Private Well Water Testing in Wisconsin
County-by-county USGS area-risk estimates for private wells across Wisconsin — arsenic exceedance probability and private-well population — plus how to test your own well at a Wisconsin-certified laboratory.
Wisconsin private-well risk summary
Counties covered
72
Wisconsin counties with modeled risk data.
People on private wells
area estimate1,519,944
estimated across covered Wisconsin counties.
Average arsenic risk
area estimate4%
average modeled chance a well exceeds 10 µg/L arsenic across covered counties.
Wisconsin counties
- Waukesha County3% arsenic exceedance (area estimate)107,199 people on private wells
- Dane County4% arsenic exceedance (area estimate)54,316 people on private wells
- Marathon County6% arsenic exceedance (area estimate)50,738 people on private wells
- Racine County6% arsenic exceedance (area estimate)37,515 people on private wells
- Washington County3% arsenic exceedance (area estimate)37,204 people on private wells
- Walworth County7% arsenic exceedance (area estimate)35,563 people on private wells
- Outagamie County11% arsenic exceedance (area estimate)34,322 people on private wells
- St. Croix County2% arsenic exceedance (area estimate)34,149 people on private wells
- Rock County3% arsenic exceedance (area estimate)33,577 people on private wells
- Dodge County7% arsenic exceedance (area estimate)31,745 people on private wells
- Fond du Lac County3% arsenic exceedance (area estimate)31,486 people on private wells
- Winnebago County14% arsenic exceedance (area estimate)30,342 people on private wells
- Chippewa County3% arsenic exceedance (area estimate)29,924 people on private wells
- Portage County4% arsenic exceedance (area estimate)29,556 people on private wells
- Kenosha County6% arsenic exceedance (area estimate)29,425 people on private wells
- Sheboygan County6% arsenic exceedance (area estimate)28,424 people on private wells
- Wood County5% arsenic exceedance (area estimate)28,076 people on private wells
- Waupaca County8% arsenic exceedance (area estimate)28,020 people on private wells
- Polk County4% arsenic exceedance (area estimate)27,898 people on private wells
- Brown County8% arsenic exceedance (area estimate)27,672 people on private wells
- Jefferson County8% arsenic exceedance (area estimate)27,032 people on private wells
- Ozaukee County6% arsenic exceedance (area estimate)25,777 people on private wells
- Oneida County2% arsenic exceedance (area estimate)25,401 people on private wells
- Oconto County4% arsenic exceedance (area estimate)24,939 people on private wells
- Sauk County5% arsenic exceedance (area estimate)23,613 people on private wells
- Barron County3% arsenic exceedance (area estimate)23,433 people on private wells
- Shawano County7% arsenic exceedance (area estimate)23,424 people on private wells
- Manitowoc County10% arsenic exceedance (area estimate)23,180 people on private wells
- Columbia County4% arsenic exceedance (area estimate)21,642 people on private wells
- Clark County4% arsenic exceedance (area estimate)21,596 people on private wells
- Marinette County2% arsenic exceedance (area estimate)21,035 people on private wells
- Monroe County3% arsenic exceedance (area estimate)20,724 people on private wells
- Eau Claire County3% arsenic exceedance (area estimate)20,674 people on private wells
- Dunn County3% arsenic exceedance (area estimate)20,645 people on private wells
- Milwaukee County5% arsenic exceedance (area estimate)19,917 people on private wells
- La Crosse County2% arsenic exceedance (area estimate)18,530 people on private wells
- Waushara County3% arsenic exceedance (area estimate)18,456 people on private wells
- Pierce County2% arsenic exceedance (area estimate)18,117 people on private wells
- Grant County4% arsenic exceedance (area estimate)17,726 people on private wells
- Vilas County3% arsenic exceedance (area estimate)17,619 people on private wells
- Door County6% arsenic exceedance (area estimate)16,948 people on private wells
- Adams County5% arsenic exceedance (area estimate)16,402 people on private wells
- Green County3% arsenic exceedance (area estimate)16,001 people on private wells
- Douglas County4% arsenic exceedance (area estimate)15,541 people on private wells
- Vernon County3% arsenic exceedance (area estimate)15,381 people on private wells
- Juneau County5% arsenic exceedance (area estimate)15,136 people on private wells
- Lincoln County3% arsenic exceedance (area estimate)15,095 people on private wells
- Taylor County3% arsenic exceedance (area estimate)14,292 people on private wells
- Trempealeau County3% arsenic exceedance (area estimate)13,455 people on private wells
- Kewaunee County9% arsenic exceedance (area estimate)12,880 people on private wells
- Burnett County3% arsenic exceedance (area estimate)12,416 people on private wells
- Marquette County9% arsenic exceedance (area estimate)12,412 people on private wells
- Sawyer County2% arsenic exceedance (area estimate)11,954 people on private wells
- Calumet County9% arsenic exceedance (area estimate)11,601 people on private wells
- Washburn County2% arsenic exceedance (area estimate)11,236 people on private wells
- Jackson County2% arsenic exceedance (area estimate)11,208 people on private wells
- Langlade County4% arsenic exceedance (area estimate)10,959 people on private wells
- Bayfield County3% arsenic exceedance (area estimate)10,083 people on private wells
- Iowa County3% arsenic exceedance (area estimate)9,825 people on private wells
- Green Lake County4% arsenic exceedance (area estimate)9,700 people on private wells
- Price County3% arsenic exceedance (area estimate)9,526 people on private wells
- Richland County3% arsenic exceedance (area estimate)9,223 people on private wells
- Rusk County2% arsenic exceedance (area estimate)9,018 people on private wells
- Buffalo County3% arsenic exceedance (area estimate)8,686 people on private wells
- Lafayette County4% arsenic exceedance (area estimate)8,135 people on private wells
- Crawford County3% arsenic exceedance (area estimate)7,415 people on private wells
- Forest County3% arsenic exceedance (area estimate)6,400 people on private wells
- Ashland County5% arsenic exceedance (area estimate)5,387 people on private wells
- Pepin County2% arsenic exceedance (area estimate)4,547 people on private wells
- Florence County3% arsenic exceedance (area estimate)3,313 people on private wells
- Iron County3% arsenic exceedance (area estimate)2,887 people on private wells
- Menominee County4% arsenic exceedance (area estimate)2,251 people on private wells
Find a Wisconsin-certified testing lab
Get your well tested at a Wisconsin-certified laboratory. We list certification programs by state.
These figures are USGS area estimates: statistical groundwater models describing how likely elevated contaminant levels are across a county. They are not designed to predict the concentration in any single well. Only testing your own well reveals its water quality.
By TapWaterData Editorial
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