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" 'G~-~e!, !J.e VI' . : (3) Inundation of 6.5 miles of trout fishery and high quality river scenery by a reservoir having a maximum depth of 200 feet at the dam. (4) Increases in turbidity to the stream below the damsite during construction. C. Alternatives to the Proposed Action There are four major alternatives to the selected plan that_ have been studied. All alternatives were considered On an economic basis, primarily, and one alternative also considered environmental factors in the final decision. Evaluation of alternatives must consider that Crystal Dam with a powerplant has been included in the project plan as an integral feature of the total Curecanti Unit; thus, certain expenditures have already been made at the completed Blue Mesa and Morrow Point Dams to maximize the economic returns on power generation and river regulation, assuming that Crystal Dam and Power plant would be constructed. There are alternatives for some of the incremental parts of the proposed action such as the amount of channelizing and powerplant capacity. Factors affecting the selection of the powerplant capacity include the natural head available at the selected plant site and the power head that may be made avail- able by lowering the tailwater with excavation of the down- stream channel. The anticipated revenues from power sales were compared with estimated construction costs at the various heads. The studies were made over a range of no excavation in the channel to excavation sufficient to develop the maximum power head that is possible within physical limitations of the site. The final selection was based on a plan which required the minimum amount of channel excavation and still produced an economical power development. The plan would reduce the amount of excavation time in the channel and associated construction costs should be lower. The four alternatives to the proposed action on Crystal Dam are: (1) to construct Crystal Dam as an earthfill structure, which was the subject of the March 4, 1971, Environmental Statement; (2) to build a concrete dam and powerplant without any extra channelization in the river below; (3) to build a concrete dam without any powerplant, which would provide a reregulating reservoir so that Morrow. Point could be operated efficiently; and (4) not to construct Crystal Dam or powerplant and permit Morrow Point to operate at less than its rated capacity. Consideration was also given to construction of an underground powerplant at the site to meet National Defense suggestions, but this was eliminated because it would add ap- proximately $1 million to the construction cost.. 15