(Montreal) Montérégie ranks first among regions for wastewater spills discharged without treatment into Quebec’s lakes and rivers according to a ranking published by the Rivières Foundation, which highlights that the province experienced 57,263 spills in 2022, beyond the 36,391 spills in 2021, a year where there was exceptionally little precipitation.
Trois-Rivières, Longueuil and Terrebonne stood out, among the 10 large cities in Quebec, for their improvements in the intensity of wastewater spills for the period 2017-2022.
Taking into account all the cities and municipalities, it is Plessisville, Beauharnois and Sainte-Marie which have shown the greatest improvements while Thetford Mines, La Tuque and Lacolle present the greatest deteriorations according to the Fondation Rivières ranking which is based on on data from the Ministry of the Environment (MELCCFP).
The Rivières Foundation has developed a “per capita spill intensity index”, which takes into account “the duration of the spills and the size of the overflowing structure”. The municipalities of Caplan, in Gaspésie, followed by Huntington in Montérégie and Chandler in Gaspésie, occupy the first three positions in terms of the intensity of spills per capita.
Three municipalities in Montérégie are among the top 10 for the intensity of the highest spills.
The Rivières Foundation underlines that “despite a slight improvement, Montérégie is the region which presents the highest intensity of spills since 2017, up to six times greater than Montreal in 2022”.
Even if the intensity tends to increase in the region, particularly in the La Prairie basin, Fondation Rivières underlines the audacity of La Prairie which imposed a moratorium on real estate development in order to reduce the pressure on its network, which constitutes according to the foundation, “an example of sound environmental management”.
Spills most often occur following heavy rains and are intended to prevent sewage treatment plants from overflowing.
Each wastewater treatment plant has a maximum treatment capacity and when there is too much water due to rain, the flow can exceed what the network is capable of taking, which can cause a wastewater spill.
Climate change will increase the risks of wastewater spills due to increased periods of heavy rain.
Sewage spills come with an amount of phosphorus and E. coli which can cause impacts on fauna and flora, and also prevent the population from taking advantage of waterways for swimming.