Arsenic in Well Water

Arsenic is a part of the earth's crust and occurs naturally in some soil and rock. Arsenic from soil and rock can leach into groundwater. Groundwater is the primary source of drinking water for much of Minnesota. Almost all arsenic in drinking water is from these underground deposits of naturally occurring arsenic. Human activities can contribute to arsenic levels in drinking water, as well as in soil and air. Mining and manufacturing can displace arsenic from its original location; however, these sources are not considered a concern in Minnesota.

The health effects of arsenic depend on its chemical form, how much is in the water, how much water people drink, and for how long. In nature, pure arsenic is rare. It is usually combined with other elements to form "compounds." Arsenic combined with compounds containing carbon is called "organic arsenic." When arsenic combines with other elements, such as oxygen, chlorine, or sulfur, it is called "inorganic arsenic." Arsenic in soil, rock, and water is often inorganic. Usually, organic forms of arsenic are less harmful than inorganic forms.

Yes. Arsenic over the recommended safe level has been detected in groundwater in some private wells in Shorewood. Arsenic in water has no taste or odor, so the only way to know if drinking water contains arsenic is to have it tested. While private well owners are not required to test for arsenic, the MD recommends that every well should be tested for arsenic at least once or twice. If arsenic is detected at levels in excess of 10 µG/AL in water from a well used for drinking and cooking, and if repeat sampling confirms the results, the MD recommends that you use an alternate source of drinking water or install a treatment system to reduce arsenic levels in the water.

Private well owners must arrange and pay for testing their well water for arsenic, which typically costs about $35. Contact Minnesota Department of Health for a list of MD certified Environmental Contract Laboratories.

There are several options if your well tests over the recommended limit for arsenic. You can install a reverse osmosis filtration system, dig a new well; connect to City water where available; or use bottled water. For more information on these options, go to the Minnesota Department of Health website and type well water in the search engine.

If you have any questions about wells or well water quality, email the Well Management Section Central Office or by telephone at 651-201-4600.