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<br />I <br />I <br />I <br />I <br />I <br />il <br />I <br />I II <br />I <br />I I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />Typical ratios of RCC dam to arch dam unit prices for total volumes in <br />the ranges considered are 25 percent to 35 percent. An RCC dam at the <br />site would therefore be considerably cheaper and the arch dam alterna- <br />tive was dropped from consideration. <br /> <br />C. Preliminary Comparative Costs <br /> <br />Quantities for the major cost items were computed for each layout and <br />incremental costs were determined based on assumed unit prices. The <br />unit prices used were based on experience and unit prices bid for <br />similar recent projects adjusted by judgment for differing site condi- <br />tions. Total project costs are sensitive to the unit prices of RCC or <br />embankment materials because these items comprise a significant per- <br />centage of the total cost. The cost estimates were therefore prelimi- <br />nary and for comparative purposes only. <br /> <br />Preliminary comparative dam construction cost estimates for the alter- <br />native layouts are shown on Table 3-1. A 20 percent contingency was <br />included in the estimates to cover minor items which were not esti- <br />mated, uncertainties in foundation conditions, and uncertainties in <br />unit prices. The costs do not include other project costs including <br />road and power line relocations, access road construction (except for <br />the access road between the upstream site and downstream site which <br />affects the cost comparison and is included), recreation facilities, <br />interest during construction, administration, and engineering. These <br />other costs would be fairly constant regardless of the type of dam <br />selected or dam height. Figure 3-1 shows a plot of dam construction <br />cost vs. reservoir storage capacity. <br /> <br />Examination of Figure 3-1 shows that an RCC dam at the downstream site <br />is considerably cheaper than an ReC dam at the upstream site, except <br />for reservoir storage capacities of less than 25,000 acre-feet where <br />the curves appear to converge. An RCC dam at the downstream site with <br />a reservoir storage capacity of 60,000 acre-feet would cost over <br />$2,000,000 less than a similar dam at the upstream site. <br /> <br />3 - 5 <br /> <br />6819W/502OW <br />