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III IIIIIIIIIIIIIIII STATE OF CO~U1~yU DIVISION OF MINERALS AND GEOLOGY Depanmenl of Nawral Resources 111 1 Sherman SL. Room 275 ll~~~ Denver, Cohuarlu 80?U3 I F'honc: 13111) Hfih~356% FA%:17011 fl32-K I Ofi DEPARTMENT OF Date: February 17, 1998 NATURAL RESOURCES TO: Dave Berry & Mike Boulay I Roy Romer ~}-~- Governor ICy ~ ~( %~ Wmes 5. Lochhead FROM: Jim Pendleton '" E.ecwive Director ht¢h.~el B. Lony Divivon Dneclor 12E: Bear III. ine Lan tde 1 have completed a review of the report submitted by Wright Water Engineers, authored by John Rold and David Jubenville, PE, on behalf of Mountain Coal Company (MCC). I have also examined stereographic aerial photography of the site and adjacent area. Finally, I have visited the site to examine the landslide and surrounding terrain in the company of Bruce Stover, Susan McCannon, and the two of you. Bruce has assisted me by providing observations regarding the geotechniques and geomorphology of the landslide. W WE's report was prepazed and submitted in response to an NOV issued by the Division, which alleged that the landslide was caused by hydration of the hillslope resulting from the Bumping of water by MCC. Our consideration of the landslide has focused primarily upon the geotechnical characterization of the landslide and the geomorphology of the hillslope. Geotechnical Characterization of the Landslide The landslide involved the mobilization of the colluvium overlying bedrock. The landslide mass is bounded up slope by an extensional graben-type trough. This trough exposes an uphill headscarp which is an extension of the original Bear 111 mine portal cut slope, immediately to the east. Examination of the extensional trough determined that the C-Seam coal is exposed near the base of the uphill scarp of the trough. Moist, warm air with a distinct organic coal odor is venting from the base of the through, presumably from the C-Seam subcrop and adjacent workings. Sufficient moisture has been contributed to the colluvium exposed within the extensional trough to render it pliable, even saturated, in some locations. In places Bruce and I sunk to our shins in the mud. This moist condition is limited to the eastern half of the extensional trough, approximately 7~ feet in length. The westem half of the extensional trough slopes upward and is characterized by dryer colluvium. Further, the invading moisture (humid air and water) are sufficiently warm to prevent the wet to saturated colluvium from freezing. Clay in the colluvium immediately down slope from the western-most backfilled Bear 111 mine portal is also moist and pliable, suggesting moisture venting from the portal drain. The majority of the landslide's surface appears dry. No springs are evident on the landslide mass proper. One warm (approx. 8~° F.) spring has flowed continually since November 17, 1997, two