Project expected to start in summer 2025
The Boise X Connection Bridge over Boise Creek was built in 1956. It got its name from an old, elevated Northern Pacific Railroad trestle that used to be adjacent to it.
Why is King County replacing the bridge?
Replacing the bridge provides a safer, reliable crossing for the community.
The existing Boise X Connection Bridge was designed for much smaller vehicles compared with what we see on the road today. The bridge is nearly 70 years old. It has outlived its useful life and is showing its age in the following ways:
- Original steel deck and steel girders are rusting.
- Creosote treated timber foundations are rotting.
- Lead-based paint is peeling off.
- The bridge is weight restricted—large trucks and other heavy vehicles cannot use this bridge.
- The bridge is too narrow for the size of cars and trucks that use the road.
The replacement bridge improves driver safety and the surrounding environment. This project also includes a public art installation, funded by King County's 1 Percent for Art program.
- The new bridge will be built to modern safety design standards.
- It will be open to all vehicles, regardless of size or weight.
- The curves in the roadway approaching both ends of the bridge will be slightly straighter to make it easier for drivers to see further ahead (sight distance).
- The new bridge will have standard 11-foot-wide travel lanes, 6-foot-wide shoulders, and modern bridge railings and guardrails on both sides.
- Removes decaying creosote timber support piles that leach toxic chemicals into the soil and water.
- Eliminates the source of lead paint currently peeling off the bridge and falling into the stream.
- Relocates the bridge supports further from the stream, giving the stream extra room to move.
- Installs large woody material and new streambed gravels to improve fish habitat.
- Removes invasive plants and restores the area with native shrubs and trees.
What to expect during construction
Construction activities will include demolition and removal of existing bridge, concrete pouring, and crane lifts. After the new bridge is opened to traffic, crews will continue low impact restoration work including plantings and site clean-up.