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NE 24th Street Culvert Replacement Project
Construction of this project is expected to begin in mid-July 2025
Crews will replace an old three-and-a-half-foot corrugated metal pipe under the road with an 18-foot-wide fish passable concrete box culvert.
Status update
June 18, 2025
This project is anticipated for construction in mid-July, exact dates will be provided two weeks before the project starts. Crews will build a temporary gravel bypass lane adjacent to the work zone so that traffic can continue to use this sole access road during the project. This will help ensure neighbors can move freely in and out of the neighborhood during construction. The project is expected to last approximately ten weeks.
Project overview
Historic Langlois Creek near Carnation, WA passes under NE 24th Street in a narrow, corrugated metal pipe culvert. Because the pipe is too small, it can cause flooding in the area and the water in the pipe moves too quickly for fish. The County will remove the existing pipe and build a much larger 18-foot-wide fish passable concrete box culvert.
Travelers will use a temporary gravel bypass lane and wooden bridge to keep vehicles, bicycles, and pedestrians moving. A bypass lane is necessary because NE 24th Street is a sole access road, and the bypass lane ensures two-way traffic can come and go from the neighborhood. The single lane bypass road will be controlled with temporary traffic lights during non-work hours.
The crane work will take place on two separate days, and the road, including the bypass lane, will be completely closed during those times.
Project location
This project is located on NE 24th Street southeast of Carnation, WA. View larger (250KB)
Why is King County replacing this culvert?
We are replacing the worn out, narrow culvert because it floods, and it is a fish passage barrier.
The existing pipe culvert is too small and often floods when it rains. It is also considered a fish passage barrier for two main reasons:
- It is too small for the volume of water that passes through it. As a result, the water is pushed through extremely fast making it nearly impossible for fish to swim in it.
- At times, the water inside the existing culvert is too shallow and the bottom of the culvert is located too high above the stream bed for fish to jump into the culvert so they can continue to swim upstream.
Fish have a very difficult time swimming through extremely swift water. They also have a lot of trouble jumping up and through a pipe with very little water in it.
Benefits of concrete box culverts
A box culvert is flat and wide with streambed gravels placed in the bottom to simulate an actual stream allowing fish to move up and downstream easily. The new concrete box culvert will make it much easier for fish to pass under the roadway and continue their migration.
Box culverts can accommodate a much larger volume of water.
They are designed to simulate a natural stream and allow consistent, gentle water flow under the road.
Fish have a hard time migrating upstream if there is not enough water in the culvert, or if the culvert is too high above the stream. The box culvert helps make it easier for fish to pass underneath the road. (Image courtesy of King County Fish Passage Program)
Culverts may block fish migration because the water flow is too swift, too shallow, or has a waterfall into or out of the culvert. The new box culvert is designed to have enough water running through it at a natural pace, just like a real stream. (Image courtesy of WSDOT Fish Passage Program).
What to expect during construction
- The project will begin with the construction of a temporary gravel bypass lane so that travelers can continue using NE 24th Street to enter and exit the neighborhood.
- The project team will minimize dust and dirt caused by construction work from spreading in the air and stream.
- King County will monitor water quality in accordance to permits issued for the project.
- In addition, people living near the work area might experience the following while the culvert is built:
- Noise and odor from sawcutting, jackhammers, excavators, generators and pumps.
- Trucks hauling materials to and from the construction site.
- A large construction crane in the roadway.
- Crews will typically work Monday to Saturday from 6 a.m. to 6 p.m. Crews may occasionally work on Sundays.
Keeping neighbors informed prior to and during the project
We will update this website with more information leading up to the start of construction to keep neighbors informed of progress, temporary full road closures, and other construction information.
Crews will place electronic advanced notice message boards prior to construction, and we’ll mail postcards to all who live nearby, contact information for an on-site construction lead will be available for neighbors. In the meantime, please contact Amy Bresslour with any questions or concerns or to be added to a neighborhood outreach list.
Budget and funding sources
This project is funded by the Flood Control District and the design and construction budget is $3 million.
Frequently asked questions
A fish passage barrier is anything that hinders fish from moving upstream or downstream.
Most fish barriers in unincorporated King County are round metal pipes (culverts) that channel streams and water underneath the road. Many of these culverts were installed between 30 and 100 years ago. These older metal culverts allow water to flow but are so narrow and steep that they prevent fish from swimming through them.
Metal pipe culverts may block fish migration because the water flow is too swift, too shallow, or has a waterfall into or out of the culvert.
The ability of trout, salmon, and steelhead to swim upstream to their traditional spawning grounds is vital to their recovery across Washington and King County. Deteriorating culverts and other barriers block fish passage and undermine the state and county recovery efforts.
One of the most effective ways to ensure the survival of native fish – and the southern resident orcas that rely on them as a food source – is to remove barriers to their habitat.
Photos
The road has been repaired above the pipe many times. Here is a photo from 2016 before the area was repaved. You can see the patching that was needed because the pipe is unstable and causes the road above it to shift.
Water flows from an aging metal culvert under NE 24th Street. This pipe will be replaced with a much larger concrete box culvert to improve drainage and prevent future road damage.
The fast flow of water through the existing metal pipe creates a challenge for fish.