What are combined sewer overflows (CSOs), and how do they affect the lake?
The City of Syracuse, like many older cities in the country, has a sewer system that collects both stormwater runoff and sanitary wastewater in the same pipes. In dry weather, these pipes carry all the wastewater to the Metropolitan Wastewater Treatment Plant for treatment and disinfection. When heavy rain or snow melt leads to an increase in the amount of stormwater in the system, the volume of the combined flow of wastewater and stormwater can exceed the capacity of some of the sewer lines. Under these conditions, the combined sewer system is designed to discharge into nearby streams rather than backup in homes or in the streets. These releases from the CSOs allow bacteria, floating trash, solids and other contaminants to flow into Onondaga Creek, Harbor Brook, and Ley Creek, and from there into Onondaga Lake.
