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The vertical slot fishways constructed at the Upper and Lower Davis Dams are 50 feet long, 25 feet wide and 15 feet deep. They will facilitate continuous and unobstructed passage for adult and juvenile chinook and steelhead.
Salmon, steelhead benefit from Model Watershed project on Catherine CreekChinook and steelhead making their way up Catherine Creek in spring and summer will find the going easier with the completion of the Grande Ronde Model Watershed Program’s Davis Dam Fish Passage Project.Since early August, construction crews have been rebuilding the Upper and Lower Davis Dams on private farmland about five miles northwest of Union.
With replacement of the diversion structures and the addition of vertical slot fish ladders, passage should be continuous and unobstructed at both sites, even at times when water levels are low.
It’s a far better design compared to what was in place, said Chas Hutchins, the project’s engineer.
“When flows decline, the main channel will be blocked off by a radial gate. Then all of the flow goes through the fish ladder,” Hutchins said.
Lyle Kuchenbecker, project planner for Grande Ronde Model Watershed, said the new dams will benefit all fish populations, though species of primary concern are three protected by the federal Endangered species act: Snake River spring chinook, Snake River summer steelhead and bullhead trout.
“Those are the highest priority because of low numbers. Historically, the numbers have been declining,” Kuchenbecker said.
Kuchenbecker said Grande Ronde Model Watershed had been thinking for a long time about replacing the two Davis Dams. Then in 2007, about 20 Chinook on their way up Catherine Creek were trapped in the outdated fish ladder at the Lower Davis Dam.
The ladder, built decades ago, had slots 18 inches high, when the modern standard is six inches.
“The death of those fish upped the priority for us. That’s when we started planning in earnest,” Kuchenbecker said.
Like most watershed projects, this one would be a collaborative effort. Agencies coming on board — either as work partners or permitting agencies — included the Oregon Department of Fish and Wildlife, National Marine Fisheries Service, U.S. Fish and Wildlife, and the U.S. Army Corps of Engineers.
“This is a large, complex project and and it took a lot of planning,” Kuchenbecker said.
Since both diversion structures are located on private property, the cooperation of Sherman Hawkins, owner of the lower dam, and upper dam owner Dan Boothman, was vital.
Hutchins said the project developers worked hard to get the go-ahead from the landowners.
“We took them out to a similar facility in Echo, had them look at it and decide if they were comfortable with it,” he said.
Hutchins is a four-year employee at the La Grande engineering firm of Anderson Perry & Associates. His job was to design a system that ensured easy passage for fish, and diverted adequate water for agricultural uses.
He has been involved in several fish habitat projects, but this was one posed some special challenges.
“This is the largest fish ladder I’ve been associated with,” he said. “The main challenge was to get the right quantity of water flowing through it at the right velocity.”
The old method of diverting irrigation water, with check boards and plastic sheeting, was replaced at both sites with a system that includes a radial gate water check system, a bypass channel and a vertical slot fishway. The fishways are about 50 feet long, 25 feet wide and 15 feet deep.
The gates and bypass channels are fully open outside the irrigation season. Beginning in mid-May or early June, the landowners can lower the radial gates, sending all the water through either the bypass channel or the fishway.
The new system should alleviate adult migration delay and stranding, and reduce threats to the juvenile fish population.
“We’re providing the juvenile fish with the physical ability to jump,” Kuchenbecker said.
The project began with work area isolation and fish salvage, followed by demolition of parts of the existing structures, then construction of the bypass channels and fishways.
The $1.7 million effort was funded in large by the Bonneville Power Administration. Mike Becker of La Grande submitted the low bid to become the lead contractor.
“We were real pleased that a local contractor got it. We had a lot of out of town bidders,” Kuchenbecker said.