Laserfiche WebLink
West Elk Mine <br />• subsidence (rather than natural) cracking would be minimal. MCC will conduct visual inspections <br />of primary public access to the USFS lands on a monthly basis, weather and ground conditions <br />allowing, when these roads could be potentially impacted by undermining. MCC will mitigate all <br />roads that may have been impacted due to subsidence and provide signage, particularly on public <br />roads, warning of potential hazazds. <br />Subsidence Prediction - 2.05.6 (6)(e)(i) <br />Brief Description of Mining Method - 2.05.6 (6)(e)(i)(A) <br />Apache Rocks and Box Canyon Mining Areas -The longwall mining method will be utilized in <br />the Apache Rocks and the Box Canyon mining areas. The panel design will be similar to the <br />current West Elk Mine longwall panels. An average of ]2 feet of coal will be extracted from the B <br />Seam in both areas and an average of 11 feet will be extracted from the E Seam in the western <br />panels of the Apache Rocks mining azea. The E Seam is not planned to be mined in the Box <br />Canyon permit revision area. In the Apache Rocks mining azea, E Seam mining is planned to occur <br />in Sections 28, 29, and 30. Top coal and bottom coal may be left in place in these areas to improve <br />roof and floor stability. <br />In the Apache Rocks mining area the three eastern panels are designed to be 8,500 to 8,800 feet <br />long the three western panels will trend east-west and range from 10,600 to 12,700 feet in length. <br />As currently planned, the four eastern panels aze projected to trend N80°W and be 950 feet wide. E <br />and B Seam mining gate road entries and longwall panels aze currently planned to be vertically <br />superimposed in the western panels. In the Box Canyon mining area, the panels currently planned <br />trend about N80°W, are 1,100 feet wide, and range in length from 6,250 to 7,900 feet. The panel <br />layouts for the Apache Rocks and the Box Canyon mining azeas are shown on Map 51 (E Seam) <br />and Map 52 (B Seam). The NE longwall panels include two north-south oriented panels. Both <br />panels aze 950 feet in width. The eastern panel (LONE) is 3,325 feet in length while the western <br />panel (11NE) is 3,625 feet in length. <br />Gateroad development typicaIIy entails development of three entries leaving two rows of chain <br />pillazs; one row a rigid pillar design and one row a yielding pillaz design. Chain pillars (headgate <br />and tailgate entries) are currently planned to include one row of rigid pillars approximately 100 feet <br />wide by 130 feet long (120 x 150 foot centers and one row of yielding pillazs approximately 40 feet <br />wide by 130 feet long (50 x 150 foot centers). These planned mine and pillar designs are subject to <br />change pending geotechnical analysis and mining experience from the new areas. Panel lengths and <br />widths will be maximized as possible. Additionally, the deeper cover in the Apache Rocks and the <br />Box Canyon mining azeas may require design alterations to gate roads, pillaz sizes and barrier pillazs <br />as well. <br />South of Divide Minin¢ Area -The longwall mining method will be utilized in the South of <br />Divide mining area. The planned panel design is similaz to the current West Elk Mine longwall <br />panels where subsidence measurements were used to obtain the baseline data on which this <br />discussion is based. A range of 8 to 14 feet of coal will be extracted from the E Seam depending <br />on seam structure, coal quality, and other operating constraints. It is anticipated that extraction <br />will be limited to 12 feet only on the easternmost edge of the panels. The extraction thicknesses <br />• are projected based on exploration hole data; actual thicknesses may vary depending on mining <br />conditions encountered. <br />2.05-119 Revised June 1005 PRIO, Rev. March 2006; May 1006 PRIG <br />