Sound Transit's Federal Way Link Extension

Seattle’s first transit line only opened in 2003, and yet the city has one of the highest rates of public transit ridership per capita in the US. Over the next several years, the transit network is predicted to triple in size from 22 miles (35 kilometers) to 62 miles (100 kilometers) of track as more extensions are built.

Meeting the needs of a rapidly growing region

Sound Transit secured taxpayer support for rapid expansion through a series of ballot measures. In 2016, voters approved of Sound Transit 3, a plan that increased funding to the agency by more than $50 billion. The plan includes light rail transit (LRT) projects scheduled as far ahead as the 2040s.

Among the projects under this funding plan, the Federal Way Link Extension project includes a 7.8-mile (12.6-kilometer) extension of the Link light rail line, three new elevated stations, and parking garages totaling 3,200 parking spaces. The extension connects Kent Des Moines, Star Lake, and Federal Way Downtown Stations to the 23 existing stations on Sound Transit’s 1-Line.

Modeling success for future capital projects

As the lead in South County Transit Partners, a joint venture with AtkinsRéalis, Mott MacDonald provided design-build project management services for Sound Transit's Federal Way Link Extension project. This contract built on many years of solid design, project management, and construction management services we have provided to Sound Transit.

For Phase 1 of the project (pre-construction), we supported the procurement of the design-build contractor. For Phase 2 (design-build project management), we provided project management services and oversaw the design-build contractor during design and construction. We also provided technical and field oversight, project controls, and contract management expertise.

As the first major project in a larger expansion program, the Federal Way Link Extension sets a model for success for future Link extension projects. The delivery team has created a robust program to capture lessons learned on the project. We presented project performance and stakeholder information to the client and stakeholders through visual dashboards.

Creating a culture of collaboration and continual improvement on the Federal Way Link Extension project has enabled Sound Transit to move forward with certainty. Construction began in 2020 and the extension opened to the public in late 2025.

Connecting more people to more places

Ultimately, the Federal Way Link Extension expands transit opportunities in the region, providing local communities with easy-to-use public transportation and improved access to jobs, housing, and other services.