Best Safety, Award of Merit - Highway Bridge: Lynnwood Link Extension, L300 NE 200th to Lynnwood Transit Center

Extending Sound Transit’s Link Light Rail Line 3.7 miles from Shoreline to the Lynnwood Transit Center required two elevated stations with vertical circulation, 2.3 miles of elevated guideway and 1.4 miles of at-grade track. Additional work on this $914.85-million project included demolition, clearing and grubbing, utility relocations, track work, retaining walls, sitework and a 1,650-stall parking garage at the Lynnwood Transit Center.

A key feature is a 900-ft parabolic cast-in-place bridge over the I-5 freeway. The team employed 3D modeling to identify rebar clashes, correct camber diagrams and ensure accurate placement of ducts that house 60 miles of post-tensioning cable before construction began. When the bridge was post-tensioned, it lifted up as much as 4 in. to remain in tolerance. This approach also ensured installation proceeded within the required +/- ¼-in. rail tolerance.