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To: Chris Nyikos, Project Manager - Mountain Coal Company <br />Subject: Stability Analysis of LRP With Preparation Plant <br />Date: 8 September, 2009 <br />Project: 06/26-1004 <br />Colluvial Soils 110.0 447 19.0 3 <br />Colluvial Soils 109.0 1600 43.0 4 <br />Colluvial Soils 106.6 900 25.0 4 <br />Colluvial Soils 108.7 1400 10.0 4 <br />Colluvial Soils 102.8 0 35.0 4 <br />Colluvial Soils 112.4 0 50.0 4 <br />Colluvial Soils 117.3 700 40.0 4 <br />Colluvial Soils 111.2 2100 10.0 4 <br />Coal Waste 93.0 706 11.0 5 <br />Coal Waste 80.0 89 32.0 5 <br />Coal Waste 115.0 0 33.0 5 <br />Coal Waste 80.0 118 10.0 5 <br />Coal Waste 121.0 346 24.0 5 <br />Coal Waste 66.0 288 30.0 5 <br />Coal Waste 45.0 72 41.0 6 <br />Coal Waste 68.0 72 41.0 6 <br />Comments: <br />1. From triaxial shear strength testing by Rocky Mountain Geotechnical, 1985. <br />2. From back-analysis by Michael Baker Associates, 1984. <br />3. From previous testing by Rocky Mountain Geotechnical in the North Fork Valley. <br />4. From direct shear testing by IECO, 1976. <br />5. Tests on samples from a temporary waste pile east of the mine portals. <br />For the Debris Flow and Colluvial Soils, which were not major factors in the slope stability analysis, <br />unit weights and strength values were selected based on average values. For the Coal Waste material, the <br />unit weights were based on average values, but the strength envelope was derived from a test performed on <br />a sample obtained from a temporary waste pile east of the mine portals. This strength envelope is <br />considered reasonable for this soil type and it was used historically in the Harding Lawson analysis so it is <br />consistent with previous results. The selected parameters for the analysis are shown below in Table 2. <br />Table 2. Parameters Used in Analysis <br /> <br /> <br />Material Description Sat. Unit <br />Weight <br />cf Moist Unit <br />Weight <br />cf <br />Cohesion <br />sf Friction <br />Angle <br />[degrees] <br /> <br />Comments <br />Debris Flow Soils <br />Mixed Alluvium/Debris Flow <br />131.3 <br />120.3 <br />0 <br />33.9 <br />1 <br />Colluvial Soils Colluvium 132.4 122.3 886 27.5 1 <br />Coal Waste Refuse 104.2 91.9 288 30.0 2 <br />Bedrock -- -- -- -- 3 <br />-3-