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<br />EXHIBIT 60B <br />SUBSIDENCE EVALUATION <br />FOR THE SOUTH OF DMDE MINING AREA <br />1.0 INTRODUCTION <br />This exhibit describes subsidence processes that have been observed by the author and others <br />from studies above longwall mining panels in Mountain Coal Company's (MCC) West Elk Mine <br />and from other similar operations and studies. The subsidence information obtained from the <br />current West Elk Mine area is used in this application to project subsidence processes, amounts, <br />and effects to the South of Divide mining area. lhis application document is intended to comply <br />with the Colorado Division of NtmeraLs and Geology (CDMG) Regulations for Coal Mining, <br />revised June 26, 2002, under Section 2.05.6, Mitigation of the Impacts of Mining Operations. <br />2.0 MINING METHOD <br />The longwall mining method will be utilized in the South of Divide mining area. The planned <br />• panel desigo is similaz to the B Seam West Elk Mine longwall panels where subsidence <br />measurements were used to obtain the baseline data that will be used in this report A range of 8 <br />to 14 feet of coal will be extracted from the E Seam (Figure 1). The extraction thicknesses are <br />projected based on exploration hole data; actual thiclmesses may vary depending on mining <br />conditions encountered <br />Longwall panels El through E8 are projected to be 1,080 feet wide and range from about 9,000 <br />to 11,000 feet long (without the Dry Fork Lease included), Panel E9 is projected to be 1,080 feet <br />wide and 5,750 feet long. 'The panels wil- be mined by the retreat longwall method. Panels El <br />through E8 will be mined from east to west Panel E9 is planned to be mined from south to <br />north. <br />the trend of panels EI through E8 is approximately N80°W. Panel E9 trends roughly AdIO~. <br />the overburden depth above the panels El to E4 ranges from roughly 375 to 1,425 feet, whereas, <br />the overburden depth for panels ES to E8 ranges from 500 to 1,250 feet. The overburden above <br />panel 9 ranges in thiclmess from 500 to 600 feet <br />All longwall panels are planned to be separated by two or three rows of chain pillars. the row <br />nearest to the headgate side of the panels is projected to be a rigid pillaz desigo--on enters 125 <br />feet wide by 200 feet long. The row on the tailgate side of the panel will be of a yield pillar <br />design-on centers 75 feet wide by 200 feet long. A protective homer system, 700 feet wide, is <br />currently projected to separate the longwall panels El to E4 and ES to E8. These mine plans and <br />pillaz designs may change as mining experience, geological-geotechnical conditions, and/or mine <br />operational procedures dictate, <br />ti31-032.690 Wright WaterFsgineers, Inc. <br />