Why is dilution a cleanup strategy for the Longview mill disaster?
After a tank containing about 600,000 gallons of "white liquor" imploded in Longview on May 26, killing 11 people, cleanup efforts have largely consisted of diluting affected waterways.
You might be wondering, is dilution enough to clean up a chemical spill?
The Washington State Department of Ecology, which is helping manage the response, and an independent expert say it is, and that it comes down to the composition of white liquor.
White liquor mostly consists of two chemical compounds - sodium hydroxide (commonly called lye) and sodium sulfide. What makes it dangerous to humans and the environment is primarily the high concentration of hydroxide, which results in high pH levels. That helps break down wood chips into pulp in paper mills but can burn tissue and corrode materials like concrete, plastics and rubber.
Diluting with water reduces the concentration of hydroxide, which neutralizes the pH and the danger of white liquor, the Department of Ecology said.
"High pH is not like a pollutant that persists for a long time in the environment," Scarlet Tang, a spokesperson for the department, wrote in an email.
The main risk of mixing white liquor with water is that it can produce hydrogen sulfide, which is a dangerous gas that smells like rotten eggs. It can kill fish before it escapes to the air, Tang said, and it can have respiratory effects for humans, similar to carbon monoxide. More than 2,600 dead fish have been recovered in ditch systems near the Longview facility since the incident, although officials say many likely died before the implosion. The state has been monitoring air in the area, and Tang said it has not detected hydrogen sulfide at levels of concern for human health.
The state posted an update Tuesday that Longview's drinking water, which is drawn from an aquifer below the ditches where white liquor entered, remains safe. However, residents are still being told to stay away from affected sloughs, dikes and drainage ditches until further notice.
The components that remain after diluting white liquor with water, such as sodium, oxygen, and hydrogen, are naturally occurring elements that don't pose an environmental risk, Tang said.
Jenifer McIntyre, an associate professor of aquatic toxicology at Washington State University who is not involved in the state's cleanup efforts, said she supports the strategy.
"My sort of thought on this would be that dilution really is the solution to pollution," McIntyre said.
The tank implosion released white liquor into a storm drain and a ditch connected to a drainage network that moves through the community of Longview. Officials say they have been drawing fresh water from the Cowlitz River to dilute and flush the contaminated water. That diluted water is being released into the Columbia, and state officials say that discharge remains at safe pH levels.
Most of the white liquor remained on site. Crews are using vacuum trucks with pumps to collect it and dispose of the liquid in the existing wastewater treatment plant at the mill. Tang said the state did not have an estimate for how long it would take to clean up the facility.
Copyright 2026 Tribune Content Agency. All Rights Reserved.
This story was originally published June 4, 2026 at 6:41 AM.