NYSDEC Issues New MS4 General Permit (GP-0-24-001); Electronic Notices of Intent for Coverage Due February 20

The New York State Department of Environmental Conservation’s (NYSDEC’s) new “General Permit for Stormwater Discharges from Municipal Separate Storm Sewer Systems” (GP-0-24-001) sets forth updated requirements for managing stormwater discharges from municipal separate storm sewer systems (MS4s) and promoting community education and involvement on the same. This new General Permit replaces the previous version of the permit (GP-0-15-003) and incorporates changes made in response to stakeholder input on draft versions of the permit that were released for public comment.

Important Deadlines

The new General Permit went into effect on January 3, 2024, bringing with it updates and additions to the conditions that apply to MS4s. The most immediate action item requires MS4 Operators to submit an electronic Notice of Intent (eNOI) by February 20, 2024 indicating they intend to comply with the requirements stated in GP-0-24-001. The eNOIs must be filed through NYSDEC’s nForms portal.

Note that the former annual MS4 reporting deadline of June 1, 2024 under GP-0-15-003 no longer applies. The new permit redefines the MS4 reporting year as January 3 to January 2. The first MS4 annual report under the new permit is due April 1, 2025. Interim MS4 progress certifications must now be submitted every six months, with the first certification due October 1, 2024. These dates apply to MS4 Operators that were covered under the previous permit and will continue operating under GP-0-24-001. All MS4 reports and certifications must be submitted electronically to NYSDEC.

About the General Permit

GP-0-24-001 is structured as ten parts, each covering different aspects related to the MS4 program. These parts include: permit coverage, special conditions, Stormwater Management Programs (SWMPs), recordkeeping, reporting, and minimum control measures (MCMs), among others. The permit expands upon the previous requirements and establishes schedules to submit deliverables, certifications, and reports related to MS4 compliance. It clarifies aspects related to changes in MCMs, corrective actions, and public education and outreach, aligning with MS4 Operator needs and the goal of reducing pollutant discharge to storm sewer systems and surface water outfalls.

The six MCMs remain consistent with those defined in the previous permit. A number of compliance and reporting requirements have been added under GP-0-24-001 to minimize pollutant discharge to the Maximum Extent Practicable (MEP) and to comply with the Clean Water Act. MS4 Operators are required to implement best management practices (BMPs) for each MCM. The MCMs are defined briefly as follows:

• MCM 1: Public Education and Outreach Program – Requires distribution of educational materials about stormwater impacts and pollutant reduction. Clarifications made in final GP-0-24-001 relate to where to conduct educational programs, the target audiences, and educational topics.
• MCM 2: Public Involvement/Participation – Emphasizes public involvement in SWMP development, stressing economic benefits and citizen participation.
• MCM 3: Illicit Discharge Detection and Elimination (IDDE) – Addresses illicit discharge detection and elimination, and incorporates public reporting mechanisms.
• MCM 4: Construction Site Stormwater Runoff Control and MCM 5: Post-Construction Stormwater Management – Require MS4 Operators to establish programs for construction and post-construction pollutant reduction, detailing SWPPP review, construction site control, and post-construction management.
• MCM 6: Pollution Prevention and Good Housekeeping – Highlights pollution prevention and good housekeeping, and refines BMPs for municipal facilities and operations.

The new permit contains expanded MS4 system mapping requirements, with a phased approach to mapping. The permit encourages collaboration to promote more efficient compliance and to enhance water quality protection. GP-0-24-001 does not specify a format for comprehensive system mapping but does require development of a map demonstrating a clear understanding of the MS4.

Since the release of GP-0-24-001 was first announced, Walden has been evaluating the changes to help ensure our clients are in compliance, and we are prepared to help you. If you have questions about the new MS4 Stormwater Management Program, contact us today at 516-588-6859.