Wisconsin is moving closer to establishing enforceable groundwater standards for six per- and polyfluoroalkyl substances (PFAS), a development with significant implications for contaminated site investigations, remediation, and brownfields redevelopment.

On October 28, 2026, the Wisconsin Natural Resources Board (NRB) approved revisions to Wisconsin Administrative Code chapter NR 140 under Board Order DG-02-25. Once finalized, the rule will establish numeric groundwater standards for six PFAS compounds, replacing the Department of Natural Resources’ (DNR) current reliance on site-specific cleanup standards for those substances.

What are Wisconsin’s proposed PFAS groundwater standards?

The proposed rule would establish groundwater Enforcement Standards (ESs) and Preventive Action Limits (PALs) based on recommendations issued by the Wisconsin Department of Health Services in 2025.

PFAS Compound	Proposed ES	Proposed PAL
PFOA	4 ppt	0.4 ppt
PFOS	4 ppt	0.4 ppt
PFHxS	10 ppt	1 ppt
PFNA	10 ppt	1 ppt
PFBS	2,000 ppt	200 ppt
HFPO-DA (GenX)	10 ppt	1 ppt

Concentrations are expressed in parts per trillion (ppt), equivalent to nanograms per liter (ng/L).

The proposed standards within the same order of magnitude as EPA’s April 2024 federal drinking water standards, although EPA has announced plans to reconsider portions of that federal rule.

Wisconsin’s proposed groundwater standards arise under a separate state regulatory framework and would apply more broadly than the drinking water standards governing public water systems under chapter NR 809.

How do the groundwater standards compare to other states in EPA Region 5?

Wisconsin's proposed standards reflect a broader trend toward establishing numeric PFAS groundwater standards across the Midwest. Wisconsin's regulatory framework is distinctive because chapter NR 140 establishes groundwater standards that apply across multiple DNR programs, influencing permitting, monitoring, compliance, corrective actions, and contaminated-site cleanups. A comparison with other EPA Region 5 states illustrates the different approaches.

• Illinois adopted groundwater quality standards for the same six PFAS compounds in March 2025. Those standards are identical to Wisconsin's proposed Enforcement Standards, including 4 ppt for PFOA and PFOS.
• Michigan established numeric PFAS groundwater cleanup criteria beginning in 2020. Its standards are less stringent than Wisconsin's proposed standards for PFOA (8 ppt) and PFOS (16 ppt), but more stringent for PFNA (6 ppt).
• Minnesota has adopted numeric PFAS groundwater Health Risk Limits under Minnesota Rules, chapter 4717. Updated in 2025, Minnesota's PFOA and PFOS limits are more stringent than Wisconsin's proposed Enforcement Standards. Although Minnesota's regulatory framework differs from Wisconsin's, both states use promulgated numeric standards to evaluate groundwater contamination.
• Indiana regulates PFAS groundwater contamination through its risk-based remediation framework, with published screening and closure levels for 11 PFAS compounds rather than separately promulgated groundwater quality standards comparable to Wisconsin's NR 140 standards.
• Ohio addresses PFAS groundwater contamination through its risk-based remediation programs. Although Ohio has established numeric groundwater cleanup standards for numerous other hazardous substances, it has not adopted comparable statewide numeric groundwater quality standards specifically for PFAS.

While DNR already regulates PFAS contamination through its existing remediation authority, promulgated groundwater standards should provide greater consistency and predictability for site investigations, groundwater monitoring programs, remedial action planning, and case closure decisions.

How will the new standards affect contaminated site investigations and cleanups?

A significant consequence of the proposed rule will be its effect on how the DNR evaluates PFAS contamination at remediation sites and other facilities subject to ongoing groundwater monitoring obligations.

Currently, Wisconsin has no promulgated numeric groundwater standards for PFAS. The DNR instead relies on its authority under Wis. Admin. Code § NR 722.09(2)(b)2. to establish site specific groundwater cleanup standards.

Once numeric standards are promulgated under chapter NR 140, the DNR will no longer need to rely on that site specific authority for the six regulated PFAS. Instead, Wis. Admin. Code § NR 722.09(2)(b)1 establishes the PAL as the groundwater restoration goal, to be achieved to the extent technically and economically feasible, subject to applicable provisions of NR 140.

This change could have several important practical consequences:

• Site investigations. Responsible parties addressing PFAS contamination may need to reassess whether existing groundwater investigations adequately delineate PFAS contamination in light of the new standards. In some cases, additional investigation may be necessary to evaluate PFAS transport pathways among groundwater, wastewater and biosolids management, particularly where multiple potential sources exist. As PFAS monitoring becomes more common, interpretation of background and upgradient groundwater conditions may also become increasingly important during investigations and regulatory decision-making.
• Remedial action implementation. The promulgated PALs will provide uniform groundwater restoration goals for evaluating remedial alternatives, potentially affecting remedy selection, cleanup costs, and long-term monitoring. The new Enforcement Standards will also provide the groundwater target concentrations used to calculate groundwater-protective soil residual contaminant levels (RCLs) under Wis. Admin. Code § NR 720.10, affecting soil cleanup requirements for PFAS.
• Case closure. Numeric standards will provide clearer benchmarks for evaluating whether PFAS-impacted sites qualify for regulatory closure under chapter NR 726, although closure determinations will remain site-specific.
• Brownfields redevelopment and transactions. The standards may affect environmental due diligence, remediation cost estimates, and the allocation of environmental liabilities in property transactions.

The new standards should provide greater regulatory predictability by replacing the current process of developing site-specific groundwater cleanup standards. While the DNR has existing authority to regulate PFAS contamination at remediation sites, uniform standards may affect the scope and cost of investigations and remedial actions, particularly at sites where PFAS has already been detected.

Responsible parties with ongoing investigations, pending remedial action approvals, or anticipated case closure requests should evaluate how the proposed standards may affect their existing remediation strategies.

What happens next with the rule?

On October 28, 2026, the NRB approved Board Order DG-02-025, which was subsequently approved by Governor Evers and the DNR. Assuming timely filing and publication, the rule is most likely to become effective on December 1, 2026. If publication is delayed, the effective date could shift to January 1, 2027. Actual timing will depend on completion of the remaining rulemaking and publication requirements.

Although the rulemaking process ordinarily provides for review of proposed administrative rules by legislative standing committees and the Joint Committee for Review of Administrative Rules, the role of legislative committee review has changed significantly following recent court decisions. Accordingly, although the rule may be submitted to legislative committees, the extent to which such review may delay promulgation is likely limited. Ultimately, the rule must be filed with the Legislative Reference Bureau and published in the Wisconsin Administrative Register before becoming effective. Once complete, the new standards will apply within Wisconsin’s existing groundwater protection and remediation framework.

What new PFAS sampling programs has the DNR launched?

The DNR also recently launched two PFAS sampling programs funded through Wisconsin’s PFAS Trust Fund and authorized under 2025 Wisconsin Acts 200 and 201.

The PFAS Community Grants Sampling Program provides financial assistance to eligible municipalities and other governmental entities for PFAS sampling of private wells, certain drinking water supplies, wastewater, and biosolids. The DNR has allocated $2 million for the initial grant cycle, with applications accepted through April 30, 2027, or until funds are awarded.

The Wisconsin PFAS Private Well Testing Program offers eligible private well owners and users free PFAS testing. Depending on test results and eligibility, participants may also qualify for assistance with alternative drinking water supplies, treatment systems, or replacement wells.

These programs will expand access to PFAS testing and may identify contamination that warrants further evaluation. Municipalities and private well owners should review program eligibility and available funding.

What should regulated entities consider?

Businesses, property owners, developers, responsible parties, and operators of facilities with ongoing groundwater monitoring obligations should consider reviewing existing PFAS investigation data, assessing the potential effect of the proposed groundwater standards on remediation objectives, and evaluating whether pending regulatory submissions or closure requests may be affected.

Municipalities and eligible well owners should also consider opportunities to obtain financial assistance for PFAS sampling.

How can Godfrey & Kahn help?

Godfrey & Kahn’s Environmental team continues to monitor Wisconsin’s evolving PFAS regulatory framework, including groundwater standards, contaminated-site cleanup requirements, and available funding programs.

Our team advises businesses, municipalities, developers, and property owners on PFAS compliance, site investigations, remediation strategies, environmental liabilities, and brownfields redevelopment.

For more information, contact a member of Godfrey & Kahn’s Environmental practice.