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• 10. There is a small portion of the Deep Creek Ditch that lies on bedrock and above the chain <br />pillars of panel E5 in the Dry Fork mining area. This should be monitored for cracks and <br />appropriate steps taken to seal them, if they occur. <br />11. Subsidence effects on buildings have not been observed in the Apache Rocks and Box <br />Canyon mining areas. Baseline information on buildings, such as foundations, walls, <br />chimneys, and roofs, has already been obtained prior to any mining on the Dry Fork Cow <br />Camp in July 2004 (Dunrud 2004b). a pre-mmining survey of the Cow Camp structures was <br />performed by West Elk Land Surveying in February 2006. The Minnesota Creek ditch <br />rider's cabin is located near the headwaters of Dry Fork in the Dry Fork mining area. An <br />exterior inspection of the cabin was performed in 2004 by the U.S. Forest Service and <br />Agapito Associates, Inc. (Agapito, 2005). The structure waas reported to be in average <br />structural condition. A pre-mining survey should be conducted for this structure. <br />As the longwall mining face moves westward within the area of mining influence of the Cow <br />Camp cabin, a subsidence wave - moving at about the same rate as the mining face - will <br />pass beneath the cabin, subjecting it to (1) tilt and strain, (2) then maximum vertical <br />displacement, (3) then relaxation of these effects, as the longwall mining face moves out of <br />the area of mining influence. <br />The cabin, though temporarily tilted until the longwall face moves out of the area of influence <br />of the cabin, is expected to remain inteact during the subsidence episode, because it is <br />small and light, and of wood construction. However, cracks are expected to occur in the <br />foundation, in response to the tilt and strain caused by the subsidence wave produced by <br />the moving longwall mining face below. <br />• The Minnesota Creek Ditch Rider's cabin is located outside of the angle of draw for the <br />planned mining and thus no impacts from mining are expected. <br />0 <br />Tetra Tech - 0907171P 37