Some older areas of Toronto have combined sewers, where one pipe carries both sewage and stormwater to wastewater treatment plants.
Combined sewers can reach capacity during heavy rain or snowmelt, which can lead to a combined sewer overflow. When this happens, the excess untreated sewage and stormwater are released into rivers, streams or Lake Ontario. This helps prevent flooding and damage to properties, public spaces and wastewater treatment plants.
While combined sewer overflows help prevent flooding, they contain more harmful bacteria, pathogens and other pollutants than normal stormwater. This reduces water quality in our local waterways.
The City has a long-term, multi-billion-dollar infrastructure plan to reduce combined sewer overflows by capturing and treating the excess flow. This will help:
Learn more about what the City is doing to reduce combined sewer overflows.