Connecticut Department of Energy & Environmental Protection

Municipal Stormwater

The General Permit for the Discharge of Stormwater from Small Municipal Separate Storm Sewer Systems (MS4 General Permit) regulates stormwater discharges from storm sewer systems owned and operated by eligible municipalities, institutions, and state and federal facilities.

Stormwater runoff can carry pollutants such as sediment, nutrients, bacteria, trash, and other contaminants into Connecticut's rivers, streams, lakes, and coastal waters. The MS4 General Permit requires permittees to implement a comprehensive stormwater management program designed to reduce pollutants in stormwater runoff and protect water quality. Permit requirements include public education and outreach, illicit discharge detection and elimination, construction and post-construction stormwater management, pollution prevention, and other measures to reduce the impacts of stormwater runoff on Connecticut's surface and groundwater resources.

Permittees must develop and maintain a Stormwater Management Plan (SWMP) describing how they will meet permit requirements.

They must also implement control measures, track progress, and submit annual reports documenting program performance and effectiveness.

What the Program Does

The Municipal Stormwater Program helps reduce pollution carried by stormwater runoff and protects Connecticut's rivers, streams, lakes, wetlands, coastal waters, and groundwater resources.

The program focuses on identifying and addressing sources of stormwater pollution, improving stormwater infrastructure, and promoting responsible land use and maintenance practices. Key program activities include:

  • educating residents, businesses, and municipal staff about stormwater pollution prevention.
  • detecting and eliminating illicit discharges to storm sewer systems.
  • managing stormwater impacts from construction and development activities.
  • maintaining and improving stormwater management infrastructure.
  • implementing pollution prevention and good housekeeping practices for municipal operations.
  • monitoring program effectiveness and adapting management practices as needed.
Our Goals

The program is designed to improve water quality and reduce pollution by:

  • reducing contaminants in stormwater runoff.
  • protecting rivers, lakes, wetlands, coastal waters, and groundwater.
  • preventing illicit discharges to storm sewer systems.
  • reducing impacts from development and construction.
  • supporting effective stormwater management practices.
  • increasing public awareness and engagement.
  • ensuring consistent permit compliance and reporting.
  • promoting long-term, sustainable stormwater solutions.

Quick Links

Permit Renewal Status MS4 2026 General Permit

Water Quality in Your Community

Application Resources - Coming Soon!

Compliance Assistance - Coming Soon!

Additional Resources

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Status of MS4 Permit Renewal

The Connecticut Department of Energy and Environmental Protection (DEEP) is currently delaying reissuance of the General Permit for the Discharge of Stormwater from Small Municipal Separate Storm Sewer Systems (MS4 General Permit). The permit was publicly noticed for reissuance in March 2025.

To ensure uninterrupted coverage, the existing MS4 General Permit will be administratively extended effective October 1, 2025, while DEEP completes review of public comments and finalizes the reissued permit. All current permittees will remain covered under the existing permit during this extension period. No action is required by permittees at this time.

2025 Public Notice and Draft Documents

On March 25, 2025, DEEP issued a Notice of Tentative Determination indicating its intent to reissue the MS4 General Permit with proposed updates, and outlining the process for submitting public comments.

The following documents are associated with the 2025 reissuance process:

2023 MS4 General Permit (Current Effective Permit)
List of 2023 MS4 Permittees

The following lists provide access to currently active MS4 permit registrations. Select a category below to view detailed information:

Water Quality in Your Community: Fact Sheets by Town

Explore water quality information for your town or city in Connecticut. The resources below provide data and maps showing local water conditions, stormwater impacts, and compliance with water quality standards.

  • View Water Quality Factsheets by Town (Coming Soon!)

Each fact sheet may include:

  • impervious cover displayed as a percentage of total municipal area, shown in a pie chart format.
  • links to applicable Total Maximum Daily Load (TMDL) plans and related information.
  • annual stormwater monitoring data for key pollutants, including bacteria, total suspended solids, total nitrogen, total phosphorus, and turbidity.
  • maps showing areas of high and low impervious cover within each municipality.
  • water quality status maps indicating whether waterbodies meet standards for aquatic life and recreational use.
  • for coastal municipalities, maps indicating whether coastal waters meet shell fishing water quality standards.

Fact Sheets for 2004 Municipal Permittees:

Fact Sheets for 2017 Municipal Permittees (Brooklyn, Haddam, Killingly, Mansfield, New Hartford, Plainfield, Sprague, Willington) 

Fact Sheets for Non-Regulated Municipalities:

Additional Resources

Mapping Resources
UCONN CLEAR

Environmental Protection Agency

Contact Us

Have a question or need help with a permit?

Email us at DEEP.StormwaterStaff@ct.gov

 

Stormwater Management

Content Last Updated August 18, 2026