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Dunn County offers free well testing for 2024

Dunn County is again offering free well testing following its 2023 project that tested nearly 1,000 wells in the county for nitrates and metals. 

“The sampling is planned to be started in July of this year with staff collecting the samples again,” said Heather Wood, water resources specialist for Dunn County. “It is open to anyone with a well within Dunn County, and there is no cost to participants.” 

Wood told the Dunn County Board of Supervisors recently that the goal is to test 240 wells, and the results will be analyzed by the Eau Claire City-County Health Department. 

The county has about $28,000 left over from the 2023 testing effort that sampled 995 wells in total, with 973 private wells and 22 wells representing town halls included. That effort, using ARPA (American Rescue Plan Act) funding, cost about $147,000. 

The testing at the town hall wells also sampled for PFAS, the so-called forever chemicals. PFAS were detected in 14 of those wells. But the findings indicated that levels of all chemicals and metals found in those wells were below current safe drinking water standards. 

“From the data, the most surprising thing was the arsenic,” Wood said about the testing of the private wells. Some 128 wells were found to have concentrations above the detection limits of 0.005 mg/L. 

The arsenic tended to be present in the western half of the county, she said, adding, “While we didn’t have any astronomically high readings, it was a little surprising in terms of quantity.” 

High nitrates, on the other hand, tended to be concentrated in the southeastern corner of the county, Wood said, which wasn’t surprising given the prevalence of the sandy soils in the areas with higher nitrate concentrations.  Nitrates often result from agricultural runoff, septic systems and fertilizers.  

Sandy soils “act like a sieve,” allowing the nitrates to percolate more freely to the groundwater, Wood said.  

Concentrations of nitrates also tended to be higher in the northern town of Hay River, she said, which has sandy soils but also sees intensive farming practices in beans and potatoes. 

“That sort of thing has a stacking effect” on nitrate concentrations, Wood said. 


The county-wide nitrate level in groundwater was 4.42 mg/L.  The EPA has set a safe drinking water standard of less than 10 mg/L.  The highest nitrate test result in the county was 40.4 mg/L, and 114 tests or nearly 12 percent had results about the 10 mg/L standard. 

Each well owner received the results with a letter from the county Land and Water Conservation Division, explaining what the samples would be used for and what resources are available if the results indicated contamination that needs to be mitigated.  The well owner also received a packet to help interpret the sampling results. 

 Besides allowing the county to establish important groundwater quality baseline data, Wood said, the effort also helped the county get in closer contact with property owners because of the samples were obtained by county employees. 

“There are a lot of things people don’t understand about groundwater,” Wood said, and this process allowed county officials to engage in some important educational efforts. 

Wood emphasized that there is no cost to participate in the second phase of the well-testing project.  Those who wish to participate in the 2024 program can sign up HERE.

Dunn County media release.


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