RJ Watson is proud to have played a key role in the Federal Way Link Extension – Structure C project, part of Sound Transit’s largest design-build transit expansion to date. This 1,097-ft-long cast-in-place concrete segmental bridge is a critical component of the Federal Way Link Extension (FWLE), which extends light rail service 8 miles from Angle Lake to Federal Way, WA.
Designed to accommodate 18,000 to 23,000 daily passengers, the FWLE will provide efficient and environmentally friendly transit options, connecting Seattle and Seattle-Tacoma International Airport to the growing communities of Des Moines, Kent, and Federal Way. When completed in 2026, it will bring faster, more reliable transportation to the region.
Project Challenges and Innovative Solutions
The Structure C segment of the FWLE presented significant geotechnical challenges, including:
- Unstable soil conditions, with undocumented landfill debris, wetlands, and a large liquefiable layer.
- The need to withstand a 2,500-year seismic event, per Sound Transit’s stringent design criteria.
- Proximity to Interstate 5, requiring long-span construction to minimize environmental impact and maintain highway safety.
To address these challenges, the project team utilized a cast-in-place concrete segmental box girder bridge, constructed using the balanced-cantilever method. This approach allowed for long spans (500-ft main span, 300-ft back spans), reducing the number of foundations needed and limiting impact on sensitive environmental areas.
RJ Watson’s Contribution: Structural Bearings
RJ Watson supplied 4 advanced multi-directionally guided bearings, specifically engineered to resist uplift forces of up to a maximum of 348 kips. If uplift forces are to exceed the maximum, the uplift restraint mechanism is designed to break off to release the seismic forces so that the structure is not damaged.
- 4 multi-directional guided expansion bearings with uplift restraint mechanism.
- Vertical service load: 1,208 kips
- Horizontal service load: 176 kips
- Horizontal extreme event load: 345 kips
- Longitudinal displacement: 11.25 inches
- Transverse displacement: 0.125”
- Service rotation: ± 0.015 radians
- Uplift Extreme Event Load (Fuse): 348 kips
Each bearing was designed for a maintenance-free service life, ensuring long-term structural integrity and reducing lifecycle costs for the transit system.
Expansion Joint Seals
RJ Watson also supplied 181 linear feet of Silicoflex expansion joint seal, a proven solution for:
✔ Watertight performance to protect structural components.
✔ Long-term durability with minimal maintenance.
✔ Seamless installation, reducing downtime and ensuring system longevity.
A Lasting Impact
The Federal Way Link Extension represents a major step forward in regional transit connectivity, and RJ Watson is honored to contribute to its success. By supplying high-performance bearings and expansion joints, we’re ensuring that Structure C meets the highest standards for strength, resilience, and long-term reliability—helping Sound Transit deliver safe and efficient transportation for decades to come.