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

Jefferson County will be replacing the existing culverts with a new fish-passable structure. This structure will mimic the characteristics of the natural stream channel. It will be 35 feet wide by 12 feet tall and the culvert bottom will be filled with between 6 and 8 feet of aggregate and streambed sediment to simulate a natural streambed. This will provide 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 road is now open as of Monday, October 31, 2022.

The project will be constructed in the summer of 2022 with a total cost estimate of $1,935,778, and is approximately 95% funded by grants from the Washington State Fish Barrier Removal Board and the U.S. Fish & Wildlife National Fish Passage Program.