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STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, Colorado 80203 <br />Phone: (303) 866-3567 <br />FAX: 1303) 832$106 <br />MEMO <br />Date: September 9, 2005 <br />To: File <br />Permit number: <br />Doc. Class: <br />Doc. Type/Sequence: <br />Doc. Name: <br />From: Tom Kaldenbach '~ <br />COLORADO <br />DIVISION OF <br />MINEBRALS <br />GEOLOGY <br />RECLA MATION•MINING <br />SA FE TY•SCIENCE <br /> Bill Owens <br /> Governor <br /> Russell George <br /> Executive DIreCTGf <br /> Ronald W. Cattany <br />C-1980-007 (West Elk Mine) Division Director <br /> <br />Revision Natural Resource Trustee <br />TR-101 <br />Memo -Summary of Review <br />of Slope Stability Analysis <br />I have reviewed the above-referenced slope stability analysis. The analysis assumed <br />mudpits will be excavated in fill that is a sandy loam, a valid assumption for colluvial <br />hillslope material in the permit azea. The analysis found the fill slope will have a <br />a Factor of safety of 1.49. The weight of fill used in the analysis of 85 pcf indicates dry <br />material. As a check, I ran Galena using the vaziables used by MCC's consultant and <br />derived a FOS of 1.46, very close to their result. I also ran Galena for various <br />combinations of variables: heavier fill (wet fill), deep failure, and a phreatic surface (see <br />table below and the attached printouts). All scenarios indicated FOS above 13. <br />Scenario Factor of safety <br />AlI variables same as MCC <br />(fill = 85 pcf, no phreatic 1.46 <br />surface, shallow failure} <br />Phreatic surface (all other <br />variables same as MCC) 1.46 <br />Fi11= 150 pcf, phreatic <br />surface, other variables 1.46 <br />same as MCC) <br />Fill = 150 pcf, phreatic l 84 <br />surface, deep failure <br />Office of Office of Colorado <br />Mined Land Reclamation Active and Inactive Mines Geological Survey <br />