2010-05-03_REPORT - C1980007 (9)

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Fall 2009 Subsidence and Geologic Field Observations Box Canyon, Apache Rocks, and South of Divide Mining Areas 5.12 Traverse J-J' Traverse J-J' begins at Traverse I-P and continues in a west/northwestward direction along a ridgeline across most of Longwall Panel E1 (and a small portion of Longwall Panel E2) to numerous MDW drill pads (see Maps 2 and 4). Overburden depths along this traverse vary from 1,390 to 1,450 feet over the B-seam and 1,050 to 1,250 feet over the E-seam. This traverse is generally flat and stable on soil and colluvium derived from the Wasatch Formation and from intrusive rocks of the West Elk Mountains overlying consolidated bedrock units of the Barren Member of the Mesaverde Formation. Numerous MDW drill pads are accessible from this traverse including El-15, El-19, El-26.5, E I -3 0.5, E I -34, El-38, E2-38, E1-42, E242, E244.5, E1-45, and E247.5. Each of these sites was visited during the fall field activities. Mining had already occurred beneath Longwall Panel E1 MDW pads with numbers greater than 26.5. Only a select number of MDW pads were identified for specific discussion in this report. These included MDW pads E1-45 (Location 10), E1-34 (Location 11), E1-26.5 • (Location 12), and EI-19 (Location 13). 5.12.1 Location 10 The drill pad for MDW E1-45 is Location 10. This location is over the headgate entries of Longwall Panel E1 near its eastern end (Map 2). Longwall mining occurred beneath this area approximately two months prior to the spring 2009 field visit. Overburden thickness to the E- seam at this location is approximately 1,200 feet. In spring 2009, several cracks were noted in the drill pad near its outer edge and over the greatest fill placement. One relatively continuous crack (approximately 35 feet in length and 25 feet from the outer edge) was noted near the northeast corner of the pad. The overall orientation of the crack was approximately N75°E and measured no more than 0.5 inches in width. Approximately 20 feet of the crack is located on the pad with the remaining 15 feet continuing off the pad into native vegetation where it was eventually lost in shrubs and underbrush (Figure 44). This latter observation could not be attributed to differential settlement of fill material, therefore, this crack • was considered to be the result of subsidence. A photograph taken during the fall 2009 field visit 831-032.791 Wright Water Engineers, Inc. Page 51 April 2010