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I~~ II~I~~~~~II~~ I~~ Mountain Coal Company West Elk Mine ' ` Post OIRce Box 591 Somerset, Colorado 81434 Telephone 970 929-5015 Fax 970929-5595 RECEIVED ` September 22, 1997 SEp 2 3 1991 Mr. Michael Boulay Colorado Division of Minerals and Geology Division of Minerals 8 Geology 1313 Sherman Street, Room 215 Denver, CO 80203 RE: Technical Revision No. 80, Probable Hydrologic Consequences (PHC); West Elk Mine; Permit No. C-80-007 Dear Mike: Mountain Coal Company (MCC) has reviewed the Division's adequacy review questions for the above-referenced technical revision (TR), and provides the following additional information. Please note that MCC has riot provided revised permit text with these responses, but proposes to make final text changes once MCC and the Division agree on the PHC. MCC understands that the Division must review the revised text prior to permit approval. In addition, please recall that the Technical Memorandum prepared by Wright Water Engineers, Inc. (WWE), was provided to the Division to assist in the review of the TR, but MCC does not intend to include it as an exhibit in the permit. All of the discussions presented in the Technical Memorandum appear in the revised permit text submitted with the TR application. A summary of the key findings included in this response follows: 1. Based on Bear's 1995 and 1996 Annual Hydrology Reports, it appears that the Bear No. 3 Mine experienced groundwater inflows of 18 gpm during 1995, and approximately 30 gpm during 1996, well before MCC began to store increased quantities of water in the NW Panels sealed sump and before the Bear Mine was closed. The inflows that Bear experienced in 1995 and 1996 are similar when compared to West Elk Mine inflows in the same vicinity, and simply cannot be attributed to MCC's operations, since MCC did not begin to store increased quantities of water from the B East Mains fault inflow to the sump began on November 11, 1996, as discussed in response #2. 2. WWE refined their hydrogeologic analysis of seepage from the NW Panels sealed sump. As discussed in response #14, the original estimate was based on overly-conservative assumptions. The result of the refined analysis is an estimated range of seepage of 0.7 to 8.4 gpm, based on B-Seam permeability data ranging from 4 x 10~ to 5 x 10"5 cm/sec. 3. The findings associated with many of the technical evaluations regarding PHCs conducted by MCC and WWE are nearly identical, whether a natural B-Seam inflow rate of 30 gpm is adopted from Bear Mine alone or 31 gpm to 38 gpm, assuming both Bear Mine natural inflows and MCC sump contributions, as discussed in response #13. ~: