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C~ <br />SCOPE <br />This report presents the results of a geotechnical evaluation of slope <br />stability in the area of a vacated 8050 pit on the Colorado Yampa Coal <br />Company property near Oak Greek, Colorado. The purpose of our work was to <br />evaluate stability of existing spoil within the area of planned entries for the <br />proposed Twenty Mile Park underground mining operation, to develop recommended <br />cross-sections for enhancing stability of the existing spoil, and to determine <br />design criteria for rock cuts. This report was prepared based upon conditions <br />observed during excavation of exploratory test pits, a geologic reconnaissance <br />of the existing pit highwall, and laboratory testing of samples obtained from <br />• test pits. A review was made of previous work we performed for the Eckman Park <br />Mine and in the area of the 8050 pit, logs of an exploratory boring drilled by <br />Colorado Yampa Coal near the highwall, and the results of testing of rock core <br />performed by Science Applications, Inc. <br />The report includes the results of our field and laboratory investigations, <br />summary of pertinent data obtained from our previous work, analysis of stability, <br />and recommended slope configurations. Short-term and indefinite mining lives <br />have been considered in our analysis. The conclusions and recononendations <br />presented are based on laboratory testing, our previous work, analytical re- <br />sults, and our experience within the area. <br />CONSTRUCTION HISTORY <br />The slope uphill of the 8050 pit has been disturbed by previous surface <br />• mining. We understand that mining began near the crest of the slope and <br />