The following is a release from the Washington State Department of Transportation:

Another six pontoons for the new State Route 520 floating bridge are floating out of their Aberdeen casting basin Friday, marking completion of the fifth of six cycles of pontoons being built in Grays Harbor County.

“With this float-out we have only three pontoons left to build in Aberdeen,” said Julie Meredith, SR 520 program administrator for the Washington State Department of Transportation. “These massive concrete structures are built to last for generations. They’re the backbone of the new floating bridge that will link growing population and commerce centers on both sides of Lake Washington.”

Crews this morning lifted three 50-ton gate sections to open the waterfront casting basin in Aberdeen and clear the way for tugboats to slowly tow the pontoons into the Chehalis River. The first pontoon exited the casting basin at about 10:30 a.m., with the final pontoon expected out by midafternoon.

Four of the six new pontoons are the largest, “longitudinal” type, positioned directly under the new bridge’s roadway. Each is 360 feet long, 75 feet wide and 28.5 feet tall, and weighs 11,000 tons – equivalent to 23 Boeing 747s. The two others are “supplemental stability” pontoons that give the bridge added stability and flotation. These smaller pontoons, which flank both sides of the bridge, are each the size of a basketball court – 98 feet long and 60 feet wide.

The new pontoons will be inspected at the Port of Grays Harbor and then, as weather permits, be towed to Lake Washington for bridge assembly. Full pontoon tracking details are posted online.

With today’s float-out, 66 of the new bridge’s 77 pontoons have been constructed, and 57 are on Lake Washington. The three remaining Aberdeen pontoons are scheduled for completion next spring. Forty-four of the bridge’s supplemental pontoons are being built in Tacoma, where work is underway on the final construction cycle there. Meanwhile, crews continue aligning, anchoring and bolting together pontoons on Lake Washington. The new, six-lane floating bridge – the longest in the world – is scheduled to open to traffic in spring 2016.

Completion of the fifth cycle of pontoons in Aberdeen is just one of many milestones for the SR 520 Bridge Replacement and HOV Program:

• The West Approach Bridge North Project is set to break ground in Seattle this fall. The 1.2-mile-long structure will connect the new floating bridge to the highway’s Montlake Boulevard interchange in Seattle and is designed to modern earthquake standards.
• The Eastside Transit and HOV Project has already brought new highway lanes and transit stops to the Eastside. The full project – including a regional bike-and-pedestrian path – is scheduled for completion later this year.

For information on road closures associated with SR 520 construction, visit the SR 520 Orange Page.