Many urban areas, including Hartford, utilize a "combined sewer system" in which one pipe in the street carries both sewage and stormwater. When rain events occur, the pipes can't handle the excess stormwater in the sewer that was disigned for a population much smaller than today.

In a typical sewer separation project, a second pipe is added in the street where the new pipe will serve as a sanitary sewer for household waste, and the existing combined sewer will remain in place as a dedicated storm pipe.  Once construction of the sewer separation project in the street is complete, a new second pipe, or lateral, must be connected to each and every home and business.