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VII. PRELIMINARY EVALUATION OF ALTERNATIVES Evaluation of the three alternatives are based on the criteria developed in Section III. These include hydraulic impacts on the functioning of the Hartland diversion and floodplain; fish passageway operations over a range of flows; fish swimming ability; and fish behavior. In addition, the associated construction costs and maintenance requirements are also addressed for each alternative. 7.1 Hydraulics The potential hydraulic impact on the floodplain and the ability for the Hartland diversion to operate without impact from the proposed alternatives is evaluated in this section. To perform this evaluation, the alterations to the system represented by each alternative are input into the HEC-RAS model. For Alternatives I and II, the model changes include reduction of the flow in the main channel due to the flows being diverted into the ladders and attractive flow. For Alternative III, the model changes take the form of altered cross sections to represent the cutoff walls and passage chutes constructed in the main channel. All three alternatives are analyzed for flows ranging from 350 cfs to 21,200 cfs, representing the August low flow (90% exceedence) to 100-year peak. All three alternatives are also analyzed with an additional 10 cfs being diverted at the Hartland headgates to accommodate the fish screen by-pass channel. Table 7.1 summarizes the results of the hydraulic analysis for each alternative and compares the water surface elevations with existing conditions. In Table 7.1 the column with elevation changes represents the new elevations subtracted from water surface elevations under existing conditions. Flow characteristics in the ladders for each alternative are presented in Table 7.2. Detailed HEC-RAS information is provided in Appendix E. 31 I I I I I I I I I I I I I I I I I I I