Well water by county: Minnesota
Across 86 counties in Minnesota, 1076 of 5838 sampled wells (18%) were above the arsenic limit and 434 of 7167 (6%) 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 |
|---|---|---|
| Aitkin County | 12% of 104 | 6% of 35 |
| Anoka County | 16% of 145 | 1% of 305 |
| Becker County | 37% of 114 | 7% of 86 |
| Beltrami County | 15% of 68 | 0% of 81 |
| Benton County | 2% of 90 | 11% of 114 |
| Big Stone County | – | 3% of 31 |
| Blue Earth County | 26% of 121 | 8% of 222 |
| Brown County | 32% of 100 | 0% of 12 |
| Carlton County | 9% of 130 | 0% of 157 |
| Cass County | 9% of 129 | 0% of 61 |
| Chippewa County | – | 5% of 22 |
| Chisago County | 6% of 96 | 1% of 105 |
| Clay County | 51% of 100 | 2% of 125 |
| Clearwater County | 33% of 15 | 0% of 27 |
| Cook County | 0% of 10 | 0% of 23 |
| Cottonwood County | 36% of 11 | 9% of 46 |
| Crow Wing County | 6% of 136 | 6% of 179 |
| Dakota County | 5% of 191 | 10% of 207 |
| Dodge County | 2% of 102 | 11% of 18 |
| Douglas County | 38% of 45 | 10% of 80 |
| Faribault County | 19% of 16 | 4% of 26 |
| Fillmore County | 0% of 15 | 9% of 107 |
| Freeborn County | 60% of 10 | 0% of 24 |
| Goodhue County | 3% of 31 | 5% of 174 |
| Grant County | 93% of 14 | 3% of 30 |
| Hennepin County | 14% of 213 | 2% of 303 |
| Houston County | 0% of 92 | 0% of 58 |
| Hubbard County | 6% of 109 | 13% of 115 |
| Isanti County | 9% of 111 | 30% of 50 |
| Itasca County | 11% of 37 | 1% of 98 |
| Jackson County | 67% of 15 | 2% of 41 |
| Kanabec County | 5% of 97 | 4% of 23 |
| Kandiyohi County | 38% of 101 | 15% of 41 |
| Kittson County | – | 13% of 47 |
| Koochiching County | – | 0% of 31 |
| Lac qui Parle County | 16% of 97 | 3% of 29 |
| Lake County | 2% of 114 | 0% of 47 |
| Lake of the Woods County | – | 6% of 18 |
| Le Sueur County | 38% of 13 | 0% of 19 |
| Lincoln County | 0% of 12 | 13% of 32 |
| Lyon County | 50% of 10 | 3% of 58 |
| Mahnomen County | – | 0% of 19 |
| Marshall County | 40% of 10 | 9% of 58 |
| Martin County | 12% of 17 | 0% of 16 |
| McLeod County | 56% of 79 | 0% of 86 |
| Meeker County | 46% of 94 | 6% of 17 |
| Mille Lacs County | – | 2% of 47 |
| Morrison County | 5% of 129 | 12% of 85 |
| Mower County | 9% of 23 | 1% of 113 |
| Murray County | 36% of 11 | 12% of 34 |
| Nicollet County | 25% of 106 | 3% of 115 |
| Nobles County | 23% of 78 | 10% of 62 |
| Norman County | – | 12% of 17 |
| Olmsted County | 1% of 141 | 4% of 101 |
| Otter Tail County | 31% of 229 | 14% of 263 |
| Pennington County | – | 7% of 15 |
| Pine County | 9% of 74 | 1% of 137 |
| Pipestone County | – | 22% of 18 |
| Polk County | 50% of 18 | 11% of 82 |
| Pope County | 48% of 84 | 8% of 167 |
| Ramsey County | 9% of 33 | 0% of 87 |
| Red Lake County | – | 0% of 11 |
| Redwood County | 31% of 127 | 7% of 101 |
| Renville County | 29% of 102 | 4% of 135 |
| Rice County | 45% of 76 | 0% of 96 |
| Rock County | 8% of 53 | 17% of 41 |
| Roseau County | 40% of 15 | 7% of 55 |
| Scott County | 25% of 28 | 2% of 59 |
| Sherburne County | 6% of 145 | 15% of 228 |
| Sibley County | 42% of 103 | 1% of 106 |
| St. Louis County | 8% of 287 | 1% of 165 |
| Stearns County | 32% of 162 | 20% of 327 |
| Steele County | 9% of 101 | 0% of 22 |
| Stevens County | 76% of 17 | 2% of 45 |
| Swift County | – | 2% of 58 |
| Todd County | 22% of 111 | 6% of 150 |
| Traverse County | 31% of 13 | 4% of 28 |
| Wabasha County | 10% of 21 | 3% of 109 |
| Wadena County | 5% of 106 | 14% of 92 |
| Waseca County | 17% of 12 | 0% of 12 |
| Washington County | 2% of 164 | 1% of 190 |
| Watonwan County | 25% of 20 | 3% of 32 |
| Wilkin County | 50% of 10 | 0% of 38 |
| Winona County | 1% of 97 | 4% of 23 |
| Wright County | 35% of 110 | 0% of 128 |
| Yellow Medicine County | 17% of 18 | 6% of 70 |