U.S. Steel last year settled a lawsuit brought by environmental groups over emissions that stemmed from the 2018 Clairton plant fire. The settlement with the groups and the county included $19.5 million in coke-oven upgrades and $17.5 million in other plant improvements.

The mill, which is part of the recent merger between U.S. Steel and Nippon Steel, has faced scrutiny from federal and local regulators.

Todd Barrett was with a crew of laborers at the Clairton coke works that morning when they all felt something. It was an explosion at batteries 13 and 14 at the plant. The batteries consist of dozens of tall,