Sound Transit, serving the Seattle metropolitan area, will debut the first 6.5-mile segment of its $3.67-billion East Link Extension April 27, launching light-rail service along an eight-station route between South Bellevue and the Redmond Technology Center, both east of the city.
Sound Transit's Blue Line trains won't travel across Interstate 90 from Seattle to Bellevue until 2023, but the effort to engineer how light rail will make the trip across a floating bridge — for the first time ever, anywhere — has been ongoing for years.
Permanent floating bridges are essentially boutique structures that only make sense for certain rare kinds of sites: unusually deep bodies of water and/or bodies of water with very soft bottoms, where piers are impractical.
Transitioning rail to a floating bridge that is constantly bobbing and swaying at the whims of the water required a first-ever solution for Sound Transit.
Seattle’s Sound Transit had a challenging problem: how to get a new light-rail line on and off a nearly 1-mile-long Interstate 90 floating bridge while protecting the rails from the constant movement of the water.
With the moniker of world’s longest floating bridge hovering around nearly every word written and spoken about the new State Route 520 bridge in Seattle, bridge owner Washington State Dept of Transportation has grown accustomed to the superlatives used when describing its now 1-year-old construction project.
