On October 21, 2026, the Washington State Department of Ecology (Ecology) quietly modified and re-issued the National Pollutant Discharge Elimination System (NPDES) Industrial Stormwater General Permit (ISGP). This modification contained only a few changes, most important of which is pulling forward the permit expiration and re-application deadlines by one year. The ISGP now expires December 31, 2028, and Permittees must re-apply 180 days prior to that, no later than July 4, 2028.

Reasons Behind the Change

Ecology has stated two reasons for this change: the first reason is to ease Ecology’s staff workload that piles up every five years when two of the State’s most used stormwater permits (the ISGP and the Construction Stormwater General Permit) have historically been renewed at the same time. The second reason for the shakeup is a bit more interesting: when the 2025 ISGP was issued on December 2, 2024, six separate appeals were filed with the Washington State Pollution Control Hearings Board (PCHB). All six appeals were consolidated under PCHB No. 24-088. Ecology subsequently reached two partial settlement agreements with five industrial appellant groups. The sixth appeal, filed jointly by Puget Soundkeeper Alliance and Spokane Riverkeeper, was not part of these settlements. The environmental appellants’ challenges were rejected by the PCHB in the June 2026 Findings of Fact, and a separate appeal (PCHB No. 26-010) challenging Ecology’s partial stay of certain permit conditions was dismissed later that month. The environmental appellants subsequently sought judicial review of both PCHB decisions in King County Superior Court in July 2026, where the challenges remain unresolved based on available public information. The partial settlement agreements require Ecology to propose significant changes in the next draft permit, expected to be released for public comment in early 2028. Ecology has already provided some insight into what those changes may include.

More Changes on the Horizon

Ecology participated in two public online events on May 18 and September 23, 2026, to discuss current and anticipated permit changes and has posted relevant ISGP modification documents on their website. Through these discussions and publications, Ecology has indicated it is considering the following changes:

• Corrective Actions will likely become drainage area specific. If adopted, this change could significantly ease the burden of Level 2 and Level 3 Corrective Actions, which are currently triggered on a site-wide cumulative basis.
• The Level 3 Engineering Report timeline is expected to be extended to 18 months for small businesses, public entities, or sites that are five or more acres.
• The “cause or contribute” language in Permit Condition S10 is expected to be substantially revised following a 2025 U.S. Supreme Court ruling limiting the use of broad water quality compliance conditions in discharge permits.
• Ecology plans to use the 2022 Water Quality Assessment (WQA) instead of the 2018 WQA, which may alter facility-specific numeric effluent limits or monitoring requirements.

Additional changes may be proposed before the draft permit is issued. It is also unclear whether early permit reissuance will impact the 6PPD-quinone (6PPDQ) sample only period, which is currently scheduled to begin January 1, 2028.

How Can You Participate?

The public will have opportunities for early involvement in 2027 including listening sessions and an informal feedback period. This public feedback will be considered by Ecology as they develop the next ISGP, which is anticipated to be released as a draft permit for public comment in early 2028. Once the draft permit is issued, a formal public comment will occur. Both formal and informal comment periods offer permittees the opportunity to provide input on potential permit revisions.

With changes on the horizon, permittees should pay close attention to Ecology notifications and prepare for the accelerated renewal timeline. ALL4 can help your facility evaluate how proposed permit changes may impact your operations, develop technical comments for public participation processes, and navigate the existing and future ISGP compliance requirements.

Have questions about how these changes could affect your facility’s stormwater management obligations? Contact Dan Heimbigner (dheimbigner@all4inc.com) or your ALL4 project manager.