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• 1993 INVESTIGATION <br />The 1993 slump was much more extensive than the 1988 or 1989 <br />slumps. The slope failure involved both cover material and some <br />underling waste material. The unstable material slid down from the <br />bench face to the lower bench. The failure exposed a fairly <br />significant amount of underling waste material. At least two <br />sources of water were evident in the exposed waste material.. <br />A less extensive failure to the north of the main slump also <br />occurred in the location of the 1988 failure. This area has a <br />large scarp and a bulge in the cover material below the scarp. <br />The discovery of a source of water in the waste material <br />contradicts the failure theory of the 1988 and 1989 slumps. Both <br />the prior slumps were probably caused by a source of water in the <br />waste material, not by the theorized cause, which was the cover <br />material being saturated from spring snowmelt and rain. <br />The source of water in the waste material does not appear to be <br />consistent. The bench was stable during 1986, 1987, 1990, 1991 and <br />1992. The wet winter and spring of 1993 supplied adequate water to <br />cause a failure. A substantial amount of wet snow and rain that <br />occurred after the failure eroded additional waste material from <br />the slump area. <br />• The wet winter and spring of 1993 caused numerous slides in the <br />area of the Blue Ribbon Mine. The road to the mine was closed by <br />a slide. A slide occurred at Somerset's old fan location along <br />Hubbard Creek. Numerous slides occurred along the north facing <br />slopes, south of the North Fork of the Gunnison River, from the <br />Town of Somerset to the east. The Bear No. 3 Mine access road was <br />closed temporarily by a slide. One massive slide closed the new <br />state highway for a number of weeks. The winter and spring of 1993 <br />was unusually severe with respect to causing previously stable <br />slopes to become unstable. <br />1993 REPAIR PLAN <br />The theory of the 1993 repair plan is the same as previous plans, <br />to give the source of water a path of relief. It is believed that <br />two primary problems were associated with the prior repair plans as <br />follows: <br />1) The source of water in the waste material was not identified <br />and given an escape path; and <br />2) The geotextile fabric, which was wrapped around the four inch <br />perforated pipe, probably became plugged by the clay cover <br />material. <br />• <br />113vii (Rev. 06-25-93) <br />