AtkinsRéalis completes oversight of $1.6bn Sound Transit light rail extension, connecting Seattle to Federal Way

Global infrastructure engineering group AtkinsRéalis has completed its long-term oversight responsibilities on Sound Transit’s most ambitious design-build project to date—the $1.6 billion Federal Way Link Extension. The 7.8-mile light rail corridor, now open to passengers, connects Seattle to the cities of SeaTac, Des Moines, Kent, and Federal Way. Since 2018, AtkinsRéalis has served as the primary project management consultant, delivering resident engineering, construction oversight, independent quality assurance, commercial controls, and design review services for the high-capacity commuter rail corridor.

This extension is a major expansion of the Link light rail system and includes three new stations—Kent-Des Moines, Star Lake, and Federal Way Downtown—designed to support multimodal access and future commuter growth. It is expected to serve up to 25,000 riders per day. In addition to the new stations, the project introduces two new parking garages and an extension to an existing facility, adding a total of 3,200 parking spaces to facilitate both park-and-ride users and last-mile multimodal integration.

The project encountered significant geotechnical challenges mid-construction, requiring the engineering team to adapt the original design. This led to the implementation of a 500-foot cast-in-place segmental bridge to navigate unstable soils discovered along the route. AtkinsRéalis played a critical role in managing the design evolution, risk mitigation, and stakeholder coordination throughout the complex realignment process.

What does the project reveal about evolving trends in U.S. light rail infrastructure delivery?

The Federal Way Link Extension illustrates how major urban transit projects in the United States are embracing design-build frameworks to streamline timelines, reduce risk exposure, and promote collaborative execution. Under such models, contractors and oversight engineers are integrated into the process early, allowing flexibility to address evolving construction realities. The mid-project decision to shift to a segmental bridge—triggered by soil instability—demonstrates this adaptive capacity in action.

For Sound Transit, the successful delivery of this corridor represents a continuation of its multi-decade light rail expansion strategy in the Puget Sound region. The new line enhances connectivity to growing suburban populations while reinforcing the utility of park-and-ride hubs. All three new stations have been designed for multimodal flexibility, with seamless integration to local bus networks, pedestrian infrastructure, and regional highway corridors.

Passenger service officially began in early December 2025, marking a significant milestone not only for the transit agency but also for infrastructure partners like AtkinsRéalis. The project aligns with broader federal and state goals to reduce vehicle dependence, support emissions targets, and create resilient urban mobility networks capable of handling rapid regional growth.

Why does AtkinsRéalis see this as a flagship project for its U.S. rail business?

AtkinsRéalis, which rebranded from SNC-Lavalin in 2023, has become increasingly active in high-profile rail infrastructure across the United States. With more than 5,000 experts in its global transit portfolio and over 2,000 active or completed rail projects in the U.S. alone, the firm has built a reputation for providing integrated engineering, oversight, and program management in complex, multi-stakeholder transportation environments.

Its work on the Federal Way Link Extension adds to a growing roster of marquee rail projects, including involvement with Bay Area Rapid Transit (BART) in California, the Santa Clara Valley Transportation Authority (VTA), the Los Angeles Metro network, and the Purple Line for the Maryland Transit Administration. These engagements span roles from design-build support to lifecycle asset oversight and construction auditing.

Speaking on the project’s completion, Sergio Callen, Vice President and National Rail & Transit Sector Manager at AtkinsRéalis, described the extension as a tangible example of infrastructure that improves daily life and strengthens community connectivity. He credited close coordination with Sound Transit and delivery partners for ensuring a reliable and efficient system that supports long-term regional growth. Ken Regan, who served as Resident Engineer and Senior Project Manager on the extension, emphasized the project’s success in translating smart planning into commuter-friendly, sustainable transportation solutions.

How does the Federal Way Link Extension tie into long-term infrastructure and sustainability goals?

This project aligns strongly with Washington state’s climate action and urban planning priorities. As one of the fastest-growing regions on the U.S. West Coast, the Seattle metropolitan area faces rising traffic congestion, expanding suburban sprawl, and growing demand for carbon-neutral transport systems. The addition of the Federal Way extension not only offers commuters a high-frequency, low-emission travel alternative but also supports transit-oriented development (TOD) in the surrounding communities.

Each of the three new stations is located in areas earmarked for population growth and urban densification. By integrating walking paths, bike facilities, and bus connections, the extension advances the principles of 15-minute city planning and encourages a shift away from car-centric lifestyles. From a federal funding perspective, the $1.6 billion price tag represents a strategic investment in resilient transport infrastructure that meets both economic and environmental mandates.

The role of AtkinsRéalis in this effort is illustrative of how engineering and oversight firms are evolving into delivery partners, helping public agencies manage complex variables like risk, scheduling, technical redesign, and quality assurance. Their ability to manage change—especially under conditions like unexpected soil instability—will become increasingly critical as U.S. transit agencies scale up investments under legislation such as the Infrastructure Investment and Jobs Act.

What does the project’s completion mean for transit capacity and commuter patterns in the region?

The activation of the Federal Way Link Extension significantly expands transit access for South King County residents and sets the stage for further expansion southward and eastward. By extending the line from the existing Angle Lake terminus through to Federal Way, Sound Transit is directly addressing historical gaps in transit access for underserved communities and reducing pressure on highway corridors like Interstate 5.

With initial projections estimating up to 25,000 daily boardings, the new line is expected to become a backbone route for daily commuters, students, and travelers accessing Seattle-Tacoma International Airport. Parking infrastructure enhancements and multimodal connections are expected to boost adoption rates, especially for users transitioning from automobile to transit. Regional officials view the new line as a catalyst for job access, mobility equity, and emissions reduction.

The new stations’ strategic placement, combined with flexible design features, means the infrastructure is built to scale. It is expected to accommodate both ridership growth and technological upgrades over the next two decades. For Sound Transit, this success also builds momentum for future segments of the system-wide light rail vision, including links to Tacoma, Ballard, and other urban nodes.

How does the Federal Way Link Extension reflect changing best practices in U.S. transit project delivery?

From a broader industry perspective, the project demonstrates how oversight-focused engineering firms like AtkinsRéalis can play a pivotal role in reducing delivery risk on multibillion-dollar public works projects. With increasing political and taxpayer scrutiny on cost overruns, timeline delays, and environmental compliance, having integrated oversight embedded into the project delivery process from the outset has proven advantageous.

The use of a mid-project design shift to address soil instability—without derailing timeline or budgetary goals—underscores the value of adaptive, risk-aware delivery models. AtkinsRéalis’s ongoing presence throughout this process highlights how owner’s engineering roles are evolving to become more anticipatory, not just reactive.

As U.S. cities invest more heavily in climate-smart infrastructure, engineering partners will be judged not only by design excellence but by their ability to navigate policy expectations, financial constraints, and dynamic urban conditions. The Federal Way Link Extension stands as a case study in how large-scale rail infrastructure can be delivered responsibly and resiliently through sustained public-private coordination.

What are the key takeaways from AtkinsRéalis’s oversight of the Federal Way Link Extension?

• AtkinsRéalis completed a multi‑year oversight role on Sound Transit’s $1.6 billion Federal Way Link Extension, a 7.8‑mile light rail corridor connecting Seattle to SeaTac, Des Moines, Kent, and Federal Way.

• The project adds three new stations and more than 3,200 parking spaces, supporting multimodal access and ridership projections of up to 25,000 daily passengers.

• AtkinsRéalis provided resident engineering, construction oversight, quality assurance, commercial controls, and design review since 2018.

• A major engineering shift occurred mid‑project when unstable soils were discovered, leading to the adoption of a 500‑foot cast‑in‑place segmental bridge design.

• Analysts following the U.S. transit construction sector note that the project highlights the growing importance of adaptive design‑build models in managing delivery risk.

• The extension supports Washington state’s long‑term sustainability, emissions, and transit‑oriented development goals by reducing car dependence and improving commuter mobility.

• AtkinsRéalis’s work on the project strengthens its position in the U.S. rail engineering landscape, where it also contributes to systems such as BART, VTA, LA Metro, and Maryland’s Purple Line.

• Sound Transit views the extension as a foundation for future expansions aimed at meeting regional growth and mobility equity targets.