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2.05.6(6) <br />• <br />(e)(F)(IV) The areal extent of predicted subsidence related phenomena within the <br />permit and adjacent area is shown on Map 27 Subsidence. Traditional <br />subsidence and predicted rock roll out areas are both shown on the Map. <br />The areal extent for the traditional subsidence is calculated based on a 25 <br />degree angle of draw over areas where subsidence is expected to occur. <br />The rock roll out areas are predicted using the Colorado Rockfall Simulation <br />Program, version 4.0, developed by the Colorado Department of <br />Transportation, the Colorado School of Mines and the Colorado Geological <br />Survey. The results of the rock roll out predictions are presented in Volume <br />VII, Geotechnical Studies, Tab 11. <br />0 <br />(f) A description of the subsidence control plan, prepared by appropriately <br />qualified professionals follows: <br />(f)(i) A description of the physical conditions, such as depth of cover, seam <br />thickness, and lithology, which affect the likelihood or extent of subsidence <br />is presented in Volume III, Exhibit 15. The depth of cover data is presented <br />on Map 27, Subsidence. <br />(f)(ii) A narrative of the detailed description of the mining method and other <br />measures to be taken which may affect subsidence follows: <br />(f)(ii)(A) Room and pillar and longwall mining will be used for coal removal. The size <br />sequence and timing for development is presented on Map 14, Mine Plan. <br />(f)(ii)(B) Nearly all of the areas to be mined are areas in which planned-subsidence <br />mining methods will be used. There are a few exceptions to this statement <br />as outlined below. <br />In orderto protect againstchimney subsidence, only development mining will <br />be performed in areas with less than 110 feet of overburden. <br />~~ <br />TR-031 <br />The subsidence implications dealing with mining in low overburden areas <br />adjacent to the fault trace are a concern. The First North Mains mined into <br />the fault in late 1997 or early 1998. Additionally, the Operator has probe <br />drilled the fault on numerous occasions. The fault is characterized as a <br />shear fault as opposed to a roll fault and little fracturing was noted. The <br />probe drilling has not encountered any appreciable waterwhich indicates the <br />fault trace is virtually dry. <br />2.05 - 105 - 02/04 <br />ii PPR o~J] <br />