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284th Avenue SE Culvert Replacement Project

Project completed in September 2023

Crews replaced the small culvert that runs under 284th Avenue SE just north of SE 472nd Street. This rusted out pipe in the center of the photo was replaced by a larger culvert to help prevent flooding and support fish passage.

Status update

September 25, 2023

 The new box culvert on 284th Ave SE.

Sept. 18, 2023 – The new box culvert on 284th Ave SE is complete. The crews paved the roadway above the culvert next.  


Crews have officially opened 284th Ave SE just north of SE 472nd St to all traffic. They completed the box culvert installation and paved the above roadway in September.

Thank you to the many community members and travelers for your patience this summer.

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Project location

Project location map.

284th Avenue SE at SE 472nd Street, south of Enumclaw, WA. Larger view, PDF 201KB


King County replaced a narrow, worn-out metal pipe culvert with a much larger and wider concrete box culvert under 284th Avenue SE just north of SE 472nd Street. The old metal pipe culvert was rusted and nearing the end of its useful life. A larger concrete box culvert was installed to decrease flooding and support fish passage.

The size and design of the concrete culvert is based on state requirements for fish passage design.

Budget and funding sources

The preliminary estimated total project cost was $1.4 million. This project was funded through Surface Water Management fees and property taxes.


Sept. 18, 2023 – A fresh look at the new box culvert on 284th Ave SE. The crews paved the roadway above so traffic can resume travel. 
Sept. 18, 2023 – A repurposed log lies in the base of the stream below the new box culvert on 284th Ave SE.  
Sept. 18, 2023 – A fresh look at the new box culvert on 284th Ave SE. The crews paved the roadway above so traffic can resume travel. 
Sept. 12, 2023 – Crewmembers assess the upstream channel looking toward the new box culvert. 
Sept. 12, 2023 – The brown burlap helps with erosion control to keep the soil in place until the seeds grow. When the grass grows in, it will keep the soil in place. 
Sept. 3, 2023 - An up-close view of the streambed under construction inside the culvert. Logs are positioned vertically alongside the culvert wall to guide the stream water toward the center when the flow is low. This increases the depth of the stream. The deeper water makes it easier for fish to swim upstream.
Sept. 3, 2023 – These two logs are stabilized by heavy chains to prevent them from floating away during high flows. Each log has two large boulders chained to them. 
Sept. 3, 2023 - The black pipes at the wingwalls are drainage pipes that carry treated storm water from the neighborhood into the creek.
Sept. 2, 2023 – Crews fill the culvert with sediment—naturally occurring rocks and minerals—to form the stream bed. 
Sept. 2, 2023 – These boulders—some weighing up to 2,300lbs—and ecology blocks anchor the logs in place and prevent them from floating way. This human-made logjam provides natural habitat for fish. 
Sept. 2, 2023 – A crewmember chains boulders weighing hundreds of pounds to the logs to prevent them from floating away during high flows.
Aug. 14, 2023 - The project sign for the 284th Avenue SE culvert replacement project has been installed just before the detour route at SE 472nd Street. 
Aug. 14, 2023 – Several “No Parking on Pavement” signs line SE 472nd Street near the busy trailhead of Cal Magnusson Trailhead leading up Pinnacle Peak. Large trucks need to take the detour so it’s important to park in the designated trailhead lot. 
Dec. 7, 2022 – This small, rusted culvert will be replaced by a larger concrete box culvert to decrease flooding and support fish passage.
Dec. 7, 2022 – King County crews inspect and measure the roadway and culvert on 284th Avenue SE. 

Frequently asked questions

The road closure will require a full road closure for six weeks straight while we dig a large pit in the roadway to replace the culvert. Exact project location is where 284th Avenue SE meets SE 472nd Street.

All traffic, including vehicles, trucks, emergency response, bicycles, and pedestrians will not be allowed through the active work zone. The large hole in the road will require all traffic to use the posted detour.

We are coordinating with USPS, package delivery, and emergency responders to minimize disruption.

Drivers should plan to add roughly six minutes to their drive time.

Culverts not only support fish passage, but they also help prevent flooding and help water flow below roadways.

We will do our best to keep community members informed about the project. Project updates and construction closure information will be shared in the following ways:
  • Time-stamped updates to this website and our MyCommute website
  • Project notification signs at the construction zone
  • Signs alerting drivers to upcoming intersections and closures and signed detour route
  • Road Alert email notifications about this project and others throughout unincorporated King County. Sign up for Road Alert emails here.
  • Posts on Twitter, NextDoor, Facebook, and Instagram