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(9) The final configuration of the fill shall be designed to minimize erosion. Terraces <br /> may be utilized to control erosion and enhance stability if approved by the Division <br /> and consistent with 4.14.2(2). <br /> 4.09.4 Durable Rock Fills <br /> (5) The top surface of the completed fill shall be graded such that the final slope <br /> after settlement will be no steeper than 1v.20h (5 percent) toward properly designed <br /> drainage channels constructed in undisturbed ground along the periphery of the fill. <br /> Surface runoff from the top of the surface of the fill shall not be allowed to flow over <br /> the outslope of the fill. <br /> The only specification for temporary slopes is that of 4.09.1 (7) that "spoil or waste shall <br /> be hauled or conveyed and placed in horizontal lifts in a controlled manner, <br /> concurrently compacted, as necessary to ensure mass stability and prevent mass <br /> movement. . ." <br /> Permit <br /> The most current study of the pile was done by Geo-Hydro in 1984. The study <br /> included a review of previous studies, including the Morrison-Knudsen Co.'s Refuse <br /> Disposal Study (1977) and the Lincoln DeVore's Slope Stability Analysis, Mid-Continent <br /> Tunnel Project (1979), as well as a review of construction practices. <br /> As indicated in the Operations Description (p. 47): <br /> Geo-Hydro recommended that while there was no apparent need to try to achieve <br /> compaction at temporary slopes, the permanent slopes should be built withy a slope of <br /> 2 (H):1(V) and compacted. <br /> The focus of the Geo-Hydro study was the stability of the pile, and recommendations as <br /> to construction of the pile for the sake of stability, final slopes and compaction. <br /> In our opinion, the difference between temporary and permanent slope is important. <br /> There is no reason to maintain slopes to 2 (h):1(V) or flatter on the temporary slopes. <br /> Temporary slopes are well stable at slopes equal to the angle of repose of the waste, or <br /> some 30 to 35 degrees <br /> Geo-Hydro's conclusions: <br /> We recommend that the existing slopes of the pile are classified either as temporary or <br /> as final. We do not see any need to try to achieve compaction at temporary slopes. <br /> On the other hand, we feel that the permanent slopes should be built with due care. <br /> They should be built at the design slope of 2(H) : 1(V) and compacted as specified. <br /> End-dumping or pushing the material across the crest should be avoided. <br /> 2 <br />