University Link Extension

University Link tunnel

Tunnel near midpoint at Capitol Hill station
Overview
Line	Central Link
Location	Seattle, Washington
Status	Active
Start	Downtown Seattle Transit Tunnel
End	University of Washington station
Operation
Constructed	2009–12
Opened	March 19, 2016 (2016-03-19)
Owner	Sound Transit
Traffic	Link Light Rail
Technical
Length	3.15 mi (5.07 km)
No. of tracks	Double
Track gauge	4 ft 8 1⁄2 in (1,435 mm)
Tunnel clearance	21 ft (6.4 m)
Width	21 ft (6.4 m)

The University Link tunnel is a 3.15-mile (5.07 km)light rail tunnel in Seattle, Washington. The twin-bore tunnel carries Link Light Rail service on the University Link Extension of Central Link, running from the Downtown Seattle Transit Tunnel to University of Washington station via Capitol Hill station. The 21 ft-wide (6.4 m) tunnels are lined with precast gasketed concrete segments connected with steel bolts and was excavated using three tunnel-boring machines in 2011 and 2012. Light rail service began on March 19, 2016.

Construction of light rail was originally proposed in the 1996 Sound Move measure, with plans to open a line from Seattle–Tacoma International Airport to the University District in 2006. However, Sound Transit in the 1990s was plagued with continually escalating costs, include an agreement with the University of Washington to install dampeners on the rails that run under the science buildings, air cushions to tables in the science buildings, and to mitigate environmental impacts due to construction and traffic impacts from having the station on university grounds. In 1999, Sound Transit chose their preferred route for the light rail system, including a 4.5-mile-long (7.2 km) tunnel between downtown, First Hill, Capitol Hill and the University District with a crossing under Portage Bay; the tunnel under Portage Bay was later deemed too costly and risky in 2000, and later dropped in favor of alternative options crossing the Montlake Cut. Due to many missteps, Sound Transit shortened the line in 2001 from the original 21 miles (34 km) to 14 miles (23 km), truncating the line to Downtown Seattle. In 2004, Sound Transit selected a route for tunneled light rail extensions through Capitol Hill and the University District and towards Northgate, using the Montlake Cut and a new station at Husky Stadium.