Karst geology diagram

Karst geology diagram

Water flows across fields and ends up in aquifers through absorption or conduits such as sink holes.

Taking a drink, for rural residents across Southeast Minnesota, has become a problematic endeavor.

For the thousands of households per county that get their water pumped through private wells rather than municipal water supplies, there is growing evidence the water coming from the tap is full of at least one specific health hazard. Even more likely, that water is swimming with chemicals that can poison people or animals.

This link between well water and health — and their connection to agriculture — is why former MPCA Commissioner John Linc Stine asked for a study of nitrates in the groundwater of the karst region of Southeast Minnesota.

While his successor, Commissioner Laura Bishop, said she was looking “forward to participating in a full discussion of this proposal” with the Environmental Quality Board, she has not considered the scope or funding that would be required for such a broad study, or how such a study would improve the way the MPCA does its job.

The MPCA’s call to action duplicates two current wide-ranging studies of groundwater and nitrates that include Southeast Minnesota. Still, there is plenty we need to learn about groundwater, nitrates and just how widespread the problem might be.

Parts Per Million

According to the Minnesota Department of Health, drinking water with more than 10 milligrams of nitrates per liter — or 10 parts per million (ppm) — can negatively affect human health, specifically infants under the age of six months.

Drinking water above the 10 ppm standard is most commonly found in aquifers that are vulnerable to contamination from the land surface, such as sand and gravel aquifers and fractured bedrock aquifers, the MDH states.

In Southeast Minnesota, this means the karst region that dominates the region’s geology with sinkholes. Porous rock delivers water and contaminants to flowing aquifers. The karst geology, combined with the region’s row crop agriculture, puts groundwater at risk.

There are two major studies now looking into groundwater in the karst region. The first is the Southeast Minnesota Volunteer Nitrate Monitoring Network, which has been taking samples from wells across nine karst region counties since 2006.

Douglas Eayrs, whose family has owned the same farm in northeastern Dodge County since 1863, has taken part in the VNMN since 2007. Since then, he’s seen well water nitrates rise from roughly the 10 ppm limit to more than 25 ppm.

“As a child, we took for granted the safety of the water on the farm” Eayrs said.

Dean Schrandt, water program manager for Dodge County Environmental Services, said there are about 125 wells being tested in Dodge County as part of the VNMN.

“Overall, the research has seen a slow rise in nitrate levels,” Schrandt said. “While the sources are somewhat known, about how much each is supplying to the problem hasn’t been determined yet.”

Crop fertilizer — either as manure or commercial fertilizer — is the likely top culprit, several experts agree. Other sources include human waste from septic systems and wastewater treatment. Open feedlots or fields where animals graze can be another source.

“We know enough to know which are more local problems and which are regional problems,” said Jennifer Ronneberg, a principal planner for the Minnesota Department of Health, which works with public water suppliers and wellhead protection. “Wastewater is a localized problem. Agricultural fertilizer is a regional problem.”

Township Study

While the volunteer study has been happening since 2006. The Minnesota Department of Agriculture has been systematically conducting the Township Testing Program since since 2013. In Southeast Minnesota, townships have been tested in Dodge County (seven townships), Fillmore County (24), Goodhue County (22), Olmsted County (11), Wabasha County (14) and Winona County (13).

The difference between the two studies, Schrandt said, is the VNMN study has attempted to look at the same wells over a period of time, creating nodes of data. The Township Testing Program, however, is more of a snapshot.

One of the problems with the township program, Ronneberg said, is despite the amount of data collected, it’s hard to draw serious conclusions from what we currently know.

For example, in Winona County’s Utica Township, the MDA estimated there were 202 households with private wells, but only 86 returned samples for the study. Of those 86, 35 wells were eliminated from the study because a non-fertilizer source of the nitrates was identified.

Of the 51 remaining wells in Utica Township in the survey, 10 wells, or 19.6 percent, were above the 10 ppm health limit. As Ronneberg noted, that means only 10 wells out of about 200 showed a problem with nitrates due to fertilizer.

So, is the problem in Utica Township 19.6 percent of wells, 5 percent (10 out of 200) or the 46.5 percent (40 wells out of 86 tested) from the initial data set?

All of this, Ronneberg said, shows that despite the years of data from testing wells in the region, all researchers have learned thus far is that there’s still much unknown.

“One of the biggest problems we have is lack of data for nitrates in groundwater,” Ronneberg said. “We don’t have enough monitoring wells for the DNR or the Department of Health. We don’t have enough private well data.”


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