Butte County groundwater contains radon, PFOS, manganese, arsenic, chloride, fluoride, iron, nitrate, and other contaminants that exceed EPA health standards. Several of these reach concerning levels and deserve attention from well owners in the area.
The basaltic rock that underlies much of Butte County naturally releases arsenic, fluoride, and manganese into groundwater as water moves through the stone. Radon and PFOS contamination come from both natural radioactive decay in the rock and from industrial or firefighting activities on the land surface. Nitrate and chloride often seep down from agricultural and urban areas above the aquifer. These contaminants mix into the groundwater from multiple sources unique to this region.
Groundwater in Butte County is hard, driven by calcium and magnesium that dissolve from the volcanic rock below. The basaltic geology naturally produces elevated hardness as water passes through these ancient rock layers. Hard water is widespread across wells throughout the county, making it a common trait in this area.
Wells in Butte County have been found to contain several contaminants that exceed EPA health standards. Arsenic, nitrate, and volatile organic compounds like trichloropropane and PFOA and PFOS can harm your health if you drink them over time. These chemicals can damage organs and increase cancer risk. Radon gas in well water also poses a health concern, especially when water heats up in your home and releases the gas into the air you breathe.
County well water tends to be hard, which means it has high levels of minerals like calcium and magnesium. This hardness can leave white scale buildup on your faucets, fixtures, and inside pipes. Over time, hard water can shorten the lifespan of water heaters and dishwashers. You might also notice that soap doesn't lather as well and clothes feel stiff after washing.
We recommend testing your well water to find out what is actually in it, since every well is different and yours could have higher or lower levels than the county average. A comprehensive testing panel that checks for metals, minerals, and contaminants costs between $200 and $400. Testing is the only way to know what needs treatment, whether that is a filter for arsenic and chemicals, a water softener for hardness, or both.
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 ⓘ |
|---|---|---|---|---|---|
| Radon | 21 | 19% | Moderate | High ⓘ | |
| PFOS ⓘ municipal | 138 | 14% | High | Moderate | |
| Manganese | 160 | 10% | High | Moderate | |
| Nitrate | 300 | 7% | High | Moderate | |
| PFHxS ⓘ municipal | 138 | 6% | High | Moderate | |
| Sulfate | 284 | 4% | High |
Moderate
Elevated concentration, not % above limit
|
|
| Arsenic | 165 | 4% | High |
Moderate
Elevated concentration, not % above limit
|
|
| Iron | 160 | 3% | High |
Moderate
Elevated concentration, not % above limit
|
|
| PFOA ⓘ municipal | 138 | 3% | High | Low | |
| 1,2,3-Trichloropropane | 36 | 3% | Moderate | Low | |
| Chloride | 316 | 3% | High | Low | |
| Fluoride | 183 | 1% | High | Low | |
| HFPO-DA (GenX) ⓘ municipal | 138 | 0% | High | Safe | |
| Nitrite | 98 | 0% | Moderate | Low | |
| Uranium | 92 | 0% | Moderate | Low | |
| PFNA ⓘ municipal | 138 | 0% | High | Low | |
| Boron | 35 | 0% | Moderate | Low | |
| Chromium (total) | 37 | 0% | Moderate | Low | |
| Lead | 86 | 0% | Moderate | Low | |
| Perchlorate | 35 | 0% | Moderate | Low | |
| Tds | 37 | — | Moderate | Low | |
| Sodium | 291 | — | High | Low | |
| E. coli | 26* | 0% | Moderate | Safe | |
| pH | 411 | — | High | Low | |
| Hardness | 313 | — | High | Low | |
| PFBS ⓘ municipal | 138 | — | High | Low | |
| Total Coliform | 26* | 0% | 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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