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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 />Maximum grade was kept to 10 percent or less. All design grades comply with requirements of Rule <br />4.03.1(3)(a). Detailed design will be conducted at all switchbacks as part of construction drawing <br />preparation and any necessary adjustments will be made to keep maximum slopes at 15 percent or <br />less. <br />4.7.2 Slope Stability <br />Haul roads were located on the most stable slopes available, as required by Rule 4.03.1(2)(a); <br />however, due to the steep natural slopes in the areas where haul roads must be constructed, additional <br />geotechnical measures will be required in some areas to establish stable slopes. A slope stability <br />analysis was conducted in accordance with a method developed by D.W. Taylor and W. Fellenius for <br />the anticipated range of soil conditions and the design slopes. The method is presented in <br />Appendix H. Calculations with this method are based on a range of cohesion for colluvium soils <br />anticipated in the construction area. Cohesion values were obtained from tests conducted on site <br />colluvium soils collected primarily in the vicinity of the primary coal handling facilities. The <br />minimum values shown in the calculations are for a cohesion value that 90 percent of colluvium tests <br />are expected exceed, based on a statistical analysis. The maximum values shown in the calculations <br />are for a cohesion value that 10 percent of colluvium tests are expected exceed. A final evaluation <br />will be conducted as described in the following sections for cut slope and fill slopes for site specific <br />conditions as part of the construction activity. Results of the evaluation will be provided in a <br />documentation report to be prepared after construction has been completed. <br />Revised March 19, 2010 <br />Revised July 21, 201165 <br />2C3 J�,c� <br />P: \Mpls \06 CO \26 \06261003 RPE E Permit Mod Support \WorkFiles \Permit Application \Text \Exhibit 82 RPEE design 2011 -07 -21 TR 127 doe 21 <br />