Groundwater in St. Lawrence County contains radon, uranium, chloride, nitrate, sulfate, iron, and manganese at levels that exceed EPA health standards. These contaminants are present in concentrations serious enough to warrant attention from well owners.
The limestone bedrock beneath St. Lawrence County naturally contains radioactive minerals that release radon and uranium into groundwater as water moves slowly through cracks and spaces in the rock. Chloride, nitrate, and sulfate enter through both natural dissolution from the rock and from land use such as road salt and fertilizer application. Iron and manganese leach from minerals in the limestone itself as acidic groundwater passes through.
Groundwater in this county is very hard, driven primarily by calcium and magnesium released from the limestone below. These minerals dissolve as water percolates through the carbonate rock and accumulate over time. Very hard water is common across wells throughout the county, reflecting the limestone geology that feeds the aquifer system.
Wells in St. Lawrence County commonly exceed EPA health standards for chloride, nitrate, radon, uranium, and sulfate. Radon is a radioactive gas that increases lung cancer risk with long-term exposure. Uranium is a radioactive metal that builds up in bones and organs and can damage kidneys. Nitrate at high levels is especially dangerous for infants and can interfere with oxygen in the blood.
The very hard water in county wells causes noticeable staining in sinks, tubs, and on fixtures from iron and mineral deposits. Scale builds up inside pipes and can shorten the lifespan of water heaters and dishwashers. Some people notice a metallic or unpleasant taste in the water from the mineral content.
Because multiple analytes exceed health standards in this county, we recommend a comprehensive metals and minerals panel to learn what is actually in your well. Every well is different, and your water could have higher or lower levels than what is common here. Testing is the only way to know what treatment your specific well needs. Depending on your results, options like radon aeration systems or reverse osmosis filters may help.
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 | 48 | 52% | Moderate | High ⓘ | |
| Iron | 86 | 30% | Moderate | High | |
| Manganese | 81 | 25% | Moderate | High | |
| Sulfate | 106 | 12% | High | Moderate | |
| Chloride | 687 | 4% | High |
Moderate
Elevated concentration, not % above limit
|
|
| Nitrate | 96 | 3% | Moderate |
Moderate
Elevated concentration, not % above limit
|
|
| Uranium | 49 | 2% | Moderate | Low | |
| Arsenic | 65 | 0% | Moderate | Low | |
| Fluoride | 93 | 0% | Moderate | Low | |
| HFPO-DA (GenX) ⓘ municipal | 28 | 0% | Moderate | Safe | |
| Lead | 65 | 0% | Moderate | Low | |
| Nitrite | 56 | 0% | Moderate | Low | |
| PFHxS ⓘ municipal | 28 | 0% | Moderate | Safe | |
| PFNA ⓘ municipal | 28 | 0% | Moderate | Safe | |
| PFOA ⓘ municipal | 28 | 0% | Moderate | Safe | |
| PFOS ⓘ municipal | 28 | 0% | Moderate | Safe | |
| E. coli | 15* | 0% | Moderate | Low | |
| Fecal Coliform | 14* | 0% | Low | Low | |
| Hardness | 88 | — | Moderate | Low | |
| PFBS ⓘ municipal | 28 | — | Moderate | Safe | |
| pH | 106 | — | High | Low | |
| Sodium | 88 | — | Moderate | Low | |
| Total Coliform | 15* | 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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