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Sound Transit contractor completes mining last tunnel segment for Northgate Link Extension

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Mining of seven miles of tunnel is done, cross passages and other work inside tunnels continues

Sound Transit contractors completed mining the last tunnel segment for the Northgate Link Extension twin tunnels yesterday when their tunnel boring machine holed through the wall of a retrieval shaft at the University of Washington Station.

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“In just a few years, light rail riders will be enjoying fast, frequent, congestion-free service to the U-District, Roosevelt and Northgate,” said Sound Transit Board Chair and King County Executive Dow Constantine. “By this time next month, we’ll have opened the Angle Lake station in SeaTac, our third new station in six months. These are just two examples of Sound Transit’s steady progress as we work to expand light rail throughout the Central Puget Sound region."

The hole-through completes the last of six tunnel segments mined by JCM Northlink LLC, a joint venture of Jay Dee Contractors, Frank Coluccio Construction Company, and Michels Corporation. Since work began in 2014, two tunnel boring machines weighing 600 tons each excavated more than 500,000 cubic yards of soil and installed 7,352 concrete tunnel liner rings.

JCM continues work digging 23 cross passages between tunnels that will serve as emergency evacuation routes and will contain controls for electrical and mechanical systems. Work on this contract will be complete in 2018. Future work within the tunnels includes installation of track beds, rails and communications systems. Construction of the three stations for Northgate Link begins soon, with work on the Northgate Station starting this fall. Construction of underground stations in the Roosevelt and U District neighborhoods begins next year.

When light rail service on the Northgate Link extension begins in 2021, trains will enter and exit the tunnels through the Maple Leaf Portal at First Avenue Northeast and Northeast 95th.

The $1.9 billion Northgate Link project extends light rail 4.3 miles north from the University of Washington to a station next to Northgate Mall. Riders using Northgate Station will enjoy seven-minute rides to Husky Stadium, 14-minute rides to downtown and 47-minute rides to Sea-Tac Airport.

More information on the Northgate Link Extension Project can be found at