St. Catharines Combined Sewer Overflows at Niagara Region Facilities

Data presented here is updated every three months. The data contains records from
May 01, 2025 to April 30, 2026.

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

CSO Location Date of Overflow Volume (ML) Reason for Overflow
Port Weller Plant Apr 18, 2026 0.765 ML Heavy Precipitation
Port Dalhousie Plant Apr 15, 2026 0.732 ML Heavy Precipitation
Port Weller Plant Apr 15, 2026 3.564 ML Heavy Precipitation
Port Weller Plant Apr 15, 2026 4.107 ML Heavy Precipitation
Port Weller Plant Apr 15, 2026 0.061 ML Heavy Precipitation
Jordan Valley Sewage Pumping Station Mar 31, 2026 0.025 ML Heavy Precipitation
Port Dalhousie Plant Mar 31, 2026 14.263 ML Heavy Precipitation
Port Weller Plant Mar 31, 2026 34.841 ML Heavy Precipitation
Eastchester Sewage Pumping Station Mar 31, 2026 N/A ML Heavy Precipitation
Port Weller Plant Mar 31, 2026 17.373 ML Heavy Precipitation
More Locations

Historical Overflow Data for St. Catharines

202520242023
Total Overflows: 34
Total Volume: 538.340 ML 		Total Overflows: 49
Total Volume: 540.101 ML 		Total Overflows: 44
Total Volume: 545.552 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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