After deadly explosion at US Steel mill outside Pittsburgh, maintaining safety now falls to Nippon

CLAIRTON, Pa. (AP) — For Don Furko, Aug. 11, 2025, was a normal shift. Until it became the shift he would never forget.

At 10:47 a.m., U.S. Steel’s Clairton Coke Works outside Pittsburgh — a sprawling riverside industrial facility and the largest of its kind in the Western Hemisphere — erupted in an ear-piercing boom.

A steelworker for 25 years and former Clairton local union president, Furko pulled on flame-retardant jacket and pants, a hard hat and safety glasses, left his post and rushed to the black plume of smoke rising from the facility’s batteries — the massive arrangements of industrial ovens that heat coal to some 2,000 degrees, turning it into carbon-rich coke.

Near the wharf, Renee Hough, a utility technician in charge of loading coke, sat in the cab of the plant’s screening station when the explosion ripped through the air, blinding her in black dust. “My first thought was I was dead,” Hough recalls. Flames emerged as the dust settled, and a voice crackled through the radio: Battery 13 had just exploded.

“I can’t even explain how mangled everything was,” Furko recalls. “There were flames everywhere.” Workers shuttled the injured to the helipad for evacuation. Through the chaos, Furko heard a fellow steelworker screaming, buried beneath the rubble.

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This story is a collaboration between Pittsburgh’s Public Source and The Associated Press.

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The blast killed two U.S. Steel workers and injured 11 others, including contractors, according to the Chemical Safety Board, a federal agency investigating the incident.

Six months later, workers remain rattled and community concerns about air pollution from the plant are heightened.

The blast comes on top of a string of other accidents at the Clairton plant over time as well as a long history of legal battles between U.S. Steel and Allegheny County regulators, who regularly accuse the company of flouting environmental rules at the facility. As recently as Jan. 27, pollution control equipment at the Clairton plant temporarily broke down and nearby air monitors recorded elevated air pollution, according to the Allegheny County Health Department.

To U.S. Steel’s critics, the August blast highlighted chronic problems at the facility. And some current and former workers at Clairton Coke Works say poor management and underinvestment have exacerbated air pollution and undermined workplace safety at the plant where operators already have little margin for error, Pittsburgh’s Public Source and The Associated Press have found.

The August explosion also came after Nippon Steel’s $15 billion acquisition of U.S. Steel in June 2025. It’s an open question whether the Japanese steel company will invest significantly in Clairton Coke Works and address issues raised by workers, government officials and environmental watchdogs.

The Chemical Safety Board has said that the August explosion occurred while workers were preparing to replace a damaged valve that was detected in July, as well as other valves. The agency’s investigation continues; it said in December that it has identified “potentially unmitigated hazards for workers at Clairton Coke Works that warrant immediate attention.”

“They try to say ‘safety first, safety first,’” said Brian Pavlack, a current worker at Clairton Coke Works. “Safety is not the first priority for them.”

Nippon Steel did not provide a response to written questions. In a written statement responding to detailed questions, U.S. Steel stressed its commitment to safety.

“Safety is our core value and shapes our culture, influences how we lead, and anchors our responsibility to ensure that every employee returns home safely, every single day,” the company said.

Dangerous work

The 392-acre Clairton Coke Works opened more than a century ago, 20 miles south of Pittsburgh along the west bank of the Monongahela River. The ovens at the plant heat coal at high temperatures for hours to make coke, a key component in steelmaking. Its ovens produce 3.6 million tons of coke annually, which is shipped to the company’s operations farther up the river at the Edgar Thomson Works in Braddock, and to U.S. Steel’s Gary Works in Indiana.

But making coke isn’t a clean process or without risk. The heat removes impurities, producing a flammable byproduct called coke oven gas. Coke oven gas includes hydrogen, methane, nitrogen and carbon monoxide, and some of it is used as fuel to heat the coke ovens. Coke oven gas is explosive due to high hydrogen content, said Fred Rorick, a former operations manager at Bethlehem Steel and steel industry consultant.

“At a coke works, when you have that, you have to be very, very, very careful,” Rorick said.

According to the Chemical Safety Board, the August explosion happened while workers were closing and opening a gas isolation valve in a basement after pumping water into the valve. U.S. Steel’s written procedure did not mention the use of water and a U.S. Steel supervisor directed workers to pump the water, the agency said. Kurt Barshick, U.S. Steel’s vice president of the Mon Valley Works, said during an October presentation to residents in the wake of the August explosion that workers trapped “3,000 PSI water inside of a valve that’s rated for 50 PSI.” The valve cracked and gas filled the area, Barshick added.

Drew Sahli, the Chemical Safety Board’s investigator in charge, said there was a “release of coke oven gas” and that the gas “contacted an ignition source” and exploded. The agency is still investigating how the gas was released, Sahli said.

U.S. Steel said it has “strengthened several safety protocols” based on its own ongoing investigation, including prohibiting the use of high-pressure water for valve cleaning and reviewing their “Management of Change program, which assesses proposed changes in procedures and evaluates risk.”

Before the August blast, Clairton Coke Works already had a history of accidents and explosions.

—In 2009, a maintenance worker was killed in a blast.

—In 2010, an explosion injured 14 employees and six contractors.

—In 2014, a worker was burned and died after falling into a trench.

—In February 2025, a problem at a battery led to a “buildup of combustible material” that ignited, injuring two people, according to the Allegheny County Health Department.

After the 2010 explosion, the Occupational Safety and Health Administration fined U.S. Steel and a subcontractor $175,000 for safety violations. U.S. Steel appealed its citations and fines, which were later reduced to $78,500 under a settlement agreement. U.S. Steel admitted no wrongdoing as part of the settlement.

While there’s “a lot of ways that you can get yourself hurt or killed” at Clairton Coke Works, explosions are the biggest hazard, said Calvin Croftcheck, who previously worked at the plant and served as the United Steelworkers safety coordinator for U.S. Steel.

“Since 2009, there have been three accidents that have resulted in fatalities and that is just not common in today’s age of safety,” said Phillip Kondrot, a workers’ compensation attorney who represents workers injured at Clairton Coke Works. “That is a dangerous place to work.”

“We have intensive procedures that are currently in place at Clairton and our other facilities, and our employees are charged with following them,” U.S. Steel said. “We will not respond to comments from for-profit lawyers and stand behind the safety professionals who tirelessly work at U. S. Steel.”

Management questioned

Some current and former workers at the Clairton plant fault U.S. Steel’s management of the aging facility, saying that it has caused a range of operational problems.

“A lot of things that have happened there, where they needed something fixed and something went wrong, it was because corporate wouldn’t approve them ordering the parts,” said Jonathan Ledwich, who worked at Clairton Coke Works between 2011 and 2022 trying to prevent emission leaks from the coke ovens. “We did the best we could with what we had.”

Ledwich points to a fire at the Clairton plant on Christmas Eve 2018. It shut down pollution control equipment and led to repeated releases of sulfur dioxide and hydrogen sulfide, according to a lawsuit filed by environmental groups after the incident. In the wake of the fire, Allegheny County warned residents to limit outdoor activities, with residents saying for weeks afterward that the air smelled like rotten eggs and was hard to breathe.

Ranajit Sahu, an engineer hired by the plaintiffs, wrote in a report filed in the case that he found “no indication” that U.S. Steel “has an effective, comprehensive maintenance program for the Clairton plant.” Sahu also wrote that the 2018 accident, which was precipitated by piping falling due to corrosion, was “preventable by a robust inspection and preventive maintenance program and by better plant design.”

In a 2024 consent decree settling the lawsuit, U.S. Steel agreed to measures including investing close to $20 million in facility upgrades and permanently idling a battery of coke ovens at the plant. As part of the consent decree, U.S. Steel admitted no liability.

Hough, the utility technician in charge of loading coke, said that the lack of proactive maintenance at Clairton Coke Works makes her feel unsafe at times.

“There’s a lot of things that need to be repaired that they’re not prioritizing because you can’t stop production,” Hough said of U.S. Steel.

Some current and former plant workers also describe difficulty getting coke oven doors replaced. Ledwich, the former Clairton steel worker, said some doors that needed to be replaced would leak emissions.

In a 2020 deposition for the lawsuit related to the 2018 Christmas Eve fire, James Kelly, former deputy director of the environmental health bureau at the Allegheny County Health Department – the agency that oversees emissions at the plant – said the facility is “one of the most decrepit facilities” that he’d ever seen.

The litigation surrounding the Christmas Eve fire wasn’t the first time U.S. Steel was accused in court of skimping on maintenance. In a 2017 amended federal class action lawsuit alleging violations of federal securities laws, U.S. Steel shareholders said that the company CEO hired the consulting firm McKinsey & Company in 2014 after multiple unprofitable years and “implemented extreme cost-cutting measures” in 2015 involving layoffs and deferrals of “desperately-needed maintenance and repairs.” The lawsuit was eventually settled and the U.S. Steel defendants admitted no wrongdoing.

U.S. Steel had “one of the best safety staffs in the country,” said Mike Wright, former director of the health, safety, and environment department at the United Steelworkers. But key safety department leaders were fired, according to Wright and Croftcheck, the former union safety coordinator. Wright said the dismissals occurred in 2016.

Ed Mazurkiewicz, former director of safety and industrial hygiene at U.S. Steel, said that he was let go by the company in 2016. While he knew at the time that McKinsey had been “evaluating all of U.S. Steel” and that there would be downsizing, it was still a shock when his job was eliminated, Mazurkiewicz said.

U.S. Steel said it has “worked with many advisers and partners” over the years and that the company’s “overall transformation efforts have improved our company’s performance, created a robust maintenance program, and improved employee safety over time.” In response to questions about U.S. Steel’s safety department and the firing of department leaders, the company said: “We cannot comment on personnel matters.”

“They brought in McKinsey to tell them really how to run things,” Wright said of U.S. Steel. “We were a little outraged by that.”

McKinsey said in a statement that the company is one of “many advisers that have served U.S. Steel in support of its efforts to keep manufacturing jobs in the United States, improve operational resiliency, and invest in and support the communities in which it operates.”

“As with all our work for the company – and with all our clients – safety is always a top priority,” the company added.

Maintenance practices have changed over time, some current and former workers say.

“I used to see a lot more maintenance and taking care of things and fixing things before they broke, or replacing things that were worn out,” said Hough, who has worked at the plant for 29 years. “That used to happen back when I was first hired there, and that hasn’t happened in the last 10 or so years.”

Battles over air pollution

For years, Clairton Coke Works has drawn the ire of government regulators, environmental advocates and community members concerned about air pollution originating from the plant. Air quality in the region has improved over time, but the Clairton plant has been the largest local source of air pollution – such as sulfur oxides and particulate matter – in recent years, according to the Allegheny County Health Department. Particulate matter, for instance, is linked to various health issues, including heart attacks and aggravated asthma. The plant also emits carcinogenic benzene.

While the Clairton plant is allowed to emit some air pollution, county Health Department regulators routinely clash with U.S. Steel over alleged violations of the plant’s operating permit, such as excessive emissions or failing to use pollution control equipment. In 2023, for instance, the Allegheny County Health Department fined U.S. Steel more than $2 million for violations at Clairton Coke Works.

“You’re sort of in this cycle of patching, monitoring, fining, patching, monitoring, fining, and it’s never really good enough,” said Karen Hacker, director of the Allegheny County Health Department between 2013 and 2019. “You can’t say it hasn’t improved. Just look at the sky in Pittsburgh, right? But it hasn’t removed a source of pollution.”

In response to questions from Public Source and AP, the Allegheny County Health Department said in a written statement that the agency “inspects coking operations daily” and “addresses violations as discovered during inspections” with a full compliance evaluation every two years.

The department also said that air monitoring stations near the Clairton plant “have measured a 15-25% reduction in annual average particle pollution concentrations compared to ten years ago.” The department declined to comment on “open investigations, enforcement orders, or pending litigation.”

Nationally, Clairton Coke Works’ environmental compliance track record is an outlier, according to a Public Source and AP analysis of federal Clean Air Act data from about 14,000 facilities. The analysis found that Clairton Coke Works is classified by the EPA as a “high-priority violator” – only about 11% of major emitters fall into that category. It’s even rarer for facilities to garner financial penalties on the magnitude that Clairton Coke Works has faced in the last five years, the analysis shows. Just 11 facilities, including Clairton Coke Works, have faced $10 million in penalties or more in the last five years.

“It’s a massive facility. It’s a complex facility and it’s an underfunded facility,” said Adam Ortiz, former EPA regional administrator of the Mid-Atlantic region during the Biden administration. “All those things make it tough.”

U.S. Steel said in its statement that the company spends “$100 million annually on environmental compliance at Clairton alone and has consistently achieved an environmental compliance rate exceeding 99% for regulated activities per year at our Clairton Plant, the largest cokemaking facility in North America.”

The company said that it has “invested more than $750 million in environmental improvement projects in the Mon Valley” and that preliminary data shows that a county air monitor located downwind of the Clairton plant has met the Environmental Protection Agency’s national ambient air quality standard for particulate matter since 2024.

“Our steadfast pursuit of environmental excellence will continue,” the company said. “We maintain a productive relationship with the ACHD and other regulators, with a commitment to regulation grounded in science and law.”

Some environmental advocates have argued that the Allegheny County Health Department is outgunned against U.S. Steel. The department’s air quality program, which handles oversight of Clairton Coke Works, is funded by fees paid by industrial polluters. But the program has struggled financially in recent years. In a 2018 report, the EPA asserted that revenue from emissions-based fees was “diminishing as a result of emissions reductions” and that the existing fee structure could potentially “undermine long-term program sustainability.” The Allegheny County Council approved raising the fees in 2021 and again in November.

Meanwhile, the Trump administration has signaled that it is taking a more hands-off approach with polluters. In November, President Donald Trump temporarily exempted Clairton Coke Works and other coking plants from provisions of a Biden-era rule that, for instance, required fenceline monitoring for benzene emissions. U.S. Steel previously requested an exemption.

U.S. Steel said that the rule “imposed significant compliance costs while setting technically unachievable standards and providing little or no environmental benefit.” Its Mon Valley facilities have “never been fined” for exceeding benzene emission standards, the company said.

New ownership arrives

Before the August explosion, workers and outside observers were already watching Nippon Steel closely for clues about their plans for Clairton Coke Works and the Mon Valley. Now, questions about Nippon’s intentions have become even more pressing.

In the nearly $15 billion deal to buy U.S. Steel, Nippon Steel pledged to invest $14 billion in domestic steelmaking operations, including building a new electric arc furnace somewhere in the U.S. Much of that money remains publicly uncommitted, and U.S. Steel has been firm that it wants to keep the Clairton plant operating.

“The Clairton Coke Plant is an important part of our North American Flat-Rolled integrated operations,” the company said in November. The company added that a “steady coke supply remains critical” and that the “Clairton Coke Plant will be maintained for the next generation of steelmaking.”

Since Nippon Steel acquired the company, things have started to change, according to Hough. The company has invested more in repairs and preventative maintenance, she said.

“Nippon is putting the money into the plant, and let me tell you, they’ve got a long way to go,” Hough said. “U.S. Steel let it go so bad for so long.”

However, U.S. Steel has not publicly committed to spending money at the Clairton plant to expand production, extend its life, improve efficiency, upgrade safety or reduce its polluting air emissions.

In response to questions about its investment plans for Clairton Coke Works, U.S. Steel said the company plans to invest “more than $2 billion at Mon Valley Works.”

Furko served as Clairton local union president in 2021 when U.S. Steel canceled a pledged $1 billion investment in the Mon Valley Works. He remains wary of Nippon’s promises.

“Until I see shovels start to hit dirt,” Furko said, “then I don’t believe it until I see it.”

Of the $14 billion, U.S. Steel has said $2.4 billion will go toward its Pittsburgh-area plants. A portion of that money will be spent on building a new hot strip mill to replace the one at its Irvin plant, just down the Monongahela River from Clairton, that processes steel into massive sheet rolls, primarily for the automotive, appliance and construction industries.

It’s unclear how Nippon and U.S. Steel will address recent findings from federal investigators. In December, the Chemical Safety Board recommended that U.S. Steel conduct a siting evaluation of all buildings at the Clairton plant that are occupied or could be occupied to identify and assess potential hazards for workers. The agency said that the company has not conducted a facility siting evaluation as part of efforts to rebuild and relocate its “personnel facilities” after the blast.

U.S. Steel continues to cooperate with the Chemical Safety Board and the Occupational Safety and Health Administration and “evaluate their recommendations,” the company said.

Even with Nippon’s promise of revitalizing U.S. Steel with billions of dollars of investment, the August explosion is still darkening the minds of workers. Furko said he struggles to motivate himself to go to work on some days.

“I’ve been there 25 years. There’s been guys who have lost legs from rail equipment running over them. Bad falls and stuff like that,” Furko said. “Nothing has affected me like this has.”

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Kelety reported from Phoenix. AP journalists Marc Levy in Harrisburg, Pennsylvania, M.K. Wildeman in Hartford, Connecticut, Yuri Kageyama in Tokyo, Japan and Michael Casey in Boston, Massachusetts, contributed. Quinn Glabicki is the environment and climate reporter at Pittsburgh’s Public Source, and reported from Clairton. He can be reached at quinn@publicsource.org and on Instagram @quinnglabicki.

This story was fact-checked by Katherine Weaver.