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,~~ ~ <br />8~ <br />~. .1 ~~ ~ ROCKY MOUNTAIN GEOTECHNICAL, INC. <br />Achieviny Harmony with Ear[h <br />October 15, 1982 <br />P1r. William Tate <br />Western Associated Coal <br />410 17th Street <br />Denver, CO 80202 <br />Re: Stability Analysis <br />Blue Ribbon P1ine Access Road <br />Dear P1r. Tate; <br />This letter will serve as an addendum to our letter report of Play <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-sectior. <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 entirely appropriate at some point in time to better <br />define the nature of existing stability conditions along the full <br />lengtr, of road. Upon completion of sue:; a more thorough study, <br />specific recommendations pertlining to required slope treatment <br />for the access road cuts could be n;ade. <br />With regard to the results of the initial analysis of May 26, it <br />should be pointetl 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 cf treatment in the future. <br />For those areas which have not 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 an.y additional, more detailed analyses in <br />the access road area, we would recommend the 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 P' UNTAIt; G ECHC]IC:'.L <br />h~2~L//~, .E. KLP1/sam <br />Y <br />The Railroad Sa_~on • 555 E ikes Peak Avenue. Suite 107 • Colorado Springs. Colorado 80903 • (303: E3A-1~:E <br />