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Fall 2007 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />4.0 OVERVIEW OF FALL 2007 FIELD STUDIES <br />This subsidence report is the second of two reports generated during the 2007 calendar year. <br />Beginning with spring 2007 report, the subsidence monitoring and reporting will be conducted <br />biannually. This fall report describes the field observations made on September 26 through 28, <br />2007, which was the first time that many of the subsidence monitoring areas have been observed <br />during the fall. The areas visited were much drier than that observed during the spring 2007 field <br />visit. The spring and fall observations provide additional subsidence considerations as a function <br />of season and hydrologic conditions. <br />Subsidence observations were conducted in the Box Canyon, Apache Rocks, and SOD mining <br />areas. Field observations were made from a 4-wheel drive vehicle and by foot travel to <br />efficiently complete the required work. <br />Prior field observations and experience in the West Elk Mine area during field studies over the <br />last 12 yearsl (1996 to 2007 inclusive) indicate that subsidence features (cracks and bulges) are <br />most visible on roads and trails, where the ground is more compact and free of brush. These <br />areas were therefore selected, in addition to undermined areas free of brush, in order to most <br />efficiently obtain maximum subsidence information. <br />The rockfalls and landslides in the Box Canyon, Apache Rocks, and SOD mining areas were <br />examined and photographed to evaluate changes since the last observation, and to record their <br />condition for future reference. During the summer of 2006, a geological engineering appraisal <br />was completed of the Deer Creek Ventilation Shaft and Escapeway area as well as the rockfall <br />area near the Bear Mine portal in the C-seam. These areas were again visited in September 2007 <br />to assess any potential changes to the area, make additional observations, and reconsider <br />conclusions reached from earlier evaluations. <br /> <br />~ Annual subsidence and geologic hazard reports are kept at Mountain Coal Company, LLC and at the Colorado <br />Division of Mining, Reclamation and Safety, as well as exhibits to the permit document (Exhibits 60, 60A, 60B, <br />and 60D). <br />831-032.780 <br />November 2007 <br />Wright Water Engineers, Inc. <br />Page 12 <br />