Well water by county: Maine
Across 14 counties in Maine, 155 of 261 sampled wells (59%) were above the arsenic limit and 17 of 726 (2%) above the nitrate limit. Updated 2026-10-18. Source: Water Quality Portal (USGS, EPA, NWQMC), siteType=Well.
Share of sampled wells whose latest result is above the EPA limit (arsenic 10 µg/L, nitrate 10 mg/L as N).
| County | Arsenic > 10 µg/L | Nitrate > 10 mg/L |
|---|---|---|
| Androscoggin County | 46% of 13 | 3% of 34 |
| Aroostook County | – | 7% of 44 |
| Cumberland County | 46% of 48 | 3% of 112 |
| Franklin County | – | 0% of 30 |
| Hancock County | 48% of 33 | 0% of 61 |
| Kennebec County | 93% of 60 | 0% of 65 |
| Knox County | 100% of 13 | 0% of 14 |
| Oxford County | 15% of 13 | 3% of 139 |
| Penobscot County | – | 8% of 40 |
| Piscataquis County | – | 0% of 14 |
| Somerset County | 45% of 11 | 0% of 39 |
| Waldo County | – | 0% of 13 |
| Washington County | 33% of 39 | 0% of 51 |
| York County | 71% of 31 | 4% of 70 |