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Spring 2008 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• brush. These areas were therefore selected, in addition to undermined areas free of brush, in <br />order to most 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 (using routinely <br />visited photographic observation points), and to record their condition for future reference (Maps <br />1-4). One new rockfall/landslide area was noted on the west side of West Flatiron. This site is <br />approximately 1,500 feet north of a more significant rockfall/landslide first observed in spring <br />2007 and described in both the spring and fall 2007 subsidence monitoring reports. <br />Eleven photographic observation points have been established since 2007. Many of these <br />locations had been used for annual comparative purposes even before their most recent <br />formalized establishment. Two photographic observation points were established in spring 2007, <br />seven more points were established in fall 2007, and two additional points were established <br />during the spring 2008 site visit. <br />The two spring 2007 photographic observation points include one that overlooks the Dry Fork <br />drainage, the Minnesota Creek Reservoir, the Deer Creek Ventilation Shaft and Escapeway, and <br />the lower reaches of the Deer Creek drainage. This location will be used regularly to assess <br />changes that may occur as mining of the E-seam progresses through the area. The second <br />photographic observation point established in the spring of 2007 is on the west side of Sylvester <br />Gulch and provides a good vantage point to view the rockfall and landslide area at the headscarp <br />of Box Canyon. This location is approximately 4,300 feet north of the previous location <br />established for this purpose. <br />Seven additional photographic observation points were established in the fall of 2007 to view <br />rockfalls and landslides in the Box Canyon mining area, the dam and landslide construction in <br />the Minnesota Reservoir area, and the Highway 133 landslides. <br />Two additional photographic observation points were established during the spring 2008 field <br />visit. One location is from near the train loadout facility north of Highway 133 where a full view <br />• 831-032.790 Wright Water Engineers, Inc. Page 12 <br />August 2008