Evaluation of orifice passage efficiency and descaling with an extended-length bar screen, new vertical barrier screen, and inlet flow vane at Lower Granite Dam, 1995

Tests were conducted in Turbine Unit 4 of Lower Granite Dam to evaluate orifice passage efficiency (OPE) and descaling of juvenile salmonids with a prototype extendedlength submersible bar screen, newly designed vertical barrier screen (VBS2), and inlet flow vane. Orifice traps and PIT-tagged release groups were used to measure OPE of the north and south orifices of Slot 4B. Juvenile salmonids were collected from Slots 4B and 5B (which contained a standard-length submersible bar screen) to measure and compare descaling. Contract no. E86950104