Wisconsin Groundwater Council urges action on PFAS, nitrates, and pesticides in 2025 report

Sept. 2, 2025

MADISON, Wis. (AP) — The Groundwater Coordinating Council (GCC) is calling for urgent action to address widespread contamination and supply challenges affecting Wisconsin’s groundwater, according to its 2025 annual report submitted to the state Legislature.

The report outlines four primary threats to the state’s groundwater: the persistent presence of PFAS chemicals, nitrate contamination, pesticide infiltration, and uneven water distribution across regions. These issues, the council warns, pose risks to public health, agriculture, and long-term water sustainability.

“Our groundwater is a critical priority,” said Joe Van Rossum, GCC chair and deputy administrator for environmental management at the Wisconsin Department of Natural Resources. “This resource is essential to the well-being of our communities and environment; it must not be taken for granted.”

Among the council’s top recommendations:

• PFAS Contamination: Update standards under NR 809 and NR 140, and expand efforts to identify, monitor, and research PFAS in groundwater.
• Nitrate Pollution: Increase monitoring, broaden eligibility for the NR 123 Well Compensation Program, and promote sustainable agricultural practices.
• Pesticide Presence: Found in over 40% of private potable wells. Revise standards for several pesticides and support strategies to reduce leaching into groundwater.
• Water Supply Inequities: Collaborate with public and private partners to identify sustainable sources, implement conservation strategies, and develop a regional framework for managing water withdrawals.

The GCC, composed of representatives from state agencies, universities, and stakeholder organizations, coordinates non-regulatory groundwater programs and advises on budgeting, monitoring, public education, and research funding.

The full report is available on the Groundwater Coordinating Council’s website.

Vernon County has a program for private well testing, covering bacteria, nitrates, and other contaminants. Residents are advised to test their wells annually or when changes in water quality occur. For more information on well water testing you can go to the Vernon County Health Department website.

Detailed findings and recommendations of 2025 report

Address PFAS contamination in groundwater

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are emerging contaminants in Wisconsin groundwater. PFAS have been detected in both municipal and private drinking water sources (see PFAS section of the report). Exposure to PFAS has been shown to have detrimental health effects including the potential to cause cancer.

Public water systems in Wisconsin are required to comply with state drinking water maximum contaminant level (MCL) standards under ch. NR 809, Wis. Adm. Code. In 2022, a Wisconsin NR 809 MCL standard was established for a combined limit of 70 ng/L PFOA + PFOS in public drinking water. However, the U.S. Environmental Protection Agency (EPA) has recently finalized much more stringent MCLs—setting individual limits at 4 parts per trillion (ppt) for PFOA and PFOS and establishing additional MCLs for other PFAS compounds, including PFHxS, PFNA, PFBS and GenX. Given these developments, the GCC recommends:

• Establish updated and new state drinking water MCL standards in NR 809 for specific PFAS substances.

While NR 809 standards protect residents on public water systems, those relying on private potable wells remain unprotected unless PFAS are regulated in groundwater. Ensuring safe groundwater quality requires enforceable state groundwater standards under ch. NR 140 Wis. Adm Code. Currently, Wisconsin has no established NR 140 groundwater standards for any PFAS. 

In 2019, DNR initiated a NR 140 rulemaking process to establish a combined groundwater standard of 20 ppt/nanograms per liter (ng/L) for PFOA and PFOS. However, the Natural Resources Board (NRB) did not approve proposed NR 140 standards in 2022. In 2021, the DNR began a new NR 140 rulemaking process for 16 additional PFAS, but the scope statement for that rulemaking expired in September 2023 and the effort stopped. In August 2022, a third NR 140 rulemaking effort was initiated to establish groundwater standards for four PFAS: PFOA, PFOS, PFBS and HFPO-DA (GenX), based on recommendations from DHS. This rulemaking was withdrawn in light of new scientific evidence and updated DHS recommendations. A new NR 140 rulemaking effort is currently under way to establish state groundwater standards for six PFAS compounds: PFOA, PFOS, PFHxS, PFBS, PFNA and HFPO-DA/GenX, based on the new DHS recommendations. The GCC recommends:

• Establish new state groundwater quality standards in NR 140 for several PFAS substances.

While PFAS compounds are known to be present in groundwater resources, identifying their sources is crucial for optimizing sampling strategies and site cleanup efforts. Moreover, PFAS contamination is not limited to groundwater; it also occurs in other media such as biosolids and surface water. Since these media can act as contaminant sources, potentially directly interacting with groundwater, understanding the levels of PFAS in them is essential for protecting our drinking water supply resources. Ongoing monitoring is critical to assess the extent and distribution of PFAS contamination across the state. In parallel, continued research is needed to advance our understanding of PFAS fate, transport and behavior in the environment. Therefore, GCC recommends:

• Continue to identify PFAS sources and their potential impacts to groundwater and other environmental media; and
• support continued monitoring and research.

Address nitrate contamination in groundwater

Nitrate that approaches and exceeds unsafe levels in drinking water is one of the top drinking water contaminant concerns in Wisconsin and poses known health risks. Areas of the state with a higher intensity of agriculture activity generally have higher nitrate levels in wells. To protect drinking water sources and safeguard public health, agencies need to implement improved strategies to reduce nitrogen losses and contamination of groundwater.

Over the past two decades, approximately 7% of private wells in Wisconsin have exceeded the nitrate health standard of 10 milligrams per liter (mg/L), with exceedance rates surpassing 20% in some counties. Despite the widespread nature of this issue, only an estimated one-third of private well owners have ever tested their water. Limited testing and high variability at the local level make it difficult to assess long-term nitrate trends in groundwater. County well monitoring programs have helped local communities identify groundwater quality issues and target conservation practices more precisely. These programs play a vital role in strengthening data collection and increasing awareness among residents. To improve public awareness, strengthen data and better track groundwater quality trends, the GCC recommends:

• Expand monitoring efforts to evaluate levels of nitrate and other contaminants of concern in groundwater.

Contaminated wells require costly interventions. Since October 2022, DNR allocated more than $10M to private well owners or non-community public water systems affected by groundwater contamination through the American Rescue Plan Act (ARPA) Well Compensation and Well Abandonment Grant Program for well replacement, reconstruction, treatment and/or abandonment of existing wells. This federally funded program is expected to end in FY26. Once these funds are exhausted, only Wisconsin’s statutory NR 123 well compensation program will remain. That program currently limits eligibility to wells with nitrate levels above 40 mg/L, and excludes small public water systems altogether. As a result, many impacted households, and customers of small systems, will be left without access to financial assistance, increasing their exposure to drinking water contaminants and the health risks associated with that exposure. Therefore, the GCC recommends the following actions:

• Expand eligibility in the state’s NR 123 well compensation program to include nitrate contamination exceeding 10 mg/L.
• Expand eligibility of state’s NR 123 well compensation program to non-community public water systems.

Most of the nitrate contamination in Wisconsin’s groundwater is associated with agricultural activities. During common agricultural practices, a portion of applied nitrogen is lost to the environment—including leaching into groundwater. These losses are influenced by factors such as crop type, soil characteristics, weather conditions and nutrient management strategies. While nutrient management planning is widely promoted in the state, existing tools and standards often fall short in accurately capturing nitrate loss risks at the local scale. At the same time, farmers and land managers need better access to data, decision-support tools and targeted outreach to adopt practices that reduce nitrogen losses while maintaining agricultural productivity. To address these gaps and reduce nitrate contamination from agricultural sources, the GCC recommends implementing agricultural practices that protect groundwater from nitrate by:

Establishing an interagency team to coordinate and better utilize federal and state funding sources for conservation practice implementation, align agency nutrient reduction strategies and better support nonpoint source pollution efforts to protect groundwater.

Continuing support for initiatives such as the Nitrogen Optimization Pilot Program (NOPP) and Producer-Led Watershed Protection Grants with emphasis on data gathering and monitoring to improve understanding of the nitrogen cycle and to better align nitrogen loss minimization efforts with agricultural producers’ technical and operational needs.

Assessing and quantifying the nutrient losses associated with crop-specific nitrogen application rates and new nitrogen loss-mitigating nutrient management plan options, to build the technical capacity to minimize losses to groundwater.

Incorporating nitrogen budgeting and nitrate-leaching potential into nutrient management practice standards and existing nutrient management tools (such as A2809 Nutrient Application Guidelines).

Revamping, funding and enforcing nutrient management planning.

Expanding regulation of nitrogen losses beyond concentrated animal feeding operations (CAFOs) to include all farms, regardless of type of operation or size.

Supporting collaborative development of Groundwater & Nitrogen Fertilizer Decision Support Tools that integrate agency expertise and farmer input to guide nitrogen use and protect water quality.

Enhancing groundwater data assessment and visualization tools to identify areas with elevated nitrate contamination, guide conservation efforts and improve outreach effectiveness.

Strengthening and supporting source water protection efforts to proactively prevent drinking water contamination and expand support in areas impacted by groundwater contamination.

Integrating drinking water source water protection with climate mitigation efforts by leveraging the health and environmental co-benefits of practices supported by the Inflation Reduction Act (IRA) and USDA/NRCS climate-resiliency programs.

Promoting “Climate-Smart Agricultural and Forestry Mitigation Activities” [PDF exit DNR] that will also benefit groundwater quality.

Developing educational materials and a social science-informed outreach plan for farmers, nutrient management planners and agricultural industry that promotes adoption of alternative cropping systems and nutrient management practices to minimize nitrogen losses to groundwater.

Prioritizing the protection of drinking water and public health in the planned updates to a comprehensive, stakeholder-inclusive “Wisconsin Nutrient Reduction Strategy.”

Address pesticide contamination in groundwater

A 2023 statewide survey of agrichemical in groundwater conducted by DATCP found that one or more pesticides are estimated to be present in over 40% of private drinking water wells in Wisconsin.

Of the 29 pesticides detected in DATCP’s 2023 survey, fewer than half have established NR 140 groundwater quality standards. This includes the neonicotinoid insecticides, which are currently classified as emerging contaminants. Neonicotinoids have been detected in approximately 5% of wells in randomized statewide sampling and in up to 40% of wells in targeted (biased) sampling. Neonicotinoids and other pesticides compounds were included in NR 140 rulemaking efforts Cycle 10 and Cycle 11. Cycle 10 was not approved by the Natural Resources Board in 2022, and the rulemaking scope statement for Cycle 11 expired before a rule could be drafted. To protect drinking water sources and safeguard public health, the GCC recommends:

• Update and set new state groundwater standards for several pesticides.

Establishing groundwater standards is critical to provide clean up benchmarks for regulated facilities and activities (such as pesticide spills or applications) needed to ensure compliance. Alongside regulatory requirements, voluntary agricultural actions can also be pursued to reduce pesticide impacts. Hence the GCC recommends:

• Support agricultural practices and integrated pest management strategies that minimize pesticide leaching into groundwater.

Find solutions for water-stressed areas affecting communities, economic activity and water resources

Wisconsin has abundant water supply, but these resources are not evenly distributed across the state. Some areas of the state are limited in groundwater supply by aquifers with low water availability. In other areas of the state, groundwater withdrawals along with variable climate may result in environmental harm including residential wells going dry or streams drying up. In certain areas the density of wells and the existing harm on waters of the state restricts the ability for new applicants to obtain a water supply. The GCC recommends the following actions:

• Work with counties, municipalities, businesses and individuals to identify sustainable water sources.
• Identify water conservation and efficiency measures to reduce demand in water-stressed areas.
• Develop a regional framework, like a water use district, to manage water withdrawals and address water level impacts in water stressed areas, such as the Central Sands Region.