The morning of Tuesday, Feb. 17, proves an important milestone in the State Route 520 floating bridge rebuilt. Especially for boaters.

The Tuesday morning event marks when the new floating bridge, currently taking shape on Lake Washington east of Seattle, will block the existing SR 520 drawspan permanently. With the drawspan blocked, boat traffic will no longer be able to use the passage, rerouting them to the east navigation channel.

As new pontoons take shape on the lake, fitting together as the world’s longest floating bridge, the highly noticeable portion of the $4.47 billion project remains on track for an on-time opening in spring 2016.

The rerouting of the boating traffic plays as part of the plan.

The current floating bridge opens for boaters, holding up traffic for up to 30 minutes each time.

This major milestone for the construction project eliminates bridge openings for marine traffic. Crews, however, will still open the drawspan for maintenance work late at night about once a month and high winds may necessitate opening the span to relieve stress. But all those openings go away once the new bridge opens in 2016.

The new six-lane bridge complete with a bicycle and pedestrian path won’t holdup traffic with marine openings. Instead the east navigation channel will serve as the main passage point.

During construction of the new bridge, the temporary height clearance is 58 ft, the height of the old bridge on the east channel, but that boosts to 70 ft when the project wraps and the new bridge is in place, matching the same height of the Interstate 90 East Channel Bridge to the south. 

Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for Popular Mechanics, Sports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.