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A Bridge to Nowhere – Right Now – That Is

 Airport Way S Viaduct Rehabilitation Project Update:

Airport Way South is a heavily traveled arterial, important to businesses, freight operations, the Port of Seattle, commuters, cyclists, and residents of Georgetown and the surrounding area.  With over  13,000 vehicles traveling on Airport Way South daily, the Airport Way S viaduct, built in 1938,  has experienced increased stress over time. The viaduct, currently being rehabilitated, will be a much safer for all traffic upon completion of the project.   And its useful life should be extended for at least another 20+ years!

Removing concrete panels of main span.

The old viaduct that passes over the Argo Railroad is gradually disappearing – at least partially.  In recent months, the project, which began November 30, has made big strides.   The precast concrete deck has been completely removed from the main span. The old north and south timber approaches to the bridge have been totally removed.  Now all that remains is the super structure of the main span that crosses over the railroad tracks.

The viaduct work is not made easy by the fact that it must continue over an active railroad yard, maintaining the existing mainspan super structure, working around a limited access site, and working on a foundation containing liquefiable (weak) soils. Timing of work has involved a great deal of coordination. Add to that, the crews must constantly strive to minimize the amount of movement to the high pressure gas main which runs under the viaduct and is an important north-south feed serving the region. Vertical white PVC pipes, that are visible in the photo above, designate monitoring points for the gas main.

Last week, ground improvements on the north end got underway. The south end ground improvements are planned to begin this week. The ground work has been needed due to weak soils surrounding the viaduct.  Using an injection process,  pipes are inserted into the ground and then as  the pipes are withdrawn, the voids produced are replaced with grout.  When fully hardened, the grout fills cracks and voids and strengthens the ground.  After the ground improvements, work on the mechanically stabilized earth wall structure for the approaches will occur. Rehabilitation and seismic improvements will be made to the main span of the viaduct and then it will be resurfaced with a new concrete deck.

The detour route is being monitored, maintained and modified as needed.  This week the crews will also work on the timing of the signals at Airport Way and Lucile to improve the flow of traffic. 

Rebuilding the approaches to the main span, that right now appears to be stranded, will begin in the spring.  The entire project is expected to be completed by the end of the year.

Originally, the Airport Way South Viaduct was built and financed by the railroad companies and later was transferred to the city. The current rehabilitation project is being funded by the city’s Bridging the Gap program.