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Fall 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />this location is Of the upper part of the Ohio Creek Member of the Nlesaverde Formation (Figure <br />'7). This veR high rockfall potential location (see Map 3), is located at the approximate <br />midpoint of mined Longwall Panel 22 and is 2,200 lect above the elevation of the 13-scam. <br />• <br />• <br />y r.? <br />1 ? <br />Figure 27. Fall 2008 southward view of the upper part of the active rockfall/landslide scarp located <br />at the head of the first east side canyon of Sylvester Gulch above mined Longwall Panel 22. <br />Previous observations from this location show that the rock fall landslide activity increased <br />signiticantlI after [.ongwall Panel 22 was mined. I luwcver, photographs taken in previous wars <br />sho\y little change other than seasonal differences. This headscarp area is best viewed from the <br />west side of SOvester Gulch (Photo,,raphic Observation Points 4 and 5, `lap l ). <br />5.8.4 Photographic Observation Point 4 <br />Photographic Observation Point 4 (Map 1 ) was established in Jul\ 2003 to provide an overvle\y <br />of the active rockfall/landslide area at the head of the first eastern drainage of Sylvester Gulch <br />that terminates on West Flatiron (Location I l of' this report). PhotoUraphs taken from this <br />location sho\y rockfall/landslide activities increased significantly after longwall minis`.: occurred <br />beneath Longwall Panel 22 and 23 and that there has been some minor changes since 2003 (i.e.. <br />compare Figure 28. 29. and figure 30). <br />831-032390 Wright Water Engineers, Inc. Page 42 <br />December 2008