Laserfiche WebLink
Fall 2007 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />5.11 Traverse H-H' <br />Traverse H-H' begins at a fork in the main Sylvester Gulch road, winds above planned longwall <br />pane125, mined longwall panels 19 and 20, the unmined part of longwall pane121, and ends at a <br />MDW 21-18 and photographic observation point 8. Locally deep soil and colluvium, from clay- <br />to boulder-size, derived primarily from the Barren Member of the Mesaverde Formation, and <br />local bedrock outcrops of the Barren Member were observed in the road cut. The overburden <br />depth to the B-seam ranges from about 500 to 1,150 feet. The numerous rocks on the drill road <br />indicate recent sloughing along much of the traverse. <br />No cracks were noted in the road along this traverse even though the latter half is mostly over the <br />central portion of mined longwall panels 19 and 20. A few slumps were observed in over- <br />steepened cutbanks in the road. The possibility that these small slumps are related to longwall <br />mining activities is estimated to be less than about 20 percent. <br />The drill pad for MDW 21-18 (photographic observation point 8) was visited in order obtain still <br />photographs and video of the active rockfall and landslide area on the east side of Box Canyon at <br />location 3, and also to assess any changes that may have occurred to the steep rockfall/landslide <br />area across, and on the east side of, Box Canyon from this location. <br />5.11.1 Photographic Observation Point 8 <br />This point (also H' of Traverse H-H') provides a good view of the active slabbing and <br />rockfall/landslide area on the east side of Box Canyon at location 3 (MDWs 21-32, 21-36, and <br />21-38) (Figures 39 and 40). Actively-developing cracks near the cliff rim at location 3 (Figures <br />7-13) and vertical linear features on the upper massive sandstone of the Ohio Creek Member of <br />the Mesaverde Formation (Figures 14 and 39) indicate that more rockfalls may occur in the near <br />future. <br />• <br />831-032.780 Wright Water Engineers, Inc. Page 53 <br />November 2007 <br />