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News Room Headline
Chief Joseph Dam will conduct spill test on new spill deflectors April 22
Contact: Dick Devlin (206) 764-3750
SEATTLE
– The U.S. Army Corps of Engineers plans to conduct a spill test on the first group of recently constructed spill deflectors at the Chief Joseph Dam Project near Bridgeport, Wash. on Sunday, April 22. The test will be carefully monitored and will begin at 6 a.m.; it may last for 20 hours, depending on what happens.
The concrete deflectors are being installed near the bottom of the sloped spillway surface along the entire 922 ft length of the spillway. The tops of the deflectors are submerged several feet underwater so they will not be visible. The deflectors, resembling ski jumps, include a curved transition from the spillway face that then extends horizontally 12.5 feet to direct flow in a skimming fashion across the water surface below the dam. The test is designed to investigate changes in dam uplift pressures and collect preliminary data on deflector performance.
The purpose of the Chief Joseph Gas Abatement Project is to reduce total dissolved gas (TDG) contributions from Chief Joseph Dam, to the extent economically, technically, and biologically feasible. The addition of spillway deflectors was determined to be the most effective in both gas reduction and implementation cost.
The spillway modification is in accordance with the 2000 National Marine Fisheries Biological Opinion on Federal Columbia River Power System operations, and is required per the 2004 Action Agencies’ Updated Proposed Action and 2004 NOAA Fisheries Service (NMFS) Biological Opinion. Fisheries resource agencies, including NMFS, continue to strongly support this work, and its completion is considered a legal requirement under the NOAA BiOp.
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