Wisconsin Moves Forward with PFAS Groundwater Standards

On October 28, 2026, the Wisconsin Natural Resources Board adopted Board Order DG-02-25, which would amend Wis. Admin. Code ch. NR 140 to establish Wisconsin’s first numeric groundwater quality standards for six per- and polyfluoroalkyl substances (PFAS). Governor Tony Evers subsequently approved the proposed rule, and it must now be submitted to the Wisconsin Legislature for review before it can be promulgated and take effect.

The proposed rule marks DNR’s fourth attempt to establish PFAS groundwater standards. A prior rulemaking was halted after DNR estimated that implementation and compliance costs would exceed $10 million over a two-year period, triggering Wisconsin’s REINS Act. For DG-02-25, DNR estimates the highest two-year costs at $9,917,838, approximately $82,000 below that threshold.

The DNR establishes groundwater standards based on recommendations from the Wisconsin Department of Health Services. The proposed rule would establish the following Enforcement Standards and Preventive Action Limits:

The new Enforcement Standards generally align with the federal drinking water standards established by EPA in 2024. In May 2026, EPA proposed rescinding the federal standards for PFHxS, PFNA, GenX, and certain PFAS mixtures, while retaining the standards for PFOA and PFOS. The corresponding Preventive Action Limits are set at 10 percent of the Enforcement Standards. Unlike federal drinking water standards, the NR 140 standards have broader implications because they are used across multiple state regulatory programs governing activities that may affect groundwater.

Key programs potentially affected by the new PFAS standards include remediation, wastewater, and solid waste.

Remediation and Redevelopment

DNR currently uses site-specific groundwater standards for PFAS under Wis. Admin. Code § NR 722.09(2)(b)2. Once the rule takes effect, the promulgated NR 140 standards will apply to the six covered compounds in place of the current site-specific standards. The applicable Preventive Action Limit will generally serve as the groundwater restoration goal to the extent technically and economically feasible. DNR does not expect the new standards to materially change existing cleanup obligations or remedy selection because they are consistent with the site-specific standards DNR currently uses, and PFAS investigation and cleanup obligations already arise under Wisconsin’s Spills Law. Where groundwater-protective soil residual contaminant levels are calculated under Wis. Admin. Code § NR 720.10, NR 140 Enforcement Standards serve as the target groundwater concentrations. DNR has stated that the standards will provide clarity and consistency to regulated entities on how to address these compounds when detected at sites or facilities.

Wastewater Permitting

DNR’s rules governing wastewater discharged to land incorporate NR 140 groundwater standards. Wis. Admin. Code ch. NR 206 requires municipal and domestic wastewater land-disposal systems to be designed and operated in compliance with NR 140 groundwater standards. Wis. Admin. Code ch. NR 214 similarly incorporates NR 140 standards into the regulation of industrial land-treatment systems. NR 214 also regulates land spreading of industrial by-product solids and sludge, with application rates limited to protect groundwater and prevent exceedance of applicable Preventive Action Limits. Under NR 214, wastewater parameters that may affect groundwater quality must be limited to minimize groundwater concentrations to the extent technically and economically feasible and prevent exceedance of the applicable Preventive Action Limit. If a Preventive Action Limit or Enforcement Standard is exceeded, DNR may require changes to the operation or design of the system, groundwater cleanup, alternative treatment, or other responses authorized under NR 140. Both chapters also authorize DNR to require monitoring for additional pollutants based on site-specific or discharge-specific circumstances. Domestic sewage sludge, or biosolids, is separately regulated under Wis. Admin. Code ch. NR 204, which governs land application and allows DNR to impose additional monitoring or land-application restrictions for pollutants that may threaten public health or the environment.

Solid Waste Regulation

DNR requires regulated solid waste facilities to conduct groundwater monitoring under Wis. Admin. Code ch. NR 507, with monitoring results evaluated against NR 140 groundwater standards. The monitoring parameters specified in NR 507 do not currently include PFAS, but § NR 507.17(3) allows DNR to require analysis of additional parameters based on the characteristics of the waste, the raw process materials used, or the requirements of NR 140. DNR has indicated that, once the new standards are finalized, it may exercise this existing authority to require PFAS sampling at additional landfills, with an initial focus on landfills with existing exceedances of other NR 140 standards and paper mill sludge landfills that may have accepted PFAS-containing waste. DNR’s Economic Impact Analysis includes costs for PFAS groundwater monitoring and monitoring-well installation at certain landfills.

Wisconsin’s REINS Act generally requires an agency to stop work on a proposed rule if an economic impact analysis shows that $10 million or more in implementation and compliance costs are reasonably expected to be incurred by or passed along to businesses, local governmental units, and individuals over any two-year period. An agency may resume rulemaking if a bill authorizing the rule is enacted or, in certain circumstances, if the proposed rule is modified and a revised economic impact analysis brings the expected costs below the $10 million threshold.

DNR’s final Economic Impact Analysis estimates that DG-02-25 will result in $9,917,838 in implementation and compliance costs during the highest-cost two-year period. The estimate increased from $9,893,388 after DNR revised certain sampling-cost assumptions in response to public comments. DNR characterizes the estimate as an upper bound because it does not account for PFAS funding available under 2025 Wisconsin Acts 200 and 201.

DNR’s estimate falls below the REINS Act threshold in part because the agency treats several categories of PFAS-related costs as arising under legal authorities that exist independently of DG-02-25. For example, DNR attributes no additional remediation costs to the rule because PFAS investigation and cleanup obligations already arise under Wisconsin’s Spills Law. DNR similarly excludes biosolids-management costs on the basis that Act 201 independently requires PFAS limitations or conditions in sewage-sludge land-application permits.

Industry and municipal commenters argued that DNR’s analysis understates costs associated with remediation, biosolids management, dewatering, landfill investigation, and wastewater treatment. DNR rejected those arguments, defending its cost assumptions and maintaining that the analysis appropriately excludes costs attributable to existing authorities that DNR may exercise independently of the new groundwater standards. The approximately $82,000 difference between DNR’s estimate and the REINS Act threshold makes the treatment of these costs particularly significant. During legislative review, the Joint Committee for Review of Administrative Rules may request an independent economic impact analysis, subject to the approvals required by Wisconsin law. If that analysis estimates $10 million or more in implementation and compliance costs over a two-year period, the REINS Act’s stop-work requirement would apply.

The new PFAS groundwater standards will provide greater consistency in how DNR evaluates PFAS in groundwater by establishing uniform statewide benchmarks for the six covered compounds. Although DNR does not expect the standards to materially change existing PFAS cleanup obligations, the new numeric standards will become relevant whenever NR 140 standards are used in DNR’s regulatory decision-making.

Businesses, property owners, municipalities, and other regulated entities with known or potential PFAS issues should consider how the new standards may affect existing regulatory obligations and future interactions with DNR. The practical significance of the standards will depend on the particular activity and regulatory framework involved and may continue to develop as DNR implements the standards through its existing programs.

If you have questions about how Wisconsin’s new PFAS groundwater standards may affect your business, property, permits, or environmental obligations, please contact any of the Michael Best attorneys listed below.