Photo courtesy of Hatch Mott MacDonald The design for Sound Transit’s SeaTac/Airport light-rail station involved two sky bridges and several entrances. Hatch Mott MacDonald was the prime consultant.

Sound Transit’s light-rail system has been a long time in the making, but things speeded up significantly when the agency told its design and construction team that they needed to complete the last 1.75-mile segment between Tukwila and the Seattle-Tacoma International Airport in time for the 2010 Winter Olympics in nearby Vancouver, B.C.

Hatch Mott MacDonald, the prime consultant, was responsible for preliminary and final design as well as bid and design support during construction of the elevated and at-grade guideways and SeaTac/Airport Station.

HMM had just completed the adjacent 4.9-mile Tukwila section of the light-rail line, which ends at the Tukwila International Boulevard Station, so the transition to the Airport Link project was fast and cost-effective.

The firm had already overcome numerous challenges associated with the Tukwila line and was able to incorporate into this project many of the same materials and concepts, including precast concrete segmental technology, which was adapted for the cast-in-place guideway. Its use enabled the 2,400-foot-long guideway to get built in just 22 months.

The span crossing state Route 518 is one of the longest concrete segmental bridges in the state, and it was designed for unusually high seismic loads using special “shock transmission units” to help distribute seismic forces. The elevated guideway was constructed in an extremely congested environment, resulting in complicated staging to allow airport traffic to flow freely.

The elevated Airport Station was designed with both functionality and aesthetics in mind, providing a wing-like image of flight and emulating nearby mountain peaks. The station design included several entrances and two sky bridges, one connecting to the airport’s parking garage and one spanning International Boulevard, connecting to a “kiss-and-ride” lot.

The project was completed on budget and within plenty of time to greet fans of the Vancouver Winter Games.