Laserfiche WebLink
<br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />131 3 Sherman 51., Room 215 <br />Denver, Colorado 80203 <br />Phone: (3071 866-7567 <br />FAX: 13031 832-8106 <br />September 3, 1998 <br />To: Erica Crosby, Car~l//Mount, James Stevens <br />From: lames Dillie yt~- <br />Re: Review of TR-01, Slope Stability Analysis, Baseline Resource Pit, M-97-058 <br />II~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />lame. S. Luc hhead <br />E+ecuiive Dmecior <br />Michael B Long <br />Division Director <br />Per your request, I reviewed the technical revision submittal regarding stability of the excavated pit <br />highwalls. The slope stability analysis was required to evaluate the effects of mining activities on nearby <br />structures since the operator was unable to obtain an agreement, or agreements, with the owner(s) of the <br />structure(s). Pursuant to Rule 6.4.19(b), where such an agreement can not be reached, the applicant shall <br />provide an appropriate engineering evaluation [hat demonstrates [hat such structure shall not be damaged <br />by activities occurring at the mining operation. <br />The stability analysis submittal adequately demonstrates that the nearby structures will not be adversely <br />affected by a catastrophic slope failure since the factor of safety is in [he 2.6 - 2.8 range. However, the <br />operator did not address the possible effects of slope failures along the highwall face. The calcttla[ed <br />factor of safety for the mined highwall is less than unity (0.34) which means it will fail. The failure <br />footprint would not migrate out of [he permit area if sufficient setback is available. So, it is highly <br />recommended, that the operator provide a sufficient buffer zone to prevent slope failure problems at, or <br />near, the permit boundary. Or, as an alternative, the operator could commit to mining the highwalls at a <br />2:1, or 3:1, slope as mining activities get close to the permit boundary. <br /> <br />STATE OF COLORADO <br />In my opinion, [he applicant has met the requirements of Exhibit S -Rule 6.4.19(b) concerning offsite <br />strucmres where the applicant could not reach an agreement with the structure owner. <br />