CTDEEP Industrial Stormwater General Permit Reissuance

The Connecticut Department of Energy and Environmental Protection (DEEP) reissued the industrial stormwater general permit (IGP) on October 1, 2025 with an effective date of November 1, 2025. The previous DEEP National Pollutant Discharge Elimination System (NPDES) General Permit for the Discharge of Stormwater Associated with Industrial Activities, also known as the IGP, expired on September 30, 2024 and coverage has been administratively continued. The IGP re-issuance has been in progress for over a year, with multiple draft iterations and public comment periods. A public hearing was held in May 2025 where a majority of public concerns surrounding bulk de-icing storage were heard. DEEP has responded to these comments and others in an October 2025 update with the final IGP re-issuance.

Existing permittees are covered under interim permit coverage during the transition to the newly issued IGP provided that a complete and timely application for coverage under the reissued permit is submitted by the deadline of April 1, 2026. Registration will open on November 1, 2025 and registration will require a fee, an electronic copy of the facility’s updated Stormwater Pollution Prevention Plan (SWPPP), and completed online registration form. The proposed IGP contains more substantive changes than the previous re-issuances in 2016 and 2021, including updated effluent limit guidelines, new SWPPP requirements, and annual reports due in April for the previous calendar year.

ALL4 published a blog on August 1, 2024 discussing the modifications from the previous permit compared to the draft permit. Facilities seeking coverage under the new IGP will need to update their SWPPP in accordance with the new requirements including the “Resiliency Measure” element similar to the U.S. Environmental Protection Agency (U.S. EPA) multisector general permit issued in 2021. The facility must consider various stormwater control measures (SCM) defined in the permit. The permit “does not require nor prescribe specific SCMs to be implemented; however, the permittee must document in their SWPPP the considerations made to select and design control measures at their facility to minimize pollutants discharged via stormwater.” These SCMs include structural improvements, enhanced/resilient pollution prevention measures, and other mitigation measures to minimize impacts of stormwater discharge from major storm events such as hurricanes, storm surge, extreme precipitation, and flood events. The template SWPPP provided on DEEP’s website provides a tabular format for presenting this information in the SWPPP.

The IGP lists additional SCMs that may be considered, but are not limited to the following:

• Reinforce materials storage structures to withstand flooding and additional exertion of force.
• Prevent floating of semi-stationary structures by elevating to the Base Flood Elevation (BFE) level of securing with non-corrosive device.
• When a delivery of exposed materials is expected, and a storm is anticipated within 72 hours (three days), delay delivery until after the storm or store materials as appropriate (refer to emergency procedures).
• Temporarily store materials and waste above the BFE level.
• Temporarily reduce or eliminate outdoor storage.
• Temporarily relocate any mobile vehicles and equipment to higher ground.
• Develop scenario-based emergency procedures for major storms that are complementary to regular stormwater pollution prevention planning and identify emergency contacts for staff and contractors.
• Conduct staff training for implementing the permittee’s emergency procedures at regular intervals.

ALL4 recommends that permittees allow sufficient time to consider these “Resiliency Measures” and other site-specific measures while making the required SWPPP updates.

If you have any questions regarding the scheduled IGP reissuance in October 2025 or what your next steps should be to prepare your facility (and SWPPP) for the issuance of the IGP, please reach out to Shane Galloway, at sgalloway@all4inc.com or 215-372-0865.