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assumed to have moderate strength characteristics of a sandstone bedrock. Base values for friction <br />angle, cohesion and dry density for the refuse were assumed 30, 400 psf and 90 pcf respectively. A <br />factor of safety of 1.9 was obtained. Table D-1 summarizes the parametric and stability analysis results, <br />stability analysis results can be found on figures D-1 through D-14 in appendix D. Figure 4 shows how <br />each strength parameter affects the computed factor of safety. <br />To see what would happen with a worst case scenario concerning the water in the fill, we ran <br />a stability analysis assuming the entire existing pile became saturated. The resulting factor of safety <br />was 1.0. Development of free water in the refuse should be avoided. <br />Proaosed Refuse Pile <br />Wyoming Fuel company provided us with a proposed profile of the refuse area (Fig. 3). We <br />used this for the geometry in our stability analysis of the proposed refuse pile. We assumed the same <br />soil characteristics as in the 1991 analysis but with the larger volume of fill. <br />We ran analyses on the proposed refuse with two major assumptions. One assumption was <br />that the wet layer which exists now will exist in the future but will not get any thicker. The second <br />assumption was that wet fill would extend to the top of the proposed pile. Our analyses indicated a <br />computed factor of safety of 1.6 if drier materials are placed in the future. If wet materials continue to <br />be placed without other precautions, we believe stability of the refuse will fall below reasonable <br />standards; the computed factor of safety for this condition was 0.8. <br />CONCLUSIONS <br />The results of our site investigations, stability analyses and experience lead us to the following <br />conclusions regarding stability concerns for the Refuse Disposal Area at the New Elk Mine: <br />9 <br />