St. Catharines Combined Sewer Overflows at Niagara Region Facilities

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

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

CSO Location Date of Overflow Volume (ML) Reason for Overflow
Port Dalhousie Plant Jun 26, 2026 1.198 ML Heavy Precipitation
Argyle Sewage Pumping Station Jun 25, 2026 0.062 ML Heavy Precipitation
Eastchester Sewage Pumping Station Jun 25, 2026 0.030 ML Heavy Precipitation
Port Dalhousie Plant Jun 25, 2026 0.278 ML Heavy Precipitation
Port Weller Plant Jun 25, 2026 4.936 ML Heavy Precipitation
Port Weller Plant Jun 22, 2026 0.568 ML Heavy Precipitation
Port Dalhousie Plant Jun 14, 2026 16.853 ML Heavy Precipitation
Port Weller Plant Jun 14, 2026 23.461 ML Heavy Precipitation
Port Weller Plant Jun 14, 2026 8.525 ML Heavy Precipitation
Jordan Valley Sewage Pumping Station May 23, 2026 0.107 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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