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<br /> <br />,~~F ~fc <br />;: \ - <br />~ 1 <br />~_A _ ROCKY MOUNTAIN GEOTECHNICAL~ INC. <br />Achieving Harmony with Ear[h <br />October 15, 1962 <br /> <br />t•Ir. S•7illiam Tate <br />;destern Associated Coal <br />410 17th Street <br />llenver, CO 80202 <br />Re: Stability Analysis <br />Blue Ribbon trine Access Road <br />Dear. i•ir. Tate; <br />`Phis letter will. serve as an addendum to our letter report of Play <br />26, 1982, concer.nina the access road. Flt that tine, the results <br />of an analysis concerning a single cross-secL-ion on the access <br />road was reported. The purpose of this letter is to elaborate on <br />anti put in proper perspective the results of that analysis. <br />As mentioned above, the analysis concerner: a single cross-section <br />and is not necessarily repr.es~ntat_ive of sr_ahility conditions <br />along the full length of the access road. In our opinion, it <br />would be entirely appropriate at so;:~c point in time to better <br />define the nature of existing stability conditions along the full <br />length of road. Dpon cc,mpletion o` ;;uch a mote thorough study, <br />specific recommendations pert=fining to required slope treatment <br />for the access road cuts could be made. <br />With regard to the results of the initial analysis of bray 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 ~':hich <br />have already exhiL-ited movement and whicF: should ob••~iously be <br />given consideration for some form cf treatment in the future. <br />For those areas which have not e::hibited any form of instability <br />or excessive movement in the past, the use of. peak strength <br />criteria would be felt t-o be more appropriate. Therefore, <br />pending the results of any additional, more detailed analyses in <br />the access road area, we would recommend the use of the 10.5-f.oot <br />[-hickness 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 />infc,rrr~ation, please do not hesitate to contact Rocky t•tountain <br />Geotechnical. <br />Sincerely, <br />PO~C~KY IJpUNTAIP: G EC HidI/C'~L <br />I~f*iS n?e~t ~i L . y ~ . E <br />Fhe Rei~r0a1 $LB Cirn' • SJh l i4 r•. I'rnl A•,r nur•.:iiri r' !' ~ • ~ <br />KLt•t/sam <br />.- . .,p.: ,.,• ..~ [.,.ice, .-. 7 1',]Un <br />