Overflows

Under the regulation on municipal wastewater treatment works (ROMAEU) of the Ministry of the Environment, the Fight against Climate Change, Wildlife and Parks (Ministry), an operator of a municipal wastewater treatment works (OMAEU) must list all the overflows that occur at his structure and report on the basis of a measurement the daily cumulative duration. As such, the City of Montreal sends the overflow conditions for all of these overflow structures in the form of a monthly report to the Ministry's monitoring system for municipal wastewater treatment structures (SOMAEU) via the Internet. The present data made available correspond to the information compiled and transmitted to the Department. It is a compilation of overflow times on a daily basis.

**Notice to users: ** The “2024 Overflows” data was corrected on March 31, 2026 following a processing error that affected the duration of the overflows. Releases downloaded prior to this date contain this error.