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Fall 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />0 <br />• <br />in the area and near vertical exposures of outcrop. This area is described in more detail in this <br />report as Location 1 (Map 1) along Traverse A-A'. <br />Another active rockfall/landslide area visited was that observed on the west side of West Flatiron <br />during the spring 2007 field visit. The area is described in this report as Location 4 (Map 1) and <br />is located in the headwater region of Box Canyon and in one of the most narrow parts of West <br />Flatiron ridge at a site where probable gravity-induced cracks were first observed. This area is <br />now actively cracking and slabbing above the mined part of Longwall Panel 21 both on the west <br />and east sides of West Flatiron. Cumulative extension of the surface cracks as observed in June, <br />2008 was on the order of 2.5 to 3 feet. As of October 2, 2008, the area historically used to <br />monitor these surface cracks (a methane drainage well [MDW] pad) has now been reclaimed and <br />nearly all evidence of surface cracks has been lost. Aside from a few remaining MDW pads near <br />the north end of West Flatiron, future mining-related activities in this area are nearly complete. <br />Nonetheless, the potential for more cracking and rockfall activity on the west- and east-facing <br />cliff faces over Longwall Panel 21 is high. Such activity is only expected to have an effect on <br />surface features, particularly vegetation. <br />Approximately 1,500 feet north of the rockfall/landslide area first observed in the spring 2007 is <br />a second rockfall area observed for the first time during the June 2008 site visit. This area is <br />described in this report as Location 9 (Map 1) and is located on the west side of another narrow <br />portion of the West Flatiron ridge between mined Longwall Panels 19 and 20. This site is <br />considerably smaller than its neighbor to the south, as shown on Map 3. <br />The Box Canyon drainage has no human inhabitants or access roads. Continued <br />rockfall/landslide activities will likely affect the drill road on West Flatiron and the MDWs <br />which remain in operation. However, access to West Flatiron and the MDW pads is expected to <br />be unnecessary after the completion of Longwall Panel 25 sometime during the latter few months <br />of 2008. <br />0 <br />831-032.790 <br />December 2008 <br />Wright Water Engineers, Inc. <br />Page 3