4th Ave S Bridge Seismic Retrofit Project

Updated April 14, 2020

What's happening now?

We are continuing to coordinate the design for the repair of the 4th Ave S Bridge with the railroad. When we closed the lane, we expected to have the lane open by now. Union Pacific owns the right-of-way (ROW) under the bridge, and because of this, we are required to obtain an access permit from Union Pacific Railroad to work around and within Union Pacific ROW. The permit prohibits construction work on the bridge from taking place from the Argo rail yard, which means that we need to complete the repairs from the bridge deck. This arrangement makes the design and construction of the bridge repairs much more complex. Thank you for your patience.   

Project overview

The 4th Ave S Bridge, or 4th Over Argo Bridge as it's commonly known, was first built in 1933 and serves as a connection between Georgetown and Downtown. In 1985, the bridge was re-channelized to its current configuration. Over time, the bridge has experienced a higher volume of vehicles and heavier trucks. The higher volume and increase loads as well as the structure's aging have caused deterioration of the cantilevered ends of the main span piers.  Inspectors took a closer look of the deterioration and concluded that the outer edges of the bridge could no longer safely support the vehicle loads it was carrying. 

Public safety is our top priority, and SDOT decided to completely close the northbound curb lane and restrict large trucks from using the southbound curb lane in order to reduce further deterioration of the piers. 

Project Map

Project map for 4th Over Argo

The short-term and long-term solutions

The short-term solution to this situation is to reduce the load on the outer edges of the bridge. This means that vehicles going northbound must merge into the inside lane. Passenger vehicles going southbound can still use the curb lane; however, large trucks and buses are required to merge into the inside lane. We expect this configuration to continue to be in place until repairs have been completed.

In the long term, we are planning to rehabilitate the segment of the piers that directly supports the outer edges of the bridge. This work requires extensive coordination with the railroad since the bridge spans across an active rail yard and railroad tracks that support freight as well as commuter rail and Amtrak. Our permit with Union Pacific Railroad prohibits us from working in the Argo rail yard, which could disrupt railroad operations. Because the repairs need to be made from the top of the bridge, these conditions have made the design and construction more complex than we anticipated. We currently have a consultant on board to help us finalize the repair plans.

Taking alternate routes

Prior to closing the curb lane, the bridge was seeing upwards of about 17,000 daily users in both directions. Since the northbound lane closure and southbound restrictions, the number of daily users has decreased by about 25% in both directions. This means commuters have started using alternate routes or taking alternative modes of transportation to and from Downtown and South Seattle. 

As the Seattle Squeeze continues, please consider giving yourself extra time to travel, working with your employer about changing your work hours, or finding alternative means to get to work such as riding a bike, walking, carpooling, vanpooling, or taking public transit. For more information, please visit: www.seattle.gov/traffic.

Schedule and construction

Our team is working with our consultant in finalizing the design and getting final approval from the railroad. The project schedule, which will note the re-opening of the northbound curb lane of the 4th Ave S Bridge, will be updated when the final permit has been approved.

Get involved

To sign up for email updates on the project, please contact us at 4thOverArgo@seattle.gov.