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Testing shows no harmful PFC levels in Cottage Grove wells; increased levels at Woodbury dump site unexplained

State officials say recent testing of private wells in Cottage Grove and Woodbury did not detect harmful levels of 3M-manufactured chemicals.

The Minnesota Pollution Control Agency said Thursday that test results returned this week showed that the level of perfluorochemicals (or PFCs) in private wells near a former 3M dump site in Woodbury did not exceed state drinking-water standards.

However, it remains unclear why increased levels of PFCs were found in groundwater at the former landfill, the agency said.

Private wells at roughly 20 Cottage Grove homes near the landfill site were tested last week and early this week for the presence of PFCs. That work was done after officials discovered elevated levels of the chemicals in two dump site wells where PFCs previously were undetected.

Pollution Control Agency Commissioner Paul Aasen said the agency moved quickly test the private wells.

"We contacted homeowners for permission and fast-tracked the sampling and lab analysis," Aasen said. "This week we called residents back to let them know that the wells that were tested were below the health-based drinking-water levels for PFCs."

Waste containing PFCs from 3M manufacturing was dumped at the Woodbury landfill and two other sites for decades. The chemical contaminated groundwater in the east metro area and the company has been working for a couple of years to clean up the Woodbury site. Part of the remediation includes using barrier wells to pump groundwater from the landfill site.

With the Pollution Control Agency's approval, 3M scaled back its pumping rate and earlier this year shut off a barrier pump after no PFCs were found on the site for several years.

However, the agency said levels of two types of PFCs had increased in monitoring wells at the site in September. The company notified the Pollution Control Agency of the increase and restarted the idled well.

The Pollution Control Agency is requiring 3M to determine the cause of the increased PFC levels, agency remediation supervisor Sandeep Burman said in a release.

"There is an intensive evaluation underway that will be completed in November," Burman said. "While that work continues, the barrier system will operate at previous pumping rates and groundwater monitoring at the site will be enhanced."