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PFC research started long before water ban

A granular-activated carbon filter is lowered onto a concrete pad ready to hold the filters at Well 10. Katie Nelson / RiverTown Multimedia

The decision to lower recommended perfluorochemical levels in drinking water, enact a watering ban in Cottage Grove and take several municipal wells offline seven weeks ago may have seemed to be a dramatic flip of a switch, but gears were in motion long before the May 23 actions.

In August 2016, the Environmental Protection Agency lowered its recommended health-based values for perfluorochemicals including PFOA and PFOS. At that time, Minnesota Department of Health officials announced they would complete their own study.

Jim Kelly, MDH environmental health manager, said that they revisit their recommended values for pollutants or contaminants such as PFCs about every five years, and that it was time to look at PFCs again when the EPA announced its new levels. MDH then announced its own study to the public and to the city of Cottage Grove.

"They were certainly aware that there was a possibility of new values coming," Kelly said.

The city took Well 2 offline last August in anticipation of upcoming MDH value changes.

The city did not act any further at the time, because neither the city nor MDH could estimate what the new values would be.

"Until they knew the values, there was nothing (the city) could do," Kelly said.

Without the levels announced, the city also could not be reimbursed by 3M under the agreement made with the Minnesota Pollution Control Agency to recover PFC mitigation costs.

"Any action we would have taken would be at the city's cost, but more importantly it could have been on the wrong wells," City Administrator Charlene Stevens said. "The more important piece is you can't design treatment until you know what to treat."

Kelly said at a June 7 PFC open house that once they finished the study they were "duty bound" to release those updated values.

"It was the city's decision to enact the watering ban ... there's no pressing health need to stop drinking the water immediately," Kelly said, but that at some point they would have to start preventing further PFC buildup in people's blood.

"The mom-to-be who just found out she's pregnant I don't think would want us to have waited six months (to announce new values) ... To stop that cycle, you have to start somewhere," he said.

The city decided to act immediately, enacting the ban and taking wells offline.

"We had to take the action we did," Stevens said. "We couldn't provide clean water without (the ban)."

The city did look at other options, such as installing filters in the approximately 11,000 homes in the community, or let residents get bottled water or filtration systems.

Stevens said the actions they took was the most feasible, and met their goal of providing safe drinking water to the community.

An unprecedented move?

MDH has announced value changes or triggered watering bans before, but Kelly said there haven't been any quite like this.

"(We've) never been in a situation where it's affected a community the same as Cottage Grove," Kelly said. "I really do wish we could have completed it in January."

Stevens said if the value changes had been announced in the wintertime, they would not have acted differently, but water use is significantly higher in summer months, making the ban a larger burden.

When the EPA announces new values, they will look into several factors beyond just the science, such as how it may affect communities. When the MDH makes changes, Kelly said it's "strictly health based."

"When the EPA promulgates values on the entire country, they do take into account cost, potential for disease, feasibility of treatment ... they do more of those kinds of analyses," he said. "We're starting to explore that question here because of situations like this."

The MDH also tends toward more conservative methods in their studies, including the PFC one.

Kelly explained at the Cottage Grove open house June 7 that they used different values for the amount of water people drink, the amount of exposure to PFC outside drinking water and length of time spent breastfeeding.

Their conservative values triggered values lower than the EPA's — whereas the EPA recommends 70 parts per trillion PFOA, the MDH recommends 35 — for this study and others.

For drinking water guidelines both the EPA and the MDH have done studies for, the MDH sets lower values the majority of the time.

When EPA and MDH values deviate from each other, 86 percent of the time the MDH has the lower value. In over 100 values determined by both organizations, 68 percent of the time the MDH has the lower value.



-3M develops perfluorochemicals


-3M analyzes blood samples of U.S. citizens and find parts per billion of PFOS and PFOA


-3M starts phasing out production of perfluorochemicals


-3M reports to MPCA that PFCs have been detected in groundwater at Cottage Grove 3M site


-3M reports to MPCA that PFCs were detected in pump out water at Woodbury 3M disposal site


-PFCs detected in south Washington County private and city wells


-MPCA requests that 3M submit an action plan for PFC monitoring, barrier wells and sentinel wells

August 2016:

-EPA announces value change to 70 ppt of PFOA, PFOS, or a combination of the two in drinking water, lowering from interim advisory level of 200 ppt PFOS and 400 ppt PFOA

-MDH began their own study of health-based values for PFCs

-Cottage Grove takes Well 2 offline

May 22, 2017:

-MDH and MPCA inform city of value change

May 23:

-MDH and MPCA announce value change to public

-City shuts down several wells, enacts watering ban

-Staff begins working on solutions to bring PFC levels in municipal water to recommended levels

June 7:

-City, MDH and MPCA hold public open house to discuss water


-Staff continues to implement solutions, including placing granular-activated carbon (GAC) filters at two city wells to ease ban

-MDH and MPCA are contacting private well owners and testing wells

-Staff evaluates long-term solutions

Upcoming dates:

Late July:

-Watering ban could ease as Well 10 is brought back online using granular-activated carbon (GAC) filters


-Well 3 set to be back online with GAC filters