Groundwater in Marathon County contains manganese, nitrate, pfoa, and pfos that well owners should be aware of. Several of these contaminants exceed EPA health standards and warrant testing and attention.
Manganese and iron come naturally from the local rock beneath the county. Nitrate enters from agricultural and septic sources on the land above. PFOA and PFOS are human-made chemicals that have contaminated groundwater through industrial use and improper disposal at specific sites.
Groundwater in this county is very hard, driven by elevated calcium and magnesium that dissolve from the underlying rock as water seeps downward. The measured hardness reflects the bedrock composition in this area. Very hard water is common across wells throughout Marathon County.
Wells in Marathon County commonly exceed EPA health standards for iron, manganese, nitrate, PFOA, and PFOS. Iron and manganese can damage your organs and affect how your body uses oxygen if you drink contaminated water over time. Nitrate is especially dangerous for babies and can cause serious illness. PFOA and PFOS are human-made chemicals linked to health problems including liver damage and immune system issues.
County wells are very hard, which means you'll likely see white, crusty scale buildup on faucets and inside pipes. Iron staining leaves orange or brown marks on sinks and laundry that are hard to remove. You may notice a metallic taste or smell in your water. Over time, very hard water can shorten the lifespan of water heaters and dishwashers.
We recommend testing your well with a comprehensive metals and minerals panel, which typically costs $200 to $400. Every well is different, and your well may have higher or lower levels than what is common in the county. Testing is the only way to know what is actually in your water so it can be properly treated. Iron and manganese removal systems, along with water softening, can help address these concerns.
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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