Rock County, MN
These figures come from wells tested in Rock County, MN, not from any one well.
- Iron is common in wells in Rock County, MN (25 of 51 tested wells were over that level), so it's worth testing for.
- Manganese is common in wells in Rock County, MN (28 of 51 tested wells were over that level), so it's worth testing for.
- Sulfate is common in wells in Rock County, MN (19 of 108 tested wells were over that level), so it's worth testing for.
- Wells in Rock County, MN are typically very hard (102 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 (common in wells here)
- sulfate (common in wells here)
- hardness
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. Minnesota'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 | 49% |
| Wells over the level / wells judged | 25 of 51 |
| Median | < DL mg/L |
| Years sampled | 1958–2022 |
| Wells | 51 |
| Test results | 113 |
| Wells left out | 0 |
| Sources | MNDNR_AGW (57), USGS (36), MNPCA_AGW (2) |
More than half the wells had results below the lab's detection limit, so the median is reported as below that limit.
Manganese Recent
| Level it's compared with | 0.05 mg/L |
|---|---|
| Share of wells over the level | 55% |
| Wells over the level / wells judged | 28 of 51 |
| Median | 0.0855 mg/L |
| Years sampled | 1958–2021 |
| Wells | 51 |
| Test results | 103 |
| Wells left out | 0 |
| Sources | MNDNR_AGW (57), USGS (36), MNPCA_AGW (2) |
Hardness Recent
| Level it's compared with | none; hardness is shown in bands |
|---|---|
| Share of wells very hard | 100% |
| Median | 376 mg/L as CaCO₃ |
| Years sampled | 1958–2023 |
| Wells | 102 |
| Test results | 123 |
| Wells left out | 0 |
| Sources | MNDNR_AGW (57), USGS (36), MNDA_PESTICIDE (7), MNPCA_AGW (2) |
Sulfate Recent
| Level it's compared with | 250 mg/L |
|---|---|
| Share of wells over the level | 18% |
| Wells over the level / wells judged | 19 of 108 |
| Median | 78.55 mg/L |
| Years sampled | 1958–2023 |
| Wells | 108 |
| Test results | 156 |
| Wells left out | 0 |
| Sources | MNDNR_AGW (57), USGS (40), MNDA_PESTICIDE (7), MNPCA_AGW (4) |