2011-09-23_REPORT - C1980007 (7)

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• 5.10 Traverse L1 -L1' 5.11 Location 9 Spring 2011 Subsidence and Geologic Field Observations Box Canyon, Apache Rocks, and South of Divide Mining Areas This traverse represents a relatively new access road to drill pads for MDW E1 -8 and E1 -11.5 as accessed from Horse Gulch road (Traverse L -L'). A significant slope failure occurred prior to the spring 2010 field visit at a switchback in the access road between the two well pads, likely in response to the mining of E -seam Longwall Panel El as it passed under the area. This access road has been reconstructed since that time and shows no additional signs of cracking of further downslope movement. There continues to be some cracking along the MDW E1 -11.5 pad near the outer edges (area of greatest fill). These cracks are parallel to the fill edges of the pad and are consistent with differential settlement. This is the site of annually observed subsidence cracks at Apache Rocks (Map 1). No • photographs of these cracks were obtained during the spring 2011 field visit. • As reported many times previously, there are essentially five individual cracks or crack zones in the Apache Rocks area. These cracks cover a lateral distance of approximately 280 feet and are above the mined B -seam Longwall Panels 12 and 13. The cracks trend primarily N65 -75 °E, but locally diverge to N40 °E, N80 °E, and E -W. The overburden depth to the B -seam in this area is about 1,350 feet. From north to south, the maximum widths of the individual cracks or crack zones, the centers of which average 70 feet apart, were measured in spring 2011 as follows: Crack 1 zone. 2.0 inches Crack 2 zone. 3.0 inches Crack 3 zone. 3.0 inches (total width of several branching cracks) Crack 4 zone. 5.0 inches (two cracks with widths of 3.0 and 2.0 inches) Crack 5 zone. 3.0 inches 831 - 032.793 September 2011 Wright Water Engineers, Inc. Page 39