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iii iiiiiiiiiiiii iii <br />STATE OF CULUI~AUO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resuurces <br />111 1 Sherman $s , Ruom ? 15 <br />Denver, Colorado 8U'03 <br />Rhunc: 111131 Hbh-35fii <br />FAX: 1 SO {7 ft {'_ N106 <br />Date: February 17, 1998 <br />TO: Dave Berry & Mike Boulay j , <br />r~, ~ ;~ <br />FROM: Jim Pendleton ~~.. <br />~/ <br />RE: Bear III. iA'1 ne Lan tde <br />~~~ <br />DEPARTMEfVT OF <br />NATURAL <br />RESOURCES <br />Roy Romer <br />Governor <br />lames 5. Lochhead <br />Executive Director <br />Michael B Long <br />Division Direcbr <br />I have completed a review of the report submitted by Wright Water Engineers, authored by John <br />Rold and David Jubenville, PE, on behalf of Mountain Coal Company (MCC). I have also <br />examined stereographic aerial photography of the site and adjacent area. Finally, I 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. W WE's report was prepazed 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 Bumping of water by MCC. Our consideration of the <br />landslide has focused primazily upon the geotechnical chazacterization 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 trough 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 neaz 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. Sufficient 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 westem 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 westem-most backfilled Bear l[I mine <br />portal is also moist and pliable, suggesting moisture venting from the portal drain. <br />The majority of the landslide's surface appears dry. No springs are evident on the landslide mass <br />proper. One warm (approx. 8~° F.) spring has flowed continually since November l7, 1997, two <br />