4th Ave S Bridge Seismic Retrofit Project

December 18, 2018

What's happening now?

We hope to have the northbound curb lane reopened by the end of 2019 or early 2020. When we closed the lane last year, we expected to have the lane open by now. However, the permit we received from the Union Pacific Railroad requires that we do not work in the Argo rail yard. Union Pacific owns the right-of-way (ROW) under the bridge. This means we need to fix the bridge from the bridge deck which makes the design and construction of the repairs much more complex. We are currently working towards a design and hope to start construction in 2019. 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, we have seen more cars and trucks go over the bridge but also deterioration of the cantilevered ends of the main span piers. Last year, we took a closer look and concluded that the outer edges of the bridge could not support the vehicle loads it was carrying. Public safety is our top priority and we decided to completely close the northbound curb lane and restrict large trucks from using the southbound curb lane. 

Project Map

Project map for 4th Over Argo

The short-term and long-term solutions

The short-term solution to this situation is to lessen the load on the outer edges of the bridge. This means cars going northbound must merge into the inside lane. Cars 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 be in place through the end of 2019 or early 2020.

In the long-term, we are planning to rehabilitate the span spiers underneath the outer edges of the bridge. This work requires coordination with the rail yard under the bridge which owns the right-of-way under the bridge. Our permit with Union Pacific Railroad requires us to not work in the Argo rail yard. We have to make repairs from on top of the bridge which makes the design and construction more complex than we anticipated. We are currently bringing a consultant on board to help us finalize design.

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 Dwotntown and South Seattle. 

As we move into what is being called the Seattle Squeeze, please consider giving yourself extra time to travel, working with your employer about changing your work hours, or finding a different way 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. The northbound curb lane of the 4th Ave S Bridge should reopen by late 2019 or early 2020.

Get involved

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