Washington Phase II Fish Diversion Screen Evaluations in the Yakima River Basin, 2000.

Pacific Northwest National Laboratory (PNNL) evaluated 21 Phase II screen sites in the Yakima River Basin as part of a multi-year study for the Bonneville Power Administration (BPA) on the effectiveness of fish screening devices. The sites were examined in 1997, 1998, 1999, and 2000 to determine if they were being effectively operated and maintained to provide fish a safe, efficient return to the Yakima River. Data were collected to determine if velocities in front of the screens and in the bypass met current National Marine Fisheries Service (NMFS) criteria to promote safe and timely fish bypass and whether bypass outfall conditions allowed fish to safely return to the river. Based on the results of our studies in 2000, we conclude that: in general, water velocity conditions at the screen sites met fish passage criteria set forth by the NMFS; most facilities were efficiently protecting juvenile fish from entrainment, impingement, or migration delay; automated cleaning brushes generally functioned properly; chains and other moving parts were well greased and inoperative; and removal of sediment build-up and accumulated leafy and woody debris are areas that continue to improve