Frequently Asked Questions

MS4 Program Basics

Stormwater runoff is a major source of flooding, erosion and the pollution of Connecticut’s waterways, and is certain to become even more of a problem as climate change progresses. Accordingly, the Connecticut Department of Energy and Environmental Protection (CT DEEP) has recently revised and expanded the principal permit used to regulate stormwater in the state: the “General Permit for the Discharge of Stormwater from Small Municipal Separate Storm Sewer Systems,” or MS4.
121 of Connecticut's 169 towns are included in the MS4 General Stormwater Permit. Click here for a map of the towns. Each of these towns have or are part of an "urbanized area," which is a designation of the U.S. Census that takes into account population, population density, impervious cover, proximity to urban areas, and other factors.

State and federal institutions that operate their own stormwater system are now also included in the MS4 permit. This includes university campuses, like UConn, state prisons, military bases, hospitals, public housing authorities, office complexes, etc. that have more than one building and an average daily population of 1,000 or more people.
There is no specific/dedicated funding available to help with costs of complying with the new MS4 permit. It is a good idea to check with your regional Council of Government (COG) to see if they are coordinating any efforts to pool resources. In other states communities have formed collaboratives to share the responsibilities and costs of equipment, monitoring, public education, etc. One example is the Central Massachusetts Stormwater Coalition.
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They will be. DEEP is negotiating a special permit that is based on the MS4 permit and will cover the Department of Transportation.
The MS4 permit generally applies town (or institution) wide but certain requirements focus on what are deemed "priority areas". These are areas in the Urbanized Area and in catchments with >11% DCIA or catchments that discharge to impaired waters.
“Surface Water” means the waters of Long Island Sound, its harbors, embayments, tidal wetlands and creeks; rivers and streams, brooks, waterways, lakes, ponds, marshes, swamps, bogs, federal jurisdictional wetlands, and other natural or artificial, public or private, vernal or intermittent bodies of water. Surface water does not include ground water.

Annual Reports and the Stormwater Management Plan

Each MS4 Town and institution must post their Stormwater Management Plan for public comment by April 1, 2017 (No joke!) and share a link or electronic copy along with a registration form to DEEP by April 3, 2017. The public must be allowed to comment for 60 days.
And Annual Reports are due to DEEP every year. The first Annual Report is due to DEEP by April 1, 2018 after being made available for public comment for 45 days.
Yes! NEMO modified a template developed by the Western Connecticut Council of Governments (WestCOG) for statewide use. It can be found here. NOTE: CT DEEP has not officially sanctioned this template, but it is based on the permit language and DEEP's MCM checklist.
And NEMO created two Annual Report templates: One for New MS4 permittees and one for Existing MS4 permittees. They are available for download under the Implementation section > Annual Reports.
There are many consultants in the area with experience in developing and implementing SWM Plans. NEMO does not have a recommended list. However some of the Councils of Government (COGs) have developed lists.
Public comments on your Stormwater Management Plan or your Annual Report should be sent to the DEEP Commisisoner.
By Email:

US Mail:
Water Permitting and Enforcement Division
79 Elm Street
Hartford CT 06106
Attn: Karen Allen


DCIA means directly connected impervious area. It is a stormwater geek's term for hard surfaces that contribute stormwater runoff to the storm sewer system. It is also sometimes referred to as effective impervious cover. Towns must determine what their baseline DCIA is in acres. Any basins with DCIA > 11% that overlap the Urbanized Area are considered "priority areas" for purposes of the permit.
UConn CLEAR worked with DEEP to identify a few methods to determine DCIA. The Mapping section has the details.
An impervious area is considered disconnected when the minimum amount of the "Water Quality Volume" has been retained in the area. This means for sites with DCIA < 40% - retain the volume of runoff generated by the first 1 inch of rainfall. For sites with > 40% DCIA – retain the volume of runoff generated by the first ½ inch of rainfall.
You can retain stormwater on site in many ways as long as it infiltrates the ground or is reused without a surface or storm sewer discharge. In most cases, disconnection will be achieved through the installations, retrofits or redevelopment projects that incorporate Low Impact Development (LID) practices like rain gardens, bioretention, pervious pavements, green roofs, etc. It can also be accomplished by simply directing runoff to a vegetated area such as a lawn rather than into the stormwater system.

Water Quality Monitoring

Every two years, CT DEEP submits an Integrated Water Quality Report (IWQR) to the U.S. EPA listing all known impairments to the state's waterbodies.
NEMO developed a CT MS4 Map which shows the impaired waters data from the IWQR (the map currently shows data from the 2014 report - we'll be updating it soon with data from the new 2016 report). Now you can see Connecticut's impaired waters on a map and easily determine a particular waterbody's impairment just by clicking on it. The map only shows the impairments related to stormwater since those are the only one's you need to be concerned with under the MS4 permit.

Additional resources:
This handy-dandy decision tree should help you figure out which outfalls have to be screened and for what. For more information, visit the monitoring section of the website.
DNA testing is available to determine sources of fecal bacteria here. The case studies are older but the technology is widely used today.