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page 2 load affecting pillars includes allowances for load transferr_•:: to waste through subsidence of panel roof segments. The applicant appears to have adjusted the equations to eliminate that transfer. I will closely review the paper to review their approach. The applicant believes the analysis to be conservative in nature because of the assumption of a 45° angle of draw, I:he presence of bridging sandstones in the overburden section and the possible occurrence of shrinkage stoping during subsidence. Some significant additions to subsidence technology have been made during the past decade. U.S.Geological Survey Professional Paper No. 9fi9, titled "Some Engineering Geologic'Factors Controlling Coal Mine Subsidences In Utah And Colorado", was published in 1976. This paper, authored by Richard Dunrud, presents specific observations of subsidence phenomena above working coal mines in the Geneva area of Utah and the Somerset Mining District of Delta and Gunnison Counties, Colorado. These specific subsidence case histories concern coal mines extracting coals from the Mesa Verde Group, synonymous with the coals targeted for extraction in the Eagle No. 5 and No. 9 mines. Observations which bear upon subsidence control consideratior..s in the Eagle No. 5 and No. 9 include, but are not limited to: (1) In the Somerset District tensional and compressional sut~sidence features are evident above mine workings as deep as 900 feet beneath the surface. (2) Extraction of coal in panels too close to the outcrop ha.s resulted in compressional failure of the narrow outcrop barriers, resulting in significant extensional surface features. (3) It is important to monitor subsidence parameters as mining progresses, as well as final results, because the subsidence processes contribute to the state of stress within the mine workings and within the rocks above and beneath the mine workings. (4) Subsidence effects have caused serious water and methane invasion. (5) Shrinkage stoping cannot account for many of the subsidence profiles observed. (6) Compressional yielding of barrier pillars between panels can produce a "super-panel" trough-like depression above the entire mined pillar complex. (7) Panel pillars designed to yield can decrease loading of overburden and result in less damaging surface subsidence phenomena than broad barrier pillars or solid-coal boundaries. (8) Mining in multiple-bed mining areas can be deleteriously affected by subsidence processes. High concentrations of stress, such as those present beneath coal barriers and pilaas can be transmitted downward, perhaps in excess of 100 feet, even if the seams are mined from top to bottom. Care must be taken to anticipate the cumulative stress concentration effects of mined-out levels on lower seams. The best remedy for many of the observed multiple-bed mining problems, in Dunrud's opinion, may be to design for uniform extraction. "If geologic conditions or thick and variable overburden preclude complete extraction, sequential partiad~;extraotion,from top to bottom, with columnized support pillars might yield the maximum resource production with maximum safety factor." In light of these recent developments in subsidence observation in the Somerset District I believe the simplistic treatment of subsidence presented in Empire Energy's permit application will require significant amendment before it can fulfill the requirements of the subsidence control plan required within the permanent federal regulations. The applicant should prepare an amended plan which should include: (1) Test results to demonstrate the strength characteristics of the involved coal and overburden andinterburden materials, and a thorough description of seam structural characteristics such as jointing and faulting which influence design of passageway configuration.