The EPA is seeking public comment on the proposed 2026 National Pollutant Discharge Elimination System (NPDES) general permit for stormwater discharges associated with industrial activity—also referred to as the “2026 Multi-Sector General Permit (MSGP).”

 

Once finalized, the proposed permit will replace the existing MSGP, which expires February 28, 2026. The permit is proposed to be issued for 5 years. Once finalized, it will be available in areas where the EPA is the NPDES permitting authority.

Proposed changes

Proposed changes from the current MSGP include:

• Removing the word “temporary” from the stormwater control measures for major storms because “it is generally best practice to implement [stormwater control measures (SCMs)] on a more regular basis than just temporarily.”
• Requiring the permit holder to consider current conditions, defined as the “100-year flood (the 1% -annual-chance flood) based on historical records,” when evaluating whether a facility has previously experienced major storm events, as well as requiring the permit holder to use the best-available data, which is defined as “the most current observed data and available forward-looking projections,” for evaluating future exposure.
• Proposing that all stormwater control measures be based on the best-available data.
• Proposing that the 2026 MSGP add specific language on what discharges can’t contain or result in.
• Requiring many industries to conduct “report-only” indicator analytical monitoring for per- and polyfluoroalkyl substances (PFAS).
• Proposing to shift some current “report-only” sectors to benchmark monitoring for pH, total suspended solids (TSS), and chemical oxygen demand (COD).
• Setting new benchmark monitoring for ammonia, nitrate, and nitrite by operators in subsector I1.
• Proposing several new subsectors that would be required to conduct benchmark monitoring for specific metals.
• Proposing that new permit holders conduct quarterly monitoring for the first 3 years of permit coverage.
• Proposing that impaired water monitoring be changed to mandatory quarterly monitoring for the entire permit term of 5 years.
• Adding an Additional Implementation Measure (AIM) Level 1 response that requires facilities to conduct a formal investigation into the reason for a benchmark exceedance.
• Proposing a requirement for operators to provide analytical results of stormwater runoff from natural backgrounds and to get EPA approval to claim a natural background exception in the 2026 MSGP. Until operators receive approval from the EPA, they must continue monitoring.
• Requiring operators to submit an AIM Triggering Event Report for any level of AIM triggers.

The EPA solicits comment on all aspects of the proposed general permit.

Industrial facilities covered by the existing MSGP are advised to submit comments to the proposed rule by February 11, 2025, “to ensure EPA adopts a reasonable final permit with the best information available and consistent with the law,” according to a Lexology article by Beveridge & Diamond PC.

Comments can be made on the federal e-Rulemaking platform under Docket # EPA-HQ-OW-2024-0481; FRL 11244-01-OW.