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West Elk Mine <br />report. The report will include a description of observations, date of observations, and needed <br />repairs, if any. <br />Buildings <br />Subsidence effects on buildings have not been observed in the Apache Rocks and Box Canyon <br />mining azeas. Baseline information on buildings, such as foundations, walls, chimneys, and roofs, <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 Ells 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 pernut as an appendix. <br />Lower Drv 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 aze of a wood, boazd-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 (Mm), and horizontal tensile and <br />compressive strain (Em and -Em) in the cow camp cabin area are as follows, assuming 14 ft of coal <br />is extracted (see Table 2, Exhibit 60B): <br />Sm=9-loft; Mm=2-5%; Em,-Em=0.8-3%. <br />As the longwall mining face moves westwazd within the area of mining influence of the cabin, a <br />subsidence wave-moving at about the same rate as the mining 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 />2.05-156 RevisedJuiu 2005 PRIG, Rev. March 2006; May 2006 PRIO <br />