Key Takeaways

• What Happened? The U.S. Environmental Protection Agency (EPA) proposed the 2026 version of the National Pollutant Discharge Elimination System (NPDES) Multi-Sector General Permit (MSGP) for stormwater discharges associated with industrial activities. When finalized, this new permit will replace the current MSGP when it expires on February 28, 2026. In addition, EPA proposed a narrow modification to its 2022 Construction General Permit for Stormwater Discharges (CGP), to expand the list of areas eligible for coverage. EPA is currently soliciting public comment on all aspects of the proposed MSGP, as well as on the CGP modification.
• Who Is Affected? In the short term, the 2026 MSGP will apply to industrial facilities from thirty different sectors where EPA is the NPDES permitting authority, including Massachusetts, New Hampshire, New Mexico, and the District of Columbia. In the long term, EPA’s proposed action will affect industrial facilities in states that model their NPDES stormwater general permits after EPA’s MSGP. Meanwhile, the CGP modification will affect construction activities in Lands of Exclusive Federal Jurisdiction.
• Next Steps? Industrial facilities covered by the existing MSGP should consider how to engage in public comment by February 11, 2025, to ensure EPA adopts a reasonable final permit with the best information available and consistent with the law. Meanwhile, entities affected by the CGP should consider submitting comments by January 13, 2025. For more information, please contact the authors.

2026 MSGP

EPA released its proposed 2026 MSGP, which authorizes stormwater discharges associated with industrial activities in jurisdictions where EPA is the NPDES permitting authority, including Massachusetts, New Hampshire, New Mexico, and the District of Columbia. This newest version of EPA’s MSGP would take effect in February 2026, when the current 2021 MSGP expires. EPA is currently soliciting public comment on the proposed 2026 MSGP, with a comment deadline of February 11, 2025.

As with the current MSGP, the proposed coverage under the 2026 MSGP would be available in jurisdictions where EPA is the NPDES permitting authority for stormwater discharges from industrial facilities in thirty different sectors, including but not limited to: timber, chemicals, glass and cement, metals and mining, landfills, and transportation. While the proposed permit, once finalized, would immediately affect industrial facilities where EPA is the permitting authority, states implementing authorized NPDES programs could also choose to model their permits after EPA’s MSGP. This proposed permit could thus have significant short-term and long-term impacts on numerous industrial facilities.

Proposed Changes Compared to the 2021 MSGP

EPA proposed that the 2026 MSGP would differ from the current MSGP in several respects:

• Considerations of Stormwater Control Measure Enhancements for Major Storms
  • The proposed 2026 MSGP would modify a number of considerations in the 2021 MSGP by, among other things, removing the word “temporarily” to indicate EPA’s view that “it is generally best practice to implement SCMs [stormwater control measures] on a more regular basis than just temporarily.”
  • The new permit also clarifies that, when evaluating whether the facility has previously experienced major storm events, the permittee must do so based on current conditions, defined as “100-year flood (the 1% -annual-chance flood) based on historical records;” and, when evaluating whether the facility may be exposed in the future to major storm and flood events, the permittee must do so based on best available data, defined as “the most current observed data and available forward-looking projections.”
  • The proposed 2026 MSGP also specifies that all stormwater control measures must be based on the best available data. EPA intends this requirement "to ensure stormwater control measures are resilient to withstand storms and properly manage stormwater through their lifespan to reduce pollutants in stormwater discharges.”
• Water Quality-Based Effluent Limitations or Other Limitations The 2026 MSGP proposes to revise the provision on water quality-based effluent limitations to add more specific language on what discharges must not contain or result in, such as: observable deposits of floating solids, scum, sheen, or substances; an observable film or sheen upon or discoloration from oil and grease; or foam or substances that produce an observable change in color. EPA’s proposed revisions also struck the current MSGP’s vague requirement that each “discharge must be controlled as necessary to meet applicable water quality standards.” The agency likely proposed this change in anticipation of a ruling from the U.S. Supreme Court in City & County of San Francisco v. EPA, No. 23-753, a case in which the Court will decide whether EPA has the authority to impose permit requirements like the language EPA has dropped from the proposed 2026 MSGP.
• Monitoring
  • The proposed 2026 MSGP would include a new provision requiring a majority of sectors to conduct “report-only” indicator analytical monitoring for Per- and Polyfluoroalkyl Substances (PFAS).
  • EPA is also proposing to shift certain sectors from “report-only” indicator monitoring to benchmark monitoring for pH, total suspended solids (TSS), and chemical oxygen demand (COD). The benchmark monitoring parameters would be based on indicator monitoring results collected under the 2021 MSGP.
  • The proposed 2026 MSGP sets new benchmark monitoring for ammonia, nitrate, and nitrite by operators in subsector I1.
  • EPA also proposes that several new subsectors conduct benchmark monitoring for various specific metals based on EPA’s industry analysis of pollutants that stem from common activities.
  • The 2026 MSGP further proposes a heightened monitoring schedule for benchmark monitoring that would require operators to conduct quarterly monitoring for the first three years of permit coverage (or a minimum of twelve quarters or monitoring periods of sampling). By comparison, the current MSGP calls for benchmark monitoring only in the first and fourth year of a permittee’s permit coverage.
  • Finally, the schedule for impaired waters monitoring would also change to mandatory quarterly monitoring for the entire five-year permit term, a departure from the current MSGP’s requirement to conduct impaired waters monitoring only in the first and fourth years of permit coverage.
• Additional Implementation Measures (AIM)
  • The 2026 MSGP would add to current AIM Level 1 response requirements by requiring facilities to conduct an inspection to identify the cause of a benchmark exceedance.
  • EPA also proposes to require operators to obtain express EPA approval of a natural background exception before discontinuing compliance with AIM. Under the current a claimed natural background exception is “automatically in place and the operator [is] not required to wait for verification from EPA to discontinue [AIM] compliance.”
  • The 2026 MSGP would require operators to submit an AIM Triggering Event Report to EPA anytime a facility triggers AIM at any level.
  • Additionally, EPA proposes required corrective action equivalent to AIM Level 1 responses when facilities discharging into impaired waterbodies detect a pollutant causing an impairment.

Public Comment

EPA welcomes, and interested parties should consider submitting, public comments on any aspect of the proposed 2026 MSGP. Additionally, EPA is requesting specific feedback on the following issues:

• A host of questions pertaining to 6PPD-quinone, including how to identify sources of 6PPD-quinone in stormwater discharges and the types of best management practices permittees might implement to reduce 6PPD-quinone in their discharges;
• What methods to use for PFAS indicator monitoring;
• Whether EPA should include benchmark monitoring for iron and magnesium;
• Whether to require PFAS-related benchmark monitoring for some or all of the sectors identified for PFAS-indicator monitoring; and
• Whether to require impaired waters monitoring throughout the entire permit term, and any alternative approaches.

CGP Modification

In parallel, on December 13, 2024, EPA proposed a narrow modification to the 2022 CGP, which covers stormwater discharges from regulated construction activities in areas where EPA is the permitting authority. If adopted, the proposed modification would take effect in early 2025. EPA is currently soliciting public comments on the proposed CGP modification, with a comment deadline of January 13, 2025.

The CGP modification aims to expand the list of areas eligible for coverage to include construction projects in Lands of Exclusive Federal Jurisdiction. As the 2022 CGP failed to clarify, this proposed modification would specifically provide eligibility for all Lands of Exclusive Federal Jurisdiction without disrupting permit coverage for ongoing construction activities. The proposed CGP modification also clarifies the requirements for projects discharging to receiving waters within the Lands of Exclusive Federal Jurisdiction. Operators of such projects would follow the same requirements as used in the CGP for discharges to sensitive waters.

Next Steps

EPA is currently soliciting public comments on both proposed permits. All comments for the MSGP should be submitted to EPA by February 11, 2025, while comments for the CGP should be submitted by January 13, 2025. While EPA has not yet scheduled any public hearings, it plans to host informational webinars on the 2026 MSGP. The agency’s timetable for acting on these permits may also change after the new Trump administration takes office. For instance, new EPA personnel may modify and re-propose a version of the 2026 MSGP that better reflects the new administration’s priorities. Ultimately, engaging in public comment is an important opportunity for regulated industries to provide information and recommendations to EPA and help shape their stormwater permit obligations in years to come.