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privatewelldata / Counties / Wisconsin

Dane County, Wisconsin

Arsenic: 4 of 25 sampled wells (16%) above the EPA limit of 10 µg/L. Nitrate: 10 of 131 sampled wells (8%) above the EPA limit of 10 mg/L as N. Samples 1935-01-01 to 2022-06-01; updated 2026-10-17. Source: Water Quality Portal (USGS, EPA, NWQMC), siteType=Well.

What wells in this county have measured for arsenic and nitrate. A local picture only: test your own well to know your water.

Arsenic

4 of 25 sampled wells (16%) had a latest result above the EPA limit of 10 µg/L.

Median (latest per well)
0 µg/L
90th percentile
10.3 µg/L
Highest
11.7 µg/L
Non-detects
15 wells' latest result was "not detected" with no detection limit reported; they are counted as below the limit.
Samples
25, 1976-05-26 to 2022-06-01
Source
Water Quality Portal (USGS, EPA, NWQMC), siteType=Well, downloaded 2026-10-17

Nitrate

10 of 131 sampled wells (8%) had a latest result above the EPA limit of 10 mg/L as N.

Median (latest per well)
0.64 mg/L as N
90th percentile
6.8 mg/L as N
Highest
37 mg/L as N
Non-detects
13 wells' latest result was "not detected" with no detection limit reported; they are counted as below the limit.
Samples
207, 1935-01-01 to 2022-06-01
Source
Water Quality Portal (USGS, EPA, NWQMC), siteType=Well, downloaded 2026-10-17

Includes monitoring, research and private wells reported to the Water Quality Portal. Non-detects count only when the lab's detection limit is at or below the EPA limit. Method: data rules.

What to do next

  1. Test your own well. County numbers cannot tell you what is in your water. See which tests fit your well.
  2. Use a lab certified by Wisconsin. Certified labs in Wisconsin.
  3. Compare your results with the EPA limits (arsenic 10 µg/L, nitrate 10 mg/L as N). If a result is above a limit, contact your county or state health department.
  4. If a result is high: arsenic guide · nitrate guide · bacteria guide · salesperson checklist.
  5. Test again every year for bacteria and nitrate. Get a yearly reminder.