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privatewelldata / Counties

Well water by county: New Hampshire

Across 10 counties in New Hampshire, 125 of 863 sampled wells (14%) were above the arsenic limit and 7 of 1685 (0%) 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).

Share of sampled wells above the limit, by county (% of wells). Source: USGS/EPA Water Quality Portal · privatewelldata.com
CountyArsenic > 10 µg/LNitrate > 10 mg/L
Belknap County0% of 310% of 166
Carroll County1% of 720% of 221
Cheshire County6% of 182% of 60
Coos County0% of 400% of 161
Grafton County2% of 620% of 234
Hillsborough County20% of 2110% of 187
Merrimack County28% of 1630% of 436
Rockingham County17% of 1672% of 119
Strafford County6% of 682% of 60
Sullivan County3% of 310% of 41