Work scheduled to begin in summer 2025
Fifteen Mile Creek Bridge No. 493C connects Issaquah, Renton, and Maple Valley. The bridge is located between Tiger Mountain State Forest and Squak Mountain State Park Natural Area.
We plan to begin construction in summer 2025. SE May Valley Road will be closed for 10-12 weeks during for construction, and a temporary signed detour route will be in place.
For the most up-to-date status, check My Commute.
The existing bridge does not have shoulders. The new bridge adds two 8-foot shoulders to the roadway.
The existing bridge has a pedestrian sidewalk on one side of the bridge. The new bridge will have pedestrian pathways on both sides of the bridge.
The wooden guardrail posts are aging and worn out. The project will replace the old wooden posts with a new, all-steel guardrail system.
King County Road Services installed steel supports under the existing bridge to help strengthen the old, worn out timber cross beams.
Some of the timber support beams on the existing bridge are worn out. The new bridge replaces the timber beams with concrete bridge foundations.
From this view of the bridge looking south, see the creosote-treated timber piles which are touching the water.