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of mining, the northeastern part of this area, which has an estimated moderate to high
<br />rockfall potential, is within the area of mining influence of the western and southern part of
<br />un-mined longwall panels E8 and E9, respectively (located mostly in the W'/2 and S'/2,
<br />Section 5, Township 14 South, Range 90 West).
<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 estimated low 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 8, 9, 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, which
<br />have only local, limited traffic on them. 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 of
<br />naturally occurring rockfalls, such as remnant boulders located at the base of steep slopes, or in the
<br />run-out zones of these areas, should be documented prior to mining.
<br />Two potential rock fall areas were identified in the Dry Fork mining area. The first area is located on
<br />the east side of the main Deep Creek channel above longwall panel E3. This area is identified as
<br />having low to moderate potential. It is located on an area remote for any access roads or manmade
<br />features. The second area is located on the northeast side of the east fork tributary of Deep Creek.
<br />This area is outside of the mining angle of draw and should not be affected by mining.
<br />. Based on annual observations in the Apache Rocks and Box Canyon mining areas during the last
<br />six years (1999-2004 inclusive), subsidence and any seismic activity caused by longwall mining is
<br />not expected to significantly affect rockfall areas with an estimated high to low rockfall potential.
<br />Only rockfall areas with an estimated very high rockfall potential were noticeably affected. However,
<br />because there are no rockfall areas in the South of Divide and Dry Fork mining areas with an
<br />estimated very high rockfall potential, the planned longwall panels in this mining area will most likely
<br />not be affected.
<br />It is suggested that signs stating, "Watch for Falling Rock," be posted in strategic places along the
<br />more well traveled roads, such as the roads along the main fork of Minnesota Creek, Dry Fork and
<br />Lick Creek, before mining begins. This procedure would be similar to signs posted along such major
<br />interstate highways as 1-70 in the Glenwood Canyon area, where the rockfall potential and risk to
<br />travelers is high to very high (compared to low to very low risk to travelers in the South of Divide
<br />and Dry Fork mining areas).
<br />10.3 Importance of Baseline Landslide and Rockfall Data
<br />The most significant landslide in the South of Divide area, in terms of proximity to man-made
<br />structures, is located above the northern part of longwall panel E9 (Map 1). Although there is a
<br />large landslide within the area of mining influence of the southeast corner of un-mined longwall
<br />panel E8 (mostly in the NE% of Section 8), the landslides located north and south of Minnesota
<br />Reservoir are the most important in the mining area. It is important to monitor the existing, natural
<br />(baseline) conditions before mining begins in order to document their natural state. The cracks,
<br />bulges, and depressions observed in the landslide areas north and south of Minnesota Reservoir
<br />are much more extensive and dramatic than those caused by subsidence. The vertical aerial
<br />photographs obtained by the West Elk Mine (dated July 2, 2004) will provide good baseline images
<br />of all the natural, pre-mine features in the South of Divide mining area.
<br />Observations made by Dunrud in the West Elk mining area indicate that mining may accelerate the
<br />natural landslide process, where there are landslides that have already become unstable. However,
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