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III IIIIIIIIIIIIIIII <br />DEPARTMENT OF NATURAL RESOURCES <br />Davitl H. Getches, Executive Director <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SHELTO N, Director <br />Richard D Lamm <br />Governor <br />T0: Gregg Squire <br />FROM: Jim Pendleton <br />RE: AUGUST, 1986.. <br />MEMORANDUM <br />1 Aug t 1986 <br />-~ <br />L SUBSIDENCE MONITORING REPORT, EAGLE #5 MINE, <br />LONGWALL AREA (Permit No: C-81-044) <br />I have completed a review of the above referenced subsidence monitoring <br />report, which presents the results of subsidence monitoring surveys performed <br />in March and June, 1986, above the Utah tract longwall mining activity. The <br />surveys and reporthave been acceptably completed. <br />The results to date have documented a maximum vertical subsidence of 6.11 feet <br />above Panel No. 1 within the Utah tract. During the past half year the <br />maximum observed vertical subsidence has reduced to 5.74 feet, probably due to <br />cantilevering of competent strata within the overburden section. This <br />compares with a maximum predicted vertical subsidence of 8.0 feet. Ground <br />surface cracking continues to be observed. In response to my suggestions <br />following the last semi-annual report, you have inspected the ground <br />conditions above the Utah tract on several occassions, including photographic <br />documentation. The old spoils being exposed to subsidence continue to be <br />stable. <br />The angle of draw observed to date has varied in relation to the bedrock dip. <br />This may be affected by the presence of the previously surface-mined spoil <br />material. The subsidence monitoring has documented an angle of draw of 17.2 <br />degrees downdip form the gob, 8.9 degrees updip from the gob, and 14.2 degrees <br />behind the gob. Additional propagation of the trough subsidence can be <br />expected to occur with time, which could cause the maximum vertical subsidence <br />and angles of draw to continue to change. <br />The report is acceptable as submitted. The operator should be commended for <br />the subsidence monitoring program it is conducting above the Utah tract <br />longwall project. <br />JP/jp <br />cc: Mike Long <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567 <br />