In many older cities, sanitary sewage has been collected along with storm water runoff by a single system known as a Combined Sewer System (CSS). Most of the time, the combined sewer system is able to convey all flows to the wastewater treatment facility. This may not be true during periods of heavy rainfall. In these instances capacity may be exceeded, resulting in combined sewer overflows (CSOs) that may cause basement backups, flooding, and contamination of receiving waters.

GBA has assisted many communities in studying and evaluating their systems and developing strategies to reduce or eliminate CSOs, including separating the two systems. With continued pressure from the EPA to reduce CSOs, GBA will continue to be a leader in CSO management and will provide our clients with cost-effective and sound approaches to eliminating CSOs.