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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />, II <br />I <br />I <br />I <br />I <br />I <br />II <br />I <br />I <br />I <br />I <br /> <br />o Site B, Downstream Site - The downstream site is about 3000 <br />feet downstream of the upstream site where the canyon becomes <br />considerably narrower. The streambed at this location is <br />about 90 feet wide and both abutments slope upward from the <br />streambed at about 1.5 horizontal to 1.0 vertical. <br /> <br />Preliminary geologic assessment indicated that with appropriate excava- <br />tion and treatment, either site would have an acceptable foundation for <br />a concrete dam. <br /> <br />B. Alternative Dam Types <br /> <br />Several alternative dam types were investigated to determine the most <br />technically suitable and the most economically favorable dam type for <br />each site. Based on site characteristics, engineering judgment and <br />previous experience, the suitable dam types were narrowed down to <br />roller-compacted concrete (RCC) gravity, rockfill, and concrete arch. <br /> <br />1. Roller-Compacted <br />layouts were made at each <br /> <br />Concrete Gravity Dam - Preliminary RCC dam <br />site for 3 different dam heights, as follows: <br /> <br />Spillway* <br />Elevation (feet) <br /> <br />Storage (acre-feet) <br />Upstream Site Downstream Site <br /> <br />8715 <br />8695 <br />8655 <br /> <br />89,700 <br />61,200 <br /> <br />97,100 <br />67,300 <br /> <br />24,000 <br /> <br />27,900 <br /> <br />* Maximum reservoir storage capacity level. <br /> <br />The various elevations were selected so that dam construction cost vs. <br />reservoir storage curves could be developed to aid in site and dam type <br />selection and in determining the most suitable dam height. The low dam <br />at the upstream site was the highest dam that could fit into the topog- <br />raphy below the left abutment ridge line. The reservoir storage of <br /> <br />3 - 2 <br /> <br />6819W/502OW <br />