Documents from the OSHA investigation into the Husky Oil refinery explosion in Superior reveal company officials knew about equipment issues years before the 2018 blast.
Wisconsin Public Radio bases its report on almost 1,300 pages of documents from the federal agency.
A critical valve malfunctioned days before the explosion and the report documented erosion on that key piece of equipment dating back 10 years.
Three dozen workers and contractors were injured and hundreds of Superior residents were forced to evacuate.
