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MORRISON-KNUDSEN COMPANY,INC. <br /> istence of these clay beds should be noted during the final design of the <br /> future refuse pile. The clay layers are found to be practically impermeable. <br /> The characteristics of the ►oundation materials as estimated from labora- <br /> tory lists are shown on Table 1 .6.2.2-1 . <br /> TABLE 1 .6:2.2-1 <br /> PHYSICAL PROPERTIES OF THE REFUSE AND FOUNDATION MATERIAL <br /> Angle of Cohesion Density <br /> Material friction (deg. ) Psf cf <br /> Coal Refuse 38 250 90 <br /> Gravelly, Silty Sand 40 0 120 <br /> Sandy Clay 20 610 121 <br /> 1 .6.3 Evaluation of Stability of Refuse Piles <br /> C• 1 .6.3.1 Discussion of Results of Stability Analysis <br /> In the past, a few profiles of the existing and proposed refuse piles <br /> were analyzed for stability using assumed physical properties for the mater- <br /> ial . The results were presented in Section 1 of the report titled "Engi-. <br /> neering Evaluations, Coal Basin Mine". <br /> The same slope profiles were analyzed using the laboratory tests re- <br /> sults. The results of the stability analyses are. shown in Tables 1 .6.3.1-1 <br /> and 1 :6.3.1-2. It may be noted that the factors of safety were greater than <br /> the ones reported earlier, in most of the slope profiles. The results should <br /> be still considered somewhat preliminary as the exact slope geometries are <br /> not known due to the lack of large scale contour maps in the project area. <br /> 1-17 <br /> 1 <br />