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r ,. i . 2 Although the proposed Ridgway powerplant is not the peaking power type addressed in the Peaking Power Status Report, the report still documents the need for increased power supplies through base load plants. Conservation measures that may be instituted in the next 20 years 'co'uld reduce the pro- jected market, but not enough to negate the demands of increased population and development. And if the increases are to be met, the use of hydropower is preferable to nonrenewable fossil fuel supplies or other alternatives which are cost prohibitive, in early stages of development, or otherwise infeasible. An environmental assessment evaluating the various power development alternatives was prepared and distributed for public review in November 1980. Comments were received from three Federal and four State agencies. The only significant issues that arose during the review process were concerns that two of the power alternatives presented (a single unit producing power for six months and a single unit for peaking power) would have significant adverse effects on fish and wildlife. These alternatives are no longer considered viable and are not discussed in this assessment. C. Need for Outlet Works Design Change The Bureau believes that a design change in the outlet works should be considered for several reasons. The dual outlet concept presented in the FES and required in the 404 water quality construction permit is no longer thought to be an efficient and cost effective method of water quality enhance- ment. Recent water quality studies simulating heavy metals concentrations and temperatures at Ridgway indicate the dual outlet proposal will not provide the environmental benefits originally sought, and may in fact cause detrimental impacts in the form of increased reservoir stagnation and eutrophication. In addition, it is now known that reservoir drawdown between September and November will render the upper outlet inoperable. Other reasons for considering design changes are that the dual outlet is more costly to build and operate than a single outlet, it poses certain functional problems and provides a path for seepage through the dam embankment. D. Changes in the FES In addition to the need for changes in the outlet design and the powerplant addition, several other changes have occurred in the project since the Dallas Creek FES was published. The spillway for Ridgway Dam has been moved from the left to the right dam abutment and spills will be reduced 31,200 acre-feet through implementation of recently acquired flood-control forecasting systems.