High levels of nitrates found in well water

By county, the percentage of private wells with nitrate levels exceeding federal standards, based on February tests.

Wabasha: 30 percent

Fillmore: 25 percent

Wionona: 22 percent

Houston: 18 percent


Goodhue: 12 percent

Dodge: 6 percent

Rice: 5 percent

Olmsted and Mower: Not available yet


By John Weiss

PRESTON — Thousands of private wells in southeastern Minnesota are contaminated by high levels of nitrates that could cause health problems such as brain damage in infants and possibly bladder cancer in adults.


The first set of results from the first random sample of private wells in the nine-county region shows up to 30 percent of wells might have unsafe levels of the chemical, which is traced to too much nitrogen from farm fertilizers or manure, Bea Hoffmann told members of the Basin Alliance for the Lower Mississippi in Minnesota on Wednesday. The worst counties are in the eastern part of the region, the ones with less contaminant-trapping topsoil over water-bearing rock formations, said Hoffman, who is the executive director of the Southeast Minnesota Water Resources Board.

One surprise was how little some people knew about nitrates and their wells despite more than 20 years of education, Hoffmann said. "There is a huge education gap," she said.

Just about everyone living outside cities gets their water from private wells. One estimate is that 1 million Minnesotans rely on private wells.

Changes in farming

Another study discussed at the meeting says nitrate levels in this region are increasing because of changes in farming. With more row crops like corn and soybeans, nitrate levels are increasing in the surface water, which, because of the region’s porous aquifers, can quickly go underground.

A third speaker strongly criticized southeastern Minnesota farmers for not doing enough to control the use of chemicals.

Hoffmann said her group asked health departments in the nine counties what their biggest worry is. All said nitrates. Nitrates in surface water can cause health and environmental problems.

Study method, results


The study randomly sampled 675 homes that chose water from various levels of water-bearing rocks. Four sampling months will be part of the study; the first was in February; the next will be in August.

Another finding was that an average of 63 percent of wells are shallow and built before new standards went into effect about 35 years ago. Those wells are generally more susceptible to contamination, Hoffmann said.

A state law says that if voluntary measures don’t improve the level of nitrates, the state must set rules. "Some people say it’s time to act," Hoffmann said, but there isn’t enough data to determine whether voluntary efforts and education about land use are working. Part of the study is assessing that question.

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