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Hundreds Of Steelhead Found Trapped In Dworkshak Turbine Tube; About 1,000 Fish Killed
Posted on Friday, November 05, 2010 (PST)

Hundreds of steelhead fish were found trapped in the draft tube area below turbine unit 1 by staff at Dworshak Dam and Reservoir Wednesday while the electricity generator was being dewatered for routine maintenance, according to U.S. Army Corps of Engineers operations officials at the Walla Walla District.


The adult fish were discovered at about noon after the unit was taken out of service and its draft tube drained to allow access for routine maintenance activities. The project involved following standard operating procedures, according to the Corps.


Some fish were floating, but many were actively swimming so staff immediately focused efforts on rescuing the hundreds of fish still alive. After placing an air line in the water to help supply oxygen, all available personnel at the dam assisted with removal of the fish via large plastic containers to a makeshift “fish slide” just outside the powerhouse where fish could slip into the North Fork of the Clearwater River on the downstream side of the dam.


“By 4:45 p.m. today, over 400 steelhead had been released into the river. So far, no salmon have been found among the fish,” Greg Parker, Dworshak operations project manager, said Wednesday during a status update. “We’re still rescuing live fish and will shift our focus to recovering any dead fish once our rescue effort is completed.”


According to Parker, Corps personnel continued the rescue effort until about midnight and then resumed Thursday morning. A total of more than 500 live fish were returned to the river. The death toll was about 1,000 adult steelhead. Corps officials have theorized that, with so many fish packed into a small area, the fish may have become oxygen deprived.


Walla Walla District staff coordinated with staff from the U.S. Fish and Wildlife Service’s Dworshak National Fish Hatchery and Clearwater Fish Hatchery, which is operated by the Idaho Department of Fish and Game. The hatcheries, both located just below the dam, provided tote containers with ice so the dead fish could be preserved. All of the fish were distributed to local food banks and to the Idaho Correctional Institute in Orofino.


“They’re all going to be put to good use,” said Corps spokeswoman Gina Baltrusch.


It is believed that most of the fish are the product of the hatcheries, both of which use water from behind the dam to rear young steelhead and salmon. A combination of attraction to the currents created by the dam’s output and the urge to home in on that reservoir water are likely reasons that the fish often congregate just below the facility.


There are no fish passage facilities at Dworshak. Steelhead spawners have not had access to the North Fork above Dworshak since the dam was completed in 1973.


The standard operating procedures require placing a bulkhead (gate) at the entrance to the penstock (pipe) and then placing stoplogs in the tailrace where the water from the unit discharges through the draft tube into the tailrace (water below the powerhouse). Prior to placing the bulkheads, the unit is run to discharge any debris that might be in the bulkhead slots and to try to move any fish out of the draft tube area. Placement of these bulkheads is done by crane and takes several hours each.


During that time, fish have the potential to re-enter into the draft tube area.


“Typically we have less than 30 fish total and they are returned back to the tailrace unharmed,” Parker said. “In this situation, we had around 1,500 fish when we dewatered which has never happened before.”


The Corps has already looking at potential solutions, such as installing screens to prevent fish from swimming into the draft tube during the time it takes to put the bulkheads into service, Parker said.


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