Local Information

Pontoons on parade this week on Lake Washington

Tuesday, December 10, 2013 - 13:41

David Gitlin, SR 520 Communications, 206-770-3566 or 206-819-7230 (cell)

SEATTLE – The new State Route 520 floating bridge being built on Lake Washington is receiving another lift this week with the arrival of more pontoons to keep the new highway crossing afloat.

Beginning with a 9:30 p.m. arrival on Monday, Dec. 9 and continuing through this week, tugs will tow a total of eight more supplemental stability pontoons through the Hiram M. Chittenden Locks into Lake Washington, where they’ll be moored for later attachment to the new bridge. The hollow, concrete and steel pontoons will flank the bridge’s larger, main pontoons and bridge deck to help stabilize the overall structure.

The public can track tugboats towing the pontoons in real-time on the Washington State Department of Transportation website.

“We’re making steady progress,” said Dave Becher, WSDOT construction manager on the SR 520 Floating Bridge and Landings Project. “With this week’s transport, we’ll have 30 pontoons on Lake Washington, with another eight already built and awaiting transit, plus 14 more in construction.”

In all, 77 pontoons will support the new bridge which, at 1.4 miles in length, will be the world’s longest stretch of floating highway.

The pontoons arriving this week were built in a facility along Tacoma’s Commencement Bay by Kiewit/General/Manson, A Joint Venture. The contractor is constructing 44 supplemental stability pontoons for the bridge. Each pontoon is 98 feet long, 50 to 60 feet wide and 28 feet tall. Their weights range between 2,500 and 2,820 tons.

By comparison, the 21 longitudinal pontoons that will form the new bridge’s buoyant foundation are 360 feet long and weigh more than 11,000 tons. These massive pontoons, together with two cross pontoons at either end of the bridge and an additional 10 stability pontoons, are being built in a casting basin in Grays Harbor, near Aberdeen, by Kiewit-General Joint Venture.

More information about the SR 520 Bridge Replacement and HOV Program is available at www.wsdot.wa.gov/projects/sr520bridge.

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