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West Elk Mine <br />. With few exceptions, most landslides along the North Fork Valley are relatively shallow in depth <br />and move relatively slowly downhill (gravity creep) providing an opportunity for monitoring and <br />evaluation. Monitoring of the landslide toe south of Highway 133 can provide an opportunity to <br />assess whether reactivation of the landslide has occurred and to what extent this reactivation may <br />have on the highway. Such monitoring will be accomplished by vertically driving steel rods into <br />the landslide area south of Highway 133 at locations potentially subject to reactivation. These <br />are then monitored by surveying to assess changes. Should movement be noted on these metal <br />stakes, additional studies and surveys can be undertaken to assess where reactivation is <br />occurring, the rate of movement, the area extent and depth of the materials that are moving, and <br />the potential for impact to the highway. <br />It should be noted that the portion of longwall panel 18A that is closest to the highway <br />(approximately 600 feet horizontal distance) includes development entries, which have the <br />smallest subsidence potential because of the room-and-pillar mining techniques used. This <br />development mining will occur before any longwall mining activities. When longwall mining <br />occurs in panel 18A, it will be further south (about 250 feet) with an angle of draw that will not <br />influence the landslide area. As a result, monitoring of the landslide during development mining <br />will serve to assess the most likely potential reactivation period, particularly during spring <br />runoff. <br />Material damages created by the activation of the landslide, should they occur, are expected to be <br />limited to the physical obstruction of traffic on Highway 133. As previously stated, it is anticipated <br />that monitoring will assist in evaluating the potential for this occurrence and minimize the health <br />threat to individuals driving on Highway 133. Should the landslide reactivate and threaten or cross <br />Highway 133, MCC will provide available assistance in the clearing of the highway and mitigation <br />of the effects. WWE fmds the likelihood of this occurrence to be extremely small except in <br />abnormally wet conditions, which will have a similar effect on numerous landslides throughout the <br />North Fork Valley. <br />Impact of Highway Construction <br />Based on a review of aerial photographs taken before highway construction and on communication <br />with Bob Barrett of CDOT, two apparently dormant landslides were located east and west of the <br />mouth of Box Canyon. In November 1996, however this area is covered by extensive slides with <br />vertical, horizontal, and rotational movements. These extensive slides began when the new <br />highway was under construction on the south side of the North Fork valley. The lower portions of <br />collluvial deposits and toes of the dormant landslides on these steep slopes were removed during <br />construction, which produced steeper, less stable slopes. The oversteepened ground soon became <br />unstable and began to slide. Some of the slides show movement as recently as a week to a few <br />months old as of November 1996. <br />Inwortance of Baseline Landslide Data <br />Baseline information on landslides in the Box Canyon permit revision area needs to be carefully <br />documented prior to mining. MCC will plan to take aerial photographs of the Box Canyon Lease <br />area and field verify any landslides seen in the photograph, prior to mining. Some of the landslide <br />. features (cracks and grabens) closely resemble subsidence features. However, it is Mr. Dunrud's <br />2.05-146 Revised June 2006 PRIO. Rev. Alarch 2006; Ala); 2006 PRIG, Nov. 2006TR107..4pri12007TR108; Sep. 2007 PR12; Feb. 2008 PR-12