Laserfiche WebLink
Fall 2007 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />• <br /> <br />edge of mined longwall pane123 and ends above mined longwall panel 22. Soil, colluvium, and <br />silty claystone, derived primarily from the Wasatch Formation, were encountered. The <br />overburden depth to the B-seam ranges from 2,200 to 2,250 feet. No subsidence features were <br />observed. <br />This traverse includes two annual observation locations; one to observe the headscarp of an <br />eastern side drainage in Sylvester Gulch (Location 8) and the second to view (at newly <br />established photographic observation point 3) the active rockfall/landslide area on the east side of <br />Box Canyon at Location 3. No subsidence features were observed above mined longwall panels <br />19 and 20 on the east side of Box Canyon. <br />5.5.1 Photographic Observation Point 3 <br />This observation point is located on the northern edge of the well site pad for MDWs 22-OS and <br />22-06. It was established to observe and document the new active rockfall/landslide area above <br />the mined part of longwall panel 21 (Figure 20). Cracking and spalling may be occurring on a <br />daily, or at least weekly, basis while coal extraction and subsidence is taking place. <br />The location also is useful to observe subsidence effects on the east side of Box Canyon above <br />mined longwall panel 20 where no subsidence effects were observed during this field visit. <br />This point was established to replace a location visited continuously over the past several years <br />(for example, location 8 in the spring 2007 field visit). Annual comparison photographs show no <br />mining related effects in the area. The new point was selected to include both the historically <br />viewed area plus the new rockfall/landslide area. <br />i <br />831-032.780 <br />November 2007 <br />Wright Water Engineers, Inc. <br />Page 33 <br />