C153604 Feasibility Study - Laserfiche WebLink

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. . Geotechnical investigations were performed by Kumar & Associates, Inc, (Kumar), on Dam No, 4 In 1990, These Included excavation of several test ptts, construction of four exploratory test holes adjacent to the outlet conduits; and together wtth Wheeler, a full length inspection of the interior of the outlet condutts and the reservoir control gates, Drill (test) holes were extended into bedrock and cased wtth slotted PVC pipe for continued use as piezometers, The water level in the lower piezometers was found to be about 22 feet below the crest of the embankment fill, corresponding to elevation 3695, This level corresponds to a layer of sand and gravel which was revealed during the test hole drilling. The reservoir level at the time of measurement was elevation 3706, . . . A report prepared by the State Engineer describes the condttions of the outlet condutt and control gates, This report is presented in Appendix H, The geotechnical report for Dam No, 4, prepared by Kumar Is presented in AppendiX I. . Mapping at a scale of 1.0 inch to 100 feet has been prepared for all four dam embankments, The mapping was prepared from aerial photographs dated May 1987, A 1-inch to 20-feet scale map has been prepared for Dam No, 4 in the vicinity of the outlet works, This map was based upon the May 1987 aerial photography mapping and supplemented with ground data points from a 1990 field survey. . Desian Several alternate design concepts for the outlet condutt and Dam No, 4 repairs were evaluated, The alternatives ranged from relining the outlet conduits with shotcrete, rebuilding the control gates and installing a filter blanket and stabilizing berm on the embankment (Alternative A), to a complete replacement of the outlet condutt, control tower, gates, and adjacent embankment fill (Alternative F), The major features of the various alternatives are described in Table 10, Generally speaking, Alternatives A, Band C focus primarily on repair of existing faciltties while Alternatives 0, E and F focus on major component replacement. Construction quanttties and order order-of-rnagnttude cost estimates were prepared which address the major components in each alternative. These are presented in Tables 11 and 12 for Alternatives A, B, C and 0, E, F, respectively. . . . 15 .