Welland 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
Welland Plant Jun 25, 2026 17.522 ML Heavy Precipitation
Welland Plant Jun 18, 2026 15.753 ML Heavy Precipitation
Welland Plant Jun 14, 2026 19.369 ML Heavy Precipitation
Welland Plant May 23, 2026 75.067 ML Heavy Precipitation
Welland Plant May 19, 2026 12.920 ML Heavy Precipitation
Welland Plant May 5, 2026 71.145 ML Heavy Precipitation
Welland Plant Apr 25, 2026 44.172 ML Heavy Precipitation
Welland Plant Apr 18, 2026 42.371 ML Heavy Precipitation
Welland Plant Apr 15, 2026 87.754 ML Heavy Precipitation
Welland Plant Apr 5, 2026 16.986 ML Heavy Precipitation
More Locations

Historical Overflow Data for Welland

202520242023
Total Overflows: 19
Total Volume: 407.413 ML 		Total Overflows: 16
Total Volume: 691.935 ML 		Total Overflows: 36
Total Volume: 1034.970 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?