Sound Transit launches second Northgate Link tunnel boring machine

Written by Jenifer Nunez, assistant editor
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Sound Transit

The second tunnel boring machine (TBM) mining Sound Transit light-rail tunnels from the Northgate neighborhood in Seattle, Wash., to the University of Washington launched November 20.


Northgate Link is expected to be one of the busiest new light-rail lines in the nation,” said Sound Transit Board Chair and King County Executive Dow Constantine. “The action we’re taking today will help us meet the increasing demand on one of the most popular corridors in the central Puget Sound region.”

The Northgate extension is expected to add more than 60,000 riders a day to the light-rail system by 2030 and be a key component of a region-wide light-rail system that will carry an estimated 280,000 riders a day by 2030.

Sound Transit contractors are using two TBMs to mine the twin Northgate Link tunnels. The first TBM launched in July and has mined about 3,200 feet so far.

The machines will mine approximately 3.6 miles from the tunnel portal just south of the Northgate Transit Center to UW where the tunnels will connect with the University Link line into downtown Seattle. That section between downtown and the UW is scheduled to open in early 2016.

The $2.1-billion Northgate extension includes underground stations in the U District and Roosevelt neighborhoods and an elevated station at Northgate. The line will add major new capacity to the region’s transportation system, offering fast, frequent and congestion-free service 20 hours a day. A trip from Northgate to downtown will take 14 minutes. Northgate to UW Station will take eight minutes.

The tunnels are being constructed by the same contractors, Jay Dee Contractors of Livonia, Mich., Frank Coluccio Construction Company of Seattle and Michaels Corporation of Brownsville, Wis., that successfully completed two one-mile tunnels for the University Link light-rail project. The University Link light-rail project is currently scheduled to open in the first quarter of 2016, six to nine months early and is estimated to be completed approximately $150 million under budget.

In 2016 Sound Transit will launch the construction of East Link light-rail from downtown Seattle to Mercer Island, Bellevue and Redmond’s Overlake area. Planning and environmental work are moving forward to establish alignments for extending light rail from Northgate to Lynnwood and from South 200th Street to the Kent/Des Moines area.

Following the 2023 opening of all the Sound Transit 2 extensions that regional voters approved in 2008, Link trains are projected to carry more than 280,000 riders each weekday by 2030.