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<br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />I <br />I <br /> <br />Option 3 - Improved Program of Slab Replacement <br />Develop and implement an enhanced program of concrete slab replacement. <br />Specific design issues would include concrete design for performance in an adverse <br />environment, and sealing/filtering of slab joints to prevent embankment materials from <br />piping. Replacement slabs would be designed at a thickness of six to eight inches. <br />Included in the first year construction would be the construction of a toe <br />foundation/seepage cutoff wall at the upstream toe of the dam. This wall would serve <br />as a seepage cutoff wall and also as a footing for future slab construction. The <br />concrete would be obtained from a local concrete supplier. The first year construction <br />would also include the construction of 2,600 feet of slab in the first year to address the <br />facing areas with the most significant potential for problems. The slab replacement <br />program would be accelerated by placing approximately 1,000 feet of slab per year for <br />the next 9 years, completing the project in ten years. Excessive layers of existing slabs <br />would be removed where necessary to limit the number of height changes in the new <br />placement. A major program for investigating voids under the existing slabs may be <br />undertaken. This program could include drilling into the slabs and probing for voids. If <br />voids were encountered, the site would be further explored. It is expected that the <br />voids would be grouted, but in some cases it may be necessary to entirely remove the <br />existing slabs. The existing parapet wall w.ould be .preserv"ld. Figure 6 also shows the <br />design concept for this option. <br /> <br />I <br />I <br />I <br /> <br />I <br />I <br />I <br />I <br />I <br />I I <br />I <br />I <br /> <br />This option would address safety issues within ten years by overlaying the <br />existing embankment facing with all new concrete facing. It is expected that to <br />perform this project in one season would adversely impact the late irrigation season use <br />of water by requiring early draining of the lake, or impact the early storage season for <br />water storage by extending the construction through the winter, or both. Problems <br />with concrete slabs include limited ability to deform with unusual dam embankment <br />movement, thin sections which when cracked allow easy movement of water and <br />embankment soils to migrate through, and moderate expected life span. These <br />problems are not addressed with this option. The potential problem of seepage. and <br />piping under the existing concrete cutoff wall at the base of the existing slabs is <br />addressed with the new slab foundation toe. The inadequate factor of safety for <br /> <br />26 <br />