This story has been updated.
A federal agency found that U.S. Steel had inadequate protocols for safety and building siting at its Clairton coke works, near Pittsburgh, leading to an explosion that killed two workers one year ago.
The U.S. Chemical Safety and Hazard Investigation Board found that the blast occurred when workers were conducting maintenance on a cast iron gas valve that was over 70 years old on August 11, 2025.
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The workers used pressurized water to clean out the valve, even though the company had no formal procedure for doing so.
This resulted in an excessive pressure buildup, which caused a valve failure one worker described to board investigators as a ‘pop’. Gas rushed out of the failed valve and exploded, according to the agency’s final report on the explosion.
The safety board found that had the company developed formal instructions for how to do the procedure, as recommended by industry standards, the accident could have been prevented.
“Had the water washing practice been proceduralized, the work performed on the day of the incident could have been accomplished in a manner that would not have caused the valve to catastrophically fail, thereby preventing the incident,” the report concluded.
Safety board chair Steve Owens said in an emailed statement the explosion was preventable.
“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,” he said. “It should never have happened.”
Siting problems
The two workers who died, Steven Menefee and Timothy “TQ” Quinn, and two of the workers who were seriously injured were stationed in buildings that were not designed to withstand an explosion, just above the area where the explosion occurred.
The board wrote that guidelines established by the Center for Chemical Process Safety, and the American Petroleum Institute, two industry groups, recommend companies that handle chemicals conduct a siting analysis to determine how to lower the risk of injury or death in the event of an accident.
gas leaking from the basement. (Credit: U.S. Steel)
U.S. Steel decided against such an analysis, even after a July 2010 explosion at Clairton injured 20 workers, the board wrote.
“U.S. Steel did not take actions that could have prevented or reduced the severity of the (explosion),” the safety board wrote. “U.S. Steel operated its … unit while routinely occupied non-blast resistant buildings were located less than 20 feet directly above a hazardous piping system.”
‘We heard a pop.’
The Clairton plant is the country’s largest producer of coke, a key component of steelmaking. The plant makes coke by heating coal to 2,000 degrees Fahrenheit, and baking it for 18 hours.
The process creates coke oven gas, which contains hydrogen and methane, the main component of natural gas. Coke oven gas is highly toxic and flammable, and the company uses it to heat furnaces at Clairton and its other plants in the region.
The faulty valve was located between two coke oven batteries, Battery 13 and Battery 14.
The report found that workers were sent to conduct maintenance on valves that could regulate the flow of coke oven gas near the batteries. Part of that maintenance was to clean out the tar-like buildup around the valves.
The company had been using high pressure water to clean the valves. When the workers closed two gates in the valve, they created a space inside where pressure could build. That pressure built over the valve’s maximum threshold. The valve failed, cracking with a sound, according to one worker the CSB quoted in the report.
“We heard a pop,” the worker said. “It sounded like when you overinflate a tire. It just went [“pop”], and in my mind, I felt like it was a breach. And I ran, and everybody ran out with me.”
Twenty four seconds after a radio call went out to evacuate the area, at 10:47 am, gas rushing out of the failed valve ignited, destroying the building and seriously injuring several workers.
In addition to the two workers who died, 11 were injured, five seriously. Injuries to two workers in a break room above the explosion included burns, broken ribs, broken vertebrae, broken tibia, shrapnel to the face, as well as broken bones in the ankle, lower legs, knees, and hands.
One worker was trapped under debris from the explosion and was found alive about four hours later. The explosion caused $52 million in damage. The company was fined $118,000 by the U.S. Occupational Safety and Health Administration for several unsafe workplace violations stemming from the explosion. The agency fined MPW Industrial Services, Inc., a contractor for U.S. Steel, another $61,000 in the incident. Both companies are contesting the citations.
“The CSB concludes that U.S. Steel’s policies, procedures, and practices for managing process safety were ineffective,” the report says. “Had U.S. Steel developed a robust process safety system and applied it to its coke oven gas systems, U.S. Steel could have prevented or reduced the severity of this incident.
U.S. Steel’s response
U.S. Steel says that since the accident, it has improved on its safety procedures.
“U. S. Steel has already strengthened several safety protocols. Multi-disciplinary teams collaborated to establish standardized best practices for industrial valve cleaning to provide operational safety and maintain a controlled work environment,” said company spokesperson Amanda Malkowski, in an email.
Malkowski said the company values safety and that it “shapes every part of our business.”
The company released a statement to commemorate the one-year anniversary of the explosion. “As we honor their memory, and those of others we have lost, we also reflect on the responsibility we all share to protect one another and ensure safety remains at the center of everything we do,” the statement says.
Bill Farrier, president of United Steelworkers Local 1557, which represents the plant’s 1100 unionized workers, declined to comment.
“Our hearts remain with the families, friends and co-workers who continue to live with the loss of two dedicated union brothers,” United Steelworkers president Roxanne Brown said, in a statement. “No family should ever have to wonder whether their loved one will make it home safely from work.”
Steelworkers’ District 10 Director Bernie Hall, said in a statement that the union, which is currently in negotiations with the company for a new contract, would push for better safety at U.S. Steel plants. Last month, a worker died at another U.S. Steel mill, the Granite City (Ill.) Works.
“Safety requires constant vigilance and a shared commitment,” Hall said. “We will continue holding U.S. Steel accountable for providing safe workplaces while working constructively to identify risks before they become tragedies.”
The Chemical Safety Board conducts accident investigations and makes recommendations to federal agencies and companies, but is not a regulatory agency. Its conclusions aren’t admissible as evidence in lawsuits resulting from the accidents it investigates.
