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_. <br />• <br />STATE OF COLORADO RiC HARD D. L/.MM. Govc moi <br />DEPARTMENT OF NATURAL RESOURC ES <br />D. Monte Pascoe, Executive Director <br />MINED LAND RECLAMATION <br />423 Centennial Building, 1313 Sherman Street <br />Denver, Colorado 80203 Tel. (303) 866-3567 <br />David C. Shelton <br />July 23, 1982 Director <br />TO: Rich Domingue <br />FROM: Jim Pendleton <br />RE: Review of Sup emen Submittals for the Blue Ribbon Mine <br />iii iiiiiiiiniiiiii <br />999 <br />Pursuant to your request, I have reviewed the supplemental materials submitted <br />by western Associates, Inc., in response to your draft findings document <br />for the Blue Ribbon Mine. The applicant submitted several revisions to the <br />operation facilities sections and to the reclamation plan sections of the <br />original application. In addition, the applicant submitted a stability <br />analysis for the haul road at the Blue Ribbon Mine. I forward the following <br />comments for your consideration. <br />Mine Facilities <br />The applicant has amended this section of the application to describe the <br />geologic setting of the haul road. The applicant observes that the cut <br />slopes do not attain the normally required static slope safety factors (Rule <br />4.03.I(3)(c) along those portions of the road cut into non-bedrock colluvial <br />material. The applicant further observes, in response to requirements of <br />Rule 4.03.1(3)(c)(i), that this inadequacy should not result in significant <br />environmental harm because sliding is not expected to occur. If landslides <br />occur, the applicant proposes to repair the damage and remove the slide debris. <br />The applicant observes that "the disturbed area is small and that reclamation <br />will provide a final slope with an adequate stability." The applicant refers <br />the reader to~Appendix D for support of these contentions. <br />Haut Road Stability Analysis <br />This stability analysis, prepared by Rocky Mountain Geotechnical, Inc., .. <br />consultant to the operator, appears to be in keeping with the state-of-the-art <br />in those techniques which it describes. It is, however, inadequate to <br />completely satisfy our regulatory requirements. <br />The stability analysis uses material strength properties derived during an <br />earlier analysis by the same consultant of a landslide problem occurring at <br />the neighboring portal facilities. Utilizing these peak and residual material <br />shear strengths, the consultant performed a sensitivity-type analysis of <br />several representative road cross-sections; (I) completely colluvial road <br />cut, (2) partial bedrock/colluvial road cut, and (3) total bedrock road cut. <br />This analysis demonstrates that the road cut slopes are marginally stable in <br />all conditions. The analysis suggests that cuts which penetrate a thickness <br />of colluvium greater than 8.5 to 10.5 feet may not achieve the required <br />static slope safety factor in excess of 1.5. The consultant's report concludes <br /> <br />