Seattle sees more milestones on LRT project

10 November 2015

USA - One of the TBMs bored through the wall of Sound Transit’s future U District light rail station on Friday, November 6, completing the third segment of the twin 3.5-mile (5.6km) tunnels that will serve light rail trains from Northgate Mall to the University of Washington starting in 2021.

"The machine has now dug out 200,000 tons of dirt to reach the U-District Station," said Sound Transit Board Chair and King County Executive Dow Constantine. "Three tunnel segments are done; three more to go to reach Husky Stadium."

The boring completed the third of six tunnel segments being mined by contractor JCM Northlink LLC, (Jay Dee Contractors, Frank Coluccio Construction Company, and Michels Corporation). This TBM, "Brenda," was manufactured by Hitachi Zosen and launched July 2014 from the Maple Leaf Portal. It will undergo maintenance at the U District station site before continuing south and connecting with the University of Washington Station, which opens with University Link first quarter next year.

A second machine named "Pamela," manufactured by Robbins, launched from the Maple Leaf Portal last November. It is expected to arrive at the U District site early next year. Both machines are 21.5ft (6.5m) in diameter

Tunnelling is expected to be complete by the third quarter of 2016. Tunnel finishes and cross-passages, are scheduled to be complete by the first quarter of 2018. When light rail service on the Northgate Link extension begins in 2021, trains will enter and exit the tunnels at the Maple Leaf Portal. The project is worth USD 1.9bn.

To date, Sound Transit has bored nine tunnel segments for Link light rail construction. Mining of the twin tunnels serving the Beacon Hill Station were completed in 2008. Mining of parallel tunnels between downtown and the University Link Capitol Hill Station, and the Capitol Hill Station and University of Washington Station, finished in 2012. When the remaining three tunnels for Northgate Link are complete, Sound Transit will have mined a total of twelve tunnels for light rail construction.