Seattle light rail construction underway on floating bridge

Seattle — Sound Transit announced that construction on the East Link light rail extension is now underway in the center lanes of the Homer M. Hadley floating bridge across Lake Washington. 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 at https://www.soundtransit.org/blog/platform/crossing-lake-washington.

“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

This summer’s construction activities 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 7-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. This segment will include two new stations at Judkins Park and Mercer Island. While construction on the bridge surface is limited to the spring and summer months, work will continue year-round in this and all segments across the East Link alignment.

East Link will extend light rail 14 miles from downtown Seattle to downtown Bellevue and the Overlake area of Redmond via Interstate 90, with 10 stations. All segments of the East Link extension are now under construction, and the entire line will be operational in 2023. The following year Sound Transit will open a 3.7-mile extension further east to new stations in Southeast Redmond and downtown Redmond under funding approved in November 2016.

The Northgate Link light rail extension that is currently under construction will reach Seattle’s University District, Roosevelt and Northgate areas in 2021. Additional Link extensions that are nearing construction will reach north to Lynnwood in 2023 and south to Federal Way in 2024. Later extensions to form a 116-mile regional system will reach Everett, Tacoma, West Seattle, Ballard, South Kirkland and Issaquah. By 2040 Sound Transit Link trains will carry approximately 600,000 riders each weekday.

For more information on the East Link Extension, visit www.soundtransit.org/Eastlink.