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Y • r <br />• ~ /~~ ~ ~~ <br />I. 1 ~ ~ ROCKY MOUNTAIN GEOTECHNICAL. INC. <br />Achiemng Harmony with Earth <br />October 15, 1982 <br />PSr. William Tate <br />Western Associated Coal <br />410 17th Street <br />Denver, CO 80202 <br />Re: Stability Analysis <br />Blue Ribbon !tine Access Road <br />Dear Fir. 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 purpcse of this letter is to elaborate on <br />ana put in proper perspective tt,e results of that analysis. <br />As mentioned above, the analysis c:,ncerned 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 existinc stability conditions along the full <br />lengtn of road. L}pon completion of such a more thorough study, <br />specific recommendations pertaining to required slope treatment <br />for the access road cuts could be mad>. <br />with regard to the results of the initial analysis of May 26, it <br />should be pointed out t;,at both residual strength conditions and <br />peak strength conditions were analyzed. Results, utilizing <br />residual strength conditions, pertain 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 khose areas which have nvt exhibited an}• 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 ir, <br />the access road area, we wculd 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 P;ountain <br />Geotechnical. <br />Sincerely, <br />ROCKY PJOCINTAIN G ECHNICAL <br />K2fine~ L. y .E. KLP1/lam <br />The Railroad S[auon • 555 E ekes Peak Avenue Swte 107 • Colerade Springs, Colorado 80963 • 13037 634 19 ~9 <br />