On December 1, 2025, the revised and reissued Connecticut Department of Energy and Environmental Protection (“DEEP”) General Permit for the Discharge of Stormwater Associated with Commercial Activities (“CSGP”) became effective.
The revised and reissued CSGP still applies to owners or operators of certain sites containing five or more acres of contiguous impervious surface. However, DEEP significantly expanded the types of land uses subject to the permit requirements and as a result, thousands of sites not previously subject to the CSGP will now have to prepare a site-specific Stormwater Management Plan (“SMP”) and comply with the other permit requirements.
Who is now covered?
Notably, the list of newly impacted land uses includes schools, hospitals and banks. The scope of CSGP was also expanded to include certain landlords and property managers, and the permit now contains specific language allocating responsibility to a property owner when a site is occupied by multiple tenants.
The prior CSGP covered only SIC codes 50-59 and 70-79, which includes e.g., shopping centers, groceries, dealerships, restaurants, hotels, amusement parks and other miscellaneous retail services.
The revised CSGP expands the list of SIC codes, and adds NAICS codes (see Appendix A beginning on page 47) to now capture:
- Health care facilities
- Educational services (public and private)
- Professional services (e.g., legal, engineering, accounting, social)
- Financial institutions (e.g., banks, insurance, brokers)
- Museums, art galleries, gardens and zoos
- Landscaping and horticultural services
- Real Estate and Rental and Leasing (e.g. “operators” of non-residential buildings)
Registration Timing and Fees
Registration under the revised CSGP opened on December 1, 2025 via DEEP’s online system with a filing fee of $625 (half for municipalities).
- Existing sites without coverage — i.e., those now captured by the expanded scope — must register by December 1, 2026.
- Existing permittees must register by April 1, 2026.
Core Compliance Requirements
Although the compliance deadlines may seem far off, particularly for first time registrants, all permittees should be mindful that completing the tasks necessary to prepare a registration are site-specific and can be time-consuming.
Most important is the development and implementation of a site-specific SMP that must include best management practices to control potential contamination of stormwater runoff, e.g., sweeping impervious surfaces at least four times per year, cleaning out stormwater catch basins, maintaining spill prevention and response procedures and employee training.
Each permittee must also prepare a site plan identifying impervious surfaces, outfalls and drainage systems and complete annual sampling and quarterly monitoring and reporting. Information about the additional CSGP requirements can be found in the Fact Sheet and FAQs, both available on DEEP’s website.
Next Steps
If your site is covered by the expanded list of SIC and NAIC codes, we recommend coordinating early with experienced legal counsel and technical consultants to ensure you understand your obligations, how to manage risks proactively and effectively, complete the necessary CSGP registration and comply with its requirements. In contrast, if you conclude your site is not subject to the CSGP (e.g., less than five acres of contiguous impervious surface), it will be important to document and retain the determination of non-applicability in your files.
