Connecticut DEEP Reissues Stormwater and Pretreatment General Permits

The Connecticut Department of Energy and Environmental Protection (DEEP) has been busy reissuing its suite of general permits (GPs) for wastewater and stormwater discharges. In October, DEEP reissued the Commercial Stormwater General Permit, Industrial Stormwater General Permit, and Pretreatment General Permits for Significant Industrial Users and Non-Significant Industrial Users. Below are highlights of significant changes to each reissued GP, as well as important compliance deadlines and considerations for regulated entities.

1. The Commercial Stormwater General Permit (CSGP) covers commercial sites with 5 or more acres of contiguous impervious surface, including shopping centers, business parks, schools, retail complexes, car dealerships, and financial and health services with large campuses. The reissued CSGP includes the following notable changes:

• Expanded Industry Coverage: The new CSGP uses an updated definition of “Commercial Activities” referencing Standard Industrial Classification (SIC) and North American Industry Classification System (NAICS) codes and capturing a broader range of commercial activities than the previous permit. Businesses should review Appendix A of the CSGP to determine if their SIC/NAICS code is listed.
• New Registration Requirements: Online registration through a yet-to-be-announced platform; $625 fee.
• Stormwater Management Plan: Required for all registrants, with expanded control measures and annual analytical plus quarterly visual monitoring.
• Other Updates: Updated control measure requirements including new measures on deicing practices, spill prevention and cleanup, and lawn and garden center Best Management Practices. New quarterly visual monitoring and annual analytical monitoring of 19 parameters to better assess water quality impacts.
• Deadlines: Registration opens December 1, 2025. Existing permittees must register by April 1, 2026. Existing sites without permit coverage (not previously registered) must register by December 1, 2026. New sites must apply at least 60 days before beginning discharge.
• Potential Compliance Traps: Many facilities not previously regulated (e.g., large retail, educational campuses) may now be required to register. Failure to review the new SIC/NAICS applicability could result in unintentional noncompliance.

2. The Industrial Stormwater General Permit(IGP) covers industrial facilities, as defined by SIC/NAICS codes in Appendix A to the IGP, that discharge stormwater to waters of the state. Industrial facilities should check their SIC/NAICS code against Appendix A to the IGP. The reissued IGP includes the following notable changes:

• Alignment with EPA’s 2021 MSGP: Incorporates new “Resilience Measure” requirements in the Stormwater Pollution Prevention Plan (SWPPP) tracking the federal government’s Multi Sector General Permit.
• Corrective Actions Framework: New requirements for documenting and implementing corrective actions.
• Annual Reports: Now required each April for the prior calendar year.
• Electronic Reporting: Discharge Monitoring Reports (DMRs) must be submitted via NetDMR; online noncompliance reporting is now mandatory.
• Registration Fees: $1,250 for larger companies; $625 for smaller companies, federal, state and municipal-operated industrial activities
• Signage: Facilities must post a sign indicating permit coverage.
• Deadlines: Registration opens November 1, 2025. Existing permittees must register by April 1, 2026. New sites must register at least 90 days before discharge.
• Potential Compliance Traps: If stormwater contacts industrial materials, activities, or operations, it is likely that the facility needs coverage. If all industrial facilities are fully sheltered and qualify under related DEEP rules, such facilities may qualify for a No Exposure Certification. In addition, the expanded monitoring, reporting, and corrective action requirements are more rigorous. Facilities must update SWPPPs and ensure timely electronic submissions to avoid enforcement.

3. DEEP also reissued two Pretreatment General Permits for Significant Industrial Users (SIU GP) and Non-Significant Industrial Users (Non-SIU GP). The SIU GP covers indirect discharges from significant industrial users (SIUs), including metal finishing, process, and non-process wastewaters, as well as dewatering and remediation wastewaters to sanitary sewers. The Non-SIU GP covers non-significant industrial users (Non-SIUs) not subject to federal categorical standards. DEEP issued a Pretreatment Permit Decision Chart to aid entities in determining which pretreatment permit may be applicable. The reissued Pretreatment GPs include the following notable changes:

• Updated Definitions: Flow thresholds now based on average monthly flow (≥25,000 gpd of all process wastewater for SIUs).
• Expanded Coverage: Dewatering and remediation discharges to Publicly Owned Treatment Works (POTWs) are now included in the SIU GP.
• Application Fees: For SIU GP, between $1,000 and $6,250 depending on the discharge type. For the Non-SIU GP, there is no DEEP fee but the POTWs reserve the right to collect fees associated with initial submission of a Notification Form.
• Effluent Limits: New limits for mercury, PFAS, pH, temperature, and PCBs. Facilities may need to invest in new treatment or monitoring technologies to meet these limits.
• Streamlined Process: Certification of No Change is a registration option for existing permittees; Non-SIU GP registration is notification-only.
• Deadlines: Registration opens December 1, 2025. Existing SIUs and Non-SIUs must register by March 1, 2026. New SIUs must register at least 180 days prior to discharge. New Non-SIUs must submit a Notification Form at least 60 days prior to discharge.
• Potential Compliance Trap: The removal of Qualified Professional Engineer (QPE) and Natural Diversity Data Base (NDDB) certification requirements is intended to streamline the process, but new effluent limits (especially for PFAS and mercury) may require operational changes.

Important Considerations and Practical Tips

The reissued GPs bring significant changes and expanded coverage to stormwater and pretreatment permit requirements. Regulated entities should carefully review the reissued GPs to determine if their activities are subject to permitting registration and compliance requirements, including electronic registration, updated reporting requirements, application fees, and expanded monitoring, BMPs, and corrective action requirements. Facilities should review and update their plans (e.g., SWPPP, SMP, SPCP) and train staff accordingly. Existing permittees must pay close attention to registration deadlines to maintain interim coverage.

DEEP has also made it abundantly clear that, in an effort to increase permit processing timelines, incomplete applications will be rejected and a new application, with a new fee, will need to be submitted. DEEP has shared that the most common reasons for incomplete applications in the past were missing or improperly signed Registrant Certification and missing or incomplete sampling data.

Robinson+Cole’s Environmental group will continue to monitor developments and provide updates concerning DEEP’s general permit and other discharge permitting requirements for stormwater and wastewaters.