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Cutthroat trout get a step-up
Fish ladder helps trout swim upstream from Willamette River to Augusta Creek.
Fish ladder provides access to Augusta Creek.
Fish ladder provides access to Augusta Creek.
Black-spotted cutthroat return to their home waters to spawn, and for some, home is the Willamette River and its tributaries. But as the fish approach the confluence of an unnamed tributary, often referred to as Augusta Creek, and the Willamette River, they are stopped by a huge culvert, 400 feet long, that opens six feet above the river. The trout are only able to access the remote stream above at limited times of the year because the culvert is too high to jump when water is low.  
 
And that's the way it would have remained if not for the new Interstate 5 Willamette River Bridge project. In June 2009, ODOT's construction contractor extended the culvert to provide additional access to the area at the downstream end of Augusta Creek, which lies under Franklin Boulevard, for construction and bridge demolition. But two years later, additional permitting requests prompted the Oregon Department of Fish and Wildlife staff to consider whether the cutthroats' migration had become even more difficult.
 
"The stream provides continuity for fish passage," said Greg Apke, statewide fish passage program leader for ODFW. "We wanted to make sure this project didn't interfere with cutthroat trouts’ ability to swim upstream."
 
To allow the trout to continuously make their way up the Augusta Creek tributary during construction, ODOT proposed building a temporary fish ladder. The agency worked with ODFW and Hamilton Construction to design and install the fish ladder, and the whole process was complete in just over two months.
 
There are many kinds of fish ladders, each designed to accommodate a certain type of fish. ODFW recommended a Denil ladder design because cutthroat trout are strong swimmers that prefer to swim upstream in rapid water.
 
The Denil fishway looks and works something like an escalator: the ladder, on one side, helps fish travel upstream and a flat metal chute, on the other side, allows the rest of the waterway, and even an occasional fish, to flow downward. The ladder consists of 33 baffles ─ each is wishbone-shaped with a triangular bottom. They create a backwater effect as water flows over them, allowing fish to jump, then rest if they need to, before jumping again to reach the next level, all the way to the top. The baffles are constructed of steel beams and wood, and concrete lines each side of the ladder to hold the steel beams in place during heavy water flows.
 
"This fish ladder takes the energy created by the water flow at the bottom of the stream and creates a sweet spot to attract fish, because the velocity at the bottom of the baffles is slower and in some cases actually reverses," said Apke. "Fish are trying to conserve energy, and because of the Denil design, they can take a break at any point as they ascend the ladder."
 
The project team has seen fish using the ladder.
 
"It’s a necessary part of the project until we reroute this stream," said Karl Wieseke, ODOT project manager. "We actually have found fish on the site, so we know the creek is used."
 
The ladder is only temporary because the culvert won't be needed after 2014, when Augusta Creek will be restored to its native channel. Then the cutthroat will enjoy a passage even easier than this stairway home.