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r1 <br />LJ <br />E#ribit 60C <br />Subsidence Evaluation and 2004 Geologic Hazard Field Observations <br />West Flatiron Lease Area <br />4.0 MINING METHOD <br />The longwall mining method will be utilized in the West Flatiron Lease area. An average of 12 <br />feet of coal is currently planned to be removed from the B Seam. The coal will be mined by the <br />retreat method-from east to west Longwall mining panels 18, 19, 20, and 21 are projected <br />from the Box Canyon mining area into the West Flatiron Lease area (Map 1). Projected longwall <br />panels 18 through 21, as currently planned, will be 970 feet wide (counting the headgate and <br />tailgate entries on either side nearest to the longwall panel block of coal). Longwall panels 18 <br />through 21, as currently projected, range from 5,850 to 8,200 feet long. Longwall panel 18A is <br />projected to be 660 feet wide and about 3,000 feet long. <br />The headgate entries of the longwall panels 18 through 21 each are planned as a row of rigid <br />pillars on 200-foot centers next to the panel, and a row of yield pillars 80 feet wide and 200 feet <br />long (Map I). The long axis of the longwall panels trend about N80°E. The mine plan may be <br />• subject to change, based on such aspects as coal quality and thiclmess, geology, and topography. <br /> <br />831-032.650 Wright Wafer Engineers, InG Page 5 <br />November 2004 <br />