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Minnesota unveils new PFAS monitoring requirements for stormwater discharge

May 29, 2025
Minnesota unveils new PFAS monitoring requirements for stormwater discharge

Last week, the Minnesota Pollution Control Agency (MPCA) rolled out its new 2025–2030 Industrial Stormwater General Permit, which officially takes effect on June 1, 2025. If your facility falls under a standard industrial classification (SIC) or narrative activity specified in Minnesota’s Multi-Sector Industrial Stormwater General Permit, you’ll need to either obtain permit coverage or file for no-exposure certification, if your industrial activities are not exposed to stormwater.

Minnesota joins only a handful of other states that now require PFAS monitoring for stormwater discharge.

The most notable change from the 2020–2025 permit is the addition of new requirements related to per- and polyfluoroalkyl substances (PFAS). These updates are expected to have a major impact on certain industrial sectors. With this move, Minnesota joins only a handful of other states that now require PFAS monitoring for stormwater discharge.

New PFAS requirements

Based on our estimates, more than 100 facilities across Minnesota will now be required to monitor for PFAS in their stormwater. These requirements take effect in the first full quarter after your facility receives permit coverage. The online permit application system is not yet available but is expected to go live this summer. If it launches before the end of June, sampling could be required as early as the third quarter of 2025. Otherwise, the first round of PFAS sampling will likely be required in quarter four of 2025.

The following PFAS-related requirements will apply to any facility with a primary SIC code on this list.

PFAS-related requirements

PFAS monitoring thresholds

The PFAS monitoring thresholds listed below are very low. In fact, for sites within one mile of a drinking water system or Class I water, the thresholds are equivalent to the EPA’s drinking water maximum contaminant levels for the same analytes.

PFAS monitoring thresholds

Table listing PFAS monitoring thresholds. Compounds PFOA and PFOS each have a 10 ng/L general threshold and a 4 ng/L threshold if within one mile of drinking water supply management area and/or a Class 1 water. Compounds PFHxS, PFNA, and HFPO-DA (Gen X) each have a 10 ng/L threshold if within one mile of drinking water supply management area and/or a Class 1 water. The general threshold does not apply to these compounds.

Other notable changes

In addition to the new PFAS-related requirements, the new Industrial Stormwater General Permit also includes the following changes.

New requirements for:

  • Facilities within one mile of, and discharging to, impaired water bodies, including a lower limit for total suspended solids (TSS)

  • Salt storage and management

  • Erosion prevention at outlets

  • Stormwater-sedimentation or infiltration-basin maintenance plans

  • Dead storage space design in stormwater ponds

  • Stormwater pollution prevention in historical contamination areas (e.g., firefighting training areas)

  • Housekeeping and chemical usage restrictions for Sector C (chemical and allied products manufacturing)

  • Traction sand usage in Sector P (land transportation and warehousing)

  • Sugar beet piling sites (Sector U), with prohibitions against discharges

Removal of:

  • Iron as a sample parameter in all sectors

Administrative changes:

  • Added provisions for submitting administrative permit amendments within 30 days of certain changes in facility information, or if the site’s receiving water body is newly listed as impaired

  • New timelines for modifying SWPPPs and restarting monitoring for new impairments

  • Clarifying edits

Our experts are here to help

Training in PFAS sampling techniques is highly recommended, given that the thresholds are very close to background concentrations.

There may be significant delays in receiving PFAS analytical results, and many labs are not certified to conduct the required analysis. In fact, only one lab in Minnesota is currently certified to perform the EPA Method 1633 analysis. In addition, collecting PFAS samples can be challenging, and the results are easily subject to contamination. Training in PFAS sampling techniques is highly recommended, given that the thresholds are very close to background concentrations.

Barr’s experts are prepared to help you:

  • Investigate and identify potential sources of PFAS from desktop information

  • Determine stormwater flow patterns and likely areas of PFAS discharge

  • Develop a sampling plan and coordinate with laboratories

  • Train employees on PFAS sampling or conduct PFAS sampling

  • Evaluate analytical results and report to the MPCA

  • Develop SERPs and/or complete extensive PFAS source evaluations

  • Design and implement PFAS treatment systems

  • Obtain permit coverage and develop compliance tools and/or SWPPPs

  • Determine permit applicability for stormwater or wastewater discharges that may contain PFAS

Learn more about our two decades of PFAS experience and contact our team for help completing a PFAS monitoring plan, sampling for PFAS, or complying with any other aspect of Minnesota’s industrial stormwater program.

About the authors

Aisha Balogh, senior environmental scientist, has nearly 15 years of experience with environmental permitting, compliance, and reporting for mining, refining, and manufacturing clients. She specializes in managing complex multimedia projects, especially ones involving site evaluations, regulatory compliance and management, risk determinations and mitigation, and facility staff training. Aisha’s interest in PFAS dates to 2020, when she helped a manufacturing client assess risks to stormwater and wastewater from current and historical PFAS usage at 35 sites across the country. Since then, she’s been helping clients evaluate their potential risk for PFAS exposure, determine applicability under PFAS regulations, mitigate risk by developing management guidance documents and sampling strategies, and prepare permit applications in coordination with state agencies for PFAS mitigation projects.

Abby Morrisette, vice president, senior environmental engineer, has more than a decade of experience in industrial water treatment, multimedia environmental compliance assistance, on-site compliance management, mass and energy balances, biological processing, impaired-waters management, and agricultural systems. Abby helps clients understand how environmental compliance translates into practical implementation. Her work involves multi-sector on-site industrial environmental assistance, bench- and pilot-testing of water treatment designs, renewable-fuels lifecycle assessment, and feasibility studies for pollution-control equipment and processes. She also prepares applications for permits and documents for environmental assessments and assists with regulatory compliance and negotiations.

Related projects

Assessment of PFAS use

Barr conducted a desktop assessment to help a manufacturing client identify potential PFAS-related risks in their operations. The team analyzed safety data sheets, facility processes, and wastewater samples to detect PFAS and assess possible environmental pathways. Results were summarized in a technical memorandum outlining risks, regulatory considerations, and recommended actions. This enabled the client to evaluate chemical use and proactively address emerging PFAS regulations.

Stormwater management

Working together, Barr’s engineers, ecologists, and landscape architects design and implement integrated stormwater management systems that reduce pollutants, prevent erosion, and lower stormwater rate and volume. We also assist with planning, modeling, pollution prevention plans, National Pollution Discharge Elimination System (NPDES) permitting, design, and construction plans and specifications.

Tags:

PFAS stormwater Water permitting industrial MPCA

 

Aisha Balogh headshot
Aisha Balogh
Senior Environmental Scientist

 

Abby Morrisette headshot
Abby Morrisette
Vice President, Senior Environmental Engineer
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