Sound Transit is building a key piece of its new 15.7-mile Link light rail line connecting downtown Seattle with Sea-Tac Airport. PCL Construction Services, Sound Transit's contractor, will build a light rail bridge over the I-5 freeway just south of Boeing Access Road. This bridge will connect the seven-mile Tukwila/Airport segment of the project to the Seattle portion.
The light rail bridge will be built with pre-cast 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 pre-cast 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. Sound Transit is building four balanced cantilever bridges on the Link trackway, one of which is already completed. It is located next to E. Marginal Way S., where Link crosses the Duwamish River.
In order to safely build the balanced cantilever bridge, it is necessary to close one or more lanes of I-5 under the construction work. Sound Transit and PCL have coordinated closely with the Washington State Department of Transportation (WSDOT), which owns and controls the freeway.
Lane closures will occur Sunday through Thursday nights and possibly on some Saturday nights during evening and nighttime hours (generally between 6 p.m. and 6 a.m.). These lane closures will affect traffic on I-5, but they will occur during hours when traffic volumes are usually light.
In addition to the lane closures, it will be necessary to completely close I-5 in either the southbound or northbound direction for nine or more nights. These total closures are scheduled to occur between midnight and 5 a.m., when traffic is lightest.
WSDOT's overhead Variable Message Signs and Highway Advisory Radio systems will be utilized during these closures to provide advance notification to motorists of the construction. The construction work and its associated lane closures will take about two months. The work will halt for the holidays between Dec. 22 and Jan. 1. Link light rail construction is on schedule and heading for opening day in 2009, providing riders with a fast 36-minute trip between SeaTac Airport and Westlake Station in the downtown transit tunnel.
For more information about the design and construction of Link light rail, contact Roger Pence, Sound Transit community outreach coordinator, at 206-398-5465 or at pencer@soundtransit.org or visit "http://www.soundtransit.org" www.soundtransit.org. For I-5 lane closure information, visit www.wsdot.wa.gov/northwest/king/construction/#c755. If an urgent issue arises regarding Sound Transit construction activities, contact Sound Transit's 24-hour toll-free Construction Hotline at 888-298-2395.[[In-content Ad]]
