The U.S. Chemical Safety Board says a 2010 explosion that killed two workers at a former Horsehead Corp. zinc oxide plant in western Pennsylvania was caused by recurring problems with a sump system that the company failed to address.
The report says "human factors" played a role in a history of blockages and smaller explosions at the plant that caused hazardous conditions to be "normalized" before the July 22, 2010, blast.
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The company says in objecting to the report that the scientist who issued it didn't visit the site or personally inspect the debris. Company official Ali Alavi says hazardous conditions weren't the norm at the plant.
Workers James Taylor of Aliquippa and Corey Keller of Newell, West Virginia, died of smoke inhalation. The plant has since closed.