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~ r- M N Oak Ridge Tunnel The design of Oak Ridge Tunnel would remain exactly the same as intended under the Lake Avery plan. The length, capacity, and alignment would be unchanged. The only difference would be that storage releases from Sawmill Mountain Reservoir could be made by gravity only. Oil Shale Diversion Dam The Oil Shale Diversion Dam on the White River near Yellow Creek has been dropped as a proposed project feature since it would be entirely single purpose and for only one user. A diversion dam would still be necessary to provide the oil shale water supply, but its construction and operation would be the responsibility of the private water user rather than that of the Federal government. Water supply Under the modified plan, water supply from the North Fork would be less than under the Lake Avery plan because the new diversion location is upstream from several tributary inflows, including Marvine, Ute, and Fawn Creeks. To compensate for the loss of about 30 percent of the total anticipated water supply which comes from these streams, it is proposed that minimum fish bypasses to North Fork be set at a reduced level of 70 second-feet for October, November, and April and 90 second-feet for the May to September period. These flows compare to 100 and 130 second-feet, respectively, in the Lake Avery plan. Due to possible freezing problems in the pipeline and ice jamming in the North Fork, diversions would prob- ably not be made in the winter months of December to March. Relea~es from the reservoir for irrigation would be made directly through the Oak Ridge Tunnel. Releases for oil shale would be made through the dam's outlet works to Big Beaver Creek and would have to be routed through Lake Avery. In addition, a minimum of 2 second-feet would be released to Big Beaver Creek to maintain fish habitat between the two reservoirs. Project operation of Sawmill Mountain Reservoir would not interfere significantly with the existing fishery at Lake Avery which would remain in its non-fluctuating state. The more obvious effects on Lake Avery of the upstream reservoir would be a change in the inflow pat- tern to regulated conditions, a more complete stabilization of the lake level, a tendency to be more full than at present, assured minimum flows above Lake Avery, and less sediment inflow, thereby prolonging the useful life of Lake Avery. It is probable that the overall influence of these effects on the lake and stream fishery would be favorable. The water right filing for natural flows from the North Fork of White River would be under existing rights. The Yellow Jacket Conserv- ancy District is expected to obtain the necessary storage rights for Sawmill Mountain Reservoir, Project water rights are described in de~ail in the progress report of April 1976. 9