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_>~--: <br />~~I II~'I~II~~~~~ I~~ <br />STATE OF COLUl~AUU <br />DIVISION OF MINERALS AND GEOLOGY <br />Dcp,vtmcnl of Natural Rusour~es <br />I} 1 1 tihcrm,in SL, Ruum ? I S <br />Denver, Coluratlu ri0201 <br />rhnm~~. t {ml tu,r,-.tsa7 <br />c.~x an}I n} ~ niuh <br />DATE: August 12, 1998 f~ <br />TO: Larry Routten & Jim Bur'I II <br />FROM: Jim Pendleton ~s~~c <br />RE: West Elk ne - J 24, 1998 Request for Vacation of <br />NOV No. -022 (Permit No: C-80-007) <br />~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />lames 5. Lochhexl <br />Fecmive Dirccior <br />Michael B. Lung <br />Division Dircao. <br />I have reviewed the July 24, 1998 cover letter and exhibits submitted by Mountain <br />Coal Company (MCC) in support of its request for vacation of NOV No: CV-97-022. <br />As I have stated previously, I believe MCC and its consultants have thoroughly <br />defined the geotechnical character of the Bear No. 3 Mine landslide. <br />I characterize the slide as a translational movement of the valley slope colluvium <br />over the underlying bedrock. Unlike many of the surrounding Williams Fork <br />formation landslides, the subject slope failure is not a "flow" type mass movement <br />feature. While spring groundwater effluent flow is associated with the Edwards <br />Mine portal adjacent to the landslide's toe, the landslide debris is not saturated and <br />appears to be performing as a competent granular mass. Further, as MCC <br />observed, historic aerial photography contains artifacts which indicate that this <br />particular slope area has been the locus of slope instability previously. <br />Based on the above observations and my experience with landslide phenomena in <br />the Valley of the North Fork of the Gunnison River, as well as other numerous <br />locations, I conclude that this landslide does not demonstrate characteristics <br />common of potential high risk, "run away" landslides. For this reason, I believe this <br />particular landslide presents very minimal risk for future catastrophic failure. I <br />suspect it will continue to slide for the near future, perhaps several decades, until it <br />has reached ameta-stable configuration. Following quiescence, it will undoubtedly <br />experience repeated episodes of rejuvenation as it is influenced by normal <br />phenomena such as high precipitation events and lateral erosion of the adjoining <br />river channel meander bend. <br />In my opinion the remaining concern is the implications of this landslide for the <br />health and safety of the public and the quality of the environment of the affected <br />reclaimed Bear No. 3 Mine. As Jubenville and Rold related in their memorandum of <br />June 11, 1998, summarizing a meeting I attended, I believe it would be appropriate <br />