Regulatory Alert: EPA Releases Proposed 2026 Multi-Sector General Permit for Stormwater Discharges
December 11, 2024
Yesterday, the U.S. Environmental Protection Agency (EPA) released the agency’s proposed multi-sector general permit (MSGP), which would, if finalized, outline the terms and conditions for authorizing certain airports to discharge industrial stormwater. The current MSGP in effect is set to expire in February 2026. Based on our initial review, the proposed 2026 MSGP contains some troubling new requirements, including quarterly testing from stormwater discharge points for 40 different PFAS compounds and three other “parameters.” EPA has also requested public comment on whether PFAS-related thresholds should be established that, if exceeded, would require corrective action.
Interestingly, EPA has not issued a press release, published the proposed MSGP in the Federal Register, or otherwise brought any attention to the proposal after posting it to its website. We will be carefully monitoring when the proposal is published in the Federal Register, which will trigger a 60-day comment period. However, it is unclear at this stage whether the incoming Trump administration will pause or delay the comment period or re-propose the MSGP. Under any circumstances, we are planning to work with our Environmental Services and Sustainability Committee members and will be prepared to submit comments in response to the proposed 2026 MSGP.
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.
Initial Review of Proposed 2026 MSGP. The proposed 2026 MSGP is very lengthy but consists of two primary components that are of most interest to airports: general requirements (Parts 1 through 7) and specific requirements that apply to the air transportation/airport sector (Section S in Part 8). Under the proposal, EPA would make a number of changes and updates to the current 2021 MSGP. Based on our initial review, several are worth highlighting:
Yesterday, the U.S. Environmental Protection Agency (EPA) released the agency’s proposed multi-sector general permit (MSGP), which would, if finalized, outline the terms and conditions for authorizing certain airports to discharge industrial stormwater. The current MSGP in effect is set to expire in February 2026. Based on our initial review, the proposed 2026 MSGP contains some troubling new requirements, including quarterly testing from stormwater discharge points for 40 different PFAS compounds and three other “parameters.” EPA has also requested public comment on whether PFAS-related thresholds should be established that, if exceeded, would require corrective action.
Interestingly, EPA has not issued a press release, published the proposed MSGP in the Federal Register, or otherwise brought any attention to the proposal after posting it to its website. We will be carefully monitoring when the proposal is published in the Federal Register, which will trigger a 60-day comment period. However, it is unclear at this stage whether the incoming Trump administration will pause or delay the comment period or re-propose the MSGP. Under any circumstances, we are planning to work with our Environmental Services and Sustainability Committee members and will be prepared to submit comments in response to the proposed 2026 MSGP.
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.
Initial Review of Proposed 2026 MSGP. The proposed 2026 MSGP is very lengthy but consists of two primary components that are of most interest to airports: general requirements (Parts 1 through 7) and specific requirements that apply to the air transportation/airport sector (Section S in Part 8). Under the proposal, EPA would make a number of changes and updates to the current 2021 MSGP. Based on our initial review, several are worth highlighting:
- Indicator Monitoring for 40 PFAS Compounds: One of the most significant updates would require permitted airports to conduct quarterly “report-only indicator monitoring” of 40 different PFAS compounds using EPA Method 1633 (as listed in Table 1). Under the proposal, airports would have to conduct regular monitoring and report their data, but no follow-up action would be required. EPA asserts that monitoring will help permit holders (1) evaluate how and why data is changing over time, and (2) determine if any updates are necessary to stormwater pollution prevention plans or stormwater control measures.
- Benchmark Monitoring for PFAS: Although not proposed as a requirement, EPA requested comment on whether the agency should require “PFAS-related benchmark monitoring” for some or all of the sectors under the MSGP, including airports. In contrast to indicator monitoring, benchmark monitoring may require permit holders to take corrective action if data exceeds a specified threshold.
- Indicator Monitoring for Other Parameters: Under the proposal, permitted airports would have to conduct quarterly report-only indicator monitoring of three additional parameters: chemical oxygen demand (COD), total suspended solids (TSS), and pH. These are additional monitoring parameters included in the sector-specific requirements for airports (Section S). Under the existing 2021 MSGP, EPA only requires this type of monitoring for some airports. Similar to PFAS indicator monitoring noted above, permitted airports would only conduct regular monitoring and report their data, but no follow-up action would be required.
- Inspections for Benchmark Exceedances/Triggering Reports: 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 (1) conduct an inspection to identify the cause of a benchmark exceedance when AIM level 1 is triggered, and (2) submit an “AIM Triggering Event Report” to the agency in response to triggering AIM at any level.
- Addressing 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. Although EPA has not proposed any specific requirements regarding the contaminant, the agency has requested comment on how to identify likely sources of 6PPD-quinone in stormwater discharges, what controls may be effective in minimizing its discharge, and what monitoring requirements may be appropriate.
