St. Catharines Combined Sewer Overflows at Niagara Region Facilities

Data presented here is updated every three months. The data contains records from
January 01, 2024 to December 31, 2024.

Volume is measured in megalitres. (1 megalitre = 1 million litres)

CSO Location Date of Overflow Volume (ML) Reason for Overflow
Port Weller Plant Dec 29, 2024 0.499 ML Heavy Precipitation
Port Weller Plant Dec 10, 2024 0.043 ML Heavy Precipitation
Port Weller Plant Dec 9, 2024 0.006 ML Heavy Precipitation
Port Weller Plant Oct 29, 2024 0.801 ML Heavy Precipitation
Port Dalhousie Plant Sep 9, 2024 2.410 ML Heavy Precipitation
Port Weller Plant Sep 9, 2024 0.666 ML Heavy Precipitation
Port Weller Plant Sep 9, 2024 3.268 ML Heavy Precipitation
Port Dalhousie Plant Aug 31, 2024 0.964 ML Heavy Precipitation
Port Weller Plant Aug 31, 2024 1.544 ML Heavy Precipitation
Port Weller Plant Aug 18, 2024 0.995 ML Heavy Precipitation
More Locations

Historical Overflow Data for St. Catharines

202320222021
Total Overflows: 44
Total Volume: 545.552 ML 		Total Overflows: 34
Total Volume: 761.968 ML 		Total Overflows: 41
Total Volume: 305.509 ML

Overflows contain mostly Storm Water

While the volume of an overflow may seem large, the amount of untreated sewage present in the overflow is small when compared to the amount of stormwater or snow melt.

Niagara typically treats about 80,000 megalitres of sewage each year.  The vast majority of wastewater discharged into the sewer system receives full treatment and only a small percentage of this sewage overflows. These overflows usually only occur during periods of heavy rain or during seasonal snow melts.

Historical Data

If you require more detailed information about a specific combined sewage overflow, you can contact the water & wastewater division.

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