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~~ As discussed in Section 2.05.6(6)(e)(i) Potential Impacts from Local Seismic Activity, subsidence <br />could accelerate the naturally-occurring rockfall and landslide prophecies that aze already evident in <br />the permit area, but this will not constitute a hazazd to either people or property nor would this <br />measurably impact the surface or ground water hydrology of the area. <br />Cracking of the earth along or across the trails on unimproved roads of the coal lease area already <br />naturally occurs, but in the "worse case" could be accelerated by or additional cracks created by <br />subsidence. As the trails and roads are unimproved, typically only all-terrain or four-wheel drive <br />vehicles are utilized and rough terrain is expected, so the hazards created by any additional <br />subsidence (rather than natural) cracking would be minimal. MCC will conduct visual inspections <br />of primary public access to the US Forest Service lands on a monthly basis, weather and ground <br />conditions allowing, when these roads could be potentially impacted by undermining. MCC will <br />mitigate all roads that may have been impacted due to subsidence and provide signage, particularly <br />on public roads, wanting and potential hazards. <br />Subsidence Prediction - 2.05.6 (6)(el (i) <br />Brief Description of Mining Method - 2.05.6 (6)(e)(i~)(A) <br />The longwall mining method will be utilized in the Apache Rocks and the Box Canyon mining <br />azeas. The panel design will be similaz to the current West Elk Mine longwall panels. An average <br />• of 12 feet of coal will be extracted from the B-Seam in both azeas and an average of 11 feet will be <br />extracted from the E-Seam in the western panels of the Apache Rocks mining area. The E-Seam is <br />not planned to be mined in the Box Canyon permit revision area. hi the Apache Rocks mining azea, <br />E-Seam mining is planned to occur in Sections 28, 29, and 30. Top coal and bottom coal may be <br />left in place in these areas to improve roof and floor stability. <br />In the Apache Rocks mining area the three eastern panels aze 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 (see Wright Water Engineer's [W WE's] report of revised panel layouts dated <br />August 1996), the four eastern panels aze projected to trend N80°W and be 950 feet wide. E and B- <br />Seam mining gate road entries and longwall panels will be vertically superimposed in the westem <br />panels. The E-Seam is planned to be mined before beginning operations in the underlying B-Seam. <br />In the Box Canyon mining azea, the panels currently planned trend about N80°W, aze 1,100 feet <br />wide, and range in length from 6,250 to 7,900 feet. The panel layouts for the Apache Rocks and the <br />Box Canyon mining azeas aze shown on Map 51 (E-Seam) and Map 52 (B-Seam). The NE <br />longwall panels include two north-south oriented panels. Both panels aze 950 feet in width. The <br />eastern panel (1 ONE) is 3,325 feet in length while the westem panel (11NE) is 3,625 feet in length. <br />All panels are planned to be sepazated by two rows of chain pillazs, one row a rigid pillaz design and <br />one row a yielding pillaz design. Chain pillazs (headgate and tailgate entries) aze currently planned <br />to include one row of rigid pillazs approximately 100 feet wide b'y 130 feet long (120 x 150 foot <br />centers and one row of yielding pillars approximately 40 feet wide by 130 feet long (50 x 150 foot <br />. centers). These planned mine and pillaz designs are subject to change pending geotechnical analysis <br />and mining experience from the new azeas. Panel lengths and widths will be maximized as <br />2.05-ll0 ~ MarcH 2O05PRR <br />~T <br />