The Environmental Protection Agency’s (EPA) Multi-Sector General Permit (MSGP) is a cornerstone of Clean Water Act (CWA) implementation for industrial facilities. The MSGP regulates stormwater discharges associated with approximately 29 industrial sectors, setting specific requirements to protect water quality.

EPA must reissue a new MSGP every five years. The current 2021 permit recently expired on February 28, 2026. And while the 2026 MSGP has not been finalized or approved, the proposed updates focus on expanded monitoring, more stringent corrective action requirements, per- and polyfluoroalkyl substances (PFAS) tracking, and climate-resilient design expectations.

Regulatory Framework Behind the MSGP

Industrial stormwater permitting stems from the 1987 amendments to the CWA, which directed EPA to require National Pollutant Discharge Elimination System (NPDES) permits for stormwater discharges associated with industrial activity and that those discharges meet Water Quality Standards (WQS) under Section 402(p). In 1990, EPA subsequently defined the scope of “industrial activity” in 40 CFR 122.26(b)(14) and identified 11 categories of facilities.

The first MSGP was finalized in 1995, authorizing stormwater discharges for eligible operators in 29 sectors and establishing specific requirements to protect water quality. The permit applies to roughly 2,000 facilities nationwide in a wide range of industries. The MSGP does not cover construction stormwater (except at mines), discharges from non‑industrial portions of facilities, wastewater discharges, or non‑point source discharges.

To obtain MSGP coverage, operators in applicable industries must:

• Meet eligibility requirements (e.g., National Historic Preservation Act and Endangered Species Act requirements).
• Develop or update a Stormwater Pollution Prevention Plan (SWPPP).
• Submit a Notice of Intent (NOI).
• Comply with state or tribal water‑quality‑based requirements.
• Conduct inspections and monitoring, implement control measures, and complete corrective actions when necessary.

Key Proposed Changes

EPA’s proposed 2026 MSGP introduces several substantial updates aimed at improving water quality protection, strengthening accountability, and incorporating emerging environmental concerns.

1. Additional Implementation Measures (AIMs). AIMs are mandatory, tiered, and increasingly stringent responses triggered when industrial strormwater discharges exceed benchmarked thresholds. EPA is proposing more rigorous and time‑bound reporting for AIM‑triggering events (i.e., benchmark exceedances), shifting AIM from annual summary reporting to real‑time accountability. Under the new MSGP:
   • Operators must submit an AIM Triggering Event Report within 14 days, describing planned corrective actions and anticipated completion dates.
   • A follow‑up report is required within 14 days of completing corrective actions.
   • Facilities triggering AIM Level 1 must conduct and document an inspection within seven days to identify pollutant sources, submit findings electronically, and update their SWPPP.
2. AIM Natural Background Exception. EPA is further proposing to require operators to submit analytical results from uncontaminated stormwater to support claims that benchmark exceedances are due solely to natural background levels. EPA approval would be required before the exception is granted.
3. Benchmark Monitoring: New Schedule. The 2026 MSGP would replace the “Years 1 and 4” monitoring schedule with quarterly monitoring for the first three years. After twelve samples, operators may discontinue monitoring for a parameter if the annual average remains below benchmark thresholds. This approach will increase data resolution and reduce the risk of missing intermittent exceedances.
4. Benchmark Requirements: New Sectors. Also related to benchmarking, EPA is proposing to shift 11 subsectors that showed frequent exceedances based on 2021 MSGP data from indicator‑only monitoring to benchmark monitoring and AIM applicability. These subsectors include glass and stone products, meat and dairy, oil and gas extraction, plastics, landfills, transportation equipment, recycling, steam electric generation, non‑classified facilities, land transportation, and shipbuilding.
5. Impaired Waters Monitoring Expansion. EPA is proposing significantly more stringent monitoring requirements for impaired waters, marking a major shift toward proactive protection of impaired waterbodies.
   • All discharges to impaired waters—with or without an established Total Maximum Daily Load (TMDL)—would require quarterly monitoring for the entire permit term.
   • If pollutants of concern are detected, operators must take AIM Level 1 actions and implement all reasonable steps to prevent further discharge.
6. Resilient Stormwater Control Design. EPA is proposing to require operators to consider future climate conditions (e.g., extreme precipitation, flooding, and storm surge) when designing or upgrading stormwater controls, reflecting increasing climate‑related risks to industrial infrastructure.
7. PFAS Indicator Monitoring. For the first time, EPA is proposing to require quarterly “report‑only” monitoring for 40 PFAS compounds (as listed in EPA Method 1633) for numerous sectors, supporting growing national concern over PFAS contamination.
8. Clarified Water Quality‑Based Effluent Limits. EPA is proposing to specify water‑quality‑based effluent limitations, clarifying that discharges must not cause visible solids, scum, sheen, foam, discoloration, or odor. These clarifications reinforce longstanding CWA requirements while improving enforceability.

What’s Next

The EPA did not issue the new permit before the 2021 MSGP expired on February 28, 2026; therefore, until the new 2026 permit is finalized, the 2021 MSGP remains administratively continued for existing facilities. 

As proposed, the 2026 MSGP includes some of the most significant updates to industrial stormwater permitting in a decade, incorporating expanded monitoring, more stringent corrective action requirements, PFAS tracking, and climate‑resilient design expectations.

For industrial operators in impacted industry sectors, the changes will require earlier planning, more frequent sampling, and closer attention to stormwater control performance. Facilities should begin reviewing their SWPPPs, historical monitoring data, and potential PFAS sources to prepare for the transition once the final 2026 MSGP is issued.