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Spring 2009 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• 5.5 Traverse E -E' <br />Traverse E -E' begins at the fork in drill roads above the south gate road entries of mined <br />Longwall Panel 24 and ends at the drill pad containing MDWs 18 -39, 18 -40, 18 -41, and 18 -43 <br />near the northeast corner of the mined Longwall Panel 19 tailgate entries. This traverse winds <br />northward along a drill road above mined Longwall Panels 24 to 19. Overburden depth to the B- <br />seam varies from 2,150 to 2,250 feet along this traverse. <br />Soil and colluvium as much as 10 feet thick, derived from clays and silts of the Wasatch <br />Formation and the underlying Ohio Creek Member of the Mesaverde Formation, were <br />encountered on the road. Several cracks were observed along this traverse in 2006 and 2007 <br />including several above the northeastern edge of mined Longwall Panel 19 (on the northern edge <br />of the drill pad for MDWs 19 -01, 19 -02, and 19 -03) and adjacent to the drill road above the <br />northeast corner of mined Longwall Panel 21 (in the drill pad for MDWs 21 -32, 21 -36, and 21- <br />38). This latter location (Location 4 of this report) has been recently reclaimed and surface <br />• evidence of the previously observed cracks has been mostly obscured due to regrading. However, <br />these cracks project to the east side of West Flatiron where a small rockfall and fracture zone is <br />the exposed in the sandstone outcrop just beneath the rim (Location 5 of this report). The <br />Longwall Panel 19 locations now show no remaining signs of the former cracks as documented <br />in previous subsidence reports. These locations are not included in this report. <br />Also located along Traverse E -E' is Photographic Observation Location 1, an annually visited <br />location used to obtain distant photographs of 2007 rockfall area above Longwall Panel 21 <br />(Location 4 of this report) for comparative purposes. <br />5.5.1 Location 4 <br />This is the site of five extensive crack zones that were first observed during the spring 2007 field <br />visit. These cracks, observed both in the main West Flatiron drill road and in the drill pad for <br />MDWs 21 -32, 21 -36, and 21 -38, occur above mined Longwall Panel 21 (Map 1). The maximum <br />cumulative extension of the previously - observed crack sequences was estimated to be 2% to 3 <br />• feet at the time of our site visit in June 2008. However, observations made during our fall 2008 <br />831 - 032.791 Wright Water Engineers, Inc. Page 27 <br />November 2009 <br />