Groundwater in Sanilac County contains arsenic, iron, manganese, chloride, nitrate, and sulfate. Several of these contaminants exceed EPA health standards and warrant immediate attention.
These contaminants come from the Marshall aquifer rock itself. As groundwater moves slowly through the sandstone and related rock layers, iron and arsenic dissolve naturally from the minerals present. Chloride and nitrate accumulate partly from road salt and agricultural activity, which seep downward into the aquifer.
Groundwater in this county is very hard, driven by elevated calcium and magnesium from the rock layers below. The slow movement of water through the Marshall aquifer allows minerals to concentrate over time, creating water with high hardness and elevated iron. These mineral characteristics are common across wells throughout the county.
Wells in Sanilac County commonly contain arsenic, chloride, iron, manganese, nitrate, and sulfate at levels exceeding EPA health standards. Arsenic is a serious health concern because long-term exposure increases risk of cancer and can damage organs. Manganese and nitrate harm brain development, especially in children and infants. Chloride at elevated levels can damage kidneys over time. Iron and sulfate, while present at high levels, pose fewer direct health risks than arsenic and manganese.
The very hard water in this county creates practical problems for your home. Iron stains sinks, toilets, and laundry with reddish-brown marks that are hard to remove. You may notice a metallic taste in your water and a rotten-egg smell from sulfate. This extreme hardness causes white crusty buildup on fixtures and pipes, and can shorten the lifespan of water heaters and dishwashers.
We recommend testing your well with a comprehensive metals and minerals panel because multiple contaminants exceed health standards. 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. A comprehensive panel typically costs $200-400. Treatment options like reverse osmosis systems or whole-house water softeners paired with filtration can address these issues.
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 ⓘ |
|---|---|---|---|---|---|
| Arsenic | 28 | 57% | Moderate | High | |
| Iron | 35 | 54% | Moderate | High | |
| Manganese | 35 | 29% | Moderate | High | |
| Nitrate | 18 | 6% | Moderate | Moderate | |
| Chloride | 34 | 3% | Moderate | Low | |
| Sulfate | 34 | 3% | Moderate | Low | |
| Fluoride | 34 | 0% | Moderate | Low | |
| HFPO-DA (GenX) ⓘ municipal | 12 | 0% | Low | Safe | |
| Lead | 14 | 0% | Low | Low | |
| Nitrite | 18 | 0% | Moderate | Low | |
| PFHxS ⓘ municipal | 12 | 0% | Low | Safe | |
| PFNA ⓘ municipal | 12 | 0% | Low | Safe | |
| PFOA ⓘ municipal | 12 | 0% | Low | Safe | |
| PFOS ⓘ municipal | 12 | 0% | Low | Safe | |
| Radon | 5 | 0% | Low | Low ⓘ | |
| Uranium | 11 | 0% | Low | Low | |
| E. coli | 2* | 0% | Low | Safe ⓘ | |
| Hardness | 34 | — | Moderate | Low | |
| PFBS ⓘ municipal | 12 | — | Low | Safe | |
| pH | 36 | — | Moderate | Low | |
| Sodium | 34 | — | Moderate | Low | |
| Total Coliform | 2* | 0% | Low | 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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