Per- and polyfluoroalkyl substances (PFAS), also known as “forever chemicals,” are a large group of durable synthetic chemicals that do not readily break down over time in environmental conditions and are not easily removed in conventional pollution treatments. Even at low levels of exposure, "forever chemicals" may lead to significant health risks in humans and the environment. When released into stormwater, PFAS could contaminate groundwater and surface water crucial for drinking water, irrigation, and aquatic life in Minnesota.
The draft 2025 industrial stormwater (ISW) National Pollutant Discharge Elimination System (NPDES)/State Disposal System (SDS) general permit requires facilities in certain industries to monitor for PFAS in their stormwater runoff. The information on this webpage is being shared for transparency and is subject to change until the 2025 ISW NPDES/SDS general permit is finalized.
Stormwater PFAS monitoring
Facilities that must monitor for PFAS in stormwater operate under primary SIC codes identified by the industrial stormwater general permit.
Permitted facilities must complete and implement a PFAS monitoring plan and maintain a copy of the plan in the facility’s stormwater pollution prevention plan (SWPPP). The MPCA encourages facilities with a primary SIC code associated with PFAS that are seeking no exposure certification to complete and implement a PFAS monitoring plan.
Facilities monitoring for PFAS in stormwater should identify at least one area of concern where it will collect stormwater samples. The MPCA's PFAS desktop screening tool may be useful for identifying sources of PFAS.
Facilities may collect stormwater samples for PFAS monitoring via grab sampling, sheet flow sampling, and/or snow sampling. To sample from snow, facilities must follow the industrial stormwater program’s PFAS snow sampling guidance.
In the absence of a collectable amount of snow and/or measurable runoff during a quarter due to weather conditions and/or site soil characteristics, the facility should provide an explanation why a sample was not collected and submit the report to the MPCA.
A facility monitoring stormwater for PFAS must also:
- monitor for the 40 PFAS analytes listed in U.S. Environmental Protection Agency’s (EPA) Method 1633
- analyze the results of its PFAS monitoring in compliance with any version of the EPA’s Method 1633
- determine its proximity to a drinking water supply management area (DWSMA) and/or a Class 1 water by using the industrial stormwater special and impaired waters search tool
- provide results for all 40 PFAS analytes in Method 1633 to the MPCA via e-Services
- submit a quarterly PFAS stormwater monitoring report to the MPCA no later than the 21st day of the month following the sampling quarter
Source and exposure reduction plan
After collecting and analyzing four separate quarterly samples, facilities must average the results and compare them to the thresholds in the ISW 2025 NPDES/SDS general permit. If the averaged results are at or greater than the thresholds in the table, the permittee must complete and begin implementing a PFAS source and exposure reduction plan (SERP) within 180 days of its final sampling quarter. Facilities must use the current version of the SERP template provided by the MPCA and review and update their SERP annually. The MPCA requires facilities to submit the implemented or draft SERP with the facility’s industrial stormwater annual report.
No exposure policy change
Emerging concerns over PFAS have led the MPCA’s industrial stormwater program to require facilities with a primary SIC code associated with PFAS seeking no exposure certification to verify they meet the criteria listed in Minn. R. Ch. 7090.3060. To qualify for no exposure certification, those facilities must:
- apply for no exposure certification from the industrial stormwater general permit when the application service becomes available
- identify all possible areas of concern for PFAS at the facility and complete four separate PFAS stormwater monitoring events at least 72 hours apart at each of the facility’s areas of concern
- monitor for the 40 PFAS analytes listed in the EPA’s Method 1633
- determine the facility's proximity to a drinking water supply management area (DWSMA) and/or a Class 1 water by using the industrial stormwater special and impaired waters search tool
- analyze the results of the PFAS stormwater monitoring events in compliance with any version of EPA Method 1633 using a Minnesota Department of Health-accredited laboratory
- show averaged results of the four PFAS monitoring events below the thresholds for the PFAS analytes in Table 1 below
- submit the entire analyzed PFAS monitoring results, including copies of the facility's PFAS monitoring laboratory reports, to the MPCA via e-Services by Dec. 21, 2025
| Base thresholds | Special thresholds: facilities within 1 mile of a DWSMA or a Class 1 water |
|---|---|
10 ng/L for PFOA 10 ng/L for PFOS | 4 ng/L for PFOS 4 ng/L for PFOA 10 ng/L for PFHxS 10 ng/L for PFNA 10 ng/L for HFPO-DA (commonly known as GenX chemicals) |
If a facility does not qualify for no exposure certification, it must develop a stormwater pollution prevention plan and apply for permit coverage by Dec. 21, 2025.