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<br />.~ ~ ~ 0 <br />'i LJ .)~. <br /> <br />. <br /> <br />(11) The powerplant operation will have possible effects <br />on the physical and biological environment of Twin Lakes. <br />These include' <br /> <br />(a) Slight warming of the lake accompanied by adjust- <br />ment of the depth of,the metalimnion, with no additional <br />temperature change when summer stratification is <br />present. Destratification will not occur as a result. <br /> <br />(b) Formation of ice cover may be delayed slightly, <br />but once formed will remain intact, with the possible <br />exception of the tailrace area. When water ia with- <br />drawn, the ice will sag like a membrane and return to <br />its original level following generation. <br /> <br />(c) Opossum shrimp require 'waters with a velocity of <br />less than 0.5 ft3/s; turbulence induced during the <br />generating cycle will probably cause the shrimp to <br />avoid the environs of the tailrace channel, thereby <br />reducing their available habitat. This should be <br />offset by the enlargement of the reservoir. <br /> <br />(d) The glacial flour covering the lake bottom could <br />become suspended. Indications are that this would be <br />least likely when thermal stratification is present <br />due to the cushioning effect of the hypolimnion. <br />During the isothermal or mixing periods, the potential <br />is unknown. Studies are being conducted on this <br />aspect and the possible effects of redirecting or <br />relocating the tailrace channel. <br /> <br />. <br /> <br />(e) In rp-l~tt0~ to the ~bc~c, pu55itl~ ~[[~c~s on the <br />lake trout population are being studied. <br /> <br />(l2) Some fish will be lost through powerplant operations. <br />Screening of the'powerplant intakes to protect against the <br />losses waS considered. The Fish and Wildlife Service was_ -' <br />not able to predict the number of fish that' might b~,16st <br />in the unscreened unit; therefore, it did not recommend <br />screening to avoid these fish losses. In lieu of'screening <br />the Fish and Wildlife Service recommended Project funds be <br />made available to finance fish loss studies, which are being <br />conducted by the Colorado Division of Wildlife. These studies <br />will identify the magnitude of the impacts. On the basis of <br />these findings, recommendations will be made to minimize the <br />impacts. <br /> <br />. <br /> <br />IV-69 <br />