A second round of testing on a subset of private wells in southwestern Wisconsin that previously tested positive for fecal matter show the contamination is still present in most of those wells.
Results from the independent study released Aug. 1 indicated that 32 of 35 — or 91% — of the wells known to have been contaminated before continued to show levels of the pollutants that exceeded state health standards.
An early round of testing found 42% of 301 wells in Grant, Iowa and Lafayette counties had evidence of total coliform or nitrate that surpassed the state’s health standard. In a second round, 27% of 539 wells subsequently turned up total coliform or nitrate exceeding the state standard.
The 35 wells included in the latest round test were among the 42% initially found to be contaminated.
“As a researcher of groundwater for 25 years now, I continue to be amazed by the level of fecal contamination in Wisconsin groundwater,” said Mark Borchardt, a research microbiologist for the U.S. Agricultural Research Service.
The work was led by Borchardt, others in his agency and the Wisconsin Geological and Natural History Survey. Monetary backing came from the counties, the agencies and other local groups. Additional testing in the counties is likely, with the next round set for early August.
During testing in April, it was discovered that some of the wells contained illness-causing pathogens such as salmonella, rotavirus and cryptosporidium.
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The results are the latest in a series of examinations showing an assortment of problems with well water in the three counties and underscore the possible vulnerability of Wisconsin groundwater from agricultural practices and faulty septic systems.
Wisconsin figures indicate about one-quarter of the state’s people get their water from more than 800,000 private wells.
On July 31, Democratic Gov. Tony Evers proposed new rules aimed at farmers and their use of manure and fertilizer. The regulations would focus on the regions vulnerable to nitrates, another source of groundwater pollution.
But those measures will require authorization by the Republican-controlled Legislature.
In the meanwhile, Republican Assembly Speaker Robin Vos, of Rochester, created a water quality task force in February to highlight the heightened attention to groundwater. Vos has since been holding hearings across Wisconsin.
Vos created the legislative task force after Borchardt’s group released the results from its earlier round of testing.
[Editor's note: This story has been updated to clarify that the wells sampled in the latest round of testing constitute a subset of wells previously found to have been contaminated.]