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--. . . -2- believe that the higher tailwater is not an insurmountable problem, but that the hydraulics and sediment transport through the radial gate, the intake channel, and the flow split above the whitewater bypass must be thoroughly studied and depicted. 3. There are some other facts and relationships that must be considered in the design. The top of the intake screens is elevation 87.5. These screens should be submerged at all times. The radial gate has a modulating operator which maintains a desired water surface. Typically it is set to maintain an elevation of 89.1 to 89.5. Since the main overflow is set at 89, modest variations in flow can overflow without resulting in the radial gate moving. This overflow, which is 14 feet wide, is important to prevent "hunting" of the operator. The overflow could be moved to another location such as the entrance to the bypass, wioened ami raised. At extreme low flow, obviously the radial gate will completely close. There is a smaJJ notch within the overflow section at elevation 88 that helps to flush debris and algae even during low flow. A similar low flow debris flushing notch should be provided. The functions of debris overflow, spilling of water to minimize radial gate hunting, and flushing of all arriving sediment through the intake channel must be maintained. Therefore any changes, and particularly the new whitewater bypass, must be carefully studied. The effort will require several trials of devising a physical configuration to split the flow, and testing operating scenarios for a wide range of discharges. All of these changes may also result in the need to adjust the main dam elevation of 90.5 to correctly control floodwater surface profiles upstream. 4. .. . Boaters and in.river users must be kept out of the intake channel and from any possibility of being swept under the radial gate at all times and under any situation. With the present design, it is very easy to have a power failure, equipment problem or maintenance operation at the intake that results in the radial gate being fully opened such that the boater could be swept into the intake channel. A buoy line as proposed is insufficient for this control. There are concepts, such as a diversion dock, which will make this possible, but it is not our role to comment on the details of how this could be done. 5. The split of water and sediment at the entrance is critical. The following conditions must be satisfied: a. The entire facility should maintain the first 100 cfs of river flow through the intake channel.