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4.7 Haul Roads <br />Haul roads needed to support the RPEE waste rock 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 />Additional description of haul road design is provided below. <br />4.7.1 Haul Road Horizontal and Vertical Alignment <br />Haul roads that are located outside of the waste rock pile footprint were laid out with a horizontal <br />alignment as consistent with existing topography as practicable. Roads do not cross streams or <br />significant natural drainageways. The typical average design grade (outside of the waste rock pile) is <br />approximately 6.5 percent to facilitate efficient operation of haul trucks. Maximum grade on these <br />roads was kept to approximately 15 percent or less. <br />Roadways that are located within the waste rock pile footprint were laid out with a horizontal <br />alignment that crosses back and forth across the width of the pile to optimize waste rock pile capacity <br />and to control surface water drainage in coordination with the drainage plan. The typical average <br />design grade (within the waste rock pile) is approximately 10 percent. Maximum grade on these <br />roads was kept to 15 percent or less. <br />All design grades comply with requirements of the Rules. Grading layout at switchbacks will be <br />adjusted in the field at the time of construction to establish workable grades that comply with the <br />Rules, and to control drainage. Any necessary design adjustments will be made to keep maximum <br />grades at 15 percent or less and overall grade at 10 percent or less. <br />4.7.2 Slope Stability <br />Haul roads were located on the most stable slopes available; however, due to the steep natural slopes <br />in the areas where haul roads were constructed, additional geotechnical measures were required in <br />some areas to establish stable slopes. A slope stability analysis was conducted in accordance with a <br />method developed by D.W. Taylor and W. Fellenius for the anticipated range of soil conditions and <br />the design slopes. The method is presented in Appendix H. <br />Calculations with this method were based on a range of cohesion values for colluvium soils <br />anticipated in the construction area. Cohesion values from tests conducted on site colluvium soils <br />samples collected primarily in the vicinity of the primary coal handling facilities were used to <br />establish design and construction parameters. The minimum strength values used in the calculations <br />23 <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 />