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I-5 - SB Stillaguamish River Bridge - Major Bridge Rehabilitation

This project is currently in construction.
 Project map: Click to enlarge Enlarge map

Southbound I-5 Stillaguamish River Bridge
See more southbound I-5 Stillaguamish River Bridge photos at Flickr.


March 2015

  • The project was operationally complete on Nov. 15. Operationally complete means the roadway is open and the majority of the work is finished.
  • The speed limit has returned to 70 mph in both directions.
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Why is WSDOT replacing the deck on this bridge?
Two bridges cross the Stillaguamish River on I-5 just north of SR 530 and just south of Stanwood (SR 532). The southbound bridge is older, built in 1933.

At 81 years old, the bridge deck has pot holes and and cracks, and there are also portions of supporting steel framework underneath the deck in need of replacement. This summer, contractor crews will remove and replace the entire bridge deck and the portions of supporting framework that need replacement.

This bridge was last inspected in 2012 and is safe for drivers. However, this bridge is on WSDOT’s Structurally Deficient bridge list due to the needed deck and framework repairs. Once the bridge deck is replaced, the bridge will be taken off the Structurally Deficient bridge list.

To replace the southbound I-5 bridge deck, the bridge will be closed for the summer. To keep traffic moving, contractor crews will build a temporary roadway across the I-5 median and reconfigure the northbound bridge to accommodate traffic in both directions. As traffic approaches the bridge, both directions of I-5 will be reduced from three to two lanes, with a reduced speed limit of 55 mph.

On average, roughly 80,000 vehicles drive this section of I-5 daily. These numbers increase during the peak summer travel period.

The End Result
This project will replace the bridge deck on the southbound I-5 bridge, preserving this vital link for years to come.

Project Benefits

  • Preservation: This project improves and preserves a vital bridge in the state's bridge inventory.
  • Economic: This bridge is an important part of the I-5 corridor. Maintained properly, it will continue keeping up with the demand of commuter and freight traffic for years to come.

What is the project timeline?

  • February 2014 - Project goes to advertisement for competitive bidding.
  • March 2014 - Award project to contractor.
  • May 20, 2014 -Mowat Construction Co. is awarded contract. 
  • June 2014 - Begin construction of crossover and prepare northbound bridge to carry two-way traffic.
  • July 29, 2014 - Close and begin repairs on southbound bridge. I-5 reduced to two lanes in each direction. Speed limit lowered to 55 mph.
  • Nov. 8, 2014 - Reopen southbound bridge. 
  • Nov. 15 - The project was operationally complete.

Financial Information

Financial Data for PIN 100553V
Funding Source Amount ($ in thousands)
2003 Gas Tax (Nickel Funding) $0
2005 Gas Tax (TPA) $0
Pre-Existing Funds (PEF) $8,685
Total $8,685

Project signage will reflect the cost of construction engineering, project bid award and sales tax.

Total project cost: $8,687,999

How can I get more information?
Tom Pearce
WSDOT Communications
Phone: 206-440-4696


Kris Olsen 
WSDOT Communications
Phone: 206-440-4704
Dave Crisman
WSDOT Project Engineer
Phone: 360-848-7100

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