Swamp Creek Bridge 503 Replacement


Swamp Creek Bridge 503 is located near milepost .06 on Locust Way between the cities of Bothell and Brier. This bridge is located 400 feet north of the intersection of 228th Street SW and Locust Way. Originally constructed in 1960, the 41 foot span has narrow lanes, no shoulders and no sidewalks. Swamp Creek Bridge 503 does not support the current traffic needs of the area. The existing is bridge is structurally deficient, scour critical, and the vehicle weight limit has been reduced. Funding for a replacement bridge has been secured and construction on a new bridge is anticipated to begin in 2024.


The proposed replacement bridge will improve traffic flow for the nearly 10,000 vehicles who access this span of road and provide dedicated spaces for pedestrians and bicyclists. The new bridge would remove in-stream piles and feature a single span design to limit impact on habitats below and provide a more natural flow of water in Swamp Creek.

Traffic Impacts

During construction, a full road closure is anticipated. A detour around the project area would maintain better traffic flow and provide a safer environment for motorists and workers. The proposed detour route is approximately 4.1 miles from end to end. This page will be updated with closure dates when they are finalized.

Environmental Review

State Environmental Policy Act (SEPA) Decision: On September 14, 2022, Snohomish County Public Works determined that this project does not have a probable, significant adverse impact on the environment and has issued a Determination of Non-Significance (DNS). An environmental impact statement (EIS) under RCW 43.21C.030(2)(c) is not required. This decision was made after review of SEPA documents and other information on file with this agency. 


Federal bridge replacement funds from FHWA and administered by WSDOT Local Programs were awarded in early 2020.


Other Projects in the Area