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2005 Subsidence and Geologic Fiekl Observations <br />Box Canyon, W est Flatiron, Apache Rocks, <br />and South of Divide Mining Areas <br />4.11.1 Location 11 <br />Location 11, which is the same as Location 3 in the 2004 West Flatiron Report (Duntud 2004b), <br />provides a good view of the eastem part of the Box Canyon mining area and the western part of <br />the West Flatiron mining area. Some of the observations discussed in the 2004 West Flatiron <br />Report are repeated here as an essential review of the geologic and topographic conditions of the <br />area. <br />The coordinates of Location 11 is 291,741m E, 4,309,117m N (i1T'M, NAD 1983, circle of error: <br />3-6m). A natural rockfall potential in the high category exists in the first 200 to 300 feet in the <br />jointed and fractured sandstone cliffs below the rim of West Flatiron (Figure 12). The <br />rockfall/landslide process consists of the following: 1) lazge slabs or blocks of rocks loosen along <br />joint or fracture planes and become detached from the outcrop, 2) the rocks topple, fall, roll and <br />break up down the steep slope, 3) a landslide later may occur in rock rubble (talus) that forms <br />from the earlier rockfall. <br />As reported in 2004 (Duntvd 2004a), two small rockfall/landslide combinations occur neaz the <br />boundary between the Box Canyon and West Flatiron mining areas. One is located above the <br />southeastern corner of un-mined longwall panel 21 (Figure 12A) and the other occurs above the <br />eastern part of un-mined longwal] pane] 19 (Figure 12 and Map 2). Both of these <br />rockfall/landslide areas were present in the July 1963 U.S. Geological Survey (USGS) high <br />altitude photos, however, there has been some renewed movement of these sites. <br />831-032.710 Wright Waler Engineers, Inc. Page 25 <br />November 2005 <br />