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4. 2 ROCK TUNNEL DISPOSAL FACILITY <br /> An investigation similar to that at the coal refuse disposal <br /> facility was performed at the site of the rock tunnel waste <br /> disposal . The facility was visually inspected and a series of <br /> compaction tests performed at the site on the same day. <br /> The visual inspection confirms that the material of the dis- <br /> posal facility has the character of a fairly good quality <br /> rockfill. It consists mostly of gravel and larger size fragments <br /> of Mancos Shale, with a very limited amount of fine fraction. It <br /> is also evident that the fill has been built according to the <br /> specification, i . e. the material was hauled to the site with <br /> trucks and then spread in horizontal layers and compacted by <br /> transporting equipment. Central portions of the facility have a <br /> very good appearance and no signs of either stability or settle- <br /> ment problems. <br /> The side slopes of the facility, however, carry frequent <br /> signs of sliding , sloughing , or mudflows. According to the in- <br /> formation obtained at the site, these surficial stability prob- <br /> lems were caused by accidental removal of the uppermost waste <br /> pile layer by dozers and by dumping this material over the crest. <br /> Because of the probable presence of snow, the surface material <br /> was close to saturated, and when pushed over the crest, it <br /> created the surficial stability problems. <br /> The compaction of the rock tunnel waste was verified by a <br /> total of nine in situ tests. As in the previous case , two tests <br /> were performed by the sand cone method , and the remaining tests <br /> were carried out with the nuclear density device. Unlike at the <br /> coal refuse disposal facility, the nuclear density device tests <br /> provided apparently satisfactory results as no organic matter was <br /> present within the waste pile. <br /> The results are presented in the Appendix of the report. The <br /> laboratory moisture and density relationship on the same material <br /> was performed and is also presented in the Appendix. Maximum dry <br /> densities of 134.5 and 135.9 pcf were determined. The results of <br /> the compaction testing indicate that compaction on the order of <br /> 90 % or slightly less was achieved in most cases. An exception- <br /> ally low compaction of 68 to 69 ; was found at locations where a <br /> locally increased moisture content was observed. Such locations <br /> probably correspond to locations were snow was mixed with the <br /> waste . <br /> The results of Lincoln DeVore and recent testings show that <br /> the maximum densities estimated in 1979 and at present coincide <br /> very closely. While maximum densities of 131.2 pcf were obtained <br /> by Lincoln DeVore , only slightly higher densities of 134.5 to <br /> 135.9 pcf were estimated at present. For this reason, it appears <br /> that the results of Lincoln DeVore triaxial testing, performed on <br /> 5 <br /> GE04ftV o CONSULTING.INC. <br />