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3M reduces pumping levels at former dump site

3M has decreased the amount of groundwater pumped through barrier wells at a former dump site between Woodbury Drive and Cottage Grove Drive south of Dale Road that for decades was contaminated by pollutants manufactured by the company.

Beginning Tuesday the company started reducing its level of pumping under approval and regulation of the Minnesota Pollution Control Agency (MPCA) and the Minnesota Department of Health (MDH).

The four barrier wells at the dump site are pumping 10 to 15 percent less water each day. The company is reducing pumping from only one barrier well, decreasing it by 50 percent.

"They're reducing the pumping in one well that's somewhat redundant to the system," MDH hydrogeologist Ginny Yingling said. "They have overlapping systems. Part of the goal here is to optimize the process so we can capture all the contaminants while also pumping less water."

Barrier wells are used to capture contaminants before the water continues on to other wells in the area, especially perfluorochemicals, or PFCs.

3M manufactured products that contained PFCs at its Cottage Grove plant until the early 2000s, and dumped waste containing PFCs at three east-metro sites in the 1960s. The company cleaned up the contaminated sites beginning in 2009.

PFC levels are found in the general public, believed to be caused by a variety of exposure sources. The effect of higher-than-average PFC exposure is being studied, but state health officials said there are no conclusive findings of adverse health effects.

"PFC effects typically are long term," MPCA project manager Tim Lockrem said. "The standards are based on exposure over a lifetime."

The four barrier wells pump approximately 2,500 to 3,100 gallons per minute, which comes to about 4 million gallons of water a day. The reduction in pumping should preserve about 210 million gallons of groundwater per year.

"One reason we're OK with them trying is because, the well they're reducing is mostly pumping in clean water from outside the site," Lockrem said. "This will help preserve that in the (Prairie du Chien) aquifer. It's sort of a conservation effort."

The MPCA will monitor wells in the surrounding area more closely, testing them every six weeks for the first six months to ensure there is no raised levels of pollutants in wells, although city engineer Jennifer Levitt said there's no reason to be concerned.

"It's a safe reduction," she said. "There will be no compromising of current systems."

There has also been a contingency plan created in case contaminant levels increase in local wells around the site. The contingency plan will involve input from state agency personnel. If anything were to go wrong, there are plans in place to deal with it quickly.

"There will be sufficient monitoring by 3M, MPCA, MDH," Yingling said "It's a pretty intense monitoring plan. We'll have enough oversight to catch it quickly if anything goes wrong."

If there are any increased levels in pollutants in surrounding wells, the contingency plan will be put into effect, essentially going back to baseline well pumping levels.

"If you find something, you ramp the well [pumping] back up," Levitt said.

If increased PFC levels are found in any wells in the surrounding area outside the site, Lockrem said the short time they are raised should not be of concern.

"If they exceed standards for a few weeks, it's not as much of a concern.We're not talking high levels, just levels that exceed standard deviation. It's not like there's any immediate concern."

If all goes as planned, however, there should be no need to use the contingency plan.

"We're fairly confident that the info regarding the wells will not result in a loss of control of the pollutants," Yingling said.

If the reduction goes as planned, there will be a phase two implemented, with further pumping changes.

"3M has indicated they will send an application to MPCA after about one year for review," Levitt said.

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