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SE 432nd Street Culvert Replacement Project
Construction completed in fall 2024
Check out the smooth fresh pavement over the newly installed box culvert over SE 432nd Street. This project reduces flooding and improves fish passage in Watercress Creek.
Status update
October 2024
SE 432nd Street reopened to traffic on October 4, 2024, after the culvert replacement project was completed. We’re thankful for the patience and partnership of the community during this project. Enjoy your new road!
Overview
King County replaced two worn out, narrow pipes under SE 432nd Street with a new box culvert. Another small pipe that is parallel to SE 432nd Street was also replaced with a larger box culvert. The new culverts are located beneath and alongside SE 432nd Street between the Enumclaw-Foothill Trail and 278th Avenue SE, northeast of Enumclaw, WA. This project includes landscaping with native plants.
Project location
This project was located northeast of the City of Enumclaw, WA on SE 432nd Street between the Enumclaw-Foothill Trail and 278th Avenue SE. View larger ( 195KB)
Why did King County replace these culverts?
We replaced the worn out, narrow culverts because they caused flooding and were a fish passage barrier.
The previous pipe culverts were too small and caused flooding during storms. They were also considered a fish passage barrier for two main reasons:
- They were too small for the volume of water that passes through it. As a result, the water was pushed through extremely fast and was making it difficult for fish to swim in it.
- At times, the water inside the existing culverts was 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 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 previous pipes were 48” diameter each and made of concrete. They were replaced by a 19-foot wide, 7 foot tall, and 44-foot-long reinforced concrete box culvert.
- The previous side culvert was 60” diameter LCP pipe and was replaced by a 9-foot wide, 6.5 feet tall, and 25-foot-long reinforced concrete box culvert.
Photos
October 2024 – Crews laid a fresh layer of asphalt over SE 432nd St to complete the project. The road was reopened to traffic on October 4th, 2024.
October 2024 – Looking west on SE 432nd St: Construction is complete and the new box culverts are fully installed.
October 2024 - Water has been restored to flow downstream through the new box culvert under SE 432nd St.
October 2024 – Pipes on the southwest side of the culvert help to direct water from the roadside ditches on SE 432nd Street.
September 2024: The main box culvert is fully installed, including pipes, drains, and storm filters on the southwest side.
September 2024 – Rock, sand, wood, and soil are used to create the base of the streambed for the culvert alongside SE 432nd St.
September 2024 – Crews anchor large logs to the bottom of the streambed alongside SE 432nd St. The wood pieces have been strategically placed within the stream to provide habitat as the fish migrate upstream.
September 2024 – Crews have installed the bottom of the main culvert on SE 432nd St.
September 2024 – Crews lower the bottom piece of the main box culvert into place on SE 432nd Street between the Enumclaw-Foothill Trail and 278th Avenue SE.
September 2024 – KC Roads engineers and crew inspect the box culverts at the manufacturer before they are transported to the project site.
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)