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Pitch Reclamation Project - Sedfrnent Control Embankrnert[ November, 2002 4.2 Slope Geometry The slope geometry used in the stability models was based on the recent field survey and the as-built data found in the files at Pitch, The crest and centerline of the embankment were assumed to be as shown in existing drawings prepared by Bingham Engineering. The downstream slope of the embankment was adjusted to a 1.66H:1 V slope based on the recent survey data. In cross section, the limits of the wet area across the face of the embankment was assumed to extend horizontally back to the core of the embankment. The vertical limits of the perched water intercepted in the core during piezometer drilling falls with the limits of the wet area. Ail of the significant features noted in the field observations are within the limits of the wet area. The limits of the core were assumed to be as shown in the existing as-built drawings. The typical cross section used for the stability input model is shown in Figure 3. (Note: The downstream embankment face was set at 1.66H:1 V in the input model.) 4.3 Input Parameters The sheaz strength pazameters used in the stability analyses are listed below. Analyses were L~ L~ run using both the original parameters used by Bingham Engineering and revised parameters based on field observations and the piezometer drilling data. The differences in the two sets of data aze the reduced values of shear strength of materials in the intervals impacted by the seepage through the core. The phreatic surfaces in the analyses were set to represent estimated design conditions, and ]ow and high perched water levels recorded in the piezometers. Table 1 -Original Input Parameters Materla! Ycmoi~t> - Pcf Ycsaft - pcf tp' -degrees c' - psf Zone 1 - 142 29 920 Zone 2 - 144 39 0 Zone 3 - 139 39 0 Zone 4 - 130 30 300 Zone 1 -Core material, compacted clayey sand and clayey gravel (SC/GC Zone 2 -Upstream shell, compacted weather sandstone (GM/GP} The Homestake Mining Company The Glasgow Engineering Group,lnc.