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III. Dam and Appurtenances <br />Two dam alignments at the reservoir site identified in the Clay Report were investigated to bracket the <br />an appropriate range of reservoir sizes. The normal maximum reservoir water surface elevation for both <br />alignments was set at 4990 MSL. The capacities of appurtenant structures (spillway and outlet works) <br />were based on SEO regulations, as discussed below. Field maps prepared for site reconnaissance are <br />included in Appendix A. <br />Although the yield analysis presented in the next section includes releases for hydroelectric power <br />generation, preparation of layouts and development of an opinion of probable costs for a power plant <br />was not included in this study and, since no economic or financial analyses are included in this report, <br />no economic benefits of power generation were assessed. Future studies, if any, should address the <br />capital and operating costs of power generation versus the value of the power to be generated based on a <br />more detailed assessment of reservoir yield and the timing of power generation in relation to reservoir <br />releases made for other project purposes. Since it is currently unknown where the raw water delivered <br />from the reservoir would be used, no costs were included for these water delivery systems. Water to be <br />delivered to the Colorado River for environmental purposes were assumed to be made via Sink Creek <br />with limited improvements required for channel stability. Potential users of water delivered from the <br />reservoir for consumptive purposes including municipal, industrial and agricultural systems will need to <br />consider the routing of conveyance systems and develop their own cost estimates for delivery facilities <br />to obtain estimates of total project cost and for comparing the proposed Grand Valley Lake project with <br />other water supply alternatives. <br />The minimum and maximum active storage capacities considered in this study were 39,800 and 154,500 <br />acre-ft based on the preliminary assessment of demands as described in Section IV. <br />A. Summary of Potential Dam Alignments <br />For the reasons discussed in Section III.D, an earth embankment dam was selected for both reservoir <br />capacities and dam alignments. Figure 5, page 26, shows a typical cross section of the earth <br />embankment dam. <br />The reservoir storage volumes and embankment volumes for each alignment were developed based on <br />the USGS NED 30-meter elevation data set. Contours were interpolated for the dam and reservoir area <br />to a ten-foot interval. Figure 6, page 27, shows the elevation-capacity curve for both new dam locations <br />Alignment 1 is shown in Figure 7 on page 28 and Alignment 2 is shown in Figure 8 on page 29. A ten- <br />foot freeboard was used for both dam alignments, resulting in maximum dam heights of 144 and 199 <br />feet. Table 4, page 29, summarizes the dam configurations. <br />Embankment volumes for both reservoir alignments were also calculated using the USGS NED 30- <br />meter elevation data set and the cross section shown on Figure 11. The embankment volume <br />calculations are included in Appendix D, and are summarized for both alignments in Table 4. The <br />alignment providing a storage capacity of 154,000 acre-feet is generally the same alignment used in the <br />AECOM <br />24 <br />2/22/2010 <br />