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.

Pacific Northwest National Laboratory (PNNL) evaluated 20 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 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. In general, water velocity conditions at the screen sites met fish passage criteria set forth by the NMFS. Although velocities often fluctuated from one sampling location to the next, average sweep velocities typically exceeded approach velocities and increased toward the bypass. Mean approach velocities were below the NMFS criteria of

In 2002, the Pacific Northwest National Laboratory evaluated 23 Phase II fish screen sites in the Yakima River Basin as part of a multi-year project for the Bonneville Power Administration on the effectiveness of fish screening devices. Pacific Northwest National Laboratory collected data to determine whether velocities in front of the screens and in the bypasses met National Marine Fisheries Service criteria to promote safe and timely fish passage and whether bypass outfall conditions allowed fish to safely return to the river. In addition, Pacific Northwest National Laboratory conducted underwater video surveys to evaluate the environmental and operational conditions of the screen sites with respect to fish passage. Based on evaluations in 2002, PNNL concluded that: (1) In general, water velocity conditions at the screen sites met fish passage criteria set by the National Marine Fisheries Service. (2) Conditions at most facilities would be expected to provide for safe juvenile fish passage. (3) Conditions at some facilities indicate that operation and/or maintenance should be modified to increase safe juvenile fish passage. (4) Automated cleaning brushes generally functioned properly; chains and other moving parts were typically well greased and operative. (5) Removal of sediment buildup and accumulated leafy and woody debris should be improved at some sites.

In 2003, the Pacific Northwest National Laboratory (PNNL) evaluated 23 Phase II fish screen sites in the Yakima River Basin as part of a multi-year project for the Bonneville Power Administration on the effectiveness of fish screening devices. PNNL collected data to determine whether velocities in front of the screens and in the bypasses met the National Oceanic and Atmospheric Administration Fisheries (NOAA Fisheries, formerly the National Marine Fisheries Service [NMFS]) criteria to promote safe and timely fish passage. In addition, PNNL conducted underwater video surveys to evaluate the environmental and operational conditions of the screen sites with respect to fish passage. Based on evaluations in 2003, PNNL concluded that: (1) In general, water velocity conditions at the screen sites met fish passage criteria set by the NOAA Fisheries. (2) Conditions at most facilities would be expected to provide for safe juvenile fish passage. (3) Conditions at some facilities indicate that operation and/or maintenance should be modified to improve juvenile fish passage conditions. (4) Automated cleaning brushes generally functioned properly; chains and other moving parts were typically well greased and operative. (5) Removal of sediment buildup and accumulated leafy and woody debris could be improved at some sites.