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<br />3. Rockfill with Concrete Face <br /> <br />As in the other rockfill design, all overbur- <br />den and loose material would be removed from the <br />full base width of the dam. The dam itself would <br />be comprised of a rockfill section with upstream <br />and downstream slopes of 1.3 horizontal to 1 ver- <br />tical. The rockfill would vary in gradation <br />with the most coarsely graded rock in the down- <br />stream section and a finer, well graded layer <br />directly beneath the concrete face. An inter- <br />mediate zone would separate the coarse and fine <br />graded rockfills. The upstream face would have <br />a concrete slab which would vary in thickness <br />from a minimum of 6 inches to 12 inches at the <br />maximum section. The crest width is 15 feet <br />and is protected from wave runup by as-foot <br />high coping wall. A concrete cutoff wall at the <br />upstream toe would act as a grout cap for the <br />foundation grout curtain. <br /> <br />! <br />1 <br /> <br />1 <br />J <br /> <br />4. Concrete Arch <br /> <br />The concrete arch dam would extend to solid <br />bedrock on each abutment with a continuous foun- <br />dation on bedrock. A grout curtain would be <br />provided the full length of the dam. Additional <br />foundation preparations would be provided as <br />deemed necessary after excavation. The arch is <br />a simple single curvature arch with a vertical <br />upstream face and a 1 horizontal to 5 vertical <br />downstream face. <br /> <br />C. Comparative Cost Estimates <br /> <br />Cost estimates were prepared for the four differ- <br />ent types of dams. The costs include preliminary <br />investigations, which are the same for each dam, as <br />is the cost of the spillway. Also included is the <br />cost of engineering and construction management, <br />which is based on a percentage of the total cost. <br /> <br />The cost of the different types of dams is esti- <br />mated as follows: <br /> <br />~~j <br />.~ <br /> <br />Earthfill Dam with Impervious Core: <br />Rockfill Dam with Impervious Core: <br />Rockfill Dam with Concrete Face: $ <br />Concrete Arch Dam: $ 1,450,000 <br /> <br />$ 750,000 <br />$ 725,000 <br />781,000 <br /> <br />A breakdown of these costs can be found on the <br />following Summary Comparison (Table VII) and on the <br />itemized cost estimate sheets (Tables VIII A thru D). <br /> <br />-31- <br />