Light Rail to SeaTac Airport SeaTac, WA

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To make room for and construct the final sections of the Sound Transit Link Light Rail into SeaTac Airport, Mowat shifted the alignment of the North and Southbound Expressways and constructed six major structures. Mowat self-performed the complex bridge structures including the cut and cover tunnel under the northbound expressway, a horseshoe shaped reinforced box girder structure over the north and southbound expressways, a two-span post tensioned box girder structure, a single-span precast tub girder structure over an active substation and the LRT aerial multi-span single-cell cast-in-place post tensioned box girder structure.

  • Mowat worked with the Port of Seattle and Sound Transit to execute a change that included early construction of six grade beams for the new airport station. This early construction saved $200,000 in shoring costs and two months of schedule. Additionally, 2,900 ft of at-grade LRT was originally designed to be concrete slab-on-grade. Mowat’s proposed redesign to build the structure on ballast with concrete ties saved $600,000.The key to success was clear communication with all interested parties.
  • More than 15 significant traffic switches were required to keep the public moving safely through the construction zone to and from the airport. By self-performing the traffic management and maintaining constant communication with the multiple affected parties, high traffic flows were managed though this congested site.

Sound Transit/Port of Seattle

$101.3 M