Confronting a spaghetti bowl of roads in and out of SeaTac International Airport, south of Seattle, owner Sound Transit opted for its first-ever turnkey design-build contract to better integrate civil, structural, station and system components of a new light-rail system extension that will serve the airport.

“To get over that mess and allow for capacity for future roadway access to the airport—to avoid all of that—an elevated guideway was seen as being the best way to go,” says Miles Haupt, Sound Transit project director for the 1.6-mile South 200th Link Extension.

With columns up to 40 ft high and spaced out at an average of about 30 ft along the 1.6-mile route, the new light-rail extension, scheduled to open by September 2016, ends at a new, $169-million elevated station, straddling South 200th Street.

PCL holds a portion of the overall $383-million contract, which separately includes a parking garage at the station, property acquisition and an “alternative technical concept” that reduced the number of columns, eliminated straddle bents and minimized road detours.

Chris Stack, PCL construction manager, says the redesign of the entire north end of the project at the airport eliminated four pier locations. “At the end of the day, there are fewer obstructions when designing future expansion around that structure,” he says. “It is a win-win for everybody.”

Ahmad Fazel, executive director of design, engineering and construction management for Sound Transit, says the use of a design-build turnkey procurement allowed this project to begin in 2012, sooner than planned.

The elevated track comprises 1,166 precast segments, generally 10 ft in length, cast in Enumclaw, Wash., about 20 miles southeast of the project location. The station platform is 12,645 sq ft, with 3,200 sq ft of enclosed ancillary space. The at-grade public plaza between the parking garage and the station is about 18,000 sq ft, while the seven-level, 375,400-sq-ft garage will offer 1,050 parking spaces.