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Spring 2009 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• Another active rockfall /landslide area visited was that observed on the west and east sides of <br />West Flatiron during the spring 2007 and fall 2008 field visits, respectively. Location 4 (Map 1) <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. The rockfall area on the east side of West Flatiron is identified <br />as Location 5 (Map 1). Cumulative extension of the surface cracks, as observed in June, 2008, <br />was on the order of 2.5 to 3 feet. As of October 2, 2008, the area historically used to monitor <br />these surface cracks (a methane drainage well [MDW] pad) was reclaimed and nearly all <br />evidence of surface cracks has been obscured except at the sandstone cliff face. Aside from a <br />few remaining MDW pads near the north end of West Flatiron, future mining - related activities in <br />this area are nearly complete. Nonetheless, the potential for more cracking and rockfall activity <br />on the west- and east - facing cliff faces over Longwall Panel 21 is high. Such activity is only <br />expected to have an effect on 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 7 (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 rockfall area <br />is 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 />decrease now that mining has been completed on all the B -seam panels in the Box Canyon <br />Mining Area. <br />E -seam longwall mining began in the South of Divide mining area in December 2008. The <br />recently completed spring 2009 field visit represented the first opportunity to make post- mining <br />observations in this area. While some evidence of subsidence cracks were noted at some of the <br />• MDW drill pads, there appeared to be an equal number of observed cracks in MDW pads above <br />831 - 032.791 Wright Water Engineers, Inc. Page 3 <br />November 2009 <br />