Washington Department of Ecology (Ecology) issued the 2025 Industrial Stormwater General Permit (ISGP) on December 2, 2024. The current ISGP was issued in November 2019 and is scheduled to expire on December 31, 2024. There are notable changes for the next ISGP which will likely affect most industrial facilities. For more details regarding the new ISGP, fact sheet explaining the basis for the changes, responses to comments on the draft documents, and the small business economic impact analysis, please refer to Ecology’s website here.

In the 2025 ISGP, Ecology has made the following changes:

• Updates to deadlines, timelines, and submittal types for corrective actions, noncompliance notifications, modification of coverage applications, and stormwater pollution prevention plan (SWPPP) certification;
• Clarifications and updates to stormwater systems, activities, and allowances covered by the ISGP;
• Updates to required best management practices (BMPs) and Stormwater Pollution Prevention Plans (SWPPP);
• Additional sampling requirements for sources releasing 6PPD-quinone and per- and polyfluoroalkyl substances (PFAS);
• Clarification and additional requirements for reporting.

Updates to Deadlines, Timelines, and Submittal Types

Ecology retained the proposed change that immediate reporting is not required for numeric effluent limitation exceedance. Immediate reporting is required for any noncompliance that may endanger health or the environment, and any violation of a maximum daily discharge limit, and immediate actions to minimize potential pollution still apply.

All reports, including the Annual Gross Revenue Form due on March 15^th, should be submitted electronically through Ecology’s Water Quality Permitting Portal, unless an eReporting waiver is granted by Ecology.
Note that the proposed requirement for the annual report to include all findings identified by all review or visual means (such as audits by consultants or providers of technical assistance, inspection reports or other notification made by authorities) was removed in the issued 2025 ISGP. Ecology chose to revert it back to current permit language in response to comments from industrial groups. The annual report should focus on findings from monthly inspections and corrective actions taken in the year.

Updates to the ISGP Coverage

Discharges directly to groundwater are covered by the ISGP for sites that are otherwise required to be covered by the ISGP, and sampling is required for the groundwater discharge if it meets one of the following requirements:

• If the site is required to sample for PFAS; or
• If Ecology determines the discharge point to groundwater is functionally equivalent to a point source discharge to surface water.

Ecology reserves the right to determine groundwater sampling requirements on a case-by-case basis. All groundwater discharges should implement treatment/infiltration BMPs consistent with the 2024 Stormwater Management Manual (SWMM). Discharges to groundwater through an Underground Injection Control (UIC) well should comply with UIC regulations and requirements.

For the facilities under the transportation category (NAICS codes 482xxx-485xxx), Ecology requires permit requirements apply to all industrial activities while retaining the existing definition of “Industrial Activity” with a couple of clarifications. Per a 2024 court ruling for Puget Soundkeeper All. v. Pollution Control Hearings Bd., the court interpreted that the “Industrial Activity” definition in current 2020 ISGP should include “the entire footprint of the transportation facility”, instead of only being applicable to the activities called out in Table 1 of the ISGP that trigger permit coverage. Those facilities with existing permit coverage need to ensure that material handling and storage operations are included for BMP implementation and assessment of representative sampling locations.
Ecology removed the automatic approval for facilities applying for Conditional No Exposure (CNE) exemptions. Ecology will review the application and inform the applicant of approval or denial within 90 days of receipt of a complete and accurate CNE form.

Updates to BMPs and SWPPP

All BMPs should be designed, installed, and maintained in accordance with the 2024 SWMM. A summary of changes for the 2024 SWMM compared to the 2019 SWMM is presented in a previous Trinity eNews article. In the 2025 ISGP, dumpsters should be under cover or with a storm-resistant lid, and the cover should prevent litter from blowing out of the dumpster and prevent stormwater generating or releasing leachate. Ecology added both a definition of “dumpster”, which appears to be applicable to most waste receptacles, bins, and containers used at facilities, and a requirement to inspect dumpsters annual for potential leakage points.

Ecology has retained most proposed requirements for changes to the SWPPP for site maps, the Spill Prevention and Emergency Cleanup Plan (SPECP), employee training, and adding of a maintenance log to the SWPPP.

• The site map should identify all stormwater conveyance directions, including underground stormwater conveyance to UIC locations, as well as the groundwater discharge locations.
• Locations of all industrial activities, notably equipment cleaning and vehicle parking/storage, need to be identified on the site map. As mentioned previously, the definition of “industry activity” should compass the entire footprint of the facility.
• A maintenance log is needed to ensure that preventive maintenance required by the SWPPP is completed on time, though the log itself does not need to be kept with the SWPPP and can be provided upon request.
• As part of the SPECP, stormwater conveyance systems cannot be used as part of the secondary containment calculation. Verification of no contamination is required prior to releasing the accumulated water in containment areas, similar to the requirements in 40 CFR 112 for Spill Prevention Controls and Countermeasures (SPCC) Plans. The storm drains receiving runoff from areas where maintenance occurs should be blocked during fueling and vehicle fluid changes. Lastly, Ecology removed the requirement for documenting chemical releases “regardless of size or flowability” and transferred the responsibility for justifying the spills logged and reported back to the facility.
• Employee training should be provided within 90 days of hire, and within 30 days for contractors/vendors and part-time or seasonal employees. Additionally, contractors and vendors who have duties should be trained unless a trained employee is supervising the activity at all times. Training records need to be kept with the SWPPP, including electronic training records that can be updated on an as-needed basis.

Facilities that currently have coverage and an existing SWPPP are required to update the SWPPP per the 2025 ISGP by May 15, 2025, and implement the BMPs by July 1, 2025.

Updates to Sampling

Ecology has given more flexibility on where sampling can occur, considering the safety and logistical issues of sampling wharves and piers at marine cargo handling facilities. A sampling point waiver request may be authorized on a case-by-case via a Modification of Coverage. For facilities that are tenants or share infrastructure with other facilities, Ecology pointed out that the shared regional ponds or stormwater treatment system may be an option for sampling.

6PPD-quinone (6PPDQ) has been added to the benchmark monitoring parameter for transportation activities, petroleum bulk stations and terminals, and warehousing and storage facilities. The sampling requirement will become effective on January 1, 2028. Small businesses subject to 6PPDQ sampling may sample once per year as opposed to quarterly. PFAS monitoring is added for air transportation facilities that use aqueous film-forming foam (AFFF) and waste management and remediation services facilities.

Measuring of pH can no longer be done using a narrow-range pH strip in response to EPA’s comments. It must be done using a calibrated pH meter, and the analysis must be consistent with SM 4500-H+B.

Next Steps

We can assist you with understanding these new requirements and complying with the 2025 ISGP, including assistance with updating your SWPPP and/or site map. Please contact Hui Cheng or call 253.262.5888.