Major work continues on new SR 520 floating bridge

  • Written by WSDOT
SEATTLE – Construction crews recently completed the first concrete superstructure on top of Pontoon W at the east end of Lake Washington to support the new State Route 520 floating bridge deck.

The five columns are approximately 55 feet tall and 4 feet in diameter. In conjunction with new bridge piers in Medina, the new columns form the eastern navigation channel that will provide 70 feet of vertical clearance for passing vessels and match the Interstate 90 navigation channel. These columns also mark the transition from the floating section to land-based supports for the new six-lane bridge and highway. Pontoon W was one of six pontoons built in Aberdeen that needed additional repairs after crews found end-wall cracking and interior spalling, or chipped concrete, in May. Since then, the Washington State Department of Transportation has reported construction issues and repairs, and continues to provide updates regarding the status of the pontoons. Project information is available at

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