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3-2 <br />Considering the difficulty the constructors had in obtaining fine soils <br />for the center of the dam, the placement of coarse materials in the <br />outer portion of the dam was likely. Observation of piezometric <br />pressures within the embankment as discussed in Section 3.3 further <br />support this concept. <br />Based on information presented in the as -built drawings, the chimney <br />drain and blanket drain are apparently located between the core and <br />downstream shell and beneath the downstream shell, respectively. <br />Borings were not advanced through the drains nor were samples taken. <br />The assumption was made that the drains are constructed in the location <br />as specified and with material meeting design specifications. The <br />drains were included in the model at locations shown on as -built <br />drawings. <br />3.1.3 Hydrologic Parameters <br />The central portion of the embankment model was assigned a permeability <br />of 5 x 10-5 cm/sec, based on the rising head tests discussed in Section <br />The strengths and unit weight for the embankment materials selected for <br />stability analysis are discussed in Chapter 4.0. <br />3.1.2 Geometry <br />Figures 3 8 the fill the <br />and show assumed geometry of the within <br />embankment. The geometry of the embankment slopes is basically as <br />designed. The location of the base of the dam including the location <br />and depth of the key trench, based on data provided by Homestake, is <br />essentially as shown in Section D -D' in Figure 8. Some generalization <br />of the cross section has been made to ease the assessments. Section A- <br />A' in Figure 3 shows the extent of the key trench along the axis of the <br />dam. As shown in both Figures 3 and 8 the key trench does not extend <br />completely through the alluvial soil layer and into the bedrock in all <br />places. <br />3.1.3 Hydrologic Parameters <br />The central portion of the embankment model was assigned a permeability <br />of 5 x 10-5 cm/sec, based on the rising head tests discussed in Section <br />