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3-3 <br />• portion of the slurry wall pad during the initial excavation period. The <br />backhoe produced a finished excavation approximately four feet vide. No <br />slurry was placed in the trench at this location since the trench walls were <br />stable with no inflow of seepage. The trench from 0+00 to 0+50 was left empty <br />and the backhoe was moved to the east abutment to continue trenching. <br />The slurry wall was originally planned to end at Station 4+00 on the east end, <br />but was extended approximately 30 feet into the east abutment in an effort to <br />provide a better cut-off. As the excavation progressed from east to west, the <br />trench became unstable with seepage inflow noted. Bentonite was pumped from <br />the holding pond to the excavated trench to support the excavated trench <br />walls. Excavation proceeded along the total length of the slurry wall pad. <br />Hard, competent rock, indicated by backhoe refusal, formed the base of the <br />slurry wall along its total length. Maximum depth of the slurry wall was at <br />Station 2+60 to an approximate elevation of 8811 feet. The as-built cross <br />section of the slurry wall is shown in pigure 2. <br />• After trench excavation over a certain length, excavated soil vas mixed with <br />bentonite and placed back into the trench. The result vas a highly imperme- <br />able mixture with an estimated permeability in the range of 10-g to 10 9 <br />cm/sec. Filling proceeded until the slurry vas at the same elevation as the <br />top of the excavation, approximate elevation 8841 feet. The backfill wall vas <br />then capped with approximately three feet of compacted soil along its total <br />Length. <br />During final grading, all embankment elopes and the embankment crest were <br />compacted with a dozer. The minimum elevation of the slurry wall embankment <br />crest is approximately 8844 feet. The crest has a final graded width of <br />approximately 22 feet, and the final upstream and downstream embankment slopes <br />are approximately 3:1 to 4:1, respectively. <br />A spillway was constructed along the embankment crest from approximately <br />Station 3+05 to Station 3+20 having a bottom width of 15 feet. The spillway <br /> <br />~~~~~~ <br />