The Washington State Department of Transportation is celebrating a major milestone for the new State Route 520 floating bridge. The final three pontoons built for the bridge are in the process of leaving Grays Harbor and should arrive in Seattle as soon as Thursday, April 9, 2015.
The football-field-size structures will then move through the Hiram M. Chittenden Locks in Ballard on their way to Lake Washington. There, they’ll join the 74 previously constructed pontoons that together will support the world’s longest floating bridge.
WSDOT contractors built pontoons for the new SR 520 floating bridge in Aberdeen and Tacoma. Of the 33 constructed in Grays Harbor County, 21, including the final three, are the massive longitudinal pontoons – 360 feet long, three stories high, and 11,000 tons. They form the backbone of the new bridge.
Contractor crews on the lake continue to bolt together and anchor pontoons in their final position. The new bridge, with six lanes, a shoulder for disabled vehicles, and a bicycle/pedestrian path, is designed to resist stronger windstorms than the current bridge. The new bridge is scheduled to open in spring 2016.