Isanti County, Minnesota

Arsenic: 10 of 111 sampled wells (9%) above the EPA limit of 10 µg/L. Nitrate: 15 of 50 sampled wells (30%) above the EPA limit of 10 mg/L as N. Samples 1968-10-24 to 2018-08-16; updated 2026-10-18. 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

10 of 111 sampled wells (9%) had a latest result above the EPA limit of 10 µg/L.

Median (latest per well): 1.83 µg/L
90th percentile: 8.5 µg/L
Highest: 18.5 µg/L
Non-detects: 20 wells' latest result was "not detected" with no detection limit reported; they are counted as below the limit.
Samples: 133, 1996-05-22 to 2018-08-16
Source: Water Quality Portal (USGS, EPA, NWQMC), siteType=Well, downloaded 2026-10-18

Nitrate

15 of 50 sampled wells (30%) had a latest result above the EPA limit of 10 mg/L as N.

Median (latest per well): 1.15 mg/L as N
90th percentile: 35.014 mg/L as N
Highest: Withheld for review: 1 well's latest result was above 100 mg/L as N, far outside the usual range. It is still counted as above the limit.
Non-detects: 13 wells' latest result was "not detected" with no detection limit reported; they are counted as below the limit.
Samples: 139, 1968-10-24 to 2010-10-14
Source: Water Quality Portal (USGS, EPA, NWQMC), siteType=Well, downloaded 2026-10-18

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

Test your own well. County numbers cannot tell you what is in your water. See which tests fit your well.
Use a lab certified by Minnesota. Certified labs in Minnesota.
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.
If a result is high: arsenic guide · nitrate guide · bacteria guide · salesperson checklist.
Test again every year for bacteria and nitrate. Get a yearly reminder.