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iiiiiiiiiiiiiiuiii <br />999 <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Nalu rat Resources <br />1 313 Sherman 51., Room 215 <br />Denver, CO BO203 <br />Phone (3031 8663567 <br />FAX. (303) 832-8106 <br />November 24, 1993 <br />Mr. Henry Barbs <br />Mountain Coal Company <br />P.O. Box 591 <br />Somerset, CO 81434 <br />RE: Review of Semi-Aaaual Subsidence Report; West Elk Mine; <br />File No. C-80-007 <br />Dear Mr. Barbe; <br />of Dora <br />ti`o4 <br />Me"'~ ~ O <br />~ r816 <br />Roy Romer <br />Governor <br />Michael e. Long <br />Division Director <br />The Division has reviewed Mountain Coal Company's Semi-Annual Subsidence Report <br />submitted September 24, 1993, for the period October 1992 to July 1993. The <br />format of the report and attached map and cross-sections is generally well done. <br />Mountain Coal should respond to the following suggestions and questions on or <br />before December 31, 1993. <br />1. What were the nature of the errors discovered by MCC prior to the <br />submittal of the January 11, 1993 report? <br />2. The extreme topographic relief at the site makes the vertical scale <br />of the cross-sections relatively non-informative. It would be <br />perhaps more helpful if MCC would submit a vertically aligned <br />"Amount of Subsidence" portion of cross-section display which would <br />allow a more detailed and informative depiction of the subsidence. <br />This would include graphing the numbers shown at the top of the <br />cross-section, on a large scale, to show cumulative subsidence and <br />subsidence since the last survey. <br />3. The primary purpose of semi-annual subsidence reports is to monitor <br />the progress of subsidence at the mine site. Their secondary <br />purpose is to compare the manifestation of subsidence with the <br />projection forwarded by the operator in the permit documents. To <br />facilitate comparison with the original permit's subsidence plan <br />projections, it would be helpful if the maximum projected subsidence <br />profile was depicted on the cross-section requested above. <br />Please call if you have any questions. <br />SifS~rely <br />/ // ~ L <br />Christine E. <br />Environmental <br />ion Specialist <br />LEJ/0075UB1124 <br />