Project overview
In fall 2025 contractors working for WSDOT will begin work to remove and replace a failing culvert underneath SR 411, better known as West Side Highway, just south of Castle Rock, in Cowlitz County.
On Friday, Oct. 24, 2025, construction to replace the failing culvert was completed and SR 411 was reopened to travelers with no restrictions.
What to expect
To replace the culvert under SR 411/West Side Highway, crews will need to close the highway to all traffic at milepost 9.55 near Waters Road, just south of Castle Rock. Closing the road allows crews to remove the old, failing culvert, repair the area around it, install a new, larger culvert, and then rebuild the highway so it can fully reopen without weight restrictions.
Located just south of Castle Rock, the culvert underneath SR 411, also known as West Side Highway, failed and is being replaced. Crews will close the highway at milepost 9.5, near Waters Road, in Cowlitz County.
In spring 2025, maintenance crews found a failing culvert near Waters Road at milepost 9.55 while clearing drains after heavy rain. The culvert had worn out and could no longer carry water, which led to flooding and a 15-foot sinkhole. Crews made temporary repairs in March and have checked the site daily while waiting for permanent repairs. Once construction is finished, the new culvert will safely carry water under the highway and meet today’s standards for streams that support nearby fish habitats.
