Laserfiche WebLink
SPRING 2007 Subsidence and Geologic Field Observations <br />Box Canyon, and South of Divide Mining Neas <br />barrier pillar between longwall panels 20 and 21, provides some argument that the cracks are at <br />least partially the result of subsidence. It is estimated that the probability of the cracks being the <br />result of lateral spreading versus subsidence is about 60/40. <br />5.4 Traverse D-D' <br />Traverse D-D' is a short traverse that starts at the fork in the main West Flatiron drill road (C-C' <br />traverse) and heads to the drill pad containing MDWs 19-04 and 19-05. This traverse is above <br />mined longwall panel 19 in primarily clays and silts of the Wasatch Formation. Overburden <br />depth to the B-Seam is 2,200 to 2,250 feet. <br />Point D' (i.e., Location 6) provides a good southward view of the rockfalUlandslide above mined <br />longwall panel 22. This is an annual observation location of this area because this vantage point <br />provides the closest site for a good view of the steep cliffs along the west side of West Flatiron. <br />A new crack was observed near the southwest corner of the MDW drill pad (Location 7). <br />5.4.7 Location 6 <br />Location 6 was used to photograph arockfall/landslide area located 4,400 feet south of the <br />observation location in the upper, massive sandstone cliff of the Ohio Creek Member of the <br />Mesaverde Formation (Figure 13). The rockfall/landslide area is located above the rigid chain <br />pillars (three-pillar entry system) that separate panel blocks 18, 19, 20 and 21 (to the north) from <br />panel blocks 22, 23, and 24 (to the south). The rockfalUlandslide is therefore located in an area <br />of maximum tensile strain, both due to mine geometry and topography. It is also in an area of <br />high to very high natural rockfall potential (Map 3). Figures 13, C-4, and C-5 show the same <br />area as observed in 2006 and 2005, respectively. <br />With the exception of being more weathered in appearance, the rockfall/landslide area has not <br />changed appreciably since July 2005, even though a change was discussed incorrectly in the <br />video footage taken of the area in 2006. The rockfalUlandslide area located above and east of the <br />main rockfall/landslide appears to be more evident in the 2005 image because it was taken from <br />a point further west and north of the 2006 and 2007 vantage point. Observations from other <br />831-032.780 Wright Water Engineers, Inc. Page 20 <br />July 2007 <br />