St. Catharines Combined Sewer Overflows at Niagara Region Facilities

Data presented here is updated every three months. The data contains records from
September 01, 2025 to August 31, 2026.

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

CSO Location Date of Overflow Volume (ML) Reason for Overflow
Port Dalhousie Plant Aug 23, 2026 14.653 ML Heavy Precipitation
Port Weller Plant Aug 23, 2026 33.279 ML Heavy Precipitation
Port Weller Plant Aug 22, 2026 12.514 ML Heavy Precipitation
Riverview Sewage Pumping Station Aug 22, 2026 N/A ML Heavy Precipitation
Argyle Sewage Pumping Station Aug 22, 2026 N/A ML Heavy Precipitation
Eastchester Sewage Pumping Station Aug 19, 2026 N/A ML Heavy Precipitation
Jordan Valley Sewage Pumping Station Aug 19, 2026 0.050 ML Heavy Precipitation
Port Weller Plant Aug 19, 2026 12.558 ML Heavy Precipitation
Port Weller Plant Aug 19, 2026 4.528 ML Heavy Precipitation
Port Dalhousie Plant Aug 19, 2026 15.199 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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