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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.