On Aug. 11, 2025, an explosion at U.S. Steel\u2019s Clairton Coke Works outside Pittsburgh \u2014 a 392-acre riverside industrial facility and the largest of its kind in the Western Hemisphere \u2014 killed two U.S. Steel workers and injured 11 others, according to the Chemical Safety Board, a federal agency investigating the incident.<\/p>\n
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 and a history of legal battles between U.S. Steel and Allegheny County regulators. 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. And the August blast came after Nippon Steel\u2019s $15 billion acquisition of U.S. Steel<\/a> in June 2025. Nippon Steel did not provide a response to written questions.<\/p>\n Pittsburgh’s Public Source and The Associated Press interviewed current and former workers at Clairton Coke Works, experts, former and current government officials, reviewed court documents and analyzed federal data to produce this report.<\/p>\n Here are key takeaways from the report:<\/p>\n What we know about the explosion<\/p>\n Industrial ovens at Clairton Coke Works, which opened more than a century ago, heat coal at high temperatures for hours to make coke, a key component in steelmaking. The heat removes impurities, producing a flammable byproduct called coke oven gas.<\/p>\n 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\u2019s 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\u2019s vice president of the Mon Valley Works, said during an October presentation to residents that workers trapped \u201c3,000 PSI water inside of a valve that\u2019s rated for 50 PSI.\u201d The valve cracked and gas filled the area, Barshick added. <\/p>\n Drew Sahli, the Chemical Safety Board\u2019s investigator in charge, said there was a \u201crelease of coke oven gas\u201d and that the gas \u201ccontacted an ignition source\u201d and exploded. The agency is still investigating how the gas was released, Sahli said.<\/p>\n In a written statement, U.S. Steel stressed its commitment to safety and said that it has \u201cstrengthened several safety protocols\u201d based on its own ongoing investigation, including prohibiting the use of high-pressure water for valve cleaning.<\/p>\n Before the August blast, the plant already had a history of accidents and explosions, including a 2009 blast that killed a maintenance worker and another explosion in 2010 that injured 14 employees and six contractors.<\/p>\n Workers question management<\/p>\n Some current and former workers at the Clairton plant fault U.S. Steel\u2019s management of the aging Clairton Coke Works, saying that it has caused a range of operational problems. For instance, they describe difficulties getting coke oven doors, which can leak emissions, replaced. <\/p>\n