Umatilla County, OR
These figures come from wells tested in Umatilla County, OR, not from any one well.
- Iron is common in wells in Umatilla County, OR (43 of 268 tested wells were over that level), so it's worth testing for.
- Manganese and sulfate are not common in wells in Umatilla County, OR (19 of 268 and 3 of 430 tested wells were over). Only a test tells you about your own well.
- Wells in Umatilla County, OR are typically hard (429 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. Oregon'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 | 16% |
| Wells over the level / wells judged | 43 of 268 |
| Median | < DL mg/L |
| Years sampled | 1974–2025 |
| Wells | 268 |
| Test results | 2,176 |
| Wells left out | 18 |
| Sources | OREGONDEQ (307), USGS (122) |
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 | 7.1% |
| Wells over the level / wells judged | 19 of 268 |
| Median | < 0.05 mg/L |
| Years sampled | 1974–2025 |
| Wells | 268 |
| Test results | 2,175 |
| Wells left out | 18 |
| Sources | OREGONDEQ (306), USGS (122) |
More than half the wells had results below the lab's detection limit, so the median is reported as below that limit.
Hardness Recent
| Level it's compared with | none; hardness is shown in bands |
|---|---|
| Share of wells very hard | 34% |
| Median | 120 mg/L as CaCO₃ |
| Years sampled | 1974–2025 |
| Wells | 429 |
| Test results | 2,234 |
| Wells left out | 18 |
| Sources | OREGONDEQ (307), USGS (122) |
Sulfate Recent
| Level it's compared with | 250 mg/L |
|---|---|
| Share of wells over the level | 0.7% |
| Wells over the level / wells judged | 3 of 430 |
| Median | 14.9 mg/L |
| Years sampled | 1974–2025 |
| Wells | 430 |
| Test results | 2,598 |
| Wells left out | 18 |
| Sources | OREGONDEQ (308), USGS (122) |