284th Avenue SE Culvert Replacement Project

Project completed in September 2023

November 2023 – Burlap barriers around the edges of the streambed help to prevent soil from sliding downward into the stream.

Project location

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

Overview

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

November 2023 – The black chain link fence acts as an important safety measure by creating a barrier between passing vehicles, bicycles, and pedestrians, and the steep drop below.

November 2023 – Fragments of wood have been strategically placed within the stream to create areas of slower-moving water, where tired fish can rest before continuing to travel upstream.

November 2024 – The new box culvert measures over 33 feet across and 7 feet high, which allows water to flow naturally.

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.

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