Nippon Dynawave tank failure investigation reveals ignored safety warnings

The U.S. Chemical Safety and Hazard Investigation Board (CSB) has released findings regarding the May 26, 2026, catastrophic failure of a 1.2-million-gallon storage tank at the Nippon Dynawave Packaging Company mill in Longview, Washington. The failure of the tank, known as G Tank, released approximately 900,000 gallons of hot, highly caustic white liquor, resulting in 11 fatalities and several injuries.

Investigations revealed that the carbon-steel tank shell had thinned below safe limits. Despite inspections in July 2025, October 2025, and February 2026 identifying significant thinning and recommending repairs or internal inspections, the tank remained in service. On the day of the incident, a process upset stopped the flow of liquid to the mill’s digestor, but continued inflow caused the tank to reach 90% capacity before it failed.

Concurrently, the Washington Department of Ecology issued an administrative notice of environmental violations to Nippon Dynawave. The agency is documenting violations stemming from the spill to determine potential enforcement actions, such as monetary penalties or compliance orders. While Ecology regulates air and water quality and spill prevention, it does not oversee the structural integrity of the storage tanks.