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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 I <br />I <br />I <br />I <br /> <br />Examination of rock cores and outcrops exposed on both abutments indi- <br />cates that the site is suitable for a concrete gravity dam. Removal of <br />overburden and weathered rock and some shaping of slopes will be re- <br />quired. Depths of excavation to an acceptable foundation level are <br />expected to average 20 feet in the streambed, 25 feet on the left abut- <br />ment, and 30 feet on the right abutment. Tests indicate that with <br />normal curtain grouting, significant leakage will not occur through the <br />dam foundation. <br /> <br />B. Diversion <br /> <br />Diversion of the stream will be through a conduit located on the right <br />side of the streambed extending between upstream and downstream coffer- <br />dams. The portion of the conduit passing under the dam will be placed <br />in a trench excavated into the rock foundation and embedded in conven- <br />tional concrete. This section of the conduit will be used as the <br />permanent outlet works conduit. After diversion, the conduit will be <br />permanently plugged upstream of the outlet works intake. A temporary <br />bypass pipe will be provided through the dam to pass required minimum <br />flows in the interim period between plugging of the diversion channel <br />and reservoir filling to the sill of the intake structure. <br /> <br />C. Dam and Spillway <br /> <br />The preliminary design of the dam, spillway, and outlet works is shown <br />on Exhibits 3-9 and 3-10. The dam will be a concrete gravity dam con- <br />structed by RCC methods with a crest at El. 8690 providing 9 feet of <br />freeboard above the normal maximum reservoir elevation. The freeboard <br />will contain the routed probable maximum flood (PMfl with discharge <br />over the 100-foot wide ungated spillway with a crest at El. 8681. Peak <br />reservoir inflow corresponding to the PMF is 50,900 cfs. Maximum <br />spillway discharge will be about 10,000 cfs with a reservoir surcharge <br />of about 8.8 feet. The dam crest length will be about 710 feet, in- <br />cluding the 100-foot ogee spillway section. <br /> <br />3 - 17 <br /> <br />6819W/502(l/ <br />