A device that weighs as much as six orca whales is being tested on the Hood Canal Bridge, which blocks juvenile salmon from going out to sea, killing 50% of them.
Shaara Ainsley, senior project manager at Long Live the Kings in Seattle, was part of the assessment team, along with researchers at the state Department of Transportation. They worked with engineers to design a fish guidance structure that could be attached to the bridge and guide fish around the corners in the pontoons where researchers have found high predation by seals.
The first structure has been placed on the southern end on the east side of the bridge. Ainsley said fish get disoriented in 90-degree corners so the device takes those away to guide the fish around. The structure is 60 feet, by 60 feet, by 85 feet of plastic pipe filled with water so it’s buoyant.
During testing, researchers will be releasing fish with trackers in them, and they will be able to compare how they fare when the structures are in place and when they are not.
Ainsley said that comparison is crucial to quantify the benefit of the structures. She said they plan to build a second structure and test both sides of the bridge in 2024 and 2025. If the structures are determined to be helpful for getting young steelhead past the bridge alive, then we would look at next steps for using these structures each year to benefit fish passing the bridge, she said.
She said somewhere in the future when the bridge needs major repairs it could be time to design a new bridge. Ainsley said it could be built more fish- and people-friendly.
Because Hood Canal is a draw bridge, it is open more than 400 times a year. When that happens, it can cause vehicle backups for miles that can take an hour or more to clear up. Not having that can be crucial during a medical emergency or evacuation, and could even be better for tourism, Ainsley said.
The draw bridge can also hinder military readiness, she added. The Navy “doesn’t like to telegraph” when it sends a nuclear submarine through the bridge, so they “don’t give people a lot of heads up,” she said.
Ainsley added that a bridge similar to the longest floating bridge being built in the world in Norway could be the answer. It has a high span that ships can go under. And it floats on pontoons that are more fish friendly.