Creating Safe Passage for Salmon
/Construction on the collapsing culvert
If you explored nature as a child, you might remember those enormous metal pipes filled with ankle-deep, frigid water that cross beneath roadways. These pipes, called culverts, are still common along streams and creeks throughout Washington.
Despite their enticing mystery, culverts are not placed in waterways for childhood enjoyment. Instead, these pipes are installed to direct water under a road or bridge and ensure aquatic species, water, sediment, and fallen trees can move freely despite human development.
When District staff began scoping this site for a culvert replacement, they found the creek bed lined with freshwater mussels.
Unfortunately, many culverts are undersized, decaying, or otherwise inadequate and block fish passage for species traveling up- and downstream. This was the case with a culvert we replaced on a tributary to the Pilchuck River in the Snohomish River basin, a high-priority waterway for fish passage barrier restoration efforts.
Snohomish Conservation District elected to replace this culvert for several reasons. The decaying five-by-40 foot metal pipe was collapsing beneath the roadway and rusted out at the bottom, causing a dangerous sinkhole and risk of complete collapse. The culvert was also small, creating a barrier to fish passage and negatively impacting transport of sediment, wood, and water downstream.
When District staff began scoping this site for a culvert replacement, they found the creek bed lined with freshwater mussels. These mussels thrive when water is clear and free of sediment. District Engineer Ryan Bartelheimer explained, “Mussels are filter feeders, so if there is too much silt in the water the mussels would ‘choke.’ The fact that these mussels are present and healthy indicates that the creek water is of great quality and essential to the surrounding ecology and fish habitat.”
Due to the high-quality upstream habitat and a regional targeted strategy to replace high-priority fish passage barriers in this system, the District was able to procure multiple funding sources for both replacing the culvert and planting nearly three acres of streamside vegetation up from the culvert.
Culvert Before
The new bridge allows for safe salmon passage
To preserve the stream and its aquatic residents during construction, District staff relocated the mussels and erected screens to temporarily keep fish out of the site while water was redirected downstream with a pump. New foundation was laid, arching panels installed, utilities rerouted and, once the new culvert was complete, the road was repaved. The arching panel design was developed in accordance with strict requirements in width, flooding capacity, and fish passage ability. The new design includes ample room for a full stream corridor. Fish, salamanders, raccoons, and other animals can now pass through the culvert without restriction.
This site not only improves conditions for aquatic life, but also establishes a high standard of care for natural resources on private land.
“This story of individual landowners making a positive impact on fish populations for tribal communities and recreational fisheries for generations to come is a seed planted in our community,” said Kristin Marshall, Habitat Restoration and Floodplain Management Program Director. “We all have a part to play in protecting our natural resources.”
We are grateful to the private landowners who voluntarily work with us to complete habitat restoration projects, including this project. As this seed grows and people are empowered to make a difference, the District and our partners will continue to support landowners in removing fish passage barriers throughout Snohomish County for years to come. Learn more about our habitat restoration efforts and request support for your own property on our website.
This project was funded by the Family Forest Fish Passage Program, Adopt A Stream Foundation, and the Washington State Conservation Commission’s Natural Resource Investments grant program and Salmon Recovery Funding grant program.
