Connecticut Department of Energy & Environmental Protection

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

**Registration will open on December 1, 2025**

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

Who Needs to Register?
Registration is required for:
  • Commercial sites with 5 or more acres of contiguous impervious cover.
  • Sites with eligible Standard Industrial Classification or North American Industry Classification System found in Appendix A

Tip: “contiguous” as it is used in this permit, refers to a site that is not separated by a public right-of-way.  Impervious surfaces are considered "contiguous” if they are physically connected or close together, and they are not separated by a public right-of-way – like a public street or road owned by the city or state.

Example Scenarios Requiring Coverage Under the Commercial Stormwater General Permit

The following examples are provided to illustrate when coverage under the Commercial Stormwater General Permit is required. In general, impervious surfaces are considered contiguous if they are located on the same property and are not separated by a public right-of-way. When contiguous impervious surfaces total five acres or more, registration under the General Permit is required.

  • Scenario 1: A site has five separate buildings, each with one acre of impervious surface, and only grassed areas between the buildings. Since all five acres are located on the same property and are not divided by a public right-of-way, the impervious areas are considered contiguous. Registration under the Commercial Stormwater General Permit is required.
  • Scenario 2: A site has five separate buildings connected by a sidewalk, with a combined total of more than five acres of impervious surface. The sidewalk connection further demonstrates that the impervious areas are contiguous, and because there is no public right-of-way separating them, permit registration is required.
  • Scenario 3: A site is 20 acres in size, with five acres of contiguous impervious surface and another 15 acres of impervious surfaces located elsewhere on the same property. Since there is no public right-of-way dividing the site, the entire 20 acres are subject to coverage under the Commercial Stormwater General Permit.

Note: These examples are provided for guidance purposes only and do not replace or supersede the requirements contained in the Commercial Stormwater General Permit or applicable state regulations. Applicants should review the permit in full to ensure compliance.

Registration Timeline and Deadlines

**Registration for the 2025 Commercial Stormwater General Permit will open on December 1, 2025.**

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 

 

Registration Process & How to Apply

Starting December 1, 2025, you can register online. 

Click the link below to access the online application and submit your application in just a few easy steps.

Submit an Application

Submit a Commercial Stormwater Application Transmittal Form (.doc) (.pdf)

Explore the step-by-step Application User Guide provided in the Application Resource section below.

How to Submit your Application

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

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

Step 1 - Prepare

Review the permit, confirm eligibility requirements, and develop your Stormwater Management Plan.

Step 2 - Complete the Application Form

Refer to the Application User Guide for step-by-step instructions and the list of required information needed to complete the form.

Step 3 - Submit the Application Transmittal Form

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

  • After completing the Transmittal Form and required attachments, email it to: DEEP.CentralPermits@ct.gov
  • 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 Application Transmittal Form, upload all required documents to DEEP’s File Transfer Protocol (FTP) site – File Sharing Website - using the instructions provided in your confirmation email.

 

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 Application Transmittal Form.

 

Step 5 - Application Review and Decision

DEEP will begin processing your application upon receipt of all required documents.

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.

Need Assistance with the Online Application

The Stormwater Program 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 this 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. 

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 permits in the first 2 years of the permit term that may lead to delays in processing time - we appreciate your patience.
  • You will receive a 'Notice of Coverage' from the Agency confirming permit coverage.

Resources and Contact Information

Application Resources
Guidance and Templates
Compliance Assistance
Environmental Protection Agency
Contact Information

Stormwater Management

Content last updated December 1, 2025