Seattle— Work has begun on a key piece of Sound Transit's new 15.7-mile Link light rail line connecting downtown Seattle with SeaTac Airport.
PCL Construction Services, Sound Transit's contractor, is building a bridge over the I-5 freeway just south of Boeing Access Road to connect the seven-mile Tukwila/Airport segment of the project to the Seattle portion.
The light rail bridge will be built with precast concrete segments placed by cranes as a "balanced cantilever." Two large bridge piers are already built, one on each side of the freeway. Beginning with the pier on the southbound side of I-5, giant cranes will hang the precast segments one at a time on each side of the pier, to keep the structure in balance. Steel tensioning cables running through the segments will keep them in place as the structure extends in each direction.
The Link light rail project is the first use of this construction technique in this region.
Link light rail construction is on schedule and heading for opening day in 2009, providing riders with a 36-minute trip between SeaTac Airport and Westlake Station in the downtown transit tunnel.
In other Sound Transit news, Northlink Transit Partners JV, which consists of Earth Tech, HNTB and San Francisco-based consultant Jacobs Associates, has been awarded a $38.9-million contract for the final design of the 3.15-mile University Link light rail extension, which will run from downtown Seattle to the University of Washington.
Earth Tech's responsibilities will include providing project control systems, managing the design of two rail stations — one in the Capitol Hill area of Seattle and another at the University of Washington at Husky Stadium — and tunnel ventilation, mechanical and electrical systems. The final design project, which will involve Earth Tech design professionals in the company's Seattle and Oakland, Calif., offices, includes a tunnel that travels under the Lake Washington Ship Canal.
The design project is expected to take two years to complete. Construction is scheduled to begin in fall 2008, with service starting in 2016.