Minnesota Private Well Water Quality 2026

The 3M PFAS Contamination Plume — East Metro Minnesota

The most acute PFAS threat to Minnesota private well owners is the contamination plume spreading through the East Metro — the direct result of 3M disposing of PFAS chemical waste at four sites in Washington County for decades from the 1950s onwards. The plume originates from 3M’s Cottage Grove manufacturing facility and disposal sites in Oakdale, Woodbury, and Cottage Grove, and has contaminated the Prairie du Chien and Jordan aquifers across an area covering more than 150 square miles.

The scale of the impact on private wells is well-documented. Since testing began in 2003, more than 2,000 private wells in the East Metro contamination zone have been flagged for elevated PFAS. In 2024 alone, 420 new advisories were issued — a 30-fold increase on the previous year — driven by expanded sampling, updated health guidance metrics, and improved laboratory detection technology capable of identifying smaller traces of the chemicals.

The plume is actively moving. The MPCA has described concentrations as “slowly increasing” and the contamination is spreading toward the Mississippi and St. Croix rivers, threatening communities that have not yet been affected. West Lakeland Township — where residents rely entirely on private wells — sits in the path of the advancing plume. In response, Minnesota environmental engineers have proposed a system of 27 wells to hydraulically contain the plume, in what would be among the most complex PFAS remediation projects in the country.

Homes within the affected East Metro zone that have received a drinking water advisory are either connected to city water or provided with whole-house point-of-entry treatment systems (POETS) installed and maintained by the state at no cost — funded through the $850 million settlement reached with 3M in 2018. Private wells outside the advisory zone but near the contamination boundary are eligible for free sampling through the MPCA.

Arsenic in Minnesota Well Water

Arsenic is Minnesota’s most widespread private well contaminant. The MDH has found that arsenic is detectable in approximately 40% of new private wells drilled since 2008 — but “detectable” does not mean “safe.” Around 10% of Minnesota’s private wells have arsenic at levels above the federal MCL of 10 µg/L, the point at which the MDH strongly recommends action. The underlying cause is geological: arsenic occurs naturally in Minnesota’s bedrock and glacial till, particularly in areas covered by the Des Moines Lobe — a clay-rich glacial material stretching through much of west-central and central Minnesota. Levels vary significantly between wells, and even neighbouring wells can have very different results.

Arsenic is colourless and tasteless — it cannot be detected by sight, smell, or taste. Long-term exposure is linked to cancers of the bladder, lungs, and liver, cardiovascular and respiratory disease, and reduced cognitive development in children. Some wells in Minnesota have tested as high as 350 µg/L — 35 times the federal limit. In a 2016 MDH survey of households with arsenic-positive wells, 34% reported taking no action to reduce their exposure. Testing is the only way to know your level.

Because arsenic levels can change over time, the MDH recommends all private well owners test for arsenic at least once, and again if household circumstances change or a new well is drilled. Since 2008, Minnesota law requires all newly drilled wells to be tested for arsenic, with results shared with the well owner and the MDH.

Nitrate Contamination in Southeast Minnesota

Southeast Minnesota has a severe and formally acknowledged nitrate problem in private wells. The eight-county karst region — Dodge, Fillmore, Goodhue, Houston, Mower, Olmsted, Wabasha, and Winona counties — sits on porous fractured limestone bedrock with thin topsoil, allowing agricultural fertiliser runoff and animal waste to move rapidly into groundwater with little or no filtration. Fillmore County alone has more than 10,000 sinkholes. State data from 2018–2022 shows that 16% of wells tested across this region exceeded the federal nitrate MCL of 10 mg/L.

The situation escalated to federal intervention. In April 2023, environmental groups filed an emergency petition under the Safe Drinking Water Act. In November 2023, the EPA responded with a formal directive to Minnesota state agencies — estimating that approximately 9,218 residents in the karst region had been consuming water at or above the MCL. This triggered a coordinated three-phase response from the Minnesota Departments of Health, Agriculture, and the MPCA, including free bottled water provision for vulnerable households and a 10-year mitigation programme targeting 3,600 wells per year across the 36,000 wells in the eight-county area.

Nitrate above 10 mg/L poses the greatest risk to bottle-fed infants under six months, where exposure can cause methemoglobinemia (blue baby syndrome). The MDH also notes links between long-term nitrate exposure and certain cancers and reproductive outcomes. Central Minnesota — particularly sandy-soil counties — faces similar risks through a different geological mechanism. Outside these vulnerable regions, nitrate risk from local septic systems and shallow wells remains a concern statewide.

Regulatory Situation for Minnesota Well Owners

Private wells in Minnesota are not covered by the Safe Drinking Water Act. While public water systems are required to meet state and federal standards, private well owners are entirely responsible for testing, maintaining, and treating their own water supply. The Minnesota Well Code sets construction and siting standards for new wells, but once a well is in service, there is no requirement for routine testing and no regulatory notification system.

Minnesota is one of 14 states with its own enforceable PFAS maximum contaminant levels — and MDH’s Health Risk Limits (HRLs) have historically been more protective than the federal EPA standards. However, these state MCLs apply only to public water systems. For private wells, MDH issues health-based advisories when testing indicates elevated risk — but acting on those findings, and arranging treatment, remains the responsibility of individual well owners.

Check our Minnesota municipal water quality page for city-by-city tap water data, or use our live boil water notice tracker for active advisories across the state.

Known High-Risk Areas in Minnesota

If you live near any of the following locations, well water testing is urgent — not precautionary.

How to Test Your Minnesota Well Water — and What to Do Next

Given Minnesota’s contamination profile — arsenic detectable in 40% of new wells (10% above the safe limit), over 2,000 PFAS advisories in the East Metro, and a documented nitrate crisis in eight southeast counties — the MDH’s recommendation is clear: every private well owner should test their water regularly. Yet a recent MDH study found that fewer than 20% of well users test as often as the MDH recommends. Arsenic, PFAS, and nitrate are all colourless, odourless, and tasteless. Contamination at harmful levels produces no detectable signs.

For East Metro residents, the first step is to check the MPCA’s interactive well sampling map to determine whether your property falls within the sampling area. If you are within the zone and your well has not been tested, you may be eligible for free PFAS sampling under the 3M settlement. Contact the MPCA East Metro unit at PFAS.Well.Sampling.MPCA@state.mn.us or visit pca.state.mn.us for more information.

For all other Minnesota well owners, the MDH Public Health Laboratory accepts samples from private well owners and tests for arsenic, bacteria, nitrate, lead, and manganese. A map of accredited labs accepting private samples is available at health.state.mn.us/wells. Many county health departments also offer subsidised testing services.

For filter options, our well water filter guide covers reverse osmosis systems for arsenic and PFAS, UV disinfection for bacteria, and whole-house well systems for comprehensive treatment. You can also browse our full water filter solutions page or check your ZIP code for local water quality context.

For other Midwest well water risks, see our pages on Wisconsin wells, Iowa wells, and Michigan wells. Return to the private well water directory to find your state.