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Spring 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• these small slumps are related to longwall mining activities is estimated to be less than about 20 <br />percent. <br />A relatively small rockfall (Location 1) was noted above the drill road as it climbed over <br />unmined Longwall Panel 25. Because the site is visible from only one location along the road, it <br />is unclear whether the rockfall occurred since our fall 2007 visit or whether it had occurred <br />previously and gone unnoticed. <br />As previously noted, Photographic Observation Point 8 was not visited. However, the area <br />photographed from that location was photographed from an alternate location (Photographic <br />Observation Point 8A) on the drill pad for MDW 19-09 in order to document the active rockfall <br />and landslide area on the east side of Box Canyon at Location 3, and also to assess any changes <br />that may have occurred to the steep rockfall/landslide area across Box Canyon from this location. <br />5.1.1 Location 1 <br />• This rockfall/landslide site is located along Traverse A-A' roughly 40 feet above the roadcut at a <br />location approximately 1,200 feet north of the fork that drops back down toward the Sylvester <br />Gulch valley bottom. This rockfall is only visible from 400 feet south of the site along the road <br />(Figure 5). As observed in Figure 5, the lighter color of the sandstone outcrop of the Barren <br />Member of the Mesaverde Formation above the debris pile provides the only indication that this <br />is a relatively recent rockfall. The steepness of the hillside and incoming inclement weather did <br />not allow a closer inspection of the outcrop face and debris pile. However, though this rockfall is <br />located within the area of mining influence of the main haulageway to the Box Canyon longwall <br />mining panels (approximately 800 feet above the B-seam), this rockfall most likely is a <br />consequence of over-steepened slopes rather than mining-induced causes. <br />?J <br />831-032.790 Wright Water Engineers, Inc. <br />August 2008 <br />Page 15