Sound Transit completes first light rail tunnel from Northgate to Roosevelt

The tunnel boring machine, nicknamed Brenda, broke through the future
Roosevelt light rail station as it digs the Northgate Link Extension.
Photo courtesy Sound Transit

Tunnel boring machine for Northgate Link extension reaches site of future Roosevelt station

Sound Transit tunneling contractors reached the wall of the future Roosevelt light rail station March 17, exposing a small section of the boring machine cutterhead and completing the first 1.5-mile segment of a 4.3-mile tunnel that will serve light rail trains from Northgate Mall to the University of Washington starting in 2021.

"This machine churned through hundreds of thousands of cubic yards of earth to reach Roosevelt Station," said Sound Transit Board Chair and King County Executive Dow Constantine. "Now on to the U-District Station, and then to Husky Stadium."

The tunnel work completed today by the boring machine nicknamed "Brenda" is the first of six tunnels being mined as part of the Northgate Link light rail expansion. The machine launched last July from the Maple Leaf Portal at NE 92nd Street just east of Interstate 5 and south of Northgate Mall. Once it finishes boring through the station wall at Roosevelt, it will undergo maintenance at the site before continuing south and connecting later with the completed University of Washington Station, which opens with University Link early next year. 

A second machine nicknamed "Pamela" launched from the Maple Leaf Portal last November. It is expected to arrive at the Roosevelt site this summer. Both tunnels are expected to be complete by mid-2016. Cross-passages and tunnel finishes are scheduled for completion in early 2018. When service starts in 2021, light rail trains will enter and exit the tunnels at the Maple Leaf Portal.

Each tunnel boring machine weighs 600 tons and is more than 300 feet long including the trailing gear. The cutterheads are 21 ½ feet in diameter. By the time tunneling is finished, a total of more than 500,000 cubic yards of soil will have been excavated and over 7,200 concrete rings used to line the tunnels. 

When complete, the $2.1 billion Northgate Link Extension will connect the University of Washington Station at Husky Stadium to underground stations in the U District and Roosevelt neighborhood, and to an elevated station at Northgate. The extension from Northgate will provide 14-minute rides to downtown, seven-minute rides to Husky Stadium, and 47-minute rides to Sea-Tac Airport. Riders from Roosevelt Station will reach the airport in 45 minutes. 

More information on the Northgate Link Extension Project here