Connecticut Department of Energy & Environmental Protection

Commercial Stormwater

Commercial Stormwater

The NPDES General Permit for the Discharge of Stormwater Associated with Commercial Activity regulates the discharge of stormwater from commercial sites with 5 or more acres of contiguous impervious surface, such as malls, movie theaters, and supermarkets, to surface waters of Connecticut. The Commercial Permit was created to provide consistent regulatory coverage for a wide range of sites.  Its primary goal is pollution prevention ensuring that pollutants are controlled at the source before they can reach waterways. Rather than focusing on costly cleanup after pollution occurs, the permit emphasizes proactive solutions. Facilities must implement Best Management Practices and Stormwater Control Measures designed to reduce or eliminate potential sources of contamination.  This preventative approach is both more effective and more economical in protecting water quality.

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Commercial Stormwater General Permit Documents

The 2025 Commercial Stormwater General Permit was issued October 1, 2025 

The permit includes smart navigation - integrated smart links for fast and seamless navigation. One-click access to key sections.

Who Needs to Apply?

Application is required for any site in Connecticut that has:
  • 5 or more acres of contiguous impervious cover; AND
  • A primary activity matching one of the eligible Standard Industrial Classification or North American Industry Classification System codes found in Appendix A of the permit; AND
  • A stormwater discharge that is not covered under another permit.

For help determining if a site is eligible for coverage, check the Additional Resources section of this page.

Registration Timeline and Deadlines 

Registration Deadlines for Existing Permittees & Sites:
  • Existing Permittees: Sites covered under the previous permit are required to register by April 1, 2026 (120 days of the effective date). Interim permit coverage is provided by the Agency.
  • Existing Sites without Permit: Sites not covered under the previous permit are required to register by December 1, 2026 (1 year of effective date)

 

Existing Permittees Withnin 120 days Submit by April 1, 2026, New Permittees within 1 year, submit by December 1, 2026, New construction, 60 days before Commercial Activity, Transferred permits, revoke old permit 30 days prior; apply for new permit within 30 days 

 

Application Process & How to Apply

Starting December 1, 2025, you can apply online. 
How to Submit your Application

The application process is a 5-step time-sensitive process

 Step 1, Review Requirements, Step 2, Prepare Documents, Step 3, Transmittal Form, Step 4, Submit Documents, Step 5, Decision

 

STEP 1 - Review Requirements

Review the permit requirements and confirm site eligibility

STEP 2 - Prepare Application Documents

Prepare the following documents:

Refer to the Application User Guide for step-by-step instructions and the list of required information needed for each of these documents. These documents will be submitted in Step 4

STEP 3 - Complete and Submit the Transmittal Form

The Transmittal Form allows DEEP to track fee payments and match them to the correct application.

  • Complete the Transmittal Form (Word) (PDF)
  • Submit the completed Transmittal Form to DEEP.CentralPermits@ct.gov
  • Follow the directions received from DEEP Central Permits to pay the application fee.

Important: Keep a copy for your records. You will receive a confirmation email with instructions for submitting payment and accessing the file transfer site. Once the Application Transmittal Form is submitted, the remainder of the process is time-sensitive.

STEP 4 - Upload Required Documents

Within 10 business days of submitting the Transmittal Form, upload all documents prepared in Steps 2 & 3 to DEEP’s File Transfer Protocol (FTP) site using the instructions provided in your confirmation email from DEEP Central Permits.

Critical Deadline:  Applications will be closed and rejected if required documents are not received within 10 business days. Submit documents as soon as possible after submitting the Transmittal Form.

STEP 5 - Review and Decision

DEEP will begin processing your application upon receipt of payment and all required documents. Once DEEP has made a decision, you will receive an email with either an approval or a rejection. DEEP may reach out to provided contacts during this time for clarifications.

A high volume of applications is expected near submission deadlines, which may result in processing delays. To help avoid delays, submit your application well in advance of posted deadlines.

What to Expect
  • It will take approximately 90 to 180 days to process the application
  • Incomplete applications will result in processing delays or rejections
  • DEEP expects a high volume of permit applications in the first 2 years of the permit term that may lead to delays in processing times - we appreciate your patience
  • You will receive a 'Notice of Coverage' from DEEP confirming permit coverage

Need Assistance with the Online Application?

The Stormwater Team can assist with questions related to the information required by the permit. The team does not provide IT support and cannot assist with account, login, or system-related issues.

For questions related to the application and application process:

Refer to the Application User Guide for guidance on each of the application materials and all of the questions asked within. If you still have questions, contact the DEEP Commercial Stormwater team.

For questions related to the Commercial Stormwater General Permit:

DEEP Stormwater team DEEP.StormwaterCommercial@ct.gov

For technical issues with the online application system:

DEEP IT Support Team Deep.helpdesk.footprints@ct.gov

 

Due to anticipated high volume of inquiries, responses may take up to 2-3 business days. Your patience is appreciated. 

Additional Resources

Guidance and Templates
Compliance Assistance
NetDMR Resources
Mapping Resources
Environmental Protection Agency Resources
Contact Information

Stormwater Management Homepage

Content last updated March 12, 2026