Groundwater in Winona County contains arsenic, iron, lead, manganese, nitrate, and pfos. Several of these contaminants exceed EPA health standards, making testing and awareness important for well owners.
These contaminants come from two sources. Arsenic, iron, lead, and manganese occur naturally in the limestone bedrock beneath the county and dissolve into water as it moves slowly through the rock. Nitrate and pfos enter from surface sources like fertilizer runoff and industrial or municipal use, then travel downward into the groundwater.
Groundwater in this county is very hard, driven by elevated calcium and magnesium from the limestone below. The same limestone that makes the water hard also releases iron naturally as water passes through it over time. Very hard water and elevated iron are common across wells throughout Winona County.
Wells in Winona County contain arsenic, lead, manganese, and nitrate at levels that exceed EPA health standards, along with PFOS contamination. Arsenic and lead build up in your body over time and can damage organs like the kidneys and liver. Lead is especially harmful to children's brain development. Nitrate is dangerous for infants and can prevent oxygen from reaching their blood. Manganese can affect how the brain develops and functions.
County wells have very hard water, which means mineral buildup happens quickly on pipes and inside appliances like water heaters and dishwashers--this can shorten their lifespan significantly. Iron levels in the water are also elevated, leaving reddish or brown stains on clothes, dishes, and fixtures. You might notice a metallic taste in your water or reduced lather when using soap.
Since every well is different, your water could have higher or lower levels than what is common here. Testing is the only way to know what is actually in your well so you can treat it properly. We recommend a comprehensive metals and minerals panel, which typically costs between two hundred and four hundred dollars. Iron removal systems and arsenic treatment filters are options worth discussing with a water professional.
Not sure if your well is affected? Get certified results in 5–7 days.
Test Your Well Water with Tap Score →| Contaminant | Samples ⓘ | % Above MCL ⓘ | Distribution ⓘ | Confidence ⓘ | Risk ⓘ |
|---|---|---|---|---|---|
| Iron | 153 | 36% | High | High | |
| PFOS ⓘ municipal | 21 | 10% | Moderate | Moderate | |
| Nitrate | 55 | 4% | Moderate |
Moderate
Elevated concentration, not % above limit
|
|
| Manganese | 117 | 3% | High |
Moderate
Elevated concentration, not % above limit
|
|
| Arsenic | 134 | 1% | High | Low | |
| Lead | 136 | 1% | High | Low | |
| HFPO-DA (GenX) ⓘ municipal | 18 | 0% | Moderate | Safe | |
| PFHxS ⓘ municipal | 16 | 0% | Moderate | Safe | |
| Chloride | 190 | 0% | High | Low | |
| Fluoride | 168 | 0% | High | Low | |
| Nitrite | 45 | 0% | Moderate | Safe | |
| Radon | 1 | 0% | Low | Low ⓘ | |
| Sulfate | 179 | 0% | High | Low | |
| Uranium | 24 | 0% | Moderate | Low | |
| PFNA ⓘ municipal | 18 | 0% | Moderate | Safe | |
| PFOA ⓘ municipal | 20 | 0% | Moderate | Low | |
| Hardness | 18 | — | Moderate | Low | |
| PFBS ⓘ municipal | 17 | — | Moderate | Low | |
| pH | 22 | — | Moderate | Low | |
| Sodium | 156 | — | High | Low |
MCL = Maximum Contaminant Level (EPA limit for public water; used as benchmark for private wells). Distribution shows % of sampled wells in each concentration band. Methodology.
* Microbial contaminants (E. coli, coliform) reflect only samples from the last 10 years.
Data shows potential risk — a certified test confirms whether your water is affected.
Order a Tap Score Test →Population-level CDC data. Not individual risk prediction.
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