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<br /> <br />STATE OF iii iuiiiiiiiiii iii <br />999 <br />COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Deparlmenl of Nalu ral Re50urCe5 <br />1313 Sherman SL, Room 215 ry <br /> <br />Denver, Colorado 80203 ~ <br />~~ <br /> <br />Phone: 1703) 866-3567 II <br />FA% (3031 ft32-8106 <br /> DEPARTMENT OF <br />Date: February 17 <br />1998 NATURAL <br />, RESOURCES <br />TO: Dave Berry & Mike Boulay Roy Ramer <br /> Governor <br /> <br /> <br />~L <br />v lames S Lochhead <br />.,~~ <br />FROM: Jim Pendleton Eveculwe Director <br /> Michael B. Long <br /> Drvivon Direcbr <br />RE: Bear III ine Lan tde <br />I have completed a review of the report submitted by Wright Water Engineers, authored by Jolm <br />Rold and David Jubenville, PE, on behalf of Mountain Coal Company (MCC). 1 have also <br />examined stereographic aerial photography of the site and adjacent area. Finally, 1 have visited <br />the site to examine the landslide and surrounding terrain in the company of Bruce Stover, Susan <br />McCannon, and the two of you. Bruce has assisted me by providing observations regarding the <br />geotechniques and geomorphology of the landslide. WWE's report was prepared and submitted <br />in response to an NOV issued by the Division, which alleged that the landslide was caused by <br />hydration of the hillslope resulting from the sumping of water by MCC. Our consideration of the <br />landslide has focused primarily upon the geotechnical characterization of the landslide and the <br />geomorphology of the hillslope. <br />Geotechnical Characterization of the Landslide <br />The landslide involved the mobilization of the colluvium overlying bedrock. The landslide mass <br />is bounded up slope by an extensional graben-type trough. This [rough exposes an uphill <br />headscarp which is an extension of the original Bear III mine portal cut slope, immediately to the <br />east. Examination of the extensional trough determined that the C-Seam coal is exposed near the <br />base of the uphill scarp of the trough. Moist, warm air with a distinct organic coal odor is <br />venting from the base of the through, presumably from the C-Seam subcrop and adjacent <br />workings. Sufticient moisture has been contributed to the colluvium exposed within the <br />extensional trough to render it pliable, even saturated, in some locations. In places Bruce and 1 <br />sunk to our shins in the mud. This moist condition is limited to the eastern half of the <br />extensional trough, approximately 75 feet in length. The western half of the extensional trough <br />slopes upward and is characterized by dryer colluvium. Further, the invading moisture (humid <br />air and water) are sufficiently warm to prevent the wet to saturated colluvium from freezing. <br />Clay in the colluvium immediately down slope from the western-most backfilled Bear [It mine <br />portal is also moist and pliable, suggesting moisture venting from the portal drain. <br />The majority of [he landslide's surface appears dry. No springs are evident on the landslide mass <br />proper. One warnr (approx. 85 ° F.) spring has flowed continually since November 17, 1997, two <br />