Photo Gallery: Envisioning the New 520 Bridge

Construction moves to Lake Washington this week on the new State Route 520 floating bridge, slated to open by the end of 2014. An open house on the project is set for Tuesday in Medina.

Construction on the new State Route 520 Bridge will move to Lake Washington this week, as construction crews move barges and heavy equipment next to the bridge, the Washington State Department of Transportation announced this week.

For even more photos than the 16 we posted here, the WSDOT’s Flickr site has renderings of the future SR 520 floating bridge

The latest construction plans by contracting group Kiewit/General/Mason puts six lanes on the new structure, puts a 70 foot clearance underneath the bridge, which will eliminate the need for a drawspan, and puts a 14-foot-wide bike and pedestrian path on the bridge, according to construction plans released today.

The bridge is part of the state's  from Seattle to Redmond and which .

So far, the state has identified tolls and federal and state gas taxes to fund $2.43 billion of the project, which includes the bridge construction The state continues to seek funding for and is currently designing the bridge's connection to Interstate 5 through Seattle, which will be completed under a separate project, officials said.

"Starting floating bridge construction on Lake Washington is a huge milestone 15 years in the making," state Transportation Secretary Paula Hammond said in a prepared statement. "Crews will build a stronger, more reliable floating bridge—and designs show the integrated architectural features will be distinctive and memorable for generations to come."

Along with bus and carpool lanes in each direction, five public viewpoints will be built along the path, and four lit column-like sentinels will mark where the new bridge transitions between land and water. 

The existing State Route 520 floating bridge was originally built in 1963.

The bridge has a drawspan that is fragile enough to necessitate closure during windstorms, and water from Lake Washington sprays onto the deck and cars during strong storms, said John White, the WSDOT official in charge of the new bridge's design.

The new bridge has been designed to withstand strong winds and will be higher than the "spray zone," and will not need a drawspan, he said, which will mean fewer expected closures due to storms.

The new bridge has been designed for 75 years, though it could last longer than that, White said.

Later this summer, the first batch of 77 huge floating concrete bridge pontoons will arrive by barge and tug, officials said. The pontoons, the biggest of which are larger than some buildings, were built in Aberdeen, Tacoma and Kenmore.

"We have an aggressive schedule, and contractor crews have more than two years of challenging work ahead of them at multiple work sites around the region," Julie Meredith, WSDOT SR 520 Program director, said in a prepared statement.

520 Bridge by the numbers


33 pontoons in Aberdeen for $378 million

44 pontoons in Tacoma for $586.6 million  

58 massive concrete anchors and hundreds of concrete road decks in Kenmore, and ultimately the floating bridge

Fun fact: It will take four days for pontoons to be floated from Aberdeen to Lake Washington, by going around the Olympic Peninsula and through the Ballard Locks. From Tacoma to Lake Washington, it will be six to eight hours.


Including highway construction on the Eastside, an estimated 900 people have worked on SR 520 corridor improvements to date, with more expected as floating bridge construction ramps up on Lake Washington. 

Fun fact: For the most part, the construction will follow a weekday regular day shift, according to Kiewit/General/Mason.


WSDOT has $2.43 billion of $4.65 billion budgeted to build improvements in the 12.8-mile SR 520 corridor between Seattle and Redmond. The project is being fundd by bonds which are being repaid through the State Route 520 tolls and federal and state gas taxes.

Fun fact: , and will continue to rise every year through 2016.

If you go

WSDOT is hosting open houses in Medina and Seattle. In addition to construction and floating bridge design news, WSDOT staff will share updated information on designs in the Seattle area and our efforts to minimize effects during construction.

  • Medina: 4:30 to 7:30 p.m. Tuesday, March 27, at School, 7800 NE 28th St., Medina.
  • Seattle: 4:30 to 7:30 p.m. Wednesday, March 28, at the Museum of History & Industry, 2700 24th Ave. E., Seattle.

Details about the new SR 520 can be found at www.wsdot.wa.gov/projects/sr520bridge


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