Co-authored by Nazeefa Nezami, Summer Associate
On June 1, 2025, the Minnesota Pollution Control Agency (MPCA) issued a final NPDES/SDS wastewater permit for 3M’s Cottage Grove Chemical Operations facility. Regarded as one of the most stringent permits in state history, it marks a significant regulatory milestone in the oversight of per- and polyfluoroalkyl substances (PFAS) in industrial wastewater. This permit renewal comes after years of public scrutiny, regulatory development and two rounds of public comment, and reflects MPCA’s increasingly assertive stance on PFAS regulation. It may also signal a broader shift in environmental governance — one in which states are stepping forward to lead on emerging contaminants like PFAS.
The permit imposes the following effluent limits for five PFAS compounds — PFOS, PFOA, PFHxS, PFBS and PFBA — some of which are set below current laboratory detection capabilities. For concentrations below current detection limits, MPCA included a separate compliance limit for the purpose of compliance reporting.
To meet these requirements, 3M must implement an advanced wastewater treatment system that may include reverse osmosis, granular activated carbon (GAC) and ion exchange (IX) technologies. These systems must be fully operational by April 2027.
The permit acknowledges that the MPCA has not established a statewide water quality standard for PFAS in Minnesota, so the MPCA used the procedures outlined in Minn. R. 7050.0217, Minn. R. 7050.0218 and Minn. R. 7050.0219 to develop site-specific criteria. MPCA identified the following site-specific criteria for fish consumption and recreational exposure, which are applicable to the Mississippi River:
Beyond treatment, the permit imposes extensive monitoring and reporting obligations. The permit requires 3M to monitor for any PFAS “believed to be present,” including those identified through targeted and non-targeted analysis, a review of stormwater and wastewater discharge characteristics from other PFAS manufacturing facilities and a review of PFAS analysis in air, rooftop and other potential stormwater sources. These include monthly and quarterly discharge monitoring reports (DMRs), annual PFAS source identification and reduction reports, annual PFAS removal and disposal reports and non-targeted PFAS analysis every five years. The permit also introduces new monitoring requirements for aluminum, boron, arsenic and cobalt, and includes an acute whole effluent toxicity limit based on aquatic life response. Transparency is a central feature: 3M is required to publish water quality monitoring data online monthly and to host an annual community meeting to discuss compliance and environmental performance.
While these stringent conditions may signal a potential shift in how PFAS discharges are regulated under NPDES permits in Minnesota, it is difficult to predict how broadly such measures will be applied to other facilities, given 3M’s unique position as not only a discharger but also a primary manufacturer of PFAS. This permit shows that MPCA is comfortable with an approach that requires aggressive treatment requirements, even when it sets standards below detectable limits. And the creation of a compliance limit for the purpose of compliance reporting shows that MPCA recognizes the challenges of measuring PFAS compounds below detectable limits and may be willing to work with regulated parties to develop measurable solutions.
For more information, contact Shantal Pai or Jeremy Greenhouse.
Featured Professionals
Professionals
612.492.7175
612.492.7437
