San Juan County, NM
These figures come from wells tested in San Juan County, NM, not from any one well.
- Iron is common in wells in San Juan County, NM (20 of 34 tested wells were over that level), so it's worth testing for.
- Manganese is common in wells in San Juan County, NM (31 of 47 tested wells were over that level), so it's worth testing for.
- Sulfate is common in wells in San Juan County, NM (261 of 405 tested wells were over that level), so it's worth testing for.
- Wells in San Juan County, NM are typically very hard (410 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. New Mexico'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 | 59% |
| Wells over the level / wells judged | 20 of 34 |
| Median | 0.647 mg/L |
| Years sampled | 1956–2025 |
| Wells | 34 |
| Test results | 604 |
| Wells left out | 11 |
| Sources | USGS (237), 11NPSWRD_WQX (2) |
Manganese Recent
| Level it's compared with | 0.05 mg/L |
|---|---|
| Share of wells over the level | 66% |
| Wells over the level / wells judged | 31 of 47 |
| Median | 0.0895 mg/L |
| Years sampled | 1960–2025 |
| Wells | 47 |
| Test results | 1,122 |
| Wells left out | 11 |
| Sources | USGS (137), 11NPSWRD_WQX (2) |
Hardness Recent
| Level it's compared with | none; hardness is shown in bands |
|---|---|
| Share of wells very hard | 51% |
| Median | 180 mg/L as CaCO₃ |
| Years sampled | 1933–2025 |
| Wells | 410 |
| Test results | 1,277 |
| Wells left out | 15 |
| Sources | USGS (408), 11NPSWRD_WQX (2) |
Sulfate Recent
| Level it's compared with | 250 mg/L |
|---|---|
| Share of wells over the level | 64% |
| Wells over the level / wells judged | 261 of 405 |
| Median | 490 mg/L |
| Years sampled | 1933–2025 |
| Wells | 405 |
| Test results | 1,429 |
| Wells left out | 15 |
| Sources | USGS (405) |