Behind the Barriers: Exploring the SR57/SR60 Confluence Chokepoint Relief Project

On Friday, October 4, 2024, a group of USC students, spanning disciplines from engineering to urban planning, had the unique opportunity to explore behind the scenes of one of Southern California’s most significant highway interchanges, the State Route 57/State Route 60 interchange (SR57/SR60) in the San Gabriel Valley (SGV). The interchange is a critical juncture, not only as one of the region's busiest intersections but also as one of the nation’s most trafficked freight corridors, with over 350,000 vehicles and 26,000 trucks passing through daily. The SR57/SR60 Confluence Chokepoint Relief Project (“the project”) exemplifies the complexity of developing any major infrastructure through multifaceted consensus-building, coordination and collaboration among countless stakeholders.

The tour was an integral part of CE430: Sustainable Transportation course, taught by Professor Eric Shen in the Viterbi School of Engineering. Our host, Rene Coronel, P.E., Senior Project Manager of the San Gabriel Valley Council of Governments (SGVCOG) first provided an overview on the project scope in the joint project office then led us onto the job site for a walking tour. While walking along the barriers, we witnessed first-hand the gigantic earthwork, towering drill piles, and highly choreographed moves between different crews. We could feel the stress building just by looking at cars and trucks negotiating between lanes at high speeds. The project’s main objectives became clearer to us – enhancing traffic safety, reducing congestion, and improving air quality! Furthermore, freight traffic will continue to grow throughout the region, so completing the project will make our transportation system more sustainable by reducing time spent in traffic.

Key Project Components

The project encompasses several major milestones, namely, 1.) reconstructing the Grand Avenue Bridge to accommodate new on- and off-ramps; 2.) constructing a bypass to allow eastbound SR60 traffic to exit onto Grand Avenue; and 3.) building a new bypass for eastbound SR60 traffic to northbound SR57. The overall project development has taken nearly two decades - the conceptual plans began in 2003! After many years of environmental reviews, pursuit of fundings, and right of way acquisitions, SGVCOG finally awarded construction contracts in 2022/2023.

Managing Disruptions and Ensuring Sustainability

Minimizing disruptions during the project’s construction has been an ongoing hurdle. SR57 and SR60 are major thoroughfares through the Los Angeles Basin. Each highway carries significant traffic volume all year round. SR60, a major east-west highway, is heavily traversed by freight trucks moving cargo between the ports of Los Angeles/Long Beach and warehouses in SGV and Inland Empire. SR57, a north-south highway linking the SGV and Orange County, also carries significant commuter traffic as well as subregional freight truck trips. The project is being constructed with live traffic. Contractors must advance their work according to the project schedule while minimizing impacts on adjacent cities and businesses. Night work, while necessary to avoid daytime closures, brings concerns around noise and vibrations, which must be balanced with the need for minimal impact on traffic flow. Additionally, the long-term effects on surrounding communities, wildlife, and local habitats are carefully monitored, with sustainability measures integrated into the construction plans.

Construction Considerations

Given that Southern California is prone to earthquakes, the project includes robust seismic safety measures. These include driving pile foundations as deep as 60 feet and utilizing Cast-in-Drilled-Hole (CIDH) piles to reinforce areas beneath bridges. These measures are crucial to ensuring the freeway's resilience in the event of seismic activity.

The project also leverages advanced engineering techniques to ensure the stability and durability of the infrastructure. Wick drains and settlement periods are being used to manage subsurface water and prevent differential settlement, critical to maintaining the structural integrity of the expanded freeway.

Collaboration Is Key to Success

This project exemplifies the critical elements in delivering a major infrastructure project – environmental assessment, financial feasibility, best-valued engineering and construction, collaboration among stakeholders, and community acceptance. Mr. Coronel reminded us that the $440 million project is funded jointly by Federal, State and regional funding. LA Metro serves as the project’s lead agency. Through agreements with Metro, SGVCOG is responsible for managing the Right of Way Acquisition and Construction phases. When completed, the newly constructed physical assets will continue to be owned, operated and maintained by the state (Caltrans). The project also triggers numerous changes to surface streets before and during construction. Therefore, each affected local jurisdiction is also closely involved to minimize impacts on their constituents. This multifaceted partnership underscores the intricate balance of cooperation required for large-scale infrastructure projects in urban environments.

Conclusion

The technical tour allowed USC students to better understand many invisible complexities behind physical barriers. The push-and-pull relationships between  technical, social, political, financial and environmental dimensions must be recognized and carefully managed. Infrastructure projects of this scale require significant time, investment, and collaboration to deliver lasting improvements.

For me personally, I gained a much deeper appreciation for so many unsung heroes across many disciplines over many years to build one project. Each carefully planned and constructed project will improve the quality of life through those communities. In the future when traversing the SR57/SR60 interchange, I will proudly tell others that I once visited the site while it was under construction!