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<br />II <br />I <br /> <br />I <br />I <br /> <br />I <br /> <br />~nder this option, the State .Engineer's Office will eventually require storage <br /> <br /> <br />restrictions on the dam, which may include draining the reservoir, to ensure public <br /> <br /> <br />safety. These restrictions would become severe enough to essentially eliminate any <br /> <br /> <br />useful yield from the reservoir, Under this option, dam deficiency issues are not being <br /> <br /> <br />addressed. Costs are negligible. <br /> <br />I <br /> <br />Option 2 - Continue Current Practice of Limited Slab Replacement <br />Continue the current program of replacing an average of 100 feet of slabs each <br />year, based on 155, eight-foot wide slabs replaced from 1988 through 1999. An <br />improved slab desi9n and installation method would be utilized. Specific design issues <br />would include concrete design for performance in an adverse environment, and <br />sealing/filtering of slab joints to prevent embankment materials from piping, <br />Replacement slabs would be designed at six to eight inches thick. Concrete would be <br />obtained from a local supplier. The program would be increased to overlay somewhat <br />more than 200 lineal feet per year of the existing facing, resulting in a complete overlay <br />in approximately 50 years. The existing parapet wall would be preserved. Figure 6 <br />shows the design concept for this option. <br /> <br />I <br />I <br /> <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Based on this rate of repair, the replacement would go on perpetually, and <br />potential for failure similar to the 1999 facing failure near station 103 + 00, or worse, <br />would always be present. The dam would eventually have all slabs replaced, but with <br />an expected life span of 50 years, the slabs first replaced would be deteriorated before <br />the last slabs are constructed, requiring a new or continuing program of replacement. <br />Problems with concrete slabs include limited ability to deform with excessive dam <br />embankment movement, for example, under seismic loading condition. Additional <br />issues include the thin concrete sections which, when cracked, allow easy movement of <br />water and embankment soils to migrate through; and moderate expected life span. The <br />potential problem of seepage and piping under the existing concrete cutoff wall at the <br />base of the existing slabs is not addressed. The inadequate factor of safety for stability <br />of the existing upstream slope would not be addressed. <br /> <br />I <br />I <br />I <br />I <br />I <br /> <br />25 <br />