University Link Light Rail U220 Tunnel


Seattle, WA


Central Puget Sound Regional Transit Authority


$310 million

The Central Puget Sound Regional Transit Authority’s (Sound Transit) University Link project is a 3.15-mile extension of Sound Transit’s light rail system in Seattle, Washington. Located entirely underground, it will connect the University of Washington through-stations at Capitol Hill and the University of Washington with downtown Seattle. Scheduled to run trains by 2016,

Sound Transit is projecting a system-wide ridership increase of 70,000 upon completion.
Project challenges include stakeholder issues such as potential interference with the University of Washington’s athletic events; maintenance of traffic and access to University Hospital and adjacent property owners; and stormwater and sewer discharge. The project is located in a densely populated urban area of Seattle, Washington, connecting the downtown area with the University of Washington and its landmark stadium, where large-scale sporting and entertainment events regularly take place. The tunnel passes beneath numerous residential and commercial neighborhoods as well as a historically significant masonry water tower. To date, the project has incurred minimal disruptions to the surrounding areas.

The tunnels are 11,400-foot-long segmentally lined twin-bored tunnels using pressurized face techniques. Simultaneously, 16 cross passages must be excavated at intervals between the bored tunnels using sequential excavation methods. Other tasks include civil and structural work for the University of Washington Station crossover as well as permanent electrical and mechanical installations in the running tunnel and crosspassages.

The project is on a strict time schedule due to the lease agreement between Sound Transit and the University of Washington for the construction site land. The strict schedule necessitates performing multiple portions of the work simultaneously, such as the TBM running tunnel excavation, crosspassage excavation, and permanent electrical conduit installation, whereas this work is traditionally performed in series.