The Stillaguamish River Bridge was in need of new paint to preserve and protect its aging structure. Existing paint on the southbound I-5 bridge was weathered and damaged, allowing corrosion to occur. This bridge preservation project removed old peeling paint, cleaned exposed metal and applied new paint to the existing bridge structure on southbound I-5 under a full containment system. Minor maintenance and repairs were also performed such as replacing joints and rivets.
December 2020 - Summer 2022
What to expect
This project is complete and travelers should not expect any construction related travel delays.
The southbound Stillaguamish River bridge was built in 1933 to carry US 99. The steel truss bridge comprises three spans over the river and spans 607 feet. When I-5 opened in the 1960s, the bridge became part of the interstate, carrying two lanes in each direction. A new northbound bridge opened in 1971 and traffic was separated resulting in three lanes on each bridge.
Each span of the bridge carries an average of 39,000 vehicles per day, but that can rise to 50,000 per day during summer. The heaviest traffic volume occurs between 3 p.m. to 6 p.m. Thursdays and Fridays and from 11 a.m. to 4 p.m. on the weekends northbound, and from 4 p.m. to 6 p.m. on Sundays southbound.
In the summer of 2014, WSDOT contractor crews replaced the southbound bridge deck which was worn out after 81 years of use that caused cracks, ruts and potholes. It took about four months to complete the work and the bridge reopened in November 2014.
I-5 southbound bridge closed
Project painting complete
Project paused for winter
Final elements of project complete
Federal funds will be used for this preservation project totaling approximately $2.6M.
Financial Data for PIN 100555U
Amount ($ in thousands)
2003 Gas Tax (Nickel Funding)
2005 Gas Tax (TPA)
Pre-Existing Funds (PEF)
This map shows the location of the I-5 Stillaguamish River Bridge. This bridge preservation project removed old peeling paint, cleaned exposed metal and applied new paint to the existing bridge structure on southbound I-5 under a full containment system.
Beginning in June, all southbound traffic was diverted onto the existing median bypass on the adjacent northbound bridge through mid-October. This kept both directions of I-5 flowing during the work.