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Fall 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />therefore located in an area of maximum tensile strain, both due to mine geometry and <br />topography. It is also in an area of high to very high natural rockfall potential (Map 3). <br />With the exception of being more weathered in appearance, the rockfall/landslide area has not <br />changed appreciably since July 2005. Observations from multiple directions suggest that there <br />has been little change over the past several years. The only apparent changes appear to be the <br />result of seasonal differences (i.e., no leaves on the aspen trees, snow, etc.) as opposed to <br />additional rockfall/landslide occurrences. <br />5.8.2 Photographic Observation Point 3 <br />This observation point is located on the northern edge of the well site pad for MDWs 22-05 and <br />22-06. It was established to observe and document the new active rockfall/landslide area above <br />the eastern part of mined Longwall Panel 21 (Location 4 of this report) and to continue <br />observations of the areas above Longwall Panels 19 and 20. <br />The location has historically been used to observe and photograph subsidence effects on the east <br />side of Box Canyon above mined Longwall Panels 19 and 20. Figure 22 shows the area as <br />observed in October 2008. A comparison to a photograph from the same location in June 2008 <br />(Figure 23) shows little change. <br />A photographic comparison between 2008 (Figures 22 and 23) and 2006 (Figure 24) shows that <br />new rockfall/landslide activity occurred before June 2008 as noted in the left central portion of <br />the photograph. The reason for the new activity is difficult to assess, but believed to be at least <br />partially related to mining activities given that the area in under the Longwall Panel 19 tailgate <br />and an area of increased tensile strain. This area is also considered a medium to very high <br />rockfall potential area (Map 3) and subject to longwall mining directly beneath it during the first <br />half of 2008. Although not shown on Map 3, rockfall potential is high to low on slopes and <br />canyons around West Flatiron. <br />• <br />831-032.790 Wright Water Engineers, Inc. Page 38 <br />December 2008