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Memo to Christine Johnston MCC Upper Repuse Pile page 2 bench crest, adjacent to the head of the chronically unstable slope above the portals. No foundational stability analyses are presented for these stockpiles, In accordance with Rule 2.05.3(6), I believe it appropriate for MCC to demonstrate that this location will be stable in order to protect their topsoil and subsoil resources. Page 6 The text states that the 600 foot high steep slope to the south of the proposed URP "appears quite stable, being thickly covered with old growth pine, scrub oak, and aspen vegetation". My examination of our stereographic aerial photography of this site determined this slope, like almost every other slope at the West Elk mine site, to be a general assemblage of superimposed generations of rotational slope failures. In the case of this slope, the URP will buttress the slope. However, in general it focuses attention on the relatively unstable nature of Williams Fork formation slopes. The majority of these failures are shallow rotational failures of the high-clay content siltstone and shale members of the formation. However, shallow failures of this sort could be problematic for structures such as the subsoil and topsoil stockpiles proposed to be set back only 10 feet from crest of existing unstable slopes. Page 8 - 10 The expressed objectives and failure modes examined by the stability analyses appear to include all the appropriate scenarios. However, table 2, which presents the material properties utilized in completing the various analyses, appears to have overlooked one potentially critical material. In the early 1980's concern was focused upon the possible of a decapitation failure along the F seam workings. A stability analysis was successfully completed by Anaconda to address and discount this possibility. ["Supplemental Engineering Design Report, Refuse Disposal Facility...", by Michael Baker, Jr., Inc., March, 1985.] In completing that analysis, various material strengths were determined and assumed. A continuous low strength floor clay was assumed to exist immediately beneath the F seam. This bed might be a specific possible locus of failure. It should be included in the stratigraphic section for the stability analyses. In earlier analyses conservative strength parameters of cohesion equal to 1,350 psf with a friction angle of 9° were assigned to the floor clay.