Electrical Power for Valdez and the Copper River Basin-1981

The lake may be drawn down to the level of the tap upon completion of theproject to secure necessary gating and screening structures. Tnedrawdown would decrease water quality in Allison Creek by increasingturbidity and flows, and by changing the temperature regime. Becausewater quality degradation could have an effect on the fisheries resourcesof Allison Creek the drawdown for lake tap structure placelnent wouldoccur at the optimal time for the fishery.During the operation of the proJect, the lake would be drdwn downapproximately 100 feet during the winter months when the lake is icecovered. Little erosion is anticipated because of the large bouldershoreline which surrounds most of the lake. A small delta is located atthe head of tile lake which consists mainly of fine grain glacialoutwash. This area could experience some erosion during drawdown, but towhat degree is unknown. The Snettisham hydroelectric project near Juneautaps Long Lake which is similar in configuration to Allison Lake.Althougn the depth, size of the lake and size of the delta are greater,Long Lake experiences a drawdown of 114 feet. To date, little waterquality degradation is occuring and the delta area appears to be stable.The drilling of the penstock tunnel would require approximately 300gallons of water per hour which would probably be pumped from the lake.The discharged water from the drills would be allowed to flow out of thetunnel, and diKes and diversion ditches would be used to assure that thewater does not enter Allison Creek.Pressure Reducing Turbine: Tnere would be no hydrology or waterquality impacts associated with the construction and operation of thePRT.c. Esthetics:Hydroelectric: Approximately 20,000 cubic yards of tunnel tailingswould be disposed of on a dense stand of alder, devils club, redelderberry, and salmonberry. Tne talus created by the disposal would bevisible from Valdez. The natural landscape of weathered rock andvegetative cover would be visually marred by tne deposition of lightercolored rock. If the disposal site is visually offensive, a revegetationprogram coula be initiated in attempt to cover the talus.Other aspects of the project would probably not degrade the visualquality of the area. The powerhouse is small and located in an improvedarea. The majority of the aboveground penstock would not be in viewexcept by air or pOSSibly boat. The lake can only be viewed by air andvisual impacts of the drawdown could only be seen by a few.Pressure Reducing TurDine: The constructlon of the housing for thePRT unit would distract from the existing natural visual environment,however, it appears the structure would not be visible from Valdez or theroad system. The transmission line would connect with the proposedValdez-Glennallen intertie, and little aaditional clearing would berequired.EIS-1D