Expanding Sound Transit’s light rail system to serve a growing Seattle

As Seattle prepares for significant population and job growth, expanding efficient transit options is critical.

The West Seattle and Ballard Link Extensions will add more than 12 miles of new light rail, introducing 13 new stations, twin-bored tunnels, and a high-level bridge to connect communities with reliable public transportation.

Meeting the region’s transportation needs

Seattle is home to industry giants like Boeing, Microsoft, Amazon, and Starbucks, and by 2050, the region is expected to grow by 1.6 million residents and 1.1 million jobs. To keep pace, Sound Transit is delivering a $54 billion program to expand and improve its transit network – ensuring that communities have access to fast, reliable, and sustainable transportation.

Strategic project support for seamless rail delivery

In partnership with WSP, Mott MacDonald was awarded an 18-month contract to provide project management support services (PMSS) for the engineering and construction of these transformative light rail extensions. Currently in the design phase through 2027, these projects will significantly enhance connectivity across Seattle:

• West Seattle Link Extension (4.3 miles): Adds four new stations, twin-bored tunnels into West Seattle, an elevated guideway, and a high-level cable-stayed bridge over the Duwamish River.
• Ballard Link Extension (7.7 miles): Introduces nine new stations, a new twin-bore tunnel through downtown Seattle, and a rail tunnel beneath the Lake Washington Ship Canal into Ballard.

Our team is managing the procurement and administration of construction contracts and consultancy agreements, ensuring the efficient planning and execution of these major expansions. We are also leading requirements management, systems integration, and interface coordination – including specifying and setting up an ISO compliant common data environment, 4D modeling, digital design oversight and construction impacts visualizations, safety and security requirements, and agile reporting at all levels.

Driving innovation for the community

Beyond technical expertise, our work focuses on driving efficiency and enhancing public understanding:

• Streamlining project delivery: By refining BIM processes and design information workflows, we are improving communication and collaboration between designers, contractors, and Sound Transit, resulting in a smoother and more cost-effective project execution.
• Enhancing public engagement: Using advanced visualizations, we help Sound Transit clearly communicate design solutions and construction impacts to local communities. By illustrating multiple scenarios and explaining key decisions, we are making complex engineering concepts more accessible to the public.

Looking ahead

Construction is set to begin in 2027, with the West Seattle extension expected to be completed by 2032 and Ballard between 2037 and 2039.

“We’re honored to be entrusted with a program that will have such a deep and positive impact on transportation options in Seattle and the surrounding areas,” says project manager, Conrad Fawcett.

Through smart infrastructure planning and innovative project management, we are helping Sound Transit expand its network in a way that supports communities, improves mobility, and builds a more connected future for the Seattle region.