Lynnwood Link Extension

Stacy Witbeck was the managing joint venture partner on this GC/CM contract for a 4.8-mile double-track extension of Sound Transit’s light rail system. The alignment is in a narrow corridor parallel and adjacent to Interstate 5. The route consists of 1.9 miles of elevated guideway with direct fixation track, and three miles of ballasted track in an at-grade guideway on retained cuts/fills.

Significant obstacles were overcome to complete on schedule, including challenging weather events, such as unusually heavy rains, snow, and wildfires. There was also a local concrete strike, as well as the global pandemic starting right as construction was set to begin. 

The team found solutions to navigate these hurdles, coordinating schedules to start systems work before construction was completed. To build in this tight corridor, a temporary trestle with oscillating drill rigs and cofferdams over a wetland was built, along with a cast-in-place overpass requiring 200 shafts up to 20 feet in diameter and 80 feet deep. 

The scope included two stations, infrastructure for a future third station, and two large parking garages. Other work was demolition, clearing and grubbing, utility relocations, extensive retaining walls, site work, civil aspects of systems work, road work, site improvements around stations, and restoration. 

Building a stormwater management system was a significant component of the overal project. A temporary system was created during construction to collect and treat 55 acres spanning the alignment. This included six basins, 157 baker tanks, 4 ponds, 147 pumps, and 108 generators. The system processed an average of 850,000 gallons of water each month, with a peak month of 9 million gallons treated.