Snake River White Sturgeon Conservation Plan ... - Idaho Power

Idaho Power CompanyChapter 4: Conceptual Design for White Sturgeon Passage FacilitiesThe main advantage to these systems would be their cost, which would be lower than for someoptions. However, before this alternative could be considered further, detailed research on thesurvival of sturgeon passing over spillways while using these passage systems would have to beconducted. There would be some disadvantages: it may be difficult to attract fish because of thecompeting large flows entering the intake channel, power production would be decreased byincreasing spill, and the spillway release might increase the dissolved gas in the tailrace to unsafelevels.5.2.3. Pressurized Passage SystemsBrownlee Dam could be modified to include a system for pressurized passage by mining throughthe rock in or near the power supply channel. The intake for this system would be locatedupstream of the trash racks associated with the power intake. To efficiently attract and capturesturgeon, this system would be designed to make entrance flows perceptibly faster thansurrounding flows. Either a chute, lock, or fish lift could be used to lower fish to the tailrace.When combined with a fish lock or lift, this system could be used for both upstream anddownstream passage. During the spawning period in the spring, the system would be operated topass sturgeon upstream. In summer, with minor modifications, the system would be operated toattract migrants and transfer them downstream (Figure 24).5.2.4. Trap and TransportTrapping and hauling sturgeon is a viable alternative at Brownlee Dam. Based on the assumptionthat sturgeon would be guided by the predominant downstream flow, a productive trappingfacility would probably be located in or near the entrance of the power supply channel(Figure 25). Once captured, the sturgeon would be transported to a loading facility, transferredinto specially designed trucks, and hauled downstream and released into the tailrace.Section 4.2.5. provides a more complete description of a trap and transport system.Because the reservoir levels fluctuate by over 100 ft at Brownlee Dam, the design and locationof the facility for holding sturgeon would become somewhat complicated. It would need to bedesigned to allow vehicle access to all reservoir levels, a constraint that would require very longaccess ramps, possibly with winch systems to haul transport vehicles up steep grades on aninclined railway. One possible solution is to construct a loading and hauling system that ismounted on a trailer so that only vehicle access is needed for loading and hauling sturgeon.5.2.5. Capture and TransportA capture and transport system is a practical method of passing sturgeon over Brownlee Dam.It could be implemented quickly, it uses proven methods, and it provides considerable flexibility.Additionally, capital costs would be relatively low. Implementing this passage option iscomplicated by the widely fluctuating water levels in the forebay: current access ramps wouldhave to be modified to provide access to the water when water levels are low.Hells Canyon Complex Page 35