Thorndyke Creek Culverts Replacement

Thorndyke Creek previously flowed under Thorndyke Road through a pair of 5-foot corrugated metal pipe (CMP) culverts. The culvert outlets were perched due to outlet scour and the Washington Department of Fish and Wildlife (WDFW) classified the site as a partial barrier to fish passage.

Thorndyke Culvert #2In 2022 Jefferson County replaced the existing culverts with a new fish-passable structure. This structure mimics the characteristics of the natural stream channel. It is 35 feet wide by 12 feet tall and the culvert bottom is filled with 6 to 8 feet of aggregate and streambed sediment to simulate a natural streambed. This has opened up access to many miles of spawning and rearing habitat for the native fish population of Summer and Fall Chum, Coho, Steelhead, and Sea Run Cutthroat.

The project was completed on October 31, 2022 for a total cost of $2,150,500, and was 95% funded by grants from the Washington State Fish Barrier Removal Board and the U.S. Fish & Wildlife National Fish Passage Program.

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On June 21, 2023 Jefferson County Public Works met with County Commissioner Greg Brotherton and Washington Recreation and Conservation Office representative Josh Lambert at the Thorndyke Road MP 4.71 Culvert Replacement project to commemorate successful completion of the project. Representatives from the Fish Barrier Removal Board and the National Fish Passage Program were also invited but unable to attend.  In attendance from Public Works were Monte Reinders (Public Works Director), Eric Kuzma (Engineering Services Manager), and Mark Thurston (Project Manager).  Attendees discussed the value of this project in opening up 15 miles of high quality stream habitat for salmon and other species.  Jefferson County expressed appreciation for the funding sources that made this project possible, and a desire to work with the funding agencies again on future fish passage projects.  Attendees erected two commemorative signs that were provided by the Recreation and Conservation Office. 

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