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2006 Subsidence and Geologic Field Observations <br />Box Canyon, West Flatiron, Apache Rocks, and South of Divide Mining Areas <br />and weathered bedrock of the Barren Member of the Mesaverde Formation. No subsidence <br />features were observed. <br />4.11 Traverse L-L' <br />This traverse begins at the fork in the Minnesota Creek road and a newly constructed access road <br />to the excavation area for the new Deer Creek Ventilation Shaft and Escapeway (Map 1). <br />The new access road is in soil and colluvium of clay and silt derived primarily from deposits of <br />Wasatch Formation. The upper part of the road near the shaft excavation area cuts the toe area of <br />a landslide (Location 10). The overburden depth to the E-Seam varies from approximately 375 <br />to 400 feet. The depth of the colluvium and local landslide material is estimated to be in the <br />range of 75 to 125 feet. The estimated overburden depth to the E-Seam at the shaft excavation <br />azea is about 400 feet. <br />4.11.1 Location 10 <br />Location 10 is the excavation area for the Deer Creek Ventilation Shaft and Escapeway, which is <br />at least partially excavated in the lower part (toe area) of a landslide slump block. Examination <br />of the azea south of the excavation area revealed a linear depression that divides hummocky <br />topography to the south and a hill of unconsolidated landslide material to the north. The <br />structural fabric of the material in the hill to the north of the linear depression appears to be <br />dipping southward. Field evidence suggests a slump block, which is detached from the main <br />landslide along the lineaz depression, and is tilted back southward toward the main part of the <br />slide above a concave upward glide plane (or zone). <br />The landslide, which is visible in the 1963 USGS aerial photographs, appeazs to have been stable <br />since 1963, even during the very wet periods of the mid 1980s and 1990s. No changes in the <br />slide are observed when the 1963 USGS photos and the 2004 West Elk Mine color photos are <br />compared in stereo pairs. <br />831-032.750 Wright Water Engineers, Inc. Page 27 <br />December 2006 <br />