Vertical Alignment <br />Haul roads were laid out with a horizontal alignment as consistent with existing topography as <br />practicable, as required by Rule 4.03.1(3)(b). Roads do not cross streams or significant natural <br />drainageways. The typical design grade is 8 percent to facilitate efficient operation of haul trucks. <br />Revised March 19, 2010 <br />.3s�J /o <br />PAMpls \06 CO\26\06261003 MCC Refuse Pile Site Review & Permit \WorkFiles\Permit Application \Text \2010- 08- 31_RPE East Permit Application 16 <br />MR.doc <br />