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April 26, 2011

MADISON -- Private well owners should test their well water at least once a year for bacteria, periodically for nitrate, and should consider testing for other contaminants to keep their families safe, state health and drinking water officials say.

A recent survey found that well owners are not testing as regularly as they should and are not testing for the range of contaminants that may be in groundwater, says Dr. Lynda Knobeloch, a senior toxicologist with the Wisconsin Department of Health Services.

More than 7,300 Wisconsin residents took part in the 2008-9 Behavioral Risk Factor Survey that included questions about well testing.

The survey found that one-third of Wisconsin families depend on private wells for their drinking water and that less than a quarter of those wells had been tested within the past year, the recommended frequency. Far fewer families tested their water for other kinds of contamination such as solvents, gasoline, fuel oil, toxic metals, or pesticides.

The Department of Natural Resources advises people to test their water for bacteria at least once a year and if they notice changes in taste, odor and appearance of their water. Private wells also should be tested periodically for nitrate, and more often if they are near corn, soybean or vegetable fields, operations where fertilizer is manufactured, or animal feedlots and manure storage facilities, says Mark Putra, who leads the private water section for the DNR drinking water and groundwater program.

And well owners may need to test for other contaminants such as arsenic or agricultural chemicals, depending on the surrounding land use practices.

Spring thaw often brings increase in bacterial contamination

Most private wells provide safe drinking water if they are properly located, constructed, installed and maintained, Putra says. "However, we tend to see an increase in well contamination problems after spring thaw when melting snow soaks into the ground."

Some wells may become contaminated with bacteria that is not filtered out as the water soaks into the ground; such problems may be exacerbated during flooding. Surviving microbes can enter the groundwater by moving through fractured bedrock, quarries, sinkholes, inadequately grouted wells or cracks in the well casing. Insects or small rodents can also carry bacteria into wells with inadequate caps or seals, he says.

When flooding occurs, well owners should suspect that their drinking water is contaminated by floodwaters if the well casing becomes inundated; if there's a change in taste, color or sediment; or if the well does not have a deep casing and is near areas that have been flooded. Well owners should not drink from flooded wells until waters recede and the well test shows the water is safe. Wells located in pits and basements are especially susceptible to contamination.

Knobeloch urges well owners to find out more about common contaminants in their area and have their water tested regularly. "While contaminated water often looks and tastes fine, it can increase your risk of illnesses ranging from diarrhea to cancer and heart disease."

She noted that the main reason well owners provided when asked why they didn't test their water was that the water seemed to be safe based on its taste, odor and appearance. Nearly half of the homeowners who had never tested their water stated that they didn't know what to test for or weren't sure where to send their water for testing.

More information about testing, which laboratories can do the analysis, and what contaminants to test for can be found on the Test Your Private Well Water Annually of the DNR website. /org/water/dwg/privatewelltest.htm

FOR MORE INFORMATION CONTACT: Mark Putra (608) 267-7649; Lynda Knobeloch, DHS (608) 266-0923

Last Revised: Tuesday, April 26, 2011

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