Groundwater in Marathon County contains manganese, iron, radon, and PFOA and PFOS at levels that exceed EPA health standards. Iron and manganese are the most widespread concerns, with radon also present at concentrations that warrant attention.
Iron and manganese seep into the water as it moves slowly through the mixed rock types beneath this county. Radon comes from the natural breakdown of radioactive minerals scattered throughout these same rock layers. PFOA and PFOS likely enter from industrial or commercial sites and contaminated soil, though these are less widespread than the metal contaminants.
The water in Marathon County carries elevated iron but remains soft overall, meaning calcium and magnesium are low. The iron concentration here reflects the composition of the underlying rocks, which naturally release iron as groundwater passes through them. Elevated iron is common across wells in this county, though levels vary from well to well.
Wells in Marathon County commonly exceed EPA health standards for iron, manganese, PFOA, PFOS, and radon. Iron and manganese can build up in your body over time and damage your organs. PFOA and PFOS are chemicals that may weaken your immune system and affect your health. Radon is a radioactive gas that increases lung cancer risk when you breathe it in over many years.
The high iron in county wells leaves orange or brown stains on sinks, toilets, and laundry. Water may taste metallic or have an unpleasant odor. These stains are hard to remove and can damage fixtures. The good news is that wells here are soft, so you won't see white scale buildup on pipes and appliances.
We recommend testing your well with a comprehensive metals and minerals panel that checks for all these concerns, since every well is different and yours may have higher or lower levels than what's common in the county. Testing is the only way to know what is actually in your water so it can be properly treated. A comprehensive panel typically costs $200 to $400. Iron removal systems, radon mitigation, and PFAS filtration are available treatment options.
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 ⓘ |
|---|---|---|---|---|---|
| Manganese | 22 | 32% | Moderate | High | |
| Nitrate | 20 | 25% | Moderate | High | |
| PFOA ⓘ municipal | 44 | 20% | Moderate | High | |
| PFOS ⓘ municipal | 44 | 20% | Moderate | High | |
| Iron | 22 | 14% | Moderate | Moderate | |
| Arsenic | 5 | 0% | Low | Low ⓘ | |
| Chloride | 21 | 0% | Moderate | Low | |
| Fluoride | 19 | 0% | Moderate | Low | |
| HFPO-DA (GenX) ⓘ municipal | 44 | 0% | Moderate | Safe | |
| Lead | 5 | 0% | Low | Low ⓘ | |
| Nitrite | 7 | 0% | Low | Low ⓘ | |
| PFHxS ⓘ municipal | 44 | 0% | Moderate | Low | |
| PFNA ⓘ municipal | 44 | 0% | Moderate | Low | |
| Radon | 2 | 0% | Low | Low ⓘ | |
| Sulfate | 21 | 0% | Moderate | Low | |
| Uranium | 6 | 0% | Low | Low ⓘ | |
| Hardness | 22 | — | Moderate | Low | |
| PFBS ⓘ municipal | 44 | — | Moderate | Low | |
| pH | 23 | — | Moderate | Low | |
| Sodium | 19 | — | Moderate | 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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