On the eve of the one-year anniversary of a deadly explosion at U.S. Steel Clairton Coke Works, federal investigators released a long and sharply worded report, accusing U.S. Steel and its contractor of not just ignoring procedures to ensure safety but not even having them.

The U.S. Chemical Safety and Hazard Investigation Board, a federal agency, has been analyzing what happened on Aug. 11, 2025 when coke oven gas escaped from a cracked valve and caused a blast that killed two workers, injured 11 others and caused more than $52 million in property damage to the 125-year-old Clairton facility.

Its final report, released on Monday, follows interim findings and recommendations issued last year, which found that workers from U.S. Steel and its contractor, MPW Industrial Services Inc., had over-pressurized a piece of equipment while cleaning it, causing the large cast-iron valve to crack and allowing highly flammable coke oven gas to escape into the air and catch fire.

The workers were turning the valve back and forth to test its ability to fully close and, finding coke oven residue blocking its action, they pumped high-pressure water into its seat to wash off the gunk, according to the report.

But “U.S. Steel had no procedure for how to safely conduct this operation,” the CSB’s final report states. Its written procedures call for the use of steam to clean stubbornly blocked valves. Yet the company had been using water for at least three years, the agency found, “on an ad hoc basis.”

The U.S. Steel supervisor who was overseeing the task was even referred to as Clairton’s “water washing expert,” CSB said.

Nevertheless, when U.S. Steel held a hazardous job meeting to go over the planned task before work began, it did not include plans to exercise or wash the isolation valve. And none of the workers that actually did the exercising and washing on the day of the explosion were at that hazardous job meeting.

“If a task can be performed incorrectly and in a way that could result in harm to people, property, the environment, or the community, there should be a detailed written procedure prescribing the correct way to perform the task, and workers should be trained on the procedure,” the CSB report said.

“Had either company conducted a hazard analysis and addressed the hazards appropriately, the incident could have been prevented.”

In a statement, U.S. Steel said that since the explosion “multi-disciplinary teams collaborated to establish standardized best practices for industrial valve cleaning to provide operational safety and maintain a controlled work environment.

“Additionally, we improved our Management of Change (MOC) program to better assess procedural changes. Employees have completed comprehensive training on these new program elements and procedural changes.”

U.S. Steel said it appreciates the CSB’s work and is evaluating its recommendations.

Learning from mistakes

Mistakes and accidents at industrial plants are, in many ways, the building blocks for regulations, safety standards and industry best practices.

The premise of the Chemical Safety Board’s work is that to prevent future catastrophes, it is imperative to learn from previous ones.

That’s why the agency’s investigators zeroed in on U.S. Steel’s coke oven gas explosion on July 14, 2010, when a dozen workers suffered severe injuries and required hospitalization.

That was an opportunity for the company to evaluate how the location of its buildings impacted the risk and consequence of an incident that causes injury or death, the CSB said.

For years, U.S. Steel did not conduct a facility siting analysis, which is required for chemical facilities under rules established by the Occupational Safety and Health Administration. The steel operator believed those rules did not apply to coke oven gas that was used as fuel at its facility.

The CSB disagreed with U.S. Steel’s interpretation, but requirements aside, the agency said U.S. Steel’s 2010 explosion should have been enough to compel the company to look at how the densely packed arrangement of buildings and occupied work spaces at Clairton affects the risk of catastrophic events.

On Aug. 11, 2025, about two dozen people were working in, below and above the area of the explosion at the time of the incident. The two U.S. Steel employees who died were in two separate control rooms. Two of the five seriously injured workers were inside a break room. An air permit inspector from the Allegheny County Health Department was on top of one of the batteries impacted by the fire.

“None of the buildings were designed or constructed to withstand an explosion,” the CSB report said. “In the years leading up to the explosion, U.S. Steel had multiple opportunities to evaluate and address the inherent hazards resulting from the co-location of occupied buildings and the hazardous coke oven gas piping. However, U.S. Steel affirmatively chose not to do so, based on the company’s belief that it was not required to do so.”

As U.S. Steel moved to quickly rebuild its damaged buildings after the 2025 explosion, the CSB grew concerned that its lack of facility siting analysis would leave employees unprotected from future potential hazards.

“Coke oven gas is hazardous regardless of whether U.S. Steel handles more than the regulatory threshold quantity… and regardless of how and whether regulatory exemptions apply,” the investigators wrote.

United Steelworkers, the union that represents employees at U.S. Steel’s Mon Valley facilities, is currently bargaining a new contract with management and has included facility siting in its safety proposals.

The union has proposed the establishment of a joint labor-management facility siting committee to guide decisions on where new facilities and those damaged by accidents are rebuilt.

“Workers are the ones who will experience the first and most extreme consequences of a failure, and they must have a strong voice in evaluating siting decisions, hazard assessments and reconstruction plans,” the union said.

‘You’ve got to be on your game’

U.S. Steel declined to answer specific questions from the Post-Gazette about facility siting. It has previously said the company has implemented a number of changes after the incident.

Richard Tikey, vice president of United Steelworkers Local 1557 who has worked at Clairton for 28 years, said he has noticed more diligence since the explosion.

“Right in the same area, we had a small dump valve that was cracked,” he said. The company noticed it and called for a hazardous job meeting, “where you go over all of what can happen.”

The process usually takes an hour, he said.

“This took 7 hours. They went through EVERYTHING. I was there all night.”

None of the injured workers have returned to work and likely won’t for a while, said Tikey, who tries to keep in touch with all of them.

As the anniversary of the explosion approached, Andrew Macey, a mechanical repairmen who believes he is the longest-tenured employee at Clairton, said there has been more talk about it around the plant.

“It’s just like 9/11,” he said. “When that date comes around, you get that feeling.”

He thinks of it every time he passes the coke ovens.

He thinks of the two men who would have been in the blast radius but had forgotten a hose and went to retrieve it — the oversight saving their lives.

He thinks of the worker who switched his shift with one of the deceased. “And their life was taken, and the other one spared.”

This is the third explosion that Macey has witnessed during his time in Clairton, when colleagues didn’t come home at the end of their shift.

“A year ago at this time, life was good for them — good employment, good paycheck. Then you get that call — there’s been an accident.

“I know that call first-hand. My father, back in 1975, was injured in an accident. He lost his leg.”

Macey’s dad was working at U.S. Steel’s pipe mill in McKeesport. Macey was 20 then. He said he arrived at the hospital and heard his father’s screams long before he reached his room.

The first night, they didn’t know if he was going to make it.

But two years after the accident, when Macey was laid off from his job, his father suggested he try the mills.

He even called in a favor to get his son hired during a time when the company wasn’t hiring. It was Thanksgiving day, Macey said. The following Tuesday, he showed up for work at U.S. Steel.

His father didn’t hesitate, Macey said. And when, two months ago, Macey’s grand nephew applied for a job with U.S. Steel at Clairton, Macey didn’t hesitate either.

“I said, ‘You may get hired where this explosion took place,’ ” Macey said. “He said, ‘I’m not worried about that. I believe that the company corrected it and it’s going to be OK.’ ”

“And it is,” Macey said.

Now, his grand nephew works in the exact spot where the explosion happened. They talk daily. Macey tells him which things to avoid, when to talk to a manager, when to call him.

“When you’re in a facility where the whole facility runs on gas, you’ve got to be on your game,” he said.

U.S. Steel said in a statement: “We continue to hold in our thoughts the employees who were injured or lost during the August 11 incident. We remain mindful of their families, colleagues, and loved ones. Their memory guides our commitment to safety every day.”

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