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t-� <br /> ❑ <br />0 <br />�� <br />The above data were used for inputs in the HEGHMS computer program developed by the <br />Army Corps of Engineers (COE)[2008]. A 20% reduction was used for the general storm based <br />on the basin elevation, per SEO regulations. Table 5 lists the storm inflow volumes and inflow <br />rates. The hydrology calculations are included in Appendix C. <br />2. Spillway Sizing <br />' The spillway for dam Alignment 1 is routed through a saddle on the south side of the reservoir, <br />as shown in Figure 7. For dam Alignment 2 the spillway is incorporated into the dam near the <br />center of the crest, as shown on Figure 8. Spillway flows will enter a stilling basin located at the <br />' foot of the dam where energy is dissipated prior to discharging water into the unnamed drainage <br />for Alignment 1, or Sink Creek for Alignment 2. <br />� <br />�J <br />� <br />❑ <br /> I' <br /> I, <br />��J <br />� <br />� <br />In order to size the spillway, both PMFs described in the previous section, were routed through <br />the reservoir. The routing was performed for both dam alignments. The COE HEC-HMS <br />program was used to route general and local PMP storm events (described above) through the <br />reservoirs. Table 5 presents the results of the routings. As shown in Table 5, the general storm <br />controls for both reservoir sizes. <br />For dam Alignment 1, a 50-ft wide spillway is estimated to pass the PMF. T'he capacity of the <br />50-ft spillway is estimated at 1,600 cfs with approximately 5 feet of head on the spillway crest, <br />resulting in five feet of residual freeboard. Dam Alignment 2 requires a 100-foot-wide spillway <br />with a capacity of 5,000 cfs with four feet of residual freeboard. The additional required <br />spillway capacity for Alignment 2 is due to the less attenuation from a smaller reservoir. <br />Additional analysis of the PMF and spillway design will be necessary if this project is taken <br />through final design. <br />Table 5. PMP Hydrology and Routing Summary <br />Storm-Dam Peak Intlow Inflow Spillway Maximum Peak <br />Alignment (cfs) Volume (a� Crest Length Reservoir Outflow <br />(ft) Water (cfs) <br />Surface El. <br />Local-1 8,825 6,300 50 4992 500 <br />Local-2 8,825 6,300 75 4994 2,175 <br />General-1 10,900 19,700 50 4995 1,600 <br />General-2 10,900 19,700 100 4996 5,000 <br />' <br />I AECOM <br />' <br />35 <br />2/22/10 <br />