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Doug Wetzstein, Superfund unit supervisor at the Minnesota Pollution Control Agency, said the findings show that it will be time consuming and complicated for 3M to clean up contamination from the perfluorochemicals.
“It’s right up there with dioxins and PCBs if you want to have a hierarchy of difficult contaminants to clean up,” Wetzstein said. The chemicals do not break down in the environment and move quickly through water.
The same chemicals, which are no longer made but were once used in Scotchgard and other products, have shown up in drinking water wells in Lake Elmo, Oakdale, and other east metro communities, likely from three former 3M dumps.
3M has already reached an agreement with the state to clean up pollution on its property, but the contamination in the river will likely make things more complicated.
The new study looked at a fire training area and a spot where wastes were burned. It also looked at sludge that was buried and where runoff entered two coves along the Mississippi.
3M spokesman Bill Nelson said the findings, which include “some data points that are higher than others,” should be taken in context of the entire study.
“Now that we have this very complete set of data we can now put forward a plan and work with the state to develop an effective remediation plan,” Nelson said. “It’s not productive to go back in time and discuss why this wasn’t done earlier.”
The concentrations of one compound, perfluorooctanoic acid, were as high as 619 parts per billion in groundwater taken near a former dump site at the plant. The state’s recommended maximum level of PFOA in drinking water is 0.5 parts per billion.
PFOA levels in soil 2 to 3 feet beneath a fire training area reached up to 262 parts per billion, and sediment 3 feet beneath a cove next to the Mississippi was as high as 1,845 parts per billion.
Another compound, perfluorooctane sulfonate, was up to 2,948 parts per billion in soil at the fire training area, 65,450 parts per billion in sediment in the cove, and 104,000 parts per billion at the former sludge disposal site.
Matt Simcik, associate professor of occupational health at the University of Minnesota, said the levels are among the highest he has ever seen reported or studied.
He said it will be difficult to determine how extensive the cleanup should be, and how it will be accomplished.
“We’re kind of plowing new ground here in terms of trying to determine how to get rid of these,” Simcik said.
3M’s Nelson said it’s premature to speculate about methods of cleanup.
Wetzstein, of the MPCA, said the company will submit a general cleanup plan soon, followed by a more detailed feasibility study later this year.
Contaminated soil and groundwater at the Cottage Grove plant should not pose serious public health risks, said John Linc Stine, environmental health division director at the Minnesota Department of Health.
