Report: Clairton Coke Works blast could have been prevented
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U.S. Steel's Clairton Coke Works after explosions on Aug. 11, 2025. Photo: Rebecca Droke/AFP via Getty Images
Federal investigators say last year’s deadly explosion at U.S. Steel’s Clairton Coke Works “could have been prevented or reduced in severity.”
Why it matters: A year after the explosion killed two workers, injured 11 and caused more than $52 million in damage, the U.S. Chemical Safety and Hazard Investigation Board recommended U.S. Steel strengthen its safety procedures at the plant in a final report released this week.
What they’re saying: “This deadly incident was the result of an ad hoc informal procedure, poor facility siting and an ineffective process safety management system at the Clairton facility,” CSB chairperson Steve Owens said in a public statement. “It should never have happened.”
U.S. Steel, in a statement shared with Axios, said it has bolstered safety measures, established best practices for cleaning industrial valves and improved how it reviews changes to workplace procedures after the explosion. The company said employees have been trained on the updates. U.S. Steel is evaluating CSB’s recommendations.
- “Safety is our core value and shapes every part of our business, influences how we lead and anchors our responsibility to ensure that every employee returns home safely, every single day,” U.S. Steel said in the statement.
Zoom in: Investigators said workers used pressurized water to wash a large cast-iron gas valve during maintenance; the valve ruptured, releasing highly flammable gas that ignited within 24 seconds of an evacuation order.
- The company had used the washing method for years without a formal written safety procedure, per the report.
The report also found that several buildings in the “transfer area,” where the explosion occurred, were routinely occupied by workers and sat less than 20 feet above the gas piping system. Those buildings were not designed to withstand an explosion, per the report.
- The two workers who died were in separate control rooms, while two seriously injured workers were in a break room directly above the explosion.
- The report says U.S. Steel had several opportunities to identify the potential hazards of gas piping near occupied buildings, particularly after a July 2010 explosion injured more than a dozen workers.
By the numbers: The company is facing lawsuits as well as more than $118,000 in OSHA fines related to the 2025 explosion, while its contractor, Pittsburgh-based MPW Industrial Services, faces more than $61,000.
Between the lines: The Mon Valley facility, one of the largest coke plants in the world, has faced criticism for past environmental and safety violations. The incident happened about two months after Nippon Steel’s acquisition.
What’s next: The United Steelworkers union is including facility siting in its contract safety proposals to management, the Post-Gazette reports.