More Tacoma-built SR-520 pontoons head to Seattle this week

Washington State Department of Transportation crews began float-out of the second cycle of six supplemental pontoons for the new State Route 520 floating bridge.

This float-out follows six months of construction at the Concrete Tech Corporation site, wrapping up the second of six pontoon construction cycles in Tacoma. Crews completed 12 of 44 pontoons to be built in Tacoma and towed from Commencement Bay to Lake Washington. The pontoons built in Tacoma, known as supplemental pontoons, will provide stability and flotation when attached to longer longitudinal pontoons built in Aberdeen. The supplemental pontoons each weigh 2,500 to 2,820 tons and measure 100 feet long, 50 to 60 feet wide and about 28 feet tall.

Two of the pontoons from the latest cycle will be towed to Lake Washington this week and four will remain in Tacoma until additional longitudinal pontoons arrive on the lake. During the course of bridge construction, 44 Tacoma pontoons will be joined with 33 pontoons built in Aberdeen for a total of 77 pontoons needed to construct the world’s longest floating bridge.

“Tacomans love bridges, and we’ve helped build the second Tacoma Narrows Bridge, the Hood Canal Bridge and now SR-520,” said Tacoma Mayor Marilyn Strickland, who joined U.S. Rep. Derek Kilmer (D-Gig Harbor), Washington State Department of Transportation Secretary Paula Hammond, Pierce County Executive Pat McCarthy, and Port of Tacoma Commissioner Connie Bacon. “We’re proud to be part of the team that is building a floating bridge that will serve the Puget Sound region for generations to come and is the longest in the world, to boot!”

More information is available online here.