The maps in this section represent private drinking water samples submitted to the State Public Health Laboratory since 2010. Maps show the total number of wells per county as well as 10 contaminant maps. These contaminant maps show the total number of samples collected, number and percent of samples with detections above Environmental Protection Agency’s (EPA) Maximum Contaminant Level (MCL), the number of samples less than or equal to the MCL , and the number of samples with results below a level of detection.

Public drinking water systems are tested regularly for a variety of contaminants: however, testing of private drinking water wells is the responsibility of the well owner. These maps rely solely on private drinking water samples submitted voluntarily from homeowners across the state.

These maps are not intended to replace the need to test your well water. Well water quality varies with local site conditions and well structure. Therefore, the Missouri Department of Health and Senior Services (MDHSS) recommends testing your well annually. For information regarding how to have your well water tested, see the MDHSS Private Drinking Water page (bacteria and chemical testing):