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i <br />• <br />1- <br />^ <br />f <br /> <br />I• <br /> <br />L <br />L <br />1 <br />(c• <br />L_ <br />CHAPTER I <br />REPORT SUhfAtARY <br />An engineering investigation has been carried out by W. A. Wahler and <br />Associates to determine the acceptable pit slopes for an open pit coal <br />mine to be opened and operated in the Red lJing Mine area near Craig, <br />Colorado, by the Colowyo Coal Company, a Division of W. R. Grace and <br />Company. The investigation consisted of a field program, laboratory <br />testing, and engineering analysis. <br />The field program was conducted to provide lithologic, hydrologic, and <br />structural daCa for the evaluation. Laboratory studies were performed <br />to determine the strength ranges of slope rock and soil from soil layers <br />interbedded with sedimentary rocks. The effect of ground water was <br />evaluated on the basis of primary subsurface wafer data obtained by the <br />U.S. Geological Survey (USGS). <br />The safety factors were computed for various combinations of slope heights <br />and slope angles, and the maximum feasible slope angles were determined <br />for two mining plans: <br />1. Mining to the "F" Seam 56.5° overall slope <br />2. Mining to the "J" Seam 40° overall slope <br />According to the officials of the Moffat County Planning Commission, <br />Colorado State Pfine Inspectors Office, and MESA District Office No. 9, <br />there are no current regulations and/or limitations on open pit slope <br />angles. <br />The submission of these data fulfills the immediate assignment specified <br />by Colowyo Coal Company and will enable the company to evaluate and com- <br />pare the long-term feasibility of mining the coal to two different <br />depths. <br />WR.WRNIEfl Project 0807 I-1 <br />& ASSOCIA~ <br />