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0 <br />• The model used consisted of 3 soil types including spoil, native alluvial soils, <br />and bedrock. The presence of alluvial soils was estimated based upon our field <br />observations of the portal areas, and was not included in analysis sections where <br />bedrock is judged to be relatively shallow. To be conservative, the alluvial soil layer <br />was estimated to be on the order of 20 feet deep. The strength of the compacted <br />spoil was conservatively selected as the lowest value obtained from the direct shear <br />testing. This value (~ = 28 degrees, cohesion = 400 psf) was for R1 typical spoil, <br />residual strengths at 85 percent compaction. <br />The natural alluvial soils are anticipated to be somewhat variable, however <br />predominantly granular soils with occasional clay layers are anticipated. We utilized <br />a conservative strength estimate for the alluvial soils of friction angle of 30 degrees <br />with no cohesion. This strength value assumes a loose to medium dense sand soil. <br />Based upon our observations of the bedrock and our experience, we believe the <br />• bedrock has sufficient strength such that the properties of the compacted spoil and <br />alluvial soils will control stability. The model was set up to preclude penetration of <br />the failure surface through the bedrock layer. <br />Significant water build up within the reclaimed areas is not anticipated. <br />Provision of a drain across the portal areas to prevent excessive water build up in the <br />area is discussed in a following section. The results of the stability analysis are <br />summarized on the table below. <br />The results of the stability analysis indicate factors of safety which <br />significantly exceed the 1.3 minimum required by regulation. We believe the post- <br />mining topography (as shown on Figs. 2 and 4) results in a stable configuration. <br />The post-mining slopes range from about 2:1 (H:V) to 4:1. Erosion control will <br />be required until vegetation is established. If benches or ditches are required, the <br />slopes between the benches will be slightly steeper than the average slope analyzed. <br />• <br />LORENCITO COAL COMPANY, LLC <br />CTLlT 25,863 7 <br />