Stormwater Management / MS4

Public Notice - MS4 Annual Report for 2023

CLICK HERE to read the public notice. 

Stormwater Basics

What is Stormwater?

Stormwater runoff is water from precipitation that does not soak into the ground but rather flows over rooftops, paved areas, bare soil, and sloped lawns and flows through natural or man-made conveyance systems without treatment. Natural conveyance systems are rivers, streams, brooks, wetlands, etc. Man-made conveyance systems are bridges, culverts, pipes, catch basins, etc. 

Why are Stormwater Drainage Systems Important?

Stormwater infrastructure is critical in protecting roads and the environment by helping to move rainwater (or snow) to the Long Island Sound. An adequately sized drainage network is critical for a stormwater drainage system to function properly. 

Why is Our Work Important? 

With more frequent high-intensity storms, drainage systems will be even more critical in the future to alleviate flood risk. The Town's drainage system requires periodic rehabilitation, repair, and maintenance to continue functioning efficiently and mitigating pollution. 

What are Common Stormwater Pollutants?

  • Soil, sand, and sediments.
  • Chemicals (pesticides, fertilizer, weed & bug killers, vehicle fluids, coal tar pavement sealers, etc.).
  • Pet/animal waste.
  • Salt.
  • Debris, like cigarette butts, household trash, and other forms of litter. 

MS4 General Permit Basics

What is an MS4?

The Town of Greenwich owns and maintains a Municipal Separate Storm Sewer System (MS4) that functions as a collection network, which helps move rainwater and melted snow through the watershed area to the Long Island Sound. The network includes infrastructure like catch basins, pipes, and ditches. In the Town, stormwater does not mix with sewage (the water from our toilets and sinks). MS4's purpose is to prevent flooding and keep our water clean.

Human activities have impacted the environment by the creation of impervious surfaces and the dispersal of residual pollutants. These changes have impacted surface waterbodies such as lakes, rivers, and streams, through increased pollutant loads and changes to natural hydrologic patterns.  Nationwide EPA studies have identified runoff directly related to stormwater as a major contributor to water quality degradation.    

What is the MS4 Permit?

The objective of the Stormwater Management Plan (SWMP) is to develop stormwater pollution mitigation for the Town of Greenwich based on the guidelines established under the MS4 stormwater management program, the U.S. Environmental Protection Agency’s (EPA) National Pollutant Discharge Elimination System (NPDES) Stormwater Phase II Rule. This MS4 program was created to improve the nation’s waterways by reducing pollutant discharges to surface water bodies from stormwater.

The Connecticut Department of Energy & Environmental Protection (CTDEEP) locally regulates the enforcement of the U.S. Environmental Protection Agency (EPA) program through its General Permit for the Discharge of Stormwater from Small MS4s (permit). The Town Greenwich Department of Public Works has received a Small MS4s Permit from CTDEEP.  

Annual MS4 Reports

Required under the CTDEEP MS4 Permit, the Town of Greenwich is required to publish the report annually, which includes the progress towards the goals that are set in the Stormwater Management Plan. Included in this annual report are the status and goals for the following Minimum Control Measures:

  • Minimum Control Measure No. 1 – Public Education and Outreach
  • Minimum Control Measure No. 2 – Public Involvement/Participation
  • Minimum Control Measure No. 3 – Illicit Discharge Detection and Elimination
  • Minimum Control Measure No. 4 – Construction Site Runoff Control
  • Minimum Control Measure No. 5 – Post-construction Stormwater Management
  • Minimum Control Measure No. 6 – Pollution Prevention/Good Housekeeping