Janesville wells meet nitrate regulation levels

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Katherine Krueger
Thursday, August 1, 2013

JANESVILLE--After a water quality report on Rock County private wells sparked concern from local residents, city officials say Janesville's water remains at healthy levels.

Water utility officials test quarterly and annually for a range of substances to make sure a system that can handle 32 million gallons every day is providing residents with safe water that complies with both Wisconsin Department of Natural Resources and federal Environmental Protection Agency standards.

The substances include nitrates, the inorganic compound that finds its way into groundwater from fertilizer runoff and poses serious health risks to infants and those with compromised immune function in high concentrations.

According to the city's 2012 Water Quality Report, the average nitrate level across the city's eight wells is 8.77 ppm. Individual well results ranged from no nitrates detected to 9.03 ppm. The EPA has set the maximum contaminant level, a standard that balances both health goals and a cost-benefit analysis for enforcing the regulation, at 10 ppm.

Craig Thiesenhusen, city water utility superintendent, said nitrate levels can increase or decrease during year, but the city has not seen levels exceeding 10 ppm in “a really, really long time.” Before Congress approved the Safe Drinking Water Act in 1974, he said, the maximum nitrate level was capped at 50 ppm.

Although some individual wells have elevated levels, the variations become negligible when the water is blended in city reservoirs, Thiesenhusen said.

In Rock County, health officials have expressed concern about rural wells after more than 50 percent of them in testing this year showed unsafe levels of nitrate. That compares to 25 percent to 30 percent in a normal year. County officials believe last year's drought could be to blame because many fertilizers applied to fields were not used.

Janesville's Water Quality Report from 2010 found average nitrate levels at 7.44 ppm in city wells, and levels were reported at 6.68 ppm in the report from 2011.

Wells that test between 5 and 10 ppm meet the “trigger level” for the city to test them quarterly, but no health risk is associated with drinking water within that range, Thiesenhusen said. Otherwise, they are tested for nitrates annually.

Janesville's water supply comes from groundwater rather than surface water sources such as the Rock River. Four of the city's wells draw water from 100-200 feet below the surface, while four wells reach more than 1,100 feet deep to tap into the sandstone aquifer, according to the city reports.

The city also runs monthly tests for bacteria in the water supply. Tests are either positive or negative for coliform. If a test is positive, Thiesenhusen said, the city would test for E. coli. All tests have been negative, he said.

After a Rock County Health Department analysis found 31 percent of private wells have tested positive for coliform in the last eight years, he said the water utility office has fielded a number of calls about the city's water quality.

“In every system, (officials) should know what's in there, and nitrates is one of them,” he said. “We haven't seen the increase the Rock County Health Department has seen.”

The city spends $30,000 to $70,000 annually testing for water contaminants, Thiesenhusen said. One city official will conduct the annual well contaminant tests during August, and the results will be publicly available, he said.

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