Regulatory Alert: AAAE Submits Comments on EPA’s Proposed 2026 MSGP for Stormwater Discharges
May 20, 2025
Yesterday, AAAE submitted comments to the U.S. Environmental Protection Agency (EPA) on the agency’s proposed multi-sector general permit (MSGP), which would, once finalized, outline the terms and conditions for authorizing certain airports to discharge industrial stormwater. AAAE’s response to the agency primarily opposed a troubling new provision in the proposed 2026 MSGP that would require quarterly testing of stormwater discharge points for 40 different PFAS compounds. We argued that monitoring requirements in the MSGP would be an ineffective tool to address PFAS-related concerns and are well beyond the scope and purpose of the MSGP. We also raised concerns with several other proposed requirements—relating to corrective action procedures if monitoring results exceed benchmark values—as unnecessary and unsubstantiated by any data.You can read AAAE’s full comments here.
Background. In accordance with the Clean Water Act, EPA implements the National Pollutant Discharge Elimination System (NPDES) program, which requires permits for any person or organization, including airports, to discharge industrial stormwater into waters of the United States. The MSGP only provides coverage for a handful of states, Washington, D.C., many Tribal areas, and U.S. territories, where EPA is the NPDES permitting authority. However, many states use the MSGP as a model for developing their own industrial stormwater discharge permits, reflecting its importance for the industry and airports.
EPA’s first MSGP was issued in 1995 and revised in 2000, 2008, 2015, and 2021 to provide operators with coverage for such stormwater discharge. The latest MSGP, which went into effect on March 1, 2021, is set to expire on February 28, 2026. EPA must release another MSGP—or extend the existing general permit—before the 2026 expiration date.
Summary of Recommendations. Based on key feedback from members, AAAE provided EPA with a series of recommendations for the 2026 MSGP that focused on ensuring EPA-permitted airports have the flexibility to implement their stormwater management program in a manner that is best suited for their particular circumstances. These included:
- PFAS Monitoring Requirements: One of the most significant proposed updates to the MSGP would require permitted airports to conduct quarterly “report-only indicator monitoring” of 40 different PFAS compounds, which includes testing and reporting data, but no follow-up action would be required. AAAE strongly opposed the new provision on the grounds that airport operators do not engage in any “industrial activities”—as defined in EPA’s regulations—where potential PFAS exposure to precipitation could even occur. Equally important, the proposed monitoring requirement could lead to operators implementing control measures that (a) focus more on remediation rather than stormwater management, which is well beyond the purpose of the MSGP, and (b) are ineffective at addressing potential PFAS exposure to precipitation.
- Corrective Action/Triggering Reports for Benchmark Exceedances: Under the 2021 MSGP, EPA implemented a three-level protocol that requires permitted airports to take progressively more actions when monitoring results exceed or repeatedly exceed benchmark values, known as Additional Implementation Measures (AIM). Under the proposed 2026 MSGP, EPA would require permitted airports to (a) submit an “AIM Triggering Event Report” to the agency in response to triggering AIM at any level and (b) receive approval from the agency before it could discontinue compliance if the operator believed the “natural background exception” applied. AAAE opposed both new requirements as unnecessary, as the agency did not justify these provisions or explain what problem they were trying to solve.
- 6PPD-quinone in Stormwater Discharge: 6PPD-quinone is an emerging contaminant that has received significant attention by EPA and state environmental agencies, especially in the Pacific Northwest region. Some airports have had development projects inhibited by concerns over 6PPD-quinone during environmental reviews. EPA requested comment on whether to include requirements in the proposed 2026 MSGP to address 6PPD-quinone related concerns. In our response, AAAE argued that inclusion of requirements related to 6PPD-quinone would be premature at this stage because of the lack of data to justify what measures may be necessary. To the extent any data does become available, concerns should be addressed through individual permits or managed by state environmental agencies instead, not on a nationwide basis.
