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Water quality of the L'Assomption River: Swimming is possible in summer!

Plage L'Assomption Léo Jacques - Fondation Rivières


Montreal, March 15, 2021 – The Fondation Rivières and the City of L’Assomption make public the results of the continuous monitoring of water quality in the L’Assomption River at the water intake of the Jean-Perreault Treatment Center and at the relaxation area of Léo-Jacques Park in L'Assomption. This pilot project reveals surprising information which now allows us to make these three main observations:

  • the water is generally adequate for swimming in the summer months;
  • from September, there is persistent pollution and intensive municipal discharges upstream;
  • contamination of water by coli is mainly of human and non-agricultural origin.

The general director of Fondation Rivières, Mr. André Bélanger, is amazed by the results of the study: “Initially, we wanted to know, among other things, whether the ColiMinder rapid detection system was effective in ensuring the safety of swimmers at the swimming pool. relaxation Léo-Jacques, in the event that the City makes this place accessible for swimming. Today we learn not only that the effectiveness has been demonstrated, but that the water in the river is of much better quality in summer than we had anticipated. In the fall, however, it’s a completely different picture unfortunately.” Indeed, from the month of September, with heavier rains, analyzes demonstrated persistent pollution and intensive municipal discharges of wastewater upstream during periods of rain.

The human origin of contamination by E.coli also provoked strong reactions: “For years, agricultural activities have been identified as the main cause of poor water quality in the L'Assomption River, but this is probably not the case! This new portrait will make it possible to guide future actions in a much more optimal manner by allowing the stakeholders concerned to better target the real priorities: upstream wastewater spills.. This is major news! », to add M. Bélanger.

The project was all the more beneficial as it made it possible to optimize the operation of the Water Treatment Center and to quickly adjust operations during unexpected periods of contamination. On September 17, the ColiMinder has in fact detected a peak of contamination which extended from 11:00 a.m. to 5:00 p.m. While there should be a strong correlation between turbidity and contamination, the Treatment Center's turbidimeter did not reflect this. Thanks to ColiMinder, it was possible to detect a spill occurring more than 10 kilometers upstream and adjust the treatment more quickly.

The results of this collaboration are now leading the City of L'Assomption to consider the follow-up to this study: “We are delighted with the work of Fondation Rivières and their professionalism. In its recommendations, the Foundation offers us very relevant actions to implement for better sanitation of river water. As always, we are ready to take concrete actions in collaboration with the various stakeholders in the area concerned about the quality of our waterways”, concluded the mayor of L’Assomption, Mr. Sébastien Nadeau.

The project

The project consisted of performing analyzes automatically every two hours. These were carried out with a device ColiMinder deployed in the factory which makes it possible to detect in 15 minutes the presence and quantity of E.coli in water. The results were transmitted in real time to the operators. The project ran from August to December 2020 and pursued three objectives:

  1. Validate whether the measures provided by the ColiMinder device can ensure the safety of citizens at the Léo-Jacques Park relaxation area in the event of occasional contamination, in the context where the City is evaluating the possibility of making the place accessible for swimming;
  2. Validate the relevance for the Water Treatment Center to use a rapid analysis tool to monitor contamination in real time;
  3. Identify sources of contamination that may present risks to the City's drinking water intake.

Documents to consult

Full report

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For informations :

Geneviève Tardy
Communications Manager
514 424-3556


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