'Unexpected' PFC levels at Woodbury dump site lead to private well testing
City and state officials are awaiting test results from nearly two dozen private wells in Cottage Grove near the city's northern border after what officials described as an unexpected spike in levels of a 3M-manufactured chemical at a Woodbury dump site.
Around 20 Cottage Grove homes were tested for the presence of perfluorochemicals - or PFCs -- late last week and early this week by the Minnesota Pollution Control Agency after routine testing of wells at a former 3M landfill near the Cottage Grove-Woodbury border revealed elevated levels of the chemicals where none had been detected previously, according to city officials who were briefed last Friday by representatives from the MPCA and 3M.
In a Sept. 27 letter sent to impacted residents and obtained by the Bulletin, the MPCA said the detection of PFCs in early warning wells on the Woodbury property led to the testing of private wells that it termed "a precautionary measure."
According to the letter, the MPCA is not recommending any restrictions in water use at this time. The agency has regularly sampled water from private wells as part of ongoing remediation efforts directed by the state and carried out by 3M.
"We saw some unexpected levels of [a PFC] in a few wells and the levels were out of character given the history of sampling that has been conducted by 3M, and the MPCA and the [Minnesota Department of Health] over these past few years," 3M spokesman Bill Nelson said Tuesday.
PFCs are the same chemicals found in private well water in the Langdon area of Cottage Grove near the 3M Cottage Grove plant and in groundwater elsewhere in the east metro. The chemicals were manufactured by 3M for roughly 50 years for use in heat- and stain-resistant materials.
Results from the sampling of private wells in north Cottage Grove would likely be made available this week, said Jennifer Levitt, the city engineer for Cottage Grove. It isn't yet known if contaminated groundwater has migrated off the dump site, she said.
"The key thing for us is to determine if any materials left the 3M property," Levitt said.
Barrier wells pump out millions of gallons of groundwater per day from underneath the disposal site in an effort to contain PFC contamination on the 3M property. The testing followed a 3M proposal -- approved by the state last year -- to reduce the amount of groundwater pumped by up to 50 percent.
The company had reduced the amount of groundwater being captured by 10 percent when PFCs were discovered in a well on the southern edge of 3M's property during tests in May and August. 3M was made aware of the results in September, 3M's Nelson said, and resumed previous pumping levels within 48 hours of the discovery.
"3M acted quickly at first in notifying the MPCA and then in resuming the previous pumping protocol," Nelson said. "We will be working with the state agencies to best determine what caused this result. But in the meantime our previous pumping protocol, which has been very effective, will continue."
The city of Cottage Grove opposed 3M's plan to reduce pumping, citing concerns it could lead to PFCs moving off of the 3M property.
"We need to have a conversation with the [MPCA] as to what is the next step," said Cottage Grove Mayor Myron Bailey.
A Minnesota Pollution Control Agency official could not be reached immediately for comment.