Groundwater in Modoc County contains radon, manganese, and iron at levels that exceed EPA health standards. These contaminants are present at concerning enough levels that well owners should take them seriously.
The rock beneath Modoc County is volcanic basalt, which naturally releases these metals and radon into groundwater as water moves through cracks and pores. Radon comes from natural radioactive decay in the rock itself. Manganese and iron are released when groundwater comes into contact with the basalt, especially in areas where the water is slightly acidic or sits in the rock for a long time.
Groundwater in this county is moderately hard and carries elevated iron from the volcanic rock below. The basalt that makes up the aquifer dissolves slowly as water flows through it, releasing iron and other minerals. Most wells in Modoc County show these same characteristics because the same volcanic rock sits beneath the entire region.
Wells in Modoc County commonly have radon, iron, and manganese at levels above EPA health standards. Radon is a radioactive gas that increases the risk of lung cancer when breathed in over time. Iron and manganese can harm your nervous system and organs with long-term exposure, especially in children. These concerns need your attention.
County well water often has moderate iron levels that cause orange or brown staining on fixtures, laundry, and dishes. The moderately hard water can leave scale buildup in pipes and reduce the life of water heaters and dishwashers. You may also notice a metallic taste or smell related to the iron and manganese present in wells here.
We recommend having your well tested with a comprehensive panel that covers metals, minerals, bacteria, and radon--testing typically costs $200 to $400. Every well is different, and your water could have higher or lower levels than what is common in the county. Testing is the only way to know what is actually in your well so you can treat it properly. Radon ventilation systems and iron or manganese filters are treatment options that work for many homeowners in this area.
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 | 8 | 88% | Low | High ⓘ | |
| Manganese | 19 | 37% | Moderate | High | |
| Iron | 31 | 3% | Moderate |
Moderate
Elevated concentration, not % above limit
|
|
| Lead | 19 | 0% | Moderate | Low | |
| Nitrate | 26 | 0% | Moderate | Low | |
| PFHxS ⓘ municipal | 8 | 0% | Low | Low ⓘ | |
| Sulfate | 27 | 0% | Moderate | Low | |
| PFOA ⓘ municipal | 8 | 0% | Low | Safe ⓘ | |
| Arsenic | 31 | 0% | Moderate | Low | |
| Uranium | 16 | 0% | Moderate | Low | |
| PFOS ⓘ municipal | 8 | 0% | Low | Safe ⓘ | |
| Nitrite | 16 | 0% | Moderate | Low | |
| HFPO-DA (GenX) ⓘ municipal | 8 | 0% | Low | Safe ⓘ | |
| Fluoride | 22 | 0% | Moderate | Low | |
| Chloride | 34 | 0% | Moderate | Low | |
| PFNA ⓘ municipal | 8 | 0% | Low | Safe ⓘ | |
| Sodium | 33 | — | Moderate | Low | |
| Hardness | 45 | — | Moderate | Low | |
| pH | 57 | — | Moderate | Low | |
| PFBS ⓘ municipal | 8 | — | Low | Safe ⓘ |
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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