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maximum stable slope heights using this design method. Some slopes shown in the permit drawings <br />exceed the maximum allowable slope height based on the lowest cohesion value used in the analysis. <br />Additional geotechnical investigation and design or other slope stabilization methods will be needed <br />prior to haul road construction in these areas. The approach to establishing a safe slope in such areas <br />will include the following steps. <br />1) Sample and test soils intended for use in constructing the embankment slopes: <br />a. Determine new maximum slope height based on actual test data from soils intended <br />for construction <br />b. If design requirements are met, construct slope as designed <br />c. If design requirements are not met, proceed to Step 2 or Step 3 <br />2) Design embankment with geogrid, crushed rock (1.3511:1V slope), or other geotechnical <br />stabilization method to achieve design requirements. <br />3) Embankment slopes not demonstrated to be stable in Step 1 or Step 2 will be stabilized with <br />other methods such as retaining walls, soil nailing, or other technology. <br />4.7.3 Haul Road Surfacing <br />Haul roads will be surfaced with a total of 12 inches of aggregate base, including 4 inches of <br />Colorado Division of Transportation (CDOT) Specifications 703.03 Class 5 aggregate over 8 inches <br />of CDOT Specifications 703.03 Class 3. <br />4.7.4 Other Design Considerations <br />Haul roads will be constructed with methods and with erosion control measures to control erosion <br />within the construction area. The extent of site disturbance for haul road construction will be kept to <br />a minimum. <br />Haul road ditches will be used to divert clear water away from the refuse pile in areas west of the <br />refuse pile footprint. Water will drain in the road ditches and will discharge in a controlled manner <br />to natural ground adjacent to westerly switchbacks, then over natural ground to Sylvester Gulch. <br />Drainage flows will typically be small in these areas due to the limited size of drainage areas above <br />Revised Marq.11 1,9, 2010 <br />I/' /� 3 <br />6 <br />PAMpls \06 CO\26 \06261003 MCC Refuse Pile Site Review & Permit\WorkFiles\Permit Application \Text \2010- 08- 31_RPE East Permit Application 19 <br />MR.doc <br />