Planning for Sewer Separation in Boston, MA

Partial or complete separation of combined sewers is one of the strategies that can be employed to control or eliminate combined sewer overflow (CSO) discharges. Separation of combined sewers can be expensive and disruptive to communities since it involves digging up streets and in many cases disconnecting roof leaders or downspouts from private buildings. In addition, experience has shown that it is very difficult to remove 100 percent of the rainfall-induced inflow in a sewer. As storm drainage is removed from the combined sewers, the combined sewers become sanitary sewers carrying a small amount of residual inflow. The residual inflow may originate from a variety of sources such as leaky manholes, leaks in pipes, building sump pumps, or roof drainage from old buildings that are uneconomical to disconnect.