Sound Transit launches tunnel boring machine for Northgate extension

The first of two tunnel boring machines that will dig twin light-rail tunnels from Seattle's Northgate neighborhood to the University of Washington began operating on Wednesday, according to Sound Transit.

The machine will mine about 3.5 miles from the tunnel portal just south of the Northgate Transit Center to the university, where the tunnels will connect with the University Link line into downtown Seattle. University Link is scheduled to open in early 2016.

A second tunnel boring machine is being assembled at the Northgate site and is expected to begin operating in October. Scheduled to open in 2021, the $2.1 billion Northgate extension will include underground stations in the U District and Roosevelt neighborhoods, and an elevated station at Northgate. By 2030, the extension is expected to add more than 60,000 riders to the system daily.

Sound Transit is targeting 2030 to open all Sound Transit 2 extensions that were approved by voters in 2008. The agency plans to launch construction on the East Link light-rail corridor — running from downtown Seattle to Mercer Island, Bellevue and Redmond's Overlake area — in 2016. Planning and environmental work is moving forward to establish alignments that would extend light-rail service from Northgate to Lynnwood, and from South 200th Street to the Kent/Des Moines area.