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., . STATE OF COLORADO DIVISION OF MINERALS AND GEOLOGY Depanmenl of Natural Resources 1313 Sherman St., Rnom ?15 Denver, Colorado 80?03 Phone: U03) 866 3567 FA%: (3031 832-81 06 DATE: June 18, 1998 [Revised July 31, 1998] TO: Dan Mathews FROM: Jim Pendleton ~~~~~ DEPARTMENT OF NATURAL RESOURCES Roy Romer Governor 1ame~ S Lochhead Executi.e Director Michael B LnnR Division DireUOr RE: Deserado Mine; TR-48; B-Seam Subsidence Control ; (Permit No: C-81-018) Blue Mountain Energy (BMEI, Inc., proposes to mine the B-Seam within it's approved permit area by longwall methods. In places both the D-Seam and B-Seam will be mined, resulting in additive effects of superimposed subsidence. Western Fuels Assoc. Mine plan for the D-Seam and it's B-Seam portal construction have been approved previously. The Division's previous adequacy comments have specified the submittal of a detailed analysis of the projected impacts of mining within the B-Seam. Western Fuels Assoc has now submitted its projection of the B-Seam subsidence impacts upon the overlying surface and potentially impacted structures located within the subsided area In general, the application is very well prepared, with the exception of the unique inclusion of multiple "B-Seam Mine Plan" maps (Maps 120 & 135). Obviously, the correct map should be retained and the incorrect map should be deleted from the permit documentation. Statements are clear and thorough. The subsidence prediction is prepared using the British National Coal Board (NC6) techniques, which are usually conservative for U.S. situations. Mining experience in the D-Seam workings has proven previous D-Seam subsidence predictions to be conservative. Subsidence monitoring of the surface above mined panels, structures and hydrology of Red Wash have all proven the original predictions to be accurate. Some settlement cracking was experienced at water storage facilities. Appropriate repairs were completed. All mechanical subsidence reports were submitted and all hydrologic impacts were reported in the annual hydrology reports. During mining in both room-and-pillar and longwall sections of the D-Seam, the various monitoring, public notice and mitigation procedures contained within the permit have been implemented. Experience has proven them to be adequate to protect the environment and the public's health and safety.