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West Elk Mine
<br />• Lick Creek. Vertical displacement, tilt, and strain produced by mining may locally trigger
<br />already unstable rocks to fall during, or shortly after mining.
<br />The areas with steep slopes in the South of Divide mining area, which have the greater potential
<br />for rockfalls, are located either in areas with local access roads, which have only limited travel,
<br />or are in areas remote from any access roads or other man-made features. Based on a review of
<br />aerial photographs and analysis of the USGS 7.5 minute quadrangles, there are seven areas with
<br />slopes ranging from 30 to 80 percent that contain local cliffs and ledges (small cliffs 5 to 10 feet
<br />high). The areas listed below (listed in an east-to-west, north-to-south direction) have a low to
<br />medium rockfall potential (see Map 1 of Exhibit 60):
<br />1. Steep slopes (with an estimated rockfall potential ranging from moderate to high) located
<br />north of Dry Fork and west of Minnesota Reservoir. However, no mining is planned in this
<br />area, so this rockfall area will not be affected.
<br />2. Two steep ridges with cliffs and ledges, located above the northern part of longwall panel E9
<br />east of the landslide area (mostly in the SE'/4, Sec 32, T 13 S, R 90 W). There are no roads or
<br />man-made structures in the area.
<br />3. The south end of a steep ridge containing cliffs and ledges located north of the confluence of
<br />Deer Creek and Dry Fork above the western edge (within the area of mining_influence) of un-
<br />mined longwall panels El and E2 S '/z, Sec 29 and NW'/4, Sec 33, T 13 S, R 90 W). The Dry
<br />Fork road is located 400 to 500 feet south of nearest area boundary.
<br />4. A steep to moderately steep slope containing eight separate rockfall areas, located north and
<br />south of Dry Fork and its tributaries. The estimated rockfall potential is low to moderate.
<br />The rockfall areas are located above longwall panels El through E4 ( Sec 33, Sec 34, and NE
<br />'/2 Sec 35, T.13 S, R 90 W).
<br />5. The area is located in the southwestern part of the South of Divide mining area east of the
<br />main fork of Minnesota Creek. The northeastern part of this area, which has an estimated
<br />moderate to high rockfall potential, is within the area of mining influence of the un-mined
<br />longwall panels E8 and E9 (W'/2 and S1/2, Sec 5, T 14 S, R 90 W).
<br />6. This area contains six rockfall areas that have locally steep ridges. The area is located near
<br />the headwaters of Deer Creek, Poison Creek, Lick Creek, and a tributary of Dry Fork. The
<br />areas, which have an estimated low to moderate rockfall potential, are located above, or
<br />partly within, the area of mining influence of un-mined longwall panels E5 through E8
<br />(located in parts of Sections 3, 4, 9, and 10, Township 14 South, Range 90 West).
<br />7. This area contains 3 rockfall areas that have an eStiMPIted 10t7,7 to high rockfall potential. It is
<br />located in the Lick Creek area south of any currently planned mining (located in parts of
<br />Sections n. and 16, Township 14 South, Range 90 West).
<br />Of the seven areas listed above, six occur near local drill roads or agricultural access roads,
<br />which have only local, limited traffic. Any rocks that may fall in these areas could be readily
<br />removed before local traffic is impacted, should rockfalls occur on these remote roads. Evidence
<br />of naturally occurring rockfalls, such as remnant boulders located at the base of steep slopes, or
<br />in the run-out zones of these areas, will be documented prior to mining.
<br />2.05-148 Revised June 2005 PRIG, Rev. Uarch 2006; play 2006 PRIO. Nov. 2006TR107,.4Pril 2007TR108; Sep. 2007 PR12; Feb. 2008 PR-12
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