Connecticut MS4 Supporting Layers


The 2017 Municipal Separate Storm Sewer System (MS4) General Permit regulation includes several mapping requirements. New and existing statewide data layers are compiled here to assist municipalities and institutions in complying with the permit requirements.

CT DEEP has funded the acquisition of a new statewide impervious layer (based on 2012 imagery) that may be useful in calculating directly connected impervious area and tracking disconnects of impervious cover. UConn CLEAR has used this data to create both an impervious cover by basin and an impervious cover by town layer. The 1 foot resolution data contains three classes (buildings, roads and other impervious).

UConn CLEAR has also created an impaired waters layer that highlights only stormwater related impairments.

View Layers

CT MS4 Viewer

The CT MS4 Viewer includes data layers that are helpful in registering for and complying with the 2017 CT MS4 General Permit.

Get Layers

Map Services

for advanced users
Go to the Map and Image Services page and click on Built Environment.

Download 2012 Impervious Surface by Town

for GIS users
Download 2012 impervious surface by town in vector or raster format.

Download 2012 Simplified Statewide Impervious Surface

for GIS users
The 2012 raster-based impervious surface was converted to vector, simplified and separated into three separate layers: buildings, roads and other impervious.