It was unclear who was responsible for maintaining the Packaging Corporation of America tank that exploded and killed three contract workers last year, and that caused turpentine to accumulate in the vessel that the U.S. Chemical Safety Board said is not subject to certain OSHA safety regulations.
CSB has completed its investigation into the DeRidder explosion, it announced on Tuesday. The accident happened when workers were welding atop a foul condensate vessel subject to hazards because "in the months leading up to the incident, confusion as to who at the mill was responsible for foul condensate tank operations led to turpentine accumulating in the tank.
"And although some air in the vapor space of the foul condensate tank is normal, because of the non-routine conditions present during the annual shutdown, more air than usual found its way into the tank, resulting in an explosive atmosphere," the CSB wrote in a release on Tuesday.
Welding activities sparked the vapor, and the exploded, launched up and over a six-story structure and landed on other equipment about 375 feet away, the CSB said.
OSHA’s "process safety management" regulations don’t apply to the mill’s "non-condensable gas system" that includes the foul condensate tank, CSB said. But PCA could have voluntarily employed "good-practice guidance" to instill more rigorous safety management in its processes, which produce cardboard.
"The CSB found that PCA did not do this. Using a more robust safety system approach could have helped PCA to identify, evaluate, and control the hazards present in the process, and likely could have prevented the explosion," CSB stated in the release.
KATC Investigates found after the explosion that nationwide, PCA has a history of worker fatalities and safety violations. Read more on that here.
OSHA has lodged five violations against PCA’s DeRidder mill because of the accident. Read more on that here.
As of Tuesday, PCA was still contesting OSHA’s enforcement action.
CSB is a non-regulatory federal agency and does not issue any fines or enforcement actions in its accident reviews, although they said they "issued safety guidance to the pulp and paper industry and a recommendation to PCA to apply process safety management principles to non-condensable gas systems, even if not required by regulations."
Read the full CSB release here.