An inspection contractor determined a chemical tank at a Washington state paper mill was “not fit for continued service” 10 months before it failed in May, killing 11 people, according to a report from the U.S. Chemical Safety Board. The May 26 failure in Longview released enough caustic liquid to damage building walls, and the ongoing investigation by the federal agency is still working to determine the exact cause.
The contractor had recommended internal inspections and shell repairs for the tank, which Nippon Dynawave Packaging Company did not undertake between the July 2025 inspection and the May 2026 failure. During the July 2025 inspection, the contractor noted “significant thinning” below the minimum safe thickness in the tank's lower sections. This minimum thickness is critical for a tank's ability to withstand the pressure of its contents and support its own weight.
Subsequent external inspections in October 2025 and February 2026 also identified that large portions of the tank's wall remained thinner than the calculated safe minimum. The report states the company did not remove the tank from operation or reduce its service capacity.
The tank contained approximately 900,000 gallons of white liquor, a substance used in paper production that can cause severe burns. The failure resulted in the deaths of 11 workers and injured several others, including a firefighter. The white liquor flooded a courtyard, damaged vehicles and destroyed part of a building, with the liquid entering lower floors where employees were gathering for morning meetings.
The July 2025 inspection excerpt noted the recommendations as “Priority 1: Not fit for continued service unless corrected,” citing a “high likelihood/consequence of failure (or) critical code/standard deficiency.” The inspector suggested the owner should plan for an internal inspection to assess the extent of necessary repairs, stating it was “likely that the entire shell course should be replaced.” The inspections were conducted by Applied Technical Services LLC.
According to the board's report, the catastrophic failure occurred shortly after employees began arriving for their shifts around 7 a.m. Earlier that morning, a digestor vessel at the facility was taken out of service for repairs, which halted the flow of white liquor into the tank in question. However, more white liquor continued to be pumped into the tank, causing it to reach near full capacity by 6:20 a.m., less than an hour before its failure.
Workers in the electrical maintenance shop were killed, as was a worker in the courtyard. In the mechanical maintenance shop, two employees died from exposure to the chemical, though five employees and the foreman managed to escape. Two individuals who escaped sustained serious injuries from chemical burns.
Following the incident, the company's emergency response team was contacted, but the nature of the released chemical was not immediately communicated. A team member, mistaking the white liquor for water, entered the pool of liquid while attempting a rescue and suffered severe chemical burns.
Separately, the Washington Department of Ecology issued Nippon Dynawave 35 environmental violation notices earlier in the week, related to the facility's air and water quality permits and compliance with environmental waste laws.
The Chemical Safety Board stated that its investigation is ongoing and a final report will detail its complete findings.