St. Catharines Combined Sewer Overflows at Niagara Region Facilities

Data presented here is updated every three months. The data contains records from
March 01, 2025 to February 28, 2026.

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

CSO Location Date of Overflow Volume (ML) Reason for Overflow
Port Weller Plant Dec 28, 2025 42.897 ML Heavy Precipitation
Snow Melt
Port Dalhousie Plant Dec 28, 2025 24.473 ML Heavy Precipitation
Snow Melt
Port Weller Plant Dec 28, 2025 19.900 ML Heavy Precipitation
Snow Melt
Port Weller Plant Oct 30, 2025 2.234 ML Heavy Precipitation
Jordan Valley Sewage Pumping Station Oct 7, 2025 0.098 ML Heavy Precipitation
Port Weller Plant Oct 7, 2025 21.410 ML Heavy Precipitation
Port Dalhousie Plant Oct 7, 2025 21.422 ML Heavy Precipitation
Eastchester Sewage Pumping Station Oct 7, 2025 N/A ML Heavy Precipitation
Port Weller Plant Oct 7, 2025 9.217 ML Heavy Precipitation
Port Weller Plant Jun 30, 2025 1.598 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.

Page Feedback Did you find what you were looking for today?