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Water Quality

Drinking Water Contaminants

Public water systems are tested regularly for a variety of contaminants, but if you have a private well, routine testing is up to you. The Minnesota Department of Health and Dakota County recommend that well owners annually test drinking water from private wells.

The Minnesota Department of Health provides information on common drinking water problems.

The following contaminants are the most common in Dakota County:

Coliform bacteria
The presence of coliform bacteria are disease-causing microorganisms that may indicate fecal contamination.   The water supply should be disinfected and retested. If the bacteria persist after repeated disinfection treatments, contact the Water Resources Department for recommendations by calling 952-891-7000.

Nitrate is derived naturally from air, soil, rock and plants in low concentrations.  High concentrations in groundwater are often associated with human and animal wastes, fertilized and irrigated crops, and landfills.  High nitrate concentrations in your water supply may indicate the presence of other contaminants that have not yet been tested or detected.

A water supply with a concentration of nitrate of more than 10 milligrams per liter indicates a significant risk to infants six months of age and younger. Infants consuming water and water-prepared formula and food containing more than 10 milligrams per liter of nitrate may be prone to methemoglobinemia or "blue-baby" disease. 

Older children and adults can ordinarily tolerate higher levels of nitrate without acute disease symptoms.  Boiling water that is high in nitrate only increases its concentration and does not make the water safe to drink.

Perfluorobutanoic Acid (PFBA)
This family of chemicals includes Scotchgard, Teflon, flame-retardants, and other coatings. Little is known about the long-term effects of these chemicals, but Minnesota Department of Health, the U.S. Environmental Protection Agency and 3M are researching these chemicals in more detail. The drinking water guidelines recommended by Minnesota Department of Health have been set at low levels because of the uncertainties surrounding these chemicals.

Dakota County residents with private wells can have their water tested for perfluorochemicals. Dakota County and the Minnesota Department of Health partnered to make the test available.   Contact the Water Resources Department at 952-891-7000 to schedule the water sampling. The water sample tested for perfluorochemicals must be collected by County personnel.

Although perfluorobutanoic acid has only been found in low levels in Dakota County, people with concerns may use a filter with granulated activated carbon to remove this chemical from their drinking water. Such filters are available in end-of-tap or pitcher filters.

A pesticide screen is a relatively low cost and highly sensitive technique to detect the presence of various groups of pesticides in water. It does not indicate which specific pesticide(s) within a group may be present. The test will confirm the presence of pesticides, within the groups tested, at concentrations above a specified limit. Get your water tested.

The immunoassay may indicate the presence of some of the pesticide breakdown products within a particular group. Dakota County offers a combination of the following two pesticide immunoassay screens:

  • Triazine screen: This test will indicate the presence of common triazine herbicides, including atrazine (AAtrex), cyanazine (Bladex), and simazine (Princep).
  • Lasso/Dual/Acetochlor screen: This test will indicate the presence of alachlor (Lasso), metolachlor (Dual), or acetochlor (Harness).

Herbicides most commonly found in Dakota County private wells include: alachlor, metolachlor, atrazine, cyanazine, and acetochlor or their breakdown products.

Last updated: 3/4/2014 9:45 AM