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To: Chris Nyikos, Project Manager - Mountain Coal Company <br />Subject: Geotechnical Review of Updated PR-2 Conveyor Alignment <br />Date: July 17, 2009 <br />Project: 06/26-1004 <br />Coal Conveyor Stabilization Review <br />The PR-2 conveyor alignment presented by Roberts & Schaefer extends PR-2 eastward from the TC-1/PR- <br />2 Transfer Station for 550 feet along the crest of the steep hillside. The conveyor is then positioned <br />beyond the slope crest for 1,450 feet before reaching the top of the proposed coal preparation plant. A <br />majority of the alignment is north of the access road. Based on current geotechnical information, including <br />recent drilling information, approximately half of the conveyor alignment is located on the main sliding <br />mass of the overall existing landslide. <br />For the purposes of this stabilization review, the PR-2 conveyor supports were conservatively assumed to <br />be a series of concrete blocks spaced at 40-foot intervals and resting on the ground surface from Stations <br />0+00 (TC-1/PR-2 Transfer Station) to 15+00. The concrete conveyor support blocks are proposed to be <br />positioned along an excavated hillside conveyor bench beginning at Station 1+00. The benefits of <br />excavating a hillside bench for positioning of the PR-2 conveyor include additional block support points <br />which can be easily re-aligned as deformation of the main landslide continues; the cut simplifies <br />construction of the recommended foundation stability measures; and removing earthen materials above the <br />bench unloads the weight along the crest of the sliding mass, thus increasing stability. <br />Between Station 15+00 and the proposed Screening and Preparation Plant at about Station 19+00, the <br />PR-2 conveyor continues to be supported on bents spaced approximately 100 feet on center. These bents, <br />which should not be allowed to experience significant movement, are located outside the overall sliding <br />mass. It is anticipated that these bents will be constructed on spread footing foundations. <br />To assess the potential for slope instability along the entire proposed PR-2 alignment, a station-by-station <br />analysis was performed. A limit-equilibrium slope stability software package, GeoStudio 2007, was used <br />to analyze two representative cross-sections. Slope geometries for Stations 0+00 through 9+00 were very <br />similar to each other with Station 6+00 appearing to be representative of this group. Slope geometries <br />were also quite similar for Stations 10+00 through 15+00, and Station 11+00 was selected as the <br />representative cross-section for this group. Thus, Stations 6+00 and 11+00 became the basis for slope <br />stability analysis. Stations 16+00 through Station 19+00, where the proposed Screening and Preparation <br />Plant are located, are positioned along the Lower Refuse Pile where slope stability is less of a concern. No <br />additional slope stability modeling was performed for this area. <br />-3-