WHAT IS THE MULTI-SECTOR GENERAL PERMIT (MSGP)?
USEPA has released a proposed draft of its updated Multi-Sector General Permit (MSGP). The MSGP offers NPDES permit coverage to 29 different industry sectors for discharging industrial stormwater from their facilities.
It does not cover stormwater discharges from construction activities, non-industrial areas, wastewater, or non-point sources. The term for the MSGP is five years.
TIMELINE: WHEN WILL THE 2026 MSGP TAKE EFFECT?
The 2026 MSGP will replace the current version of the MSGP (issued in 2021), which is set to expire on February 28, 2026. The proposed 2026 draft MSGP was published in the Federal Register on December 14, 2024, and the comment period closed on May 19, 2025.
WHO WILL BE IMPACTED BY MSGP UPDATES?
While the EPA has NPDES permitting authority in only three states—Massachusetts, New Hampshire, and New Mexico, along with the District of Columbia —the changes to the MSGP will affect all facilities subject to the MSGP in the coming years as individual states update their stormwater permitting programs based on the new federal MSGP. Industrial facilities currently discharging or planning to discharge stormwater under a state-issued general stormwater permit can expect to be impacted.
KEY CHANGES IN THE 2026 MSGP
An outline of the proposed major changes to the recent permit draft is detailed below:
MONITORING REQUIREMENTS
- Quarterly PFAS “report-only” monitoring is proposed for 23 of the 29 industry sectors covered by the MSGP. Samples are to be collected and analyzed for the 40 PFAS compounds included with EPA Method 1633. Some sectors likely to be impacted include:
- Chemical & Allied Products Manufacturing
- Primary Metals
- Oil & Gas Extraction
- Rubber, Miscellaneous Plastic Products, and Miscellaneous Manufacturing Industries
- Fabricated Metal Products
- Benchmark monitoring is proposed in 11 specific sectors and sub-sectors that previously were “report-only” monitoring. The affected sectors include:
- Oil & Gas Extraction (pH & TSS)
- Subsector Y2 within the “Rubber, Miscellaneous Plastic Products, and Miscellaneous Manufacturing Industries” sector (pH & TSS)
- There is a new benchmark monitoring schedule. Quarterly monitoring is required during the first three years of permit coverage. After this period, monitoring can be discontinued if the four-quarter annual average for a parameter is not exceeded at any point during the three years of sampling. Previously, benchmark monitoring was only required during the first and fourth years of permit coverage.
- Discharges to impaired waterbodies, regardless of whether they have Total Maximum Daily Load (TMDL) limits, must be evaluated quarterly for the pollutant(s) causing impairment. Corrective action is required whenever a pollutant that impairs the receiving waterbody is detected in the discharge.
CORRECTIVE ACTIONS
Additional Implementation Measures (AIM). The 2026 MSGP includes a tiered corrective action response to address permit exceedances. This reporting must be completed through the USEPA’s electronic NeT-MsGP program (under the CDX module). Updates to the AIM reporting and response procedures in the proposed 2026 MSGP are outlined below:
- AIM Triggering Event Report – If an AIM triggering event occurs, the permittee must submit an AIM Triggering Event Report. The initial report should include a description of the planned corrective action (including a planned completion date) and must be submitted within 14 days of receiving laboratory results indicating the triggering event. Within 14 days of completing the corrective action, a follow-up report must be submitted that includes the date of completion and notes any changes to the planned corrective action.
- AIM Level 1 Response – If an AIM Level 1 event occurs, an inspection must be conducted within 7 days to determine the cause of the benchmark exceedance(s). Under the 2021 MSGP, such an inspection requirement was not included. It remains necessary to review the SWPPP and implement other additional measures as part of the corrective action process.
- Impaired Waterways – Starting in 2026, the MSGP requires an AIM level 1 response if a pollutant that impairs the receiving waterbody is found in the discharge.
WATER QUALITY-BASED EFFLUENT LIMITATION TECHNOLOGY
In the 2021 MSGP, facilities were required to “control discharges as necessary to meet water quality standards.” In the proposed 2026 MSGP, this definition has been narrowed to state that discharges must “not contain or result in observed 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.”
STORMWATER CONTROL DESIGN
While this requirement was included with the 2021 MSGP, the updated language in the proposed 2026 MSGP requires stormwater controls to be designed based on the best available data regarding previous and anticipated future storm and flooding events. NGE’s environmental professionals have significant experience with stormwater compliance for industrial facilities.