Work to Create ‘Fish-Friendly’ Passage Continues Near Adna, Bringing Delays

Construction: State  Route 6 Travelers Over Chehalis River Tributary Should Expect  Delays Until Fall

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Travelers on state Route 6 near Twin Oaks Road just west of Adna should expect daytime delays this summer as a Washington State Department of Transportation (WSDOT) contractor begins girder placement work over an unnamed tributary of the Chehalis River.

The work, which began May 6, is part of an WSDOT project to remove two culverts — structures used to carry water beneath roadways — and replace them with a new fish-friendly structure.

“Once construction is complete, the new fish-friendly structure will be much larger and should be more resilient to changes in the landscape and provide for fish passage long into the future — giving fish better access to the habitat they need,” said WSDOT in a written statement on the project’s website.

The $8.9 million project is part of the state’s efforts to meet a March 2013 federal court injunction requiring WSDOT, State Parks, the state Department of Fish and Wildlife and the state Department of Natural Resources to provide fish passage at WSDOT-owned barrier culverts with 200 meters or more of upstream habitat by March 2030.

The injunction was issued as the result of litigation filed in 2021 by 21 Washington tribes with treaty-protected fishing rights that challenged the existence of fish-blocking culverts. The U.S. Supreme Court ruled on the case, U.S. v. Washington, in favor of the tribes in 2018.

“Most of the culverts were installed decades before scientists fully understood the needs of fish,” said WSDOT, adding that the agency “met all requirements for culvert installation and sizing at the time they were constructed.”

The injunction requires the state to develop a list of culverts that affected fish passage and then “design and build fish passage at each barrier culvert on the list in order to pass all species of salmon at all life stages at all flows where the fish would naturally seek passage,” according to court documents.

Fish passage could be achieved by “avoiding the necessity for the roadway to cross the stream,” building a “full span bridge” or utilizing a “‘stream simulation’ methodology,” where culverts are designed to simulate a natural channel as closely as possible. In the case of the two culverts on the Chehalis River tributary, WSDOT is opting for the full span bridge approach in the form of a concrete bridge.

WSDOT awarded the project to Scarsella Bros. Inc. in May 2020 and construction work officially began that summer. Project completion is scheduled for fall 2021. While no major delays are scheduled, WSDOT reports that there will be “around-the-clock flagging” until the project is finished, which could mean delays of up to 20 minutes for travelers.

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