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III IIIIIIIIIIIII III <br />ST~T~, OF COLOIZAL~999 <br />Roy Romer, Governor <br />n <br />~ti.; .~ i~~< <br />DEPARTMENT OFNATURALRESOURCES <br />MINED LAND RECLAMATION DIVISION <br />FRED R. BANTA, Dlrsetor <br />June 20, 1989 <br />Mr. Dennis Conn <br />West Elk Coal Comoan_v <br />P.O. Box 591 <br />Somerset, CO 81434 <br />Re: Technical Revision, Mt. Gunnison Mine, C-80-007 <br />Dear Mr. Conn: <br />The Division has completed a review of the mans and Deotechnically-related <br />aspects of West Elk Coal's permit revision application to mine coal from <br />the B-Seam at their Mt. Gunnison No. 1 underground coal mine. In general, <br />those portions of the application which present classical oeotechnical <br />determinations, including rock quality data (RQD) for interburden, roof <br />and floor rock, strength data for waste pile materials, and subsidence <br />projections, are thorough and comprehensive. There are some inadequacies, <br />however, which deal with the application of the data to oermittina <br />requirements. <br />A. Abandonment Seals: <br />Revised Section 3.4.A.11 entitled "Sealing and Abandonment Plan" states; <br />"Upon GDfnDletlOn of mining in the 6-Seam, the slopes and ventilation <br />shaft will be permanently sealed under the then approved M.S.H.A. <br />Ventilation plan... Portions of the slopes and ventilation shaft may <br />be left open for access to the E-Seam. Future plans are not known at <br />this time." Abandonment seal design was a significant topic during <br />original oermittina of the Mt. Gunnison No. 1 F-Seam operations. Several <br />Exhibits were dedicated to addressing the analysis and design of the <br />proposed seals. The sealing plan consists of serially installed seals <br />designed to separate portions of the workings to control potential head <br />at any point in the workings, should the workings Drove to be saturated. <br />The mine plan was specifically configured to accommodate installation <br />of the three seals to segregate portions of the dipping seam's workings. <br />Detailed specifications were included for keyed concrete manifold seals. <br />Because the B-Seam, F-Seam and E-Seam will become hydrologically <br />continuous with the excavating of the shaft and inclines, the hydrologic <br />properties in the F-Seam could be modified. The F-Seam's head could <br />conceivably be increased by the intercommunication. Hydrologic <br />connection might also allow hydrochemical exchanges to occur between <br />saturated workings, which might have potential hydrologic consequences. <br />215 Centennial Building, 1313 Sherman Street Denver, Colorado 60203.2273 Tel. (303) B66-3567 <br />