Prayers to all involved, but things at the WA State Paper Mill are looking far more serious than what the media is saying. This is looking like a “white liquor tank” event based on the images I have seen (SAFTENG members can see them below).
Emergency responders have confirmed:
10 individuals were transported to area hospitals:
-8 employee injuries,
-1 firefighter injury
-1 fatality
Officials can also confirm there are nine (9) employees who remain unaccounted for. All identified families have now been notified.
Most notably in this UPDATE:
While originally believed to contain approximately 80,000 gallons, officials now report the tank held approximately 900,000 gallons of white liquor. They estimate roughly 90,000 gallons of material may remain inside the damaged tank.
What is a “White Liquor Tank” at a Paper Mill
In the context of the Kraft pulping process, a white liquor tank is a storage vessel that holds the active cooking chemicals—primarily sodium hydroxide (NaOH) and sodium sulfide (Na2S)—before they are introduced into the pulp digester. These tanks are critical components of a mill’s chemical recovery cycle, in which the “white” cooking liquor is prepared, used, and recovered for reuse.
While white liquor itself is a non-flammable, non-combustible aqueous solution, the tanks containing it can undergo catastrophic structural failures via mechanical or chemical mechanisms.
Implosion (Vacuum Collapse) is a common risk for large storage tanks, including white liquor tanks, if proper venting is not maintained. If a tank is emptied rapidly (e.g., via high-capacity pumps) without adequate air intake, or if cooling of internal vapors creates a sudden drop in internal pressure, a vacuum can form. If the external atmospheric pressure significantly exceeds the internal pressure, the tank walls can “buckle” or collapse inward. This is often an issue of inadequate or plugged vacuum relief valves.
Based on the scene photos I have viewed (see below), this certainly appears to be a vessel failure rather than an explosion. We can see the vehicles all pushed up against the building, destroyed as if a wave of force had hit them. This wave could have been a pressure wave from an explosion, but to me, it looks more like a liquid wave from a large diameter storage tank failing at its bottom seam or very close to the bottom. “White Liquid” will weigh around 9.6 lbs per gallon (Water is 8.34 pounds per gallon). These tanks are HUGE and hold anywhere from 150,000 up to nearly 1M gallons of white liquor. That is a lot of force released by the catastrophic failure of a storage tank.
