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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />3111H <br />active. Any future studies of the Canyon site, however, would have to address <br /> <br />these faults in more detail than provided by the scope of this study. <br /> <br />Excavation of the side channel spillway cuts might present problems of <br />stability because of the landslide on the left abutment. Future site <br />investigations would have to characterize this slide in more detail. <br /> <br />Adequate construction material s are located within a short distance of the <br />damsite. All uvi al sand and gravel suitabl e for RCC aggregate, conventi onal <br />concrete, filter and drain material, or shell material for an embankment dam, <br />is avail able in the fl oodpl ai n inunedi ately upstream and downstream of the <br />dam. In addition, terrace gravels are being explored in commercial pits a few <br />miles downstream of the site. Impervious core material is available from two <br />downstream sites within one mile of the dam axis on either side of the river. <br /> <br />The reservoi r fonned by Canyon Dam is not expected to present any probl ems in <br />regard to penneability or slope stability. <br /> <br />The embankment dam alternative at the Canyon site is slightly less expensive <br />than Warner Point for the 50,000 acre-feet reservoir, slightly more at 150,000 <br />acre-feet and equal at 300,000 acre-feet. The estimates are so close, that <br />within the accuracy of this level of design and cost estimate, the Canyon and <br />Warner Poi nt embankment dams can be considered equal at all three hei ghts <br />studied. Unlike Warner Point, however, the dam axis at the Canyon site cannot <br />be adjusted with the height of dam to optimize costs. The RCC dam alternatives <br />at Canyon Dam are all about 30 percent higher than at Warner Point. <br /> <br />Powell Park Dam <br />The single most favorable natural topographic feature at the Powell Park Dam <br />site is the 200-foot-hi gh verti cal cl iff on the 1 eft abutment that gi ves way <br />to a nearly flat bench over 800 feet in width. The bench is capped with 10 to <br />25 feet of terrace deposits but provides an excellent location for an <br />inexpensive side channel spillway in conjunction with an embankment dam. The <br />cliff is at its highest at the location investigated in this study and, at <br />that point, is most favorable for the largest reservoir size. For the smaller <br />reservoi r capaciti es, a centerl i ne further downstream mi ght be more <br /> <br />E-11 <br />