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;: . Mountain Coal Company West Elk Mine Post Office Box 591 Somerset, Colorado 87434 Telephone 970 929-5015 Fax 9709235595 Ocotber 25, 1996 iii iiiiiiiiiiiiiiii 999 Mr. Michael Boulay Colorado Division of Minerals and Geology ~iECEIVEQ ~T 31 1996 1313 Sherman Street, Room 215 DIvl9lon of minarao a ljoaiogy Denver, CO 80203 RE: Annual Subsidence Monitoring Report (Year-end Report); West Elk Mine; Permit No. C-80-007 Dear Mr. Boulay: ~~ Mountain Coal Company (MCC) provides the following responses to the Division's questions regarding the review of the yeaz-end Subsidence Monitoring Report. 1. The subsidence grid shown on Map 29 was originally developed to monitor subsidence from F-seam mining. When MCC moved to the B-seam and longwall mining, the grid was extended to include the first few longwall panels, and covers an area where two seams (F- seam and B-seam) have been mined. Currently, MCC is mining in an area where only one seam (B-seam) has been and will be mined. The predicted subsidence for only B-seam longwall mining is 7.97 feet as shown on page 23 of Exhibit 60 in Volume 13. This prediction can be applied to the Jumbo Mountain mining area because mining methods in the B-seam and the geology of the area are similar to the area which is covered by the subsidence grid. 2. The visual survey is done by both field personnel and serial photography. The visual survey is intended to consist of observations made by personnel (usually MCC's or contract surveyors) as they travel in the areas of mining to complete their surveying of the grid shown on Map 29 and to set the photo control points as shown on Map 30, including the hydrologic monitoring sites on Jumbo Mountain. In addition, the aerial photos from the fall photogrammetric survey are utilized to document landslides, rockfalls, etc. No new subsidence features had been observed and features previously noted are healing. 3. The hydrologic impacts from subsidence are included in the Annual Hydrologic Report (AHR). The year-end subsidence report and the AHR are both due on April 30 of each year. In the 1995 AHR, this information appears on page 2. 4. MCC is aware of the commitment to monitor the Mautz cabin and will continue monitoring the cabin until survey information shows that subsidence is complete. At that time, a revision will be submitted to the Division which requests to cease monitoring of the structure.