CSB to Investigate Nippon Fatal Tank Implosion, Releases Louisville Explosion Report

The U.S. Chemical Safety and Hazard Investigation Board announced May 27 it is opening an investigation into a fatal tank implosion at the Nippon Dynawave Packaging paper mill in Longview, Washington, that occurred in the early morning hours of May 26.

According to local authorities, the incident involved the rupture and implosion of a large tank containing white liquor, a corrosive chemical solution used in pulp and paper processing. Initial reports indicate multiple fatalities and serious injuries, with several workers unaccounted for as emergency response and recovery operations continue. A CSB investigation team arrived at the site the same day the agency announced its investigation.

"The CSB is opening an investigation into this tragic incident to determine how it happened and what can be done to prevent something like this from happening again," said CSB chairperson Steve Owens in a statement.

Also on May 27, the CSB released its final investigation report into the November 12, 2024, explosion at the Givaudan Sense Colour caramel coloring manufacturing facility in Louisville, Kentucky, that killed two workers, seriously injured three others and caused an estimated $40 million in combined damage to the facility and surrounding community. The CSB last released an update on its investigation in early 2025. 

The CSB determined the explosion occurred when a 2,500-gallon reactor experienced a runaway decomposition reaction involving a sugar ingredient used in caramel coloring production. The rapid pressure increase overwhelmed the reactor's emergency pressure relief system, causing the reactor to rupture. According to the agency, the relief system would have needed to be approximately four times larger to safely manage the pressure generated during the runaway reaction.

The two fatalities occurred when the blast wave collapsed a non-blast-resistant control room located 40 feet from the reactor. The reactor shell, weighing approximately 2,000 pounds, was propelled 245 feet into a nearby residential neighborhood, and debris traveled as far as 400 feet beyond the facility fence line. The facility has since permanently ceased operations and been demolished.

"This tragic incident was a catastrophe waiting to happen. The reactor's pressure relief system was not designed to release pressure from a reaction like this, and Givaudan did not recognize the potential for a runaway reaction to happen," said Owens in a press statement.

"The CSB's investigation found that the company did not understand the severe reactive hazards associated with the sugar ingredients used in its caramel coloring process," added CSB Supervisory Investigator Lauren Grim. "As a result, critical safeguards, including the emergency relief system, were incapable of preventing this catastrophic reactor rupture."

The final report includes recommendations to Givaudan covering third-party reactivity testing, facility hazard analyses, improved emergency pressure relief systems and development of comprehensive process safety management systems. 

The CSB also reiterated prior recommendations to EPA and OSHA to strengthen federal oversight of reactive chemical hazards, including revising EPA's Accidental Release Prevention Requirements and expanding OSHA's Process Safety Management standard to better address reactive hazards.