A new device that helps remove debris blockages gathering in the juvenile bypass system at Little Goose Dam was put to use this spring, according to the U.S. Army Corps of Engineers.
The tool—called an orifice debris plunger—was installed May 5 after numerous modifications and tests.
Scott St. John, supervisory fish biologist at the dam, told NW Fishletter debris at Little Goose had become a significant problem after a trash shear boom that keeps logs and other material away from the juvenile bypass system failed in 2014.
The debris problem worsened with high runoff in 2017 and 2018, causing much more debris to collect in the forebay directly upstream from the turbines. The issues included plugs in the juvenile fish channel and vertical barrier screen failures.
Even after a new trash shear boom and boat barrier were installed in 2018, debris continued to create issues in the juvenile bypass system, St. John said. He said some juvenile salmon and steelhead were injured or killed through descaling, especially on high downstream migration days, when between 200,000 and 400,000 juvenile fish passed the dam.
Workers had been removing the debris manually, St. John said, but added, "There's a lot of water coming through these orifices, and it's really hard to push debris back through."
This year, Jay Haugen, a mechanical engineering technician, and Kreg Buryta, a maintenance worker, teamed up to design and fabricate a tool using a leftover pneumatic cylinder and sections of scrap aluminum.
St. John said that once the new tool is set up, it's easier and safer than manual removal.
He said other dams have issues with debris, and those with orifices, or openings, in their juvenile bypass systems could benefit from the design.
"It's really going to be up to the project biologist at each site," he said, adding, "We're continuing to improve what we can for juvenile and adult passage at these facilities."