Sound Transit begins East Link construction on I-90 bridge across Lake Washington

Written by Maggie Lancaster, assistant editor
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Sound Transit's East Link construction is now underway in the center lanes of the Homer M. Hadley floating bridge across Lake Washington.

 

Sound Transit says that “building light rail across a floating bridge is a world’s-first achievement, made possible by innovative engineering to create a track bridge that will compensate for six ranges of lake motion.”

A video illustrating the track bridge technology can be viewed here.

“In just a few years, Eastside light-rail riders will be able to cross the floating bridge safely and reliably in about a minute, no matter how congested traffic gets on I-90,” said Sound Transit CEO Peter Rogoff. “This project, in the making for four decades, moves the region forward in building a critically needed transit connection between Seattle and the Eastside. Our close partnership with the Washington State Department of Transportation continues to make this vital work possible.”

Construction on the bridge will continue through 2020 and will include the following activities:
• Demolition of the barrier on the south side of the bridge
• Pontoon post-tensioning to strengthen the bridge
• Seismic retrofitting of the footings and superstructures of the east and west approach structures
• Installations of: an overhead catenary (power) system, the track bridge system, eastbound and westbound tracks, electrical and control systems, signals, cathodic (stray current) protection, traction power substations outside the east portal to the Mount Baker Tunnel and under the east approach structure on the west end of Mercer Island
Construction this summer will include demolition of the barrier on the south side of the bridge and work inside the pontoons to prepare for post-tensioning, a process that uses cables to compress the concrete pontoons together to strengthen the bridge.

The seven-mile section of the East Link alignment that includes the floating bridge runs from the International District station in downtown Seattle to the East Channel Bridge and encompasses half of the light rail extension’s total length. Sound Transit says this segment will include two new stations at Judkins Park and Mercer Island. Although construction on the bridge surface is limited to spring and summer months, work will continue year-round in this and all segments across the East Link alignment.

All segments of the East Link extension are now under construction and the entire line is expected to be operational in 2023.

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