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West Elk Mine <br />• environment. In the case of the Oliver No. 2 Mine, fresh air reportedly was blown into the mine <br />with a 4-foot squirrel-cage blower (Boyd Emmons, Oral Communication, November 6, 1996). In <br />this type ofpositive-pressure environment, the mine workings become progressively gassy if the fan <br />does not have a sufficient air-moving capacity to ventilate sudden inflows of methane. <br />Potential Impacts of Subsidence and Mine Induced Seismic Activity on Landslides and <br />Rock ails <br />Landslides <br />Box Canyon Mining Area - In October 1996, lazge, composite landslides with numerous scarps <br />were observed between the unnamed drainage west of Box Canyon and Box Canyon and also to the <br />east of Box Canyon. As discussed in Section 2.04.6, the slides are compartmented into essentially <br />separate slides by competent sandstone ledges. Grabens, sag ponds (complete with small wetlands), <br />and tension cracks occur between the scarps. The tension cracks could easily be confused with <br />subsidence cracks, but no mining has been done in the area. The landslides aze located in or neaz <br />the northern boundary of the Box Canyon permit revision azea. The southern limit of the landslides <br />is located at least 650 feet north of the neazest planned longwall panel-well outside of the <br />conservative angle of draw. <br />In October 1996, large, composite landslides with numerous scarps were observed between the <br />unnamed drainage west of Box Canyon and Box Canyon and also to the east of Box Canyon. As <br />discussed in Section 2.04.6, the slides are compartmented into essentially separate slides by <br />• competent sandstone ledges. Grabens, sag ponds (complete with small wetlands), and tension <br />cracks occur between the scarps. The tension cracks could easily be confused with subsidence <br />cracks, but no mining has been done in the azea. The landslides are located in or near the northern <br />boundary of the Box Canyon permit revision azea. The southern limit of the landslides is located at <br />least 650 feet north of the neazest planned longwall panel-well outside of the conservative angle of <br />draw. <br />As mentioned above, a small portion of the development mining area along the northwest side <br />longwall panel 18A underlies a known azea of Landslide disturbance south of Highway 133 as <br />shown on Map 1 of Exhibit 60C. As a result, the worst possible consequence associated with <br />mining-induced subsidence in the West Flatiron lease area is that this landslide will be <br />reactivated during mining activities causing a potential crossing of Highway 133 and an <br />obstruction to traffic. <br />Based on observations made in the field both of active and inactive landslide areas before and <br />after mining activities, MCC and it's consultant (WWE) concludes that the greatest potential for <br />the worst possible consequence would occur during a very wet precipitation period. Such <br />periods have been observed in the North Fork Valley as recently as the mid-1990s causing <br />initiation or reactivation of numerous natural landslides. <br />With few exceptions, most landslides along the North Fork Valley aze 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 occun•ed and to what extent this reactivation may <br />1.05-144 Revised Jwie 2005 PR/0, Rev. March 2006; May 1006 PRI G <br />