Wanapum & Priest Rapids bypass units ready
Three spillways at Priest Rapids Dam were modified to create the Priest Rapids Dam Fish Bypass Unit.
SOUTH COUNTY - Juvenile salmon and steelhead passage is underway at Wanapum and Priest Rapids dams, accommodated through the dams' fish bypass units, spillways and advanced turbines.
At Priest Rapids Dam, the newly-installed Priest Rapids Fish Bypass was operational in time for the downstream migration, according to Public Information Officer Thomas Stredwick. Construction began in 2011.
The bypass design converts three existing spillways into fish slides at Priest Rapids Dam to provide downstream passage for migrating fish. The three chutes are each more than 200 feet long and more than 40 feet wide.
"Collectively, the fish bypass chutes are capable of passing 27,000 cubic feet per second of water, and juvenile fish survival is anticipated to be 99 percent," Stredwick said.
The bypass provides for a better use of water resources by reducing total water spilled for juvenile salmon from 110,000 cubic feet per second (cfs) to 27,000 cfs. This allows for increased power generation and improved fish passage. At a cost of $28 million, the project is anticipated to pay for itself in 5-7 years.
Last week, Grant PUD began transporting and releasing approximately 3,400 tagged juvenile steelhead and yearling Chinook salmon approximately 38 miles above Wanapum Dam via helicopter as studies on juvenile fish passage commence. These studies are a component of Grant PUD's license requirements.
"The studies will evaluate the survival and behavior of juveniles moving through the new Priest Rapids Dam Fish Bypass as well as fish passage throughout the Priest Rapids Project," Stredwick said.
Results from the studies will inform Grant PUD and other agencies of potential impacts on juvenile salmon and steelhead during the low-river conditions. Results will also provide route-specific behavior and survival information through the Wanapum and Priest Rapids dam fish bypasses, spillways and turbines.
Adult fish passage continues through modified fish ladders at Wanapum Dam. As of April 23, 31 adult spring chinook salmon and 270 steelhead have been counted exiting these ladders.
Grant PUD continues to trap and haul fish at Priest Rapids Dam while the ladder modifications are being evaluated under operating conditions. As of April 27, 74 spring chinook and 27 steelhead have been captured at Priest Rapids Dam and transported past Wanapum Dam.
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