Light rail guideway soon to cross I-90 in south Bellevue
Construction method uses specialized cranes that enable the bridge to be built over the freeway with minimal disruption to traffic
Sound Transit today briefed media on East Link light rail guideway construction that will soon cross over I-90 in south Bellevue.
Sound Transit contractor crews are constructing the bridge using a sophisticated balanced cantilever construction method. From a large column that has been constructed near Bellevue Way Southeast, two movable forms for concrete known as “travelers” will move outward as crews use them to construct bridge segments. The travelers will move outward at an equal pace, keeping the structure balanced as concrete segments are added on each side.
After the bridge extends partially over the westbound lanes of I-90, the travelers will be moved to the north side of the freeway to repeat the process. The two structures will meet above the freeway, with crews using specialized surveying equipment throughout the construction to ensure the structures are properly aligned for the connection. A video animation illustrating the process, courtesy of the American Segmental Bridge Institute (ASBI) and RS&H, can be viewed at https://vimeo.com/300545241.
The traveler was determined to be the safest and most cost-effective option for construction of this section of guideway, and least disruptive to traffic on I-90. The length and curve of the bridge and the narrow width of the westbound freeway would not allow for placement of a temporary column to support framing, similar to the method of construction of the I-405 overcrossing in downtown Bellevue.
The structure will begin extending across I-90 in the next few weeks, and is expected to be complete in early 2019. Work is taking place overnight, and will require some lane and ramp closures. People can subscribe to construction alerts at www.soundtransit.org/subscribe-to-alerts to receive updates on construction progress in south Bellevue, including planned traffic impacts.
In addition, girders are being placed for guideway along Bellevue Way Southeast between I-90 and the future South Bellevue Station, where the platform and 1,500-space parking garage are taking shape. Farther east, crews are excavating the trench in which light rail vehicles will travel in front of the Winters House; and work has started for the undercrossing on 112th Avenue Southeast.
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. Construction of the East Link extension is more than 40-percent complete, and the entire line will be operational in 2023. For more information on the East Link Extension see: www.soundtransit.org/Eastlink
Sound Transit is simultaneously working to extend light rail north, south, east and west, opening new stations every few years to form a 116-mile regional system by 2041. Starting in 2021 the Northgate project will provide reliable, congestion-free travel to Seattle’s University District, Roosevelt and Northgate neighborhoods. Northgate Link will be followed in 2023 by the opening of service to Mercer Island, Bellevue and Redmond’s Overlake community. Additional extensions to Shoreline, Mountlake Terrace, Lynnwood, Kent/Des Moines, Federal Way and downtown Redmond are planned in 2024. Further light rail extensions are scheduled to reach West Seattle, Fife and Tacoma in 2030; Ballard in 2035; Paine Field and Everett in 2036; and South Kirkland and Issaquah in 2041.
The agency is also working on further investments including, but not limited to, expansions of Sounder South service and bus rapid transit service in 2024 along the north, east and south sides of Lake Washington. More information is available at www.soundtransit.org/system-expansion