Visuals now abound for the new State Route 520 bridge, the world’s longest floating bridge. Not only has the Washington State Department of Transportation unveiled the architectural renderings of the new floater—and actually complete with a touch of style and color—but crews have started forming the base for in-water work, giving life to those visuals.

A project 15 years in the making, the new six-lane bridge being built by Kiewit/General/Mason will offer a more stable and elevated floating bridge design, all while giving pedestrians and bikers a prime link east of Seattle.

Those non-vehicle travelers will enjoy a 14-foot-wide path separated from regular traffic by a concrete wall, complete with turnouts (belvederes) that offer a chance to rest, or simply take in the views. Those five bulge-like respites provide a bit of shape to the otherwise straight-laced top deck of the bridge, elevated on the floating concrete pontoons for ease of maintenance and vehicle safety. The belvederes also come complete with wind blocks and interpretive signage.

In an effort to highlight the shift from a land-based bridge to where it floats on Lake Washington, the new design features four column-like sentinels at the two transitions points on either end of the east-west connector. The twin towers rise from the water and soar above the bridge, highlighted by beacons and lights. The pointed design, derived from the 1940 Lacey V. Murrow floating bridge, remains streamlined, but also practical, as they house stairways to allow maintenance crews go from the deck of the bridge to the pontoon level.

The entire design, from spires to bridge deck, aims to remain streamlined and lean. Even the tolling booths will move onshore to unencumber the bridge.

Along with the on-lake visuals, renderings of off-lake bridge sections include park lids.

As folks take a gander at the visuals, drivers near the bridge will see construction barges assemble to form a work zone on the water. Later this summer, the first batch of 77 massive floating concrete bridge pontoons will be towed into the lake and assembled north of the existing 1963 bridge.

Work will begin on some pile driving and onshore excavation, but expect to see a coffer dam made of vertical steel walls near the shore to allow the creation of concrete footings.

The new bridge, part of the larger $4.65-billion road project, should open in late 2014. "We have an aggressive schedule, and contractor crews have more than two years of challenging work ahead of them at multiple work sites around the region," said Julie Meredith, WSDOT SR 520 program director.

Crews for Kiewit-General are building 33 pontoons in Aberdeen as part of a $378-million project. Under a separate $586.6-million contract, KGM is building 44 additional pontoons in Tacoma, 58 massive concrete anchors and hundreds of concrete road decks in Kenmore, and ultimately the floating bridge. Judging by the new renderings, it should all come together just swimmingly. 

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