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SR 520 - Floating Bridge and Landings Project: What's Happening Now?

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Updated: November 2015

Construction of the new SR 520 floating bridge continues on Lake Washington, where crews are assembling the new structure. 

Current work

Past work

Lane and Ramp Closures

Visit the SR 520 Orange Page for specific dates and times.

Lake Washington

aerial view of SR 520 bridge Recently, floating bridge crews reached several major milestones. In July, all of the pontoons were placed in their final locations on Lake Washington. In August, crews placed the last of 776 roadway deck sections, which form the bridge’s low-rise driving surface. This October, the last high-rise deck was poured, completing the driving surface from Medina to the new West Connection Bridge in Seattle.

Crews currently are placing crushed rock inside the pontoons to serve as ballast. The rock ballast ensures that all pontoons sit at the same height on the water. Pontoons on the lake are also being outfitted various equipment including fenders, hand rails, pump wells, swimmer cables and bird ramps.

The contractor continues to work on electrical wiring throughout the structure, which will power lights, sensors, active traffic signage and other equipment on the bridge.

Crews are also completing work on various architectural elements along the bridge’s bicycle and pedestrian path, including installing hand rails and belvederes, or rest and viewpoint areas. Another feature of the new bridge is roadway stormwater drainage systems, for which crews are currently installing drainage pipes along the length of the bridge.

The new bridge will open to traffic in spring 2016. Count down to the bridge opening and follow the next steps in construction with our new  Commissioning Graphic .

Construction activities and project barges periodically block the navigation channels. These obstructions may alter boater access through the navigation channels. Find more information about boating near the SR 520 floating bridge on our boater information page .


The new bridge maintenance facility, located on the shoreline beneath the bridge’s east high-rise, is currently being outfitted with utilities and flooring.

On the east approach to the bridge, crews are constructing noise walls which will reduce traffic noise near the shoreline. Between the fixed east approach structure and the floating bridge, crews are installing the large expansion joint at the transition span. The expansion joint and transition span form the mechanism that will allow the floating bridge to adjust to seasonal changes in lake level.

Joining of longitudinal pontoons is now complete and pontoons block the center drawspan of the existing bridge. Boaters can continue to use the east navigation channel for access around the floating bridge. Find more information about boating near the SR 520 floating bridge construction site on our boater information page .


Beginning in late November 2015, crews will begin grinding the roadway deck on the new floating bridge at the west end in Seattle. This work creates the Next Generation Concrete Surface that is part of the noise mitigation measures on the new bridge.


Casting of the concrete deck sections began in March 2014 and was completed in August 2015. A total of 776 sections were built. These sections form the roadway for the new floating bridge. For more information about the work done in Kenmore, visit our project page .


Construction of the 44 supplemental stability pontoons built in Tacoma was completed in December 2014. At this time, no other SR 520 construction activities are planned in Tacoma. Check out photos of construction in Tacoma on our Flickr page


On March 10, 2015, crews floated the sixth and final cycle of pontoons from the casting facility in Aberdeen. The last three pontoons arrived on Lake Washington on April 9, 2015.

You can find more information on the Pontoon Construction Project section of the program website and watch videos of the float-out process on our YouTube page.