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~~~~ w12-03-199- 5:50PM <br />e. <br /> <br />F~OI-1 ENG. WEST ELK MINE 970 9295050 <br />Mountain Coal Company <br />West Etk Mine <br />Post Ofnee Hox 58f <br />Sornersat, Cobrado 81434 <br />Telephone 97Q929.5015 <br />December 3, 1997 <br />Mr. Michael Boulay <br />Colorado Division of Minerals and Geology <br />1313 Sherman Street, Room 215 <br />Denver, CO 80203 <br />RE: Landslide Status and Planned Mitigation; West Elk Mine; <br />Permit No. C-80.007 <br />Deaz Mike: <br />P. 1 <br /> <br />As we discussed on the telephone yesterday, the magnitude and duration of the <br />landslide at the West Elk Mine site in the main facilities area, has been greater this <br />year than in past years. In the past, there has typically been a surge of movement in <br />the spring and only gradual "creep" type movement for the rest of the year. Previous <br />creep movement was on the order of 1-inch per year. However, this year the surge of <br />movement in the spring was larger, 0.5 to 1 inch per month, and has lasted longer <br />than normal. This increased movement is still continuing. The rate of movement is <br />now a threat for catastrophic failure. <br />Through the spring and summer months of this year, an extensive drilling program <br />and some seismic work was conducted to define the landslide limits and mechanics.- <br />The enclosed figure shows the limits of the landslide mass, based on the collected data <br />as well as conventional survey monitoring data. Piezometers and inclinometers have <br />also been installed around the mine site. Inclinometers have identified the majority of <br />the movement in a shear zone of the landslide, which is about midway vertically <br />within the colluvium. As with most landslides, water appears to be the key <br />component. <br />MCC has been diligently studying and formulating a plan for the mitigation of the <br />landslide over the last several months, which has included the co}lection of data as <br />described above and involving several top geotechnical consulting firms. In review of <br />all the geotechnical data collected, the design of the landslide mitigation has focused <br />on dewatering and anchoring. The dewatering projects include stone columns, <br />vertical dewatering wells near the substation, horizontal drilled drains under the slide, <br />and improved drainage in the main entries near the portals. The anchoring projects <br />include augured caissons designed to anchor the slide to bedrock. The enclosed <br />drawing shows the proposed locations ofthe stone columns, horizontal drains, and <br />III IIIIIIIIIIIIIIII <br />999 <br />