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West Elk Mine
<br />has already been obtained prior to any mining on the Dry Fork Cow Camp in July 2004. A pre-
<br />mining survey of the Cow Camp structures was performed Wright Water Engineers and was
<br />reported in Exhibit 60D, and another survey was conducted by West Elk Land Surveying in
<br />February 2006 and is included in Exhibit 73. Another detailed pre-subsidence survey will be
<br />conducted of Cow Camp within six months prior to subsidence taking place. A survey monument
<br />will be placed in the vicinity of the structures as part of this inspection and its location will be
<br />surveyed prior to subsidence. The monument will be surveyed quarterly while within the angle of
<br />draw of subsidence and until two consecutive measurements show no significant movement. The
<br />results of the surveys will be reported semi-annually. The structures will be resurveyed after
<br />subsidence and a report detailing changes, if any, will be generated. The report will then be added
<br />to the permit as an appendix. No buildings will be impacted in the Dry Fork Lease area (Ditch
<br />Rider's Cabin).
<br />Lower Dry Fork Cow Camp
<br />The cabin exterior is approximately 13 feet wide, 20 feet long, and 8.5 feet high (the wall height).
<br />A lean-to 7 feet long and a porch 5.5 feet wide are located on the north and south ends of the cabin
<br />(see Figures 7 and 8, of Exhibit 60D for details). The outside walls are of a wood, board-and-bat
<br />construction.
<br />The foundation, which is of rock and mortar construction (and an estimated 1 feet thick), ranges
<br />from about 1 foot high in the back to 20 inches high in the front. The roof is covered with tin. The
<br />side windows, which measure 2 by 3 feet in outside dimension, are located in the approximate
<br />• center of either wall.
<br />Estimated maximum ranges of vertical displacement (Sm), tilt (M,,,), and horizontal tensile and
<br />compressive strain (E,,, and -E,,,) in the cow camp cabin area are as follows, assuming 14 ft of coal
<br />is extracted (see Table 2, Exhibit 60B):
<br />S,,,=9-10 ft; M,,,=2-5%; Em,-Em=0.8-3%.
<br />As the long wall mining face moves westward within the area of mining influence of the cabin, a
<br />subsidence wave-moving at about the same rate as the raining face- will pass beneath the cabin,
<br />subjecting it to (1) tilt and strain, (2) then maximum vertical displacement, (3) then relaxation of
<br />these effects, as the longwall mining face moves out of the area of mining influence.
<br />The cabin, though temporarily tilted until the longwall face moves out of the area of influence of the
<br />cabin, is expected to remain intact during the subsidence episode, because it is small and light, and
<br />of wood construction. However, cracks are expected to occur in the foundation, in response to the
<br />tilt and strain caused by the subsidence wave produced by the moving longwall mining face below.
<br />The trucks, 7.7hicl. may reach a maximum temporary width of a fraction of an inch to perhaps 1 to
<br />perhaps 1', 4 inches, will likely close again when the longwall raining face moves out of the area of
<br />mining iniiue ,ee of the cabin. Any cracks that develop in the foundation, however, may continue to
<br />be visible for the life of the foundation.
<br />• Cracks, of as much as 1 to perhaps 11/4 inches wide, are also expected to locally occur in the Dry
<br />Fork road near the Cow Camp and ,elsewhere during miring. The cracks will likely close again
<br />once the long wall miring face moves out of the area of influence of the road area.
<br />2.05-1.57 Revised June 2005PRIO, Rev. Afarch 2006; A1ay 2006 PRIO, >`'ov. 2006TR107,Ap7-il 2OO7TRI08; Sep. 2007 PR72; Feb. 2008 PR-12
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