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Sound Transit kicks off light-rail tunnel construction in downtown Bellevue

Rendering of the Redmond Technology Center Station, which will be part of the East Link extension.
Photo – Sound Transit

Sound Transit has begun digging a light-rail tunnel underneath downtown Bellevue, Wash., for the East Link extension.

When completed, the 2,000-foot tunnel will extend between the future East Main and Downtown Bellevue Avenue stations under 110th Avenue Northeast, agency officials said in a press release.

Because of the tunnel's short length, Sound Transit is constructing it using the "sequential excavation method" (SEM) instead of a tunnel boring machine or digging a large trench that's later covered.

The SEM method removes soil in small sections using an excavator and cutting equipment. As soon as soil is removed, pressurized concrete is sprayed on the tunnel's sides, ceiling and floor. Lattice girders provide additional structural support for the tunnel.

This method also will minimize disruption to traffic, reduce noise and dust impacts to residents and businesses, and eliminate utility service disruptions, Sound Transit officials said.

The $3.7 billion East Link project will extend light-rail 14 miles from downtown Seattle to downtown Bellevue and the Overlake area of Redmond, Wash., via Interstate 90.

Footage from a drone flying over the East Link tunnel portal in Bellevue, Wash.

Contact Progressive Railroading editorial staff.

More News from 2/28/2017