SEATTLE – The new State Route 520 floating bridge has begun its march across Lake Washington. Late last week, construction crews completed the first joining of two concrete pontoons that will support SR 520 as it crosses the water. Contractor crews working on the SR 520 Floating Bridge and Landings Project used 80 bolts, each 16 to 20 feet long and close to 800 pounds, to secure Pontoon V to Pontoon W near Lake Washington’s Medina shore.

“With this joining, the new bridge is beginning to take shape,” says Julie Meredith, director of the SR 520 Bridge Replacement and HOV Program for the Washington State Department of Transportation. “This is the first of 21 longitudinal pontoons that will be joined to form the backbone of the new floating bridge.”

Pontoon V is one of the bridge’s longitudinal pontoons. Each one is 360 feet long, 75 feet wide, three stories high, and weighs 11,000 tons. Pontoon W is one of the bridge’s two cross pontoons, which bookend the longitudinal structures on either end of the lake.

Fifty-two of the new bridge’s 77 pontoons have been built so far. They include longitudinal, cross and supplemental stability pontoons. In coming months, crews will align, anchor and bolt together additional longitudinal pontoons, Meredith said. The new, six-lane floating bridge – the longest in the world – is scheduled to open to traffic in spring 2016.

More information is available on the project website at