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- ~ IIIIIIIIIIII1111111 <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Depanmem of Natural Resources <br />1317 Sherman 51., Room 215 Ir~ <br />Denver, Colorado 80203 I <br />Phone: 13071 866-3 567 <br />FAX: f3031 832-8106 <br />DEPARTMENT OF <br />NATURAL <br />September 13, 1996 RESOURCES <br />Roy Romer <br />Mr. Henry Barbe cnvernor <br />lames S. Lochhead <br />Mountain ~'Oal Company E~ecmive Director <br />P . O . BOX 59 1 Michael B. Long <br />Somerset, CO 81434 Division Director <br />Re: Annual Subsidence Monitoring Report (Year-end Report); West <br />Elk Mine; Permit No. C-80-007 <br />Dear Mr. Barbe: <br />The Division has reviewed the Annual Subsidence Monitoring Report <br />(Year-end Report) submitted to us on June 3, 1996. The report <br />summarizes subsidence monitoring data collected during the <br />reporting period (July/August 1995 to October/November 1995). This <br />letter presents the Division's comments regarding the report. <br />As of November, 1995 the maximum observed subsidence (at point <br />No. 41) decreased 0.29 foot to 8.21 feet since its previous <br />maximum of 8.50 feet in October of 1994. This vertical <br />displacement was observed in a location overlying multiple <br />seam mining within both the F and B Seams. This observed <br />subsidence compares conservatively with the maximum projected <br />multiple seam subsidence of 10.22 feet. However, there is no <br />discussion of subsidence monitoring for the active area of <br />mining. Point No. 41 is located in an area of dual seam <br />mining that has not been actively mined for several years. <br />How is the analysis provided related to the area of active <br />mining, which is single seam (B Seam development)? The <br />maximum predicted subsidence for a typical B Seam longwall <br />panel layout is 7.97 feet as provided on page 22 of Exhibit 60 <br />in the permit document. Please provide a discussion/data <br />detailing how impacts of subsidence are being discerned in <br />areas of active mining specifically B-Seam development in the <br />B-West Mains, Jumbo Mains, Eighth Northwest Tailgate and <br />Headgate, the Ninth Northwest Headgate, and B6 and B7 <br />Northwest Longwall Panels. <br />The one page summary report provides one brief paragraph <br />stating the following: "The visual effects of subsidence for <br />this survey period were not detected by field personnel. The <br />cracks seen last year over the B-Seam panels, are healing well <br />and many are not perceptible. This is due in part to strain <br />relief over the other longwall panels." Was a visual survey <br />