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, these 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.
The 2025 Multi-Sector General Permit for Industrial Stormwater requires permitted facilities in certain industries to monitor for PFAS in their stormwater runoff or snow. This webpage provides information and guidance on how to comply with the permit’s PFAS requirements.
Stormwater PFAS monitoring
Permitted facilities operating under primary standard industrial classification (SIC) codes associated with PFAS, and identified by the permit, are required to monitor for PFAS in stormwater.
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).
Permitted facilities monitoring for PFAS in stormwater must identify at least one area of concern (AOC) where it will collect stormwater samples. The MPCA's PFAS desktop screening tool may be useful for identifying sources of PFAS.
Permitted 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 permitted facility must provide an explanation to why a sample was not collected and submit the report to the MPCA.
A permitted 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, permitted facilities must average the results and compare them to the thresholds in the 2025 Multi-Sector General Permit for Industrial Stormwater. If the averaged results are at or greater than the thresholds in the permit, the permittee must complete and begin implementing a PFAS source and exposure reduction plan (SERP) within 180 days of its final sampling quarter. Those 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
The MPCA is currently not moving forward with its no exposure and PFAS monitoring policy for this permit cycle, and facilities with a SIC code associated with PFAS seeking no exposure certification (NEC) are not required to monitor for PFAS at this time.