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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 Rivières Foundation and the City of L'Assomption make public the results of the continuous monitoring of the water quality of the L?Assomption River at the Jean-Perreault Treatment Center water intake and at the Léo-Jacques park relaxation area in L?Assomption. This pilot project reveals astonishing information which today makes it possible 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 manager of the 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 of relaxation Léo-Jacques, in the event that the City makes this place accessible for swimming. We learn today 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 is a completely different picture, unfortunately.? Indeed, from the month of September, with more marked rains, the analyzes showed persistent pollution and intensive municipal waste water discharges upstream during periods of rain.

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

The project was all the more beneficial in that 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 indeed 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 turbidimeter did not report this. Thanks to ColiMinder, it was possible to detect a spill that had occurred more than 10 kilometers upstream and to adjust the treatment more quickly.

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

The project

The project was to perform automated scans every two hours. These were made with a device ColiMinder deployed in the factory which makes it possible to detect in 15 minutes the presence and the 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 had 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 of using a rapid analysis tool to monitor contamination in real time;
  3. Identify sources of contamination that may pose risks to the City?s drinking water intake.

Documents to consult

Full report

? 30 ?

For informations :

Genevieve Tardy
Communications Manager
514 424-3556


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