Floating Train Bridge Arriving in Seattle

Sound Transit is installing train tracks on the Interstate 90 bridge that, when complete, will be the first floating bridge to carry a train. "The water level below the Interstate 90 bridge typically fluctuates 2 feet annually, as spring runoff enters Lake Washington and the Army Corps of Engineers maintains boat passage at the Ballard Locks," Mike Lindblom reports for the Seattle Times. To further complicate this engineering challenge, train tracks must remain parallel or trains will derail.

The weight of the train means the transit provider must take measures to ensure the bridge’s buoyancy. One change that I-90 drivers can see from their car windows has to do with highway barriers. "Contractors are instead replacing concrete barriers, which wouldn’t stop a train anyway, with cable fence to prevent falls into the lake," Lindblom reports.

This bridge is a component of the Sound Transit's East Link light rail extension. Sound Transit says the train will take passengers from Bellevue to Seattle and the ride would take 20 minutes. "The 14-mile extension remains on schedule to open in mid-2023, followed by two stations in Redmond by 2024, serving an estimated 50,000 passengers per day," Lindblom writes.