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<br />SCOPE <br />This report presents results of our Geotechnical Investigation for the <br />proposed West Pit Excess Spoil Disposal Site for the West Pit expansion of the <br />Colowyo Coal Mine in Moffat County, Colorado. This report was revised on <br />March I, 1991 to reflect a change in the proposed north limit of the box cut. The <br />change did not affect stability or our recommendations other than the extent of <br />subdrains. The figures were revised to reflect the new configuration. <br />The West Pit will be an extension of the existing operating mine. The report <br />includes descriptions of the foundation conditions anticipated in the proposed spoil <br />disposal area and geologic conditions at the mine; our observations regarding <br />springs, seeps, groundwater flows and surface drainage conditions; a discussion of <br />the nature of the rock material to be incorporated in the spoil fill; recommended <br />locations and materials to be used in underdrains; and the results of stability <br />analyses. The report was prepared based on conditions disclosed in exploratory <br />borings, observations made during our site investigation, and data compiled during <br />other geotechnical investigations at the Colowyo Coal Mine and mines in this part <br />of Colorado where similar rock materials were found. <br />SITE SELECTION <br />The West Pit Excess Spoil Disposal Site vas selected by Colowyo Coal <br />Company. We understand excess spoil will be generated from an initial box cut <br />which is anticipated to occur during 1993 and 1994. The spoil disposal site was <br />selected in an area where overburden thickness was sufficient to make surface <br />mining not feasible. In addition, the site was selected because the natural ground <br />surface conditions create a naturally stable condition for disposal. <br />