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,7~~. <br />.~ ~~` <br />D ~ s ROCKY MOUNTAIN GEOTECNNICAL, INC. <br />Achieving Harmony with Earth <br />October 15, 1982 <br />Fir. William Tate <br />i~lestern Associated Coal <br />410 17th Street <br />Denver, CO 80202 <br />Re: Stability Analysis <br />Blue Ribbon (line Access Road <br />Dear Mr. Tate; <br />This letter will serve as an addendum to our letter report of Ptay <br />26, 1982, concerning the access road. At that time, the results <br />of an analysis concerning a single cross-section on the access <br />road was reported. The purpose of this letter is to elaborate on <br />and put in proper perspective the results of that analysis. <br />As mentioned above, the analysis concerned a single cross-section <br />and is not necessarily representative of stability conditions <br />along the full length of the access road. In our opinion, it <br />would be entiLely appropriate at some point in time to better <br />define the nature of existing stability conditions along the full <br />length or road. Upon completion of such a more thorough study, <br />specific recommendations pertaining to required slope treatment <br />for the access road cuts could be made. <br />With regard to the results of the initial analysis of May 26, it <br />should be pointed out that both residual strength conditions and <br />peak strength conditions were analyzed. Results, utilizing <br />residual strength conditions, pertair. primarily to areas which <br />have already exhibited movement and which should obviously be <br />given consideration for some form of treatment in the future. <br />For those areas which have nvt exhibited any form of instability <br />or excessive movement in the past, the use of peak strength <br />criteria would be felt to be more appropriate. Therefore, <br />pending the results of any additional, more detailed analyses in <br />the access Load area, we would recommend tt,e use of the 10.5-foot <br />thickness or colluvial soil cover above the bedrock as a basis <br />for identifying areas of potential instability (i.e. factor of <br />sarety less than 1.5), <br />Should you have any questions pertaining to this additional <br />information, please do not hesitate to contact Rocky Mountain <br />Geotechnical. <br />Sincerely, <br />ROCKY UNTAIN G ECHNICAL <br />ne~, .E. KLM/sam <br />The Railroad Station • 555 E ikes Peak Avenue, Suite 107 • Colorado Springs, Colorado 80903 • (303) 634-1999 <br />