Foresthill Bridge Weld Inspections: Advancing Safety Standards for T-1 Steel

The Foresthill Bridge, the tallest in California and fourth highest in the U.S., stretches 2,428 feet across the American River canyon and carries more than 50,000 vehicles daily. Built in 1973 with T-1 steel, the bridge became the focus of a Federal Highway Administration (FHWA) and Caltrans initiative in 2024 to assess fracture-critical welds and guide national safety standards.

Placer County selected Atlas to perform non-destructive testing and documentation on all 288 butt welds. Using a combination of snooper trucks, custom scaffolding, and advanced ultrasonic methods, Atlas inspectors accessed welds more than 700 feet above the canyon while keeping the bridge open to traffic.

Initial results showed a defect rate much higher than the anticipated. Atlas quickly scaled operations, adapting inspection techniques for difficult locations, coordinating with Caltrans and FHWA oversight teams, and delivering real-time data to support timely repair decisions. Despite rain delays and challenging conditions, all work was completed in compliance with AWS D1.5 Bridge Welding Code and without safety incidents.

The findings from this project are already informing FHWA guidance for evaluating T-1 steel structures across the country. For Placer County, the work reinforced immediate safety, while nationally it advanced a proactive approach to bridge management.

In the numbers

Inspected using advanced non-destructive testing methods 

Welds stabilized through targeted repairs and metallurgical review to ensure long-term safety 

Maximum working height during inspections 

Maintained across months of elevated operations and weather-related delays 

Learn More and See the Work in Action

• Atlas Article: Reaching New Heights: Steel Testing on California’s Tallest Bridge

• Watch a video of the work in action