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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 />LRP Stability Evaluation <br />The proposed Preparation Plant facility is located atop and near the center of the LRP, which is north of <br />the mine access road. For the LRP review, global stability was analyzed in the area of the proposed <br />Preparation Plant facility for both static and dynamic loading conditions. <br />Methods <br />A review of conceptual plans for the LRP with the Preparation Plant facility was conducted. Two cross <br />sections were evaluated for global stability. Cross Section A is oriented in a north-south direction through <br />the proposed Preparation Plant facility and Cross Section B is oriented in an east-west direction to evaluate <br />the proximity of the building to the east slope of the LRP, near the access road. Two soil borings were used <br />to identify stratigraphic units and groundwater conditions. They are 97-163 (performed in 1997) and SB- <br />09-12 (performed in 2009). These borings are shown in section in Figures 1 and 2 and the boring logs are <br />attached in the Appendix. <br />Neither soil boring encountered the water table during drilling, so the phreatic surface used in slope <br />stability modeling was placed at the elevation corresponding to the bottom of each boring. This represents <br />a worst-case scenario in which the phreatic surface is conservatively placed higher than it is likely located <br />in the field. It should be noted that significant amounts of groundwater flow are not expected into the LRP <br />because the high-permeability coal seams that convey significant quantities to groundwater in other parts <br />of West Elk Mine are at higher elevations and are not present at this location. <br />The geotechnical properties assigned to each layer in the analysis are based on laboratory testing and back- <br />analysis reported in Exhibit 51 by Harding Lawson (1996) as shown in Table 1. The strength parameters <br />listed in Table 1 represent shear strength in the drained, or long-term, condition. <br />Table 1. Results from Laboratory Testing and Back-Analysis (after Harding Lawson, 1996) <br /> <br />Material <br />Description Dry Unit <br />Weight <br />cf <br />Cohesion <br />sf Friction <br />Angle <br />[degrees] <br /> <br />Comments <br />Debris Flow Soils 113.7 0 34.0 1 <br />Debris Flow Soils 105.0 0 33.7 1 <br />Colluvial Soils 100.0 300 30.0 2 <br />Colluvial Soils 120.0 300 30.5 2 <br />Colluvial Soils 125.0 2000 10.0 2 <br />-2-