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i'w ~ C'I') N The tentative selection of this new site necessitates a different alignment and design for the feeder system, including the diversion structure. Construction of the Sawmill Mountain Reservoir would remove the need for Avery Pumping Plant. A proposed change unrelated to the new reservoir site is the deletion of an Oil Shale Diversion Dam from the plan. All other features of the,White River Segment would remain unchanged and there would be no change at all in the Milk Creek Segment. The dropping of Lake Avery enlargement fnom consideration is neces- sary because of unacceptable abutment conditions. A routine investigation of foundation and abutment suitability by means of geologic core drilling along ,the axis reve~ledsevere problems with the left abutment. Gravel deposits at depths in excess of 100 feet were found. A cross-section drawing of the axis is shown on the following page. . Even if the axis were lengthened and the gravel excavated, there is no indication that competent bedrock exists. Before the modified plan can be definitely adopted, much additional work is needed to verify and upgrade the preliminary investigations which are based entirely on existing appraisal-level data. Hydrologic data will have to be expanded to cover reaches of both Big Beaver Creek and the North Fork of the White River upstream from previously studied points. Additional geologic drilling will be needed to confirm the suitability of the new dam site and tunnel route. It will be necessary to perform topographic mapping of the reservoir basin and feeder system alignment. Icing studies must be made to aid in the design of a diversion structure and to help establish winter operation schedules. The fish and wildlife studies that are already underway have been extended to provide additional detail in relation to the proposed relocation of features. Description of the Modified Plan The modified MOP Compromise Plan based on Sawmill Mountain Reservoir would provide exactly the same water supply at the same locations for the same purposes as the Lake Avery plan would have provided. The new feeder system alignment necessitated by Sawmill Mountain Reservoir's location includes a tunnel and pipeline from the North Fork, as shown on page 5. The tunnel portion has been named the Bob Raley Tunnel. Design Considerations Sawmill Reservoir To meet the project demands in the MOP Compromise Plan, the Sawmill Mountain Reservoir would be sized to a total capacity of 55,000 acre-feet. Of this, 52,000 acre-feet would be active capacity and 3,000 acre-feet would be for dead and inactive storage. The minimum pool would be only tor sediment storage and to provide the water surface elevation necessary 3