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Su[uidence Evaluation For <br />Exhibit 60B South o/Divrde Mining An;a Page 22 <br />• <br />7. 'This area wntains 3 rockfall areas that have an estimated low to high rockfall potential. <br />It is located in the Lick Creek area south of any currently planned mining (located in <br />parts of 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, <br />wfiich have only local, limited traffic on them. Any rocks that may fall in these areas could be <br />readily removed before local traffic is impacted, should rockfalls occur on these remote roads. <br />Evidence of naturally occurring rockfalls, such as remnant boulders located at the base of steep <br />slopes, or in the nm-out zones of these areas, should be documented prior to 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 <br />is not expected to significantly affect rockfall areas with an estimated high to low rockfall <br />potential Only rockfall areas with an estimated very high rockfall potential were noticeably <br />affected. However, because there are no rockfall areas in the South of Divide mining area with <br />an estimated very hi¢h rockfall potential, the planned longwall panels in this mining area will <br />most likely not be affected. <br />It is suggested that signs stating, "Watch for Falling Rock," be posted in strategic places along <br />the more well traveled roads, such as the roads along the main fork of Minnesota Creek, Dry <br />Fork and Lick Creek, before mining begins. This procedure would be similaz to signs posted <br />along such major interstate highways as I-70 in the Glenwood Canyon area, wfiere the rockfall <br />• potential and risk to travelers is high to very high (compared to low to very low risk to travelers <br />in the South of Divide mining area). <br />10.3 Importance of Baseline Landslide and Rockfa// Dafa <br />The most significant landslide in the South of Divide area, in temrs of proximity to man-made <br />stroctures, 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 AfE'/. of Section 8), the landslides located north and south of Minnesota <br />Reservoir are dre most important in the mining area- It is important to monitor the existing, <br />natural (baseline) wnditions before mining begins in order to document their natural state. The <br />cracks, bulges, and depressions observed in the landslide areas nordr and south of Minnesota <br />Reservoir are much more extensive and dramatic than those caused by subsidence. The vertical <br />aerial photographs obtained by the West Elk Mine (dated July 2, 2004) will provide good <br />baseline images of all the natural, pre-mine features in the South of Divide mining area. <br />Observations made by the author in the West Elk mining area indicate that mining may <br />accelerate the natural landslide process, where there are landslides that have already become <br />unstable. However, annual observations of the surface cracks and depressions in the landslide <br />area on Jumbo Mountain above mined longwall panels 8 and 9 determined [hat landslides are <br />very likely only related to natural mass-gravity movements and not related to mining. <br />Baseline information should be gathered in the eight areas with low to moderate rockfall <br />. potential that are listed in Section 102 prior to any mining activities- Evidence of naturally <br />831-032.690 WirghtWaterEngineers, Inc <br />