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' This material appeared to be hydraulically-placed fill. Above this, another dam raise was placed to <br />the present crest elevation of the dam (Elevation 7,340.2). <br />' Cross-Section C is located parallel to and about 132 feet south-southeast of Cross-Section B. It cuts <br />' through two soil borings in which three nested piezometers were installed in each borehole <br />(Appendix A). One is located on the crest (SB-06-03) and the other is located on the bench making <br />up the left abutment (SB-06-04). Bedrock depth is assumed to be horizontal and about 150 feet <br />' below the crest at an elevation of approximately 7,190. This assumption is based on information <br />provided in Western Engineers (1993). As in Cross-Section B, colluvium is found above the bedrock <br />' to an elevation of 7,315.3, above which a thin layer (about 2.5 feet) of soft sediment and the <br />accompanying starter dam on the downstream face were included in the model. Finally, the more <br />recent dam raise was included to the crest elevation (Elevation 7,340.2). <br />The colluvium at Cross-Section C is separated into three layers: Upper Colluvium, Failure Surface <br />Material, and Lower Colluvium. The extent of the failure surface material at Cross-Section C was <br />delineated by inclinometer readings, boring log descriptions, and an abrupt increase in blow counts. <br />Because it appears to be the contact between the weaker upper colluvium and the stronger lower <br />colluvium, it could also be called a "transition zone". It ranges in thickness at this cross-section from <br />about 10 to 13 feet. The failure surface material was not modeled at Cross-Section B because <br />inclinometer and visual observations have not indicated that the landslide mass is present at Cross- <br />Section B. These colluvium layers are considered to be one material type in the seepage analysis. <br />8.1.2 Parameters <br />The main parameter associated with materials relevant to the seepage analysis is the hydraulic <br />conductivity. In geotechnical practice, however, the term permeability is used to describe the same <br />parameter, and that term is used in this report. Table 3 summarizes the permeability values used for <br />seepage modeling at Monument Dam. These properties have been obtained from laboratory testing <br />and seepage model calibration. <br />P:\Mpls\06 CO\26\0626067\WorkFiles\DesignReport\FINAL\DesignReportFINAL.doc 19 <br />