St. Mary's County, MD
These figures come from wells tested in St. Mary's County, MD, not from any one well.
- Iron is common in wells in St. Mary's County, MD (3 of 24 tested wells were over that level), so it's worth testing for.
- Manganese and sulfate are not common in wells in St. Mary's County, MD (0 of 24 and 0 of 118 tested wells were over). Only a test tells you about your own well.
- Wells in St. Mary's County, MD are typically soft (119 wells tested).
- Only a test of your own well tells you about your water.
What to test for
Start with the four this site covers:
- iron (common in wells here)
- manganese
- hardness
- sulfate
Most well owners also test for these. We point to the source and don't interpret the results.
- arsenic: occurs naturally in groundwater in many regions. USGS: arsenic and drinking water
- nitrate: common near farmland and septic systems. EPA: private drinking water wells
- total coliform bacteria: the standard yearly well check. EPA: private drinking water wells
- lead and copper: from household plumbing, especially when pH is below 6.5. EPA: lead in drinking water
- PFAS: several states run private-well sampling programs. EPA: PFAS
- a certified lab: states certify labs and some run their own private-well programs. Maryland's certified-lab list (from your state drinking-water program)
The numbers
County figures describe the wells sampled there, not any one well. Exact counts, sample years and sources are below.
Iron Recent
| Level it's compared with | 0.3 mg/L |
|---|---|
| Share of wells over the level | 12% |
| Wells over the level / wells judged | 3 of 24 |
| Median | 0.032575 mg/L |
| Years sampled | 1947–2022 |
| Wells | 24 |
| Test results | 205 |
| Wells left out | 0 |
| Sources | USGS (119) |
Manganese Recent
| Level it's compared with | 0.05 mg/L |
|---|---|
| Share of wells over the level | 0.0% |
| Wells over the level / wells judged | 0 of 24 |
| Median | 0.002145 mg/L |
| Years sampled | 1950–2022 |
| Wells | 24 |
| Test results | 185 |
| Wells left out | 0 |
| Sources | USGS (110) |
Hardness Recent
| Level it's compared with | none; hardness is shown in bands |
|---|---|
| Share of wells very hard | 0.0% |
| Median | 26 mg/L as CaCO₃ |
| Years sampled | 1947–2022 |
| Wells | 119 |
| Test results | 206 |
| Wells left out | 0 |
| Sources | USGS (119) |
Sulfate Recent
| Level it's compared with | 250 mg/L |
|---|---|
| Share of wells over the level | 0.0% |
| Wells over the level / wells judged | 0 of 118 |
| Median | 8 mg/L |
| Years sampled | 1947–2022 |
| Wells | 118 |
| Test results | 205 |
| Wells left out | 0 |
| Sources | USGS (118) |