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Slope Evaluation and Remediation <br />West Elk Mine <br />Somerset, Colorado <br />data as tabulated below, we back - calculated average material parameters for the <br />landslide mass — particularly the slip surface by assuming that the factor of safety <br />against movement was 1.0. Output from the SlopeW analyses is included in Appendix <br />A. Only static loads were considered in our analysis. <br />Geotechnical Parameters Used for Preliminary Slope Stability Analyses <br />Geologic Unit <br />Unit Weight <br />Angle of Internal Friction <br />Cohesion <br />Landslide Materials <br />125 pcf <br />24 degrees <br />30 psf <br />Alluvium <br />120 pcf <br />32 degrees <br />0 psf <br />Bedrock <br />125 pcf <br />30 degrees <br />500 psf <br />We consider the parameters for the landslide materials to be conservative, more <br />representative of the zone comprising the basal slip area rather than the material as a <br />whole. <br />Stability modeling also was performed on the anticipated temporary back cut <br />configuration for the remedial excavation and for the final, reconstructed slope <br />configuration. A factor of safety of approximately 1.1 was estimated for the temporary <br />back cut (local sloughing should be anticipated at the recommended angles, particularly <br />where wet or soft soils are exposed, or seepage is encountered). A factor of safety of <br />greater than 1.3 was estimated for the recommended, final, slope configuration (these <br />results also are included in Appendix A). <br />A factor of safety of 1.3 is considered sufficient for many slopes in mountainous areas of <br />Colorado. If a greater factor of safety is desired by Mountain Coal Company, LLC, <br />GROUND should be notified to provide additional remedial recommendations. <br />REMEDIAL EARTHWORK <br />General Recommendations are provided in this section for stabilization of the slope <br />affected by the smaller, relatively rapidly moving, recent landslide by means of a drained <br />buttress fill. These measures are not intended to improve the overall stability of the <br />larger, more slowly moving landslide complex that underlies the majority of the mine <br />property, including the subject reach of roadway and the smaller, recent landslide. For <br />simplicity, subsequent references to the "landslide" and "landslide materials" in this <br />section should be understood to refer only to the smaller, relatively rapidly moving recent <br />Job No. 11 -6014 GROUND Engineering Consultants, Inc. Page 7 <br />