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<br />Raising and extending the existing ring levee protecting southwest <br /> <br /> <br />Platte Center against flooding from Shell Creek "ould provide a <br /> <br /> <br />feasible solution for some of the residencs, however. The levee <br /> <br /> <br />alignment considered for this alternative is shown in figure 5, The <br /> <br /> <br />design used to develop the cost estimate was based on the surveyed <br /> <br /> <br />June 1990 flood high-water mark at the pumphouse plus 3 feet of <br /> <br /> <br />freeboard, resulting in an average levee height of 7 feet. The cost <br /> <br /> <br />of this levee is estimated at $102,700, with total annual costs and <br /> <br /> <br />benefits of approximately $8,990 and $10.210, respectively. The <br /> <br /> <br />resulting benefit-cost ratio is 1.14, A breakdown of che cost <br /> <br /> <br />estimate is shown in appendix C. <br /> <br />DIVERSION <br /> <br />,h <br />" <br /> <br />A structure to divert Elm Creek floodflows north and west of town <br /> <br /> <br />to Shell Creek "as also evaluated. The cost of over $831,000 and <br /> <br /> <br />corresponding benefit-cost ratio of only .63 make this a1ternacive <br /> <br /> <br />economically infeasible. Quantities used to obtain this cost estimate <br /> <br /> <br />are located in appendix C, <br /> <br />Ml1[ <br /> <br />A dam on a tributary north of Platte Center was' considered. <br />Unf~rtunately, it is not likely that a dam ~apable of eliminating the <br />.' <br /> <br />flood" hazard could be constructed for lEis~. .than $500.000 Which is <br /> <br /> <br />necessary in order to have a benefit-cost ratio of 1. 0 or greater. <br /> <br /> <br />As a result, a dam was considet'ed Co be an economically infeasible <br /> <br /> <br />alternative if Platte Center benefics only are concerned. Detailed <br /> <br /> <br />costs for this alternative were not developed. <br /> <br />- <br /> <br />22 <br />