CT DEEP's New Industrial Stormwater General Permit Issued October 1st, 2025

The Connecticut Department of Energy and Environmental Protection (CT DEEP) has issued the new National Pollutant Discharge Elimination System (NPDES) General Permit for the Discharge of Stormwater Associated with Industrial Activity (Industrial Stormwater GP), effective as of November 1, 2025.

For existing permittees, who registered under the previous general permit which expired on September 30, 2025, interim permit coverage will be maintained for 180 days following the effective date of the new general permit (CTR050000).

Key Updates

Notable changes to the Industrial Stormwater GP include:
 

• Alignment with the US Environmental Protection Agency’s (USEPA) 2021 Multi‐Sector General Permit (MSGP)
• Updates to sector-specific Effluent Limitation Guidelines (“ELGs”)
• Addition of a new Resiliency Measure section in the SWPPP
• Clarifications to stormwater and non-stormwater discharge authorizations and prohibitions
• Added Control Measures and Best Management Plans
• New “Corrective Actions” framework
• New Annual Report requirement
• Electronic submittal of Discharge Monitoring Reports (NetDMR)
• Online non-compliance reporting
• Facilities will post a sign indicating they have permit coverage

Applicability 

Sector-specific industrial activities are identified by the SIC Codes specified in Appendix A of the general permit.

Important Dates for Existing Permittees & Sites  

CTDEEP’s ezFile Portal will open on November 1, 2025 for Industrial Stormwater Registration e-Filing. 

Electronic registration requesting authorization to discharge under CTR050000, and submittal of the facility’s Stormwater Pollution Prevention Plan (SWPPP) is required by April 1, 2026.

In lieu of registration, a No Exposure Certification (NEC) form may be filed if the facility meets the general permit criteria for no exposure to stormwater.

GZA Can Help 

GZA has considerable experience assisting our industrial Clients with the preparation of stormwater permit registrations and with maintaining compliance with permit requirements.

GZA staff includes environmental compliance professionals, Professional Engineers (PE) and Certified Hazardous Materials Managers (CHMM) who are available to assess eligibility for No Exposure Certification, assist with electronic permit registration, update the facility’s SWPPP to incorporate the required changes, and provide professional certification.

For more information, contact Chris Mayne, CHMM, CSP.

GZA | 95 Glastonbury Boulevard | Glastonbury, CT