On December 13, EPA published its proposed 2026 multi-sector general permit (MSGP) for stormwater discharges from industrial activities. When finalized, the 2026 MSGP would replace the 2021 MSGP that expires on February 28, 2026. 

While the MSGP is only binding in those states without authorized Clean Water Act programs, most states use the provisions in the MSGP as a model for their stormwater regulations. The proposed changes to the MSGP could have significant impact on stormwater discharges from metalcasting operations. 

Proposed Changes for the 2026 MSGP 

The proposed 2026 MSGP includes new design and planning requirements for major storm events and additional monitoring, reporting, and corrective action measures that are summarized below.

Stormwater Control Measures for Major Storm Events. EPA requires operators to select and design control measures that reduce risks to their industrial facilities and the potential impact of pollutants in stormwater discharges caused by major storm events.

Water Quality-Based Effluent Limitations. Stormwater discharges must not contain or result in observable deposits of floating solids, scum, or substances; an observable film, sheen, or discoloration from oil and grease; or foam or substances that produce an observable change in color.

Indicator Monitoring of PFAS. EPA is requiring indicator monitoring (report-only) of 40 PFAS compounds quarterly for five years. The samples must be analyzed using EPA Method 1633. Indicator monitoring is not subject to benchmark thresholds and corrective action for exceedances of those thresholds, but facilities would have to comply with any applicable water quality standards. It is, however, likely that, based on monitoring results, such control measures for PFAS in stormwater discharges would be required in the near future for many facilities.

Indicator Monitoring of Polycyclic Aromatic Hydrocarbons (PAH). EPA is also requiring indicator monitoring (report-only) of PAH compounds quarterly for five years.

Updating Monitoring for Specific Sectors. For foundries, EPA is shifting from indicator monitoring to benchmark threshold monitoring for total recoverable aluminum, copper, and zinc, and for total suspended solids (TSS). Facilities would be required to conduct quarterly monitoring of these pollutants for three years, and may discontinue monitoring only if they have no benchmark exceedances during that time. Discontinuance is, however, unlikely because nearly 80% of facilities have benchmark exceedances, many of which are not associated with industrial activities at the facility. This says more about the unrealistically low benchmark thresholds than it does about any potential risks associated with stormwater discharges from foundries.

Monitoring Discharges into Impaired Waters. Facilities must conduct quarterly monitoring for discharges of pollutants identified as causing water quality impairments for five years. If a pollutant for which the water is impaired is detected in the facility’s stormwater discharge, then the facility must implement corrective actions to prevent the pollutant from entering the waterbody.

Additional Implementation Measures (AIM). EPA is requiring additional implementation measures (AIM) for discharges into impaired waters or that exceed benchmark thresholds, thereby triggering a facility’s obligation to review its Stormwater Pollution Prevention Plan (SWPPP) and any stormwater control measures that are in place––and determine if additional control measures are needed. Each time that a facility has an exceedance of the benchmark thresholds or discharges into impaired waters, it must submit an AIM Triggering Event Report that identifies the corrective actions to be implemented and when.

Procedural Issues 

Several industry groups have raised some significant procedural issues with the 2026 MSGP and have requested that EPA withdraw it. For example, unlike all previous MSGPs, the proposed 2026 MSGP was never submitted to the White House for regulatory review and input from interested federal agencies. 

In addition, even though the proposed 2026 MSGP will have a significant impact on a substantial number of small entities, EPA did not conduct a small business panel to seek input to minimize the potential impact on small businesses, which may be profoundly impacted. 

Furthermore, as part of the 2021 MSGP, EPA made several commitments on how it would use data collected from those permit requirements but has failed to comply or follow through with them. In addition, EPA indicated it would work with external stakeholders to review and revise sector-specific fact sheets that included the best management practices for industry sectors like foundries to manage stormwater discharges from industrial activities––but EPA abandoned this effort without receiving any industry-specific input on the fact sheets.

Because of these and other deficiencies with the proposed 2026 MSGP, several industry groups have requested EPA to withdraw the proposed 2026 MSGP permit and issue a new proposed MSGP. The incoming Trump administration is likely to target this rule to reduce unnecessary burdens on U.S. manufacturing.

Comments on the proposal are due February 28. There have been several requests to also extend the comment period, if the proposal is not withdrawn. AFS will continue to work with regulators and industry groups to address the many concerns over the proposed 2026 MSGP.