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Spring 2009 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• This traverse is physically located closest to Location 8. As such, additional details about this <br />location are provided in Section 5.8.1. <br />This traverse includes two annual observation locations: 1) to view and document the upper part <br />of the rockfall /landslide areas on the east side of Box Canyon above Longwall Panels 19, 20 and <br />21 (now established as Photographic Observation Point 3), and 2) to observe the headscarp of an <br />eastern side drainage in Sylvester Gulch (Location 9). <br />5.8.1 Location 8 <br />This is a rockfall /landslide area located above the rigid three - pillar entry system that separate <br />Panels 18, 19, 20 and 21 (to the north) from Panels 22, 23, and 24 (to the south). The <br />rockfall /landslide is therefore located in an area of maximum tensile strain, both due to mine <br />geometry and topography. It is also in an area of high to very high natural rockfall potential <br />(Map 3). A photograph of this location, as observed from Photographic Observation Point 2, is <br />provided in Section 5.6.3 as Figure 26. <br />• <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 changes appear to be the result of <br />seasonal differences (i.e., no leaves on the aspen trees, snow, sun location, etc.). <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 make continued observations of the areas on the east side of Box <br />Canyon above mined Longwall Panels 19 and 20, and to observe and document the new active <br />rockfall /landslide area above the eastern part of mined Longwall Panel 21 (Location 4 of this <br />report). <br />Figure 27 shows the area as observed in May 2009. A comparison to a photograph from the <br />same location in June 2008 (Figure 28) shows little change. However, a photographic <br />• comparison between May 2009 (Figures 27), June 2008 (Figure 28) and July 2006 (Figure 29) <br />831 - 032.791 Wright Water Engineers, Inc. Page 40 <br />November 2009 <br />