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SE 432nd Street Culvert Replacement Project
Construction and eight-week-long road closure began on August 12, 2024
Crews are replacing three worn out, narrow drainage pipes beneath and alongside SE 432nd Street. The current pipes make it difficult for fish to travel and can create flooding. Photo: Google Earth.
Status update
August 2024
This project began August 12, 2024. Construction is expected to last up to eight (8) weeks.
Overview
King County is replacing two worn out, narrow pipes under SE 432nd Street with a new box culvert. Another small pipe that is parallel to SE 432nd Street is also being replaced with a larger box culvert. The new culverts will be located beneath and alongside SE 432nd Street between the Enumclaw-Foothill Trail and 278th Avenue SE, northeast of Enumclaw, WA. This project will include landscaping with native plants.
Project location
This project is located northeast of the City of Enumclaw, WA on SE 432nd Street between the Enumclaw-Foothill Trail and 278th Avenue SE. View larger ( 195KB)
Detour route
Road Services must close a portion of SE 432nd Street for approximately 8 weeks starting in mid-August. Travelers should add extra travel time through this area when this project is under construction. Larger view (210KB)
Why is King County replacing these culverts?
We are replacing the worn out, narrow culverts because they cause flooding and are a fish passage barrier.
The existing pipe culverts are too small and have caused flooding during storms. They are also considered a fish passage barrier for two main reasons:
- They are too small for the volume of water that passes through it. As a result, the water is pushed through extremely fast making it difficult for fish to swim in it.
- At times, the water inside the existing culverts are too shallow in the stream bed for fish to continue to swim upstream.
Fish have a very difficult time swimming through extremely swift water. They also have a lot of trouble swimming 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 culverts 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. 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 so that juvenile fish have a better chance of survival. (Image courtesy of WSDOT Fish Passage Program).
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 pipes (culverts) that channel streams and water underneath the road. Many of these culverts were installed between 30 and 100 years ago. These older culverts allow water to flow but are so narrow and steep that they prevent fish from swimming through them.
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 fish 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.
- The current pipes are 48” diameter each and made of concrete. They will be replaced by a 19-foot wide, 7 foot tall, and 44-foot-long reinforced concrete box culvert.
- The current side culvert is a 60” diameter LCP pipe and will be replaced by a 9-foot wide, 6.5 feet tall, and 25-foot-long reinforced concrete box culvert.
Photos
August 2024 – After excavating the trench, crews place rocky material to create a base for the box culvert.
August 2024 – Crews use a rod known as a “grade stick” to evaluate the soil after excavating the area north of the road.
August 2024 – Temporary dams and pumps were installed to allow crews to divert water around the work zone. This minimizes erosion, keeps sediment from washing downstream, and keeps fish from entering the work site.
August 2024 – The crew began to excavate channels on both sides of SE 432nd St to prepare for the box culvert.
August 2024 - A native cutthroat trout is captured and transported in a cooler, ready to be released further downstream, away from the project. Other native fish relocated out of the work zone included juvenile coho salmon, long nosed dace, sculpin, western brook lamprey, and native crayfish.
August 2024 - Environmental staff relocated fish away from the work zone so that crews can safely construct the new culvert at SE 432nd Street. These specialists use a variety of techniques to catch and release fish downstream.
August 2024 - The existing pipes are considered a fish passage barrier because their small size causes water to rush through too quickly, making it difficult for fish to swim. In the summertime, water inside the existing pipes can also sometimes be too shallow for fish to swim.
August 2024 - King County is replacing two worn out, undersized pipes under SE 432nd St with a new box culvert. The existing pipes have caused flooding during heavy storms.
Two 48-inch pipes currently flow this tributary to Newaukum Creek under SE 432nd Street under the road. In winter, these pipes are too small and can lead to flooding. They are also barrier to fish. View larger (217KB)