Figure 28 - Duwamish River Crossing – 350' Main Span (photo courtesy of International Bridge Technologies, Inc.).

The Seattle Sound Transit Light Rail Project, Tukwila Segment, consists of 5.2 miles of twin track light rail line, including of 4.6 miles of elevated precast segmental guideway. The contract was successfully bid upon by PCL Civil Constructors, Inc. in February 2005. Since that time, and additional extension has been added to the contract, bringing the total amount to approximately $270 million. The first large scale precast segmental project for the state of Washington, the majority of the elevated line consists of simple spans with a typical length of 120' and will be erected using span-by-span construction with an overhead gantry. The 7' deep box-girder utilized a new cross-sectional shape with a minimized bottom slab and tendons that are both external and internal to the section. The extension to the project, executed in September 2006, will include an additional 2447' of precast segmental superstructure. Typical spans are also 120' and simply supported. There are an additional two longspan, balanced cantilever structures. The longest is 679' between expansion joints, with a main span of 259'.

Another milestone for the project was achieved with the midspan closure of the Duwamish River Crossing (Fig. 28), which at 350', has the longest span on the project. Activity has also begun at the longspan crossing over Interstate 5, which will achieve a main span of 268' when complete. As of the end of 2006, approximately 50% of guideway erection has been completed, and 75% of the segments cast. Construction of the project is anticipated to conclude by the first quarter of 2008. The construction for the project has been very high profile in the Seattle area, and has given local citizens a tangible indication that this long desired light rail project is progressing rapidly. The use of precast segmental construction is a significant reason for this impression. Participants: Owner: Sound Transit Lead Design Consultant: Hatch Mott MacDonald Sub-Consultant to HMM, Lead Segmental Design: International Bridge Technologies, Inc. Construction Management: Parsons Brinkerhoff Contractor: PCL Civil Constructors Contractor Engineer: T.Y. Lin Int’l. Truss Supplier: Rizzani/DEAL