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The final slope , not exceeding 2 (H) 1 (V) , should be <br /> strictly maintained. Terraces should be included if present in <br /> the original design. The surface of final slopes should be com- <br /> pacted to prevent erosion. <br /> The construction of the outer shell of the pile should be <br /> performed under continuous supervision of an experienced engineer <br /> of Mid-Continent's staff. Periodically, the compaction of the <br /> outer shell should be verified by in situ density measurement <br /> using the sand cone method . <br /> The surface of the pile should be vegetated as specified in <br /> the Permit Application . <br /> 5. 2 ROCK TUNNEL DISPOSAL FACILITIY <br /> The rock tunnel waste was resigned to be deposited in a <br /> facility with ou=er slopes of 2 (H) : l (V) , with two intermediate <br /> berms, 10 feet wide. The maximum height of the facility was 60 <br /> feet. The reasons for the intermediate benches are not clear. <br /> They apparently are not required for stability purposes as in- <br /> dicated by the high factor of safety, estimated by all stability <br /> analyses. There appears to be no reason to include these benches <br /> (terraces) because of erosion control , as the slopes are rela- <br /> tive:. y very low. The original design recommended to place the <br /> waste systematically in lifts and to eliminate end-dumping. The <br /> thickness of individual lifts is not to exceed 12 inches and com- <br /> paction by the placing equipment were recommended for the outer <br /> shell of the pile. <br /> '.?o specific construction and compaction methods were recom- <br /> mended for the inner part of the waste pile, except that the <br /> thickness of lifts do not exceed 24 _nches was recommended . <br /> -he original design of the rock tunnel waste disposal <br /> facility does not distinguish the stability conditions of <br /> temporary and final slopes. In our opinion , the difference be- <br /> tween temporary and permanent slopes is iinperta,nt. There is no <br /> reason to maintain slopes to 2 (H) : 1 (V) or flatzer on the tem- <br /> porary slopes. Temporary slopes are well stable at slopes equal <br /> to the angle of repose of the waste, or some 30 to 35 degrees. <br /> Our inspection and testing shows that the waste has been <br /> deposi�_ed in horizontal lifts, as specified, and it was compacted <br /> to an acceptable degree. The only exceptions are locations where <br /> high moiscure content of the fill , probably prompted by recent <br /> snowfall , results in less satisfactory compaction. In view of the <br /> good quality of the rockfill and the extremely conservative <br /> 7 <br /> GEO,HYM CONSULTING,INC. <br />