Combined Sewer Overflow (CSO) Events

A Combined Sewer Overflow (CSO) happens when a sewer system that carries both rainwater and wastewater becomes overloaded during heavy rain or snowmelt. To prevent flooding, the system releases the excess water—mixed with untreated sewage—into nearby rivers, lakes, or streams. This is a safety measure, but it can temporarily affect water quality.

There are 5 CSO outlet locations within City of Cornwall limits. The locations are identified in the map application below along with their respective CSO statuses.