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• iii iiiiiiiiiiiuiii • <br />999 <br /> STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Dcparin~ent of Nawral Resources <br />I .31 }Sherman St., Room ? 15 Jr <br /> <br />Dunvr. r, l.nlurarlo tl0_'03 ~~~ <br /> <br />Phone 17031 Afi6-356i II <br />Fr\t. (Sfl fl riJ! 8706 <br /> DEP.ARTtvIENT OF <br /> NATURt~II. <br />September 3, 1998 RESOURCES <br />Mr <br />Jeff Gregg ~„e <br />~o;" <br />. , <br />Hall-Irwin Construction lames s. fochneaa <br />P.O. Box 519 E*ec°"ve o"e"°` <br /> <br />Greeley, CO 80632 Michael B Lang <br />0~~~:~~~n o„r~~n~ <br />RE: Baseline Resource: Permit No. M-97-058 <br />Technical Revision OOl <br />Dear Mr. Gregg, <br />The Colorado Division of Minerals and Geology received Technical Revision 001 for the <br />Baseline Resource Mine, Permit No. M-97-058. The revision provides an engineering <br />evaluation for slope stability for a number of permanent man-made structures less than 200 feet <br />from the mining boundary. Pursuant to Rule 6.4.19(6), where an agreement can not be reached, <br />the applicant shall provide an appropriate engineering evaluation that demonstrates that such <br />structures shall not be damaged by activities occurring at the mining operation. <br />The stability analysis adequately demonstrates that the nearby structures will not be adversely <br />affected by a catastrophic slope failure since the factor of safety is in the 2.6 to 2.8 range. <br />However, the operator did not address the possible effects of slope Failures along the highwall <br />face. The calculated factor of safety for the mined highwall is less than unity (0.34) which means <br />it will fail. The failure footprint would not migrate out of the permit area if sufficient setback is <br />available. The operator should provide a sufficient buffer zone to prevent slope failure problems <br />at, or neaz the permit boundary. Or as an alternative, the operator could commit to mining the <br />highwalls at a 2h:ly or 3h:ly slope as mining activities get close to the permit boundary. <br />The Division's decision due date is September 8, 1998. If additional time is needed, please send <br />the Division a letter waiving the decision due date of September 8, 1998. If you have any <br />questions, please do not hesitate to call. <br />Sincerely, -. <br />~ , <br />~. '~(~ .~ <br />~,- ~ ii <br />Erica S. Crosby <br />Environmental Protection Specialist <br />cc: Molly Orkild-Lazson, Tuttle Applegate, Inc. <br />