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West Elk Mine <br />r? Longwall Panels E1 through E8 are all projected to be 1,080 feet wide and range from about 9,000 <br />to 11,000 feet long. Panel E9 is projected to be 1,080 feet wide and 5,750 feet long. The panels <br />will be mined by the retreat longwall method. Panels El through E8 will be mined from east to <br />west. Panel E9 is planned to be mined from south to north. The panel layouts for the South of <br />Divide mining areas are shown on Map 51. The trend of Panels E1 through E8 is approximately <br />N80°W. Panel E9 trends roughly N10°E. The overburden depth above the Panels El to E4 ranges <br />from roughly 375 to 1,425 feet, whereas, the overburden depth for Panels E5 to E8 ranges from 500 <br />to 1,250 feet. The overburden above Panel E9 ranges in thickness from 500 to 600 feet. <br />All longwall panels are planned to be separated by either two or three rows of chain pillars. The <br />row nearest to the headgate side of the panels is projected to be a rigid pillar design on centers 125 <br />feet wide by 200 feet long. The row on the tailgate side of the panel will be of a yield pillar design <br />on centers 75 feet wide by 200 feet long. A protective barrier system, approximately 700 feet wide, <br />is currently projected to separate longwall Panels El-E4 and E5-E8. Mine plans and pillar designs <br />may change as mining experience, geological-geotechnical conditions, and/or mine operational <br />procedures dictate. Prior to implementing any mine plan changes, the appropriate approval will be <br />received from the Division and any other agencies as required. <br />Geologic Factors Influencing Subsidence - 2.05.6 (6)(e)(i)(B) <br />Subsidence is influenced by the local geology in the following ways: <br />Geologic Structure <br />Attitude of the bedrock, faulting, and jointing may control mine layout and mining method. In <br />steeply dipping, faulted coal beds, for example, a certain mine layout and method, such as room- <br />and-pillar or 1ullited panel-pillar may be required. Joints often control the way in which the roof <br />rocks break, cave, and fracture, both underground and at the surface during mining and subsidence. <br />In relatively flat-lying, unfaulted coal seams like the South of Divide and current mining area, <br />there is latitude to develop the most efficient layout and method to recover a maximum amount of <br />the coal resource with a minimum of impact. <br />Strength and behavioral properties of the rocks <br />These properties may control the amount and rate of subsidence. Strong, brittle sandstones and <br />siltstones tend to break and cave in large blocks on the mine floor. The bulking factor is greater for <br />strong rocks than it is for soft, weak rocks. The greater bulking factor of strong, caved material <br />commonly reduces the height of caving and the subsidence factor over soft, weak rocks. <br />Conversely, the height of fracturing often is greater for strong, brittle rocks than it is for soft, weak <br />rocks. <br />Stratiaraphic sequence <br />The stratigraphic distribution of rock units {stratigraphic sequence, iriflz.:e_ ces t?_a effects of <br />and subsidence. For example, strong and brittle sandstones in the mine roof as discussed above, <br />can reduce the height of caving compared to shales, whereas sandstones in the fractured zone above; <br />the caved zone may increase the height of fracturing compared to shales. <br />2.05-120 Revised June 2005 PR70. Rev. March 2006; A4ay 2006 PRI G, Nov. 2006TR107,Apri12007TR108; Sep. 2007 PR12; Feb. 2008 PR-12