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<br />. <br /> <br />6 <br /> <br />One way to prevent this problem is to permanently trap the metals <br />in settled reservoir sediments with a system of mechanical aerators. This <br />method of control has been tried with satisfactory results at a number of <br />lakes and reservoirs.ll Aeration would maintain minimum oxygen levels at <br />the bottom of the reservoir and inhibit release of heavy metals under anaerobic <br />conditions. This would substantially improve reservoir water quality and <br />. 6 <br /> <br />Aeration is a contingency for any of the other alternatives and is <br />relatively inexpensive. Major equipment includes a 6.0-Rp compressor, controls, <br />and a 4-inch diameter pipe discharging air above the reservoir bottom. The <br />pipe would be supported by approximately 35 steel structures mounted on <br />concrete pads. The greatest need for aeration would occur in the dual outlet <br />alternatives during times of high releases and late summer stagnation. Dual <br />outlet aeration is very expensive due to the increased volume of water and <br />length of time needed to aerate it. Aeration with a single level outlet is <br />less likely to be necessary due to the natural flushing action of water <br />traveling through the reservoir (cooler bottom water is released and fresher <br />aerated water is pulled downward, lessening the eutrophication and dissolved <br />oxygen problems). <br /> <br />R. Tabular Comparison of Alternatives <br /> <br />Table 1 summarizes the various alternatives. The multi-level <br />plan is the most expensive at $21.1 million, then the dual system at $11.2, <br />and single level at $9 million (January 19a1 costs). The addition of aeration <br />to any plan would increase costs by $260,000. Minimum streamflows and the <br />25,000 acre-foot reservoir pool established for recreation and sediment <br />retention would be maintained under all alternatives. Average water surface <br />area would vary an average of 26 acres or a maximum of 8 percent between the <br />power and no-power alternatives. An annual reduction in recreation benefits <br />of $18,000 would result from any of the power alternatives. <br /> <br />I. Environmental Considerations <br /> <br />The powerplant would be designed to be compatible aesthetically with <br />its surroundings. The transmission line would avoid recreation areas and <br />blend with the natural landscape as much as possible. Single pole powerlines <br />would be constructed to prevent electrocution of large birds of prey. <br /> <br />Environmental measures to protect water and air quality, cultural <br />resources, soils, and vegetation would continue from the present construction <br />activity. Clearing for any transmission line would be minimized and dis- <br />turbed areas would be regraded and revegetated to blend with surrounding <br />areas. <br /> <br />II Stroud, R. R., and Martin, R.G., 1973, Influence of Reservoir Dis- <br />charge Location on Water Quality, Biology, and Sport Fisheries of Reservoirs <br />and Tailwaters, 1968-71, U.S. Army Engineer Waterway Experiment Station, <br />Vicksburg, Mississippi. <br />