privatewelldata / Counties
Well water by county
Arsenic and nitrate results for 560 counties in 13 states. Source: Water Quality Portal (USGS, EPA); each county page shows its download date.
Arsenic and nitrate measured in wells, summarised per county from the Water Quality Portal (USGS, EPA and state agencies). These are monitoring and research wells as well as private wells, so treat them as a local picture, not a result for your well. Only a test of your own water tells you what is in it.
% of sampled wells above the limit
0–1%1–5%5–10%10–25%25–50%50%+
Not measuredNo published data- California (53)
- Massachusetts (12)
- Maine (14)
- Michigan (49)
- Minnesota (86)
- North Carolina (57)
- New Hampshire (10)
- New Jersey (20)
- New York (58)
- Ohio (34)
- Pennsylvania (62)
- Virginia (36)
- Wisconsin (69)