Private Well Water Testing in Missouri
County-by-county USGS area-risk estimates for private wells across Missouri — arsenic exceedance probability and private-well population — plus how to test your own well at a Missouri-certified laboratory.
Missouri private-well risk summary
Counties covered
115
Missouri counties with modeled risk data.
People on private wells
area estimate868,973
estimated across covered Missouri counties.
Average arsenic risk
area estimate3%
average modeled chance a well exceeds 10 µg/L arsenic across covered counties.
Missouri counties
- Jefferson County2% arsenic exceedance (area estimate)38,411 people on private wells
- Franklin County2% arsenic exceedance (area estimate)37,344 people on private wells
- Greene County2% arsenic exceedance (area estimate)31,950 people on private wells
- Newton County1% arsenic exceedance (area estimate)28,688 people on private wells
- Camden County1% arsenic exceedance (area estimate)21,576 people on private wells
- Webster County1% arsenic exceedance (area estimate)21,134 people on private wells
- Howell County1% arsenic exceedance (area estimate)20,328 people on private wells
- St. Francois County2% arsenic exceedance (area estimate)19,437 people on private wells
- Lincoln County3% arsenic exceedance (area estimate)19,347 people on private wells
- Washington County1% arsenic exceedance (area estimate)18,457 people on private wells
- Christian County1% arsenic exceedance (area estimate)18,174 people on private wells
- Phelps County1% arsenic exceedance (area estimate)17,994 people on private wells
- Jasper County1% arsenic exceedance (area estimate)17,195 people on private wells
- Polk County1% arsenic exceedance (area estimate)16,619 people on private wells
- Barry County1% arsenic exceedance (area estimate)16,609 people on private wells
- Lawrence County1% arsenic exceedance (area estimate)16,552 people on private wells
- Stone County1% arsenic exceedance (area estimate)16,010 people on private wells
- St. Charles County7% arsenic exceedance (area estimate)15,645 people on private wells
- Miller County1% arsenic exceedance (area estimate)14,801 people on private wells
- Morgan County2% arsenic exceedance (area estimate)13,518 people on private wells
- Taney County1% arsenic exceedance (area estimate)13,384 people on private wells
- Crawford County1% arsenic exceedance (area estimate)12,806 people on private wells
- Dallas County1% arsenic exceedance (area estimate)12,485 people on private wells
- Cape Girardeau County2% arsenic exceedance (area estimate)12,261 people on private wells
- Butler County3% arsenic exceedance (area estimate)11,979 people on private wells
- McDonald County1% arsenic exceedance (area estimate)11,908 people on private wells
- Texas County1% arsenic exceedance (area estimate)11,699 people on private wells
- Cole County2% arsenic exceedance (area estimate)11,400 people on private wells
- Pettis County3% arsenic exceedance (area estimate)11,262 people on private wells
- Scott County14% arsenic exceedance (area estimate)10,752 people on private wells
- Wright County1% arsenic exceedance (area estimate)10,739 people on private wells
- Benton County1% arsenic exceedance (area estimate)10,693 people on private wells
- Warren County2% arsenic exceedance (area estimate)10,429 people on private wells
- Douglas County1% arsenic exceedance (area estimate)9,724 people on private wells
- St. Louis County3% arsenic exceedance (area estimate)9,610 people on private wells
- Laclede County1% arsenic exceedance (area estimate)9,151 people on private wells
- Bollinger County2% arsenic exceedance (area estimate)9,081 people on private wells
- Stoddard County6% arsenic exceedance (area estimate)8,757 people on private wells
- Dent County1% arsenic exceedance (area estimate)8,734 people on private wells
- Pulaski County1% arsenic exceedance (area estimate)8,497 people on private wells
- Ozark County1% arsenic exceedance (area estimate)7,905 people on private wells
- Wayne County1% arsenic exceedance (area estimate)7,608 people on private wells
- Callaway County2% arsenic exceedance (area estimate)7,018 people on private wells
- Johnson County2% arsenic exceedance (area estimate)7,014 people on private wells
- Ste. Genevieve County4% arsenic exceedance (area estimate)6,881 people on private wells
- Osage County2% arsenic exceedance (area estimate)6,829 people on private wells
- Gasconade County1% arsenic exceedance (area estimate)6,814 people on private wells
- Ripley County1% arsenic exceedance (area estimate)6,803 people on private wells
- Maries County1% arsenic exceedance (area estimate)6,590 people on private wells
- Oregon County1% arsenic exceedance (area estimate)6,321 people on private wells
- Hickory County1% arsenic exceedance (area estimate)6,263 people on private wells
- St. Clair County3% arsenic exceedance (area estimate)5,811 people on private wells
- Perry County2% arsenic exceedance (area estimate)5,797 people on private wells
- Henry County2% arsenic exceedance (area estimate)5,752 people on private wells
- Madison County1% arsenic exceedance (area estimate)5,720 people on private wells
- Moniteau County2% arsenic exceedance (area estimate)5,502 people on private wells
- Iron County1% arsenic exceedance (area estimate)5,495 people on private wells
- Cedar County3% arsenic exceedance (area estimate)5,442 people on private wells
- Mississippi County18% arsenic exceedance (area estimate)4,970 people on private wells
- Montgomery County4% arsenic exceedance (area estimate)4,743 people on private wells
- Cooper County3% arsenic exceedance (area estimate)4,641 people on private wells
- Boone County2% arsenic exceedance (area estimate)4,640 people on private wells
- Reynolds County1% arsenic exceedance (area estimate)4,553 people on private wells
- Shannon County1% arsenic exceedance (area estimate)4,365 people on private wells
- Audrain County3% arsenic exceedance (area estimate)4,198 people on private wells
- Pike County6% arsenic exceedance (area estimate)4,087 people on private wells
- New Madrid County7% arsenic exceedance (area estimate)4,025 people on private wells
- Nodaway County3% arsenic exceedance (area estimate)3,805 people on private wells
- Carter County1% arsenic exceedance (area estimate)3,388 people on private wells
- Dade County2% arsenic exceedance (area estimate)3,334 people on private wells
- Clinton County2% arsenic exceedance (area estimate)3,233 people on private wells
- Dunklin County8% arsenic exceedance (area estimate)2,922 people on private wells
- Saline County5% arsenic exceedance (area estimate)2,686 people on private wells
- Marion County3% arsenic exceedance (area estimate)2,609 people on private wells
- DeKalb County3% arsenic exceedance (area estimate)2,532 people on private wells
- Ralls County3% arsenic exceedance (area estimate)2,518 people on private wells
- Jackson County2% arsenic exceedance (area estimate)2,462 people on private wells
- Ray County3% arsenic exceedance (area estimate)2,344 people on private wells
- Clay County3% arsenic exceedance (area estimate)2,317 people on private wells
- Cass County1% arsenic exceedance (area estimate)2,313 people on private wells
- Vernon County3% arsenic exceedance (area estimate)2,244 people on private wells
- Caldwell County2% arsenic exceedance (area estimate)2,211 people on private wells
- Lewis County2% arsenic exceedance (area estimate)2,078 people on private wells
- Andrew County5% arsenic exceedance (area estimate)2,021 people on private wells
- Monroe County3% arsenic exceedance (area estimate)1,940 people on private wells
- Platte County3% arsenic exceedance (area estimate)1,832 people on private wells
- Daviess County3% arsenic exceedance (area estimate)1,755 people on private wells
- Bates County1% arsenic exceedance (area estimate)1,743 people on private wells
- Clark County2% arsenic exceedance (area estimate)1,663 people on private wells
- Holt County9% arsenic exceedance (area estimate)1,546 people on private wells
- Gentry County3% arsenic exceedance (area estimate)1,524 people on private wells
- Buchanan County3% arsenic exceedance (area estimate)1,516 people on private wells
- Harrison County2% arsenic exceedance (area estimate)1,510 people on private wells
- Carroll County3% arsenic exceedance (area estimate)1,427 people on private wells
- Howard County2% arsenic exceedance (area estimate)1,228 people on private wells
- Atchison County8% arsenic exceedance (area estimate)1,127 people on private wells
- Schuyler County2% arsenic exceedance (area estimate)1,095 people on private wells
- Chariton County4% arsenic exceedance (area estimate)1,057 people on private wells
- Lafayette County2% arsenic exceedance (area estimate)1,055 people on private wells
- Putnam County2% arsenic exceedance (area estimate)994 people on private wells
- Livingston County3% arsenic exceedance (area estimate)953 people on private wells
- Randolph County2% arsenic exceedance (area estimate)940 people on private wells
- Knox County2% arsenic exceedance (area estimate)909 people on private wells
- Mercer County2% arsenic exceedance (area estimate)854 people on private wells
- Macon County2% arsenic exceedance (area estimate)842 people on private wells
- Scotland County2% arsenic exceedance (area estimate)832 people on private wells
- Shelby County3% arsenic exceedance (area estimate)794 people on private wells
- Adair County2% arsenic exceedance (area estimate)760 people on private wells
- Sullivan County2% arsenic exceedance (area estimate)609 people on private wells
- Worth County3% arsenic exceedance (area estimate)586 people on private wells
- Linn County2% arsenic exceedance (area estimate)485 people on private wells
- Pemiscot County7% arsenic exceedance (area estimate)460 people on private wells
- Grundy County4% arsenic exceedance (area estimate)395 people on private wells
- Barton County3% arsenic exceedance (area estimate)375 people on private wells
- St. Louis city3% arsenic exceedance (area estimate)223 people on private wells
Find a Missouri-certified testing lab
Get your well tested at a Missouri-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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