Overview
- The U.S. Chemical Safety and Hazard Investigation Board issued a final report on Monday, Aug. 10, 2026, concluding the August 11, 2025 blast at U.S. Steel’s Clairton Coke Works "should never have happened."
- Investigators found contractors and employees used pressurized water while a 70-plus-year-old cast-iron valve was closed or nearly closed, which overpressurized the part, caused a catastrophic failure, and released flammable coke oven gas that ignited.
- The CSB faulted U.S. Steel for lacking a written procedure for the valve-cleaning method and for tolerating an unsafe practice that management had long known about but did not formalize or control.
- The board called for specific fixes, including re-evaluating building distances from hazardous piping, written valve-washing procedures, and a stronger process-safety management system to prevent repeat incidents.
- U.S. Steel said it will review the recommendations and has already banned high-pressure water for valve cleaning, tightened its management-of-change program, added training, and marked the one-year anniversary with memorials and safety discussions while legal and regulatory follow-up continues.