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St. Lawrence River and Assomption River – Monitoring water quality and detecting sources of pollution

St. Lawrence River and Assomption River – Monitoring water quality and detecting sources of pollution

Is there swimming potential in Repentigny?

Being bordered by the river and the Assomption River, Repentigny has great potential for access to water. The Fondation Rivières carried out a study on the bacteriological quality of the water of the St. Lawrence River and the Assomption River in Repentigny. The objectives: evaluate the potential for swimming and water activities and identify sources of fecal contamination of municipal origin.

Water sampling at the mouth of the Assomption River during a screening tour. Photo: Fondation Rivières


  • Validation of bathing potential
  • Site vulnerability assessment – bacteriological water quality
  • Screening for main sources of pollution

Partners and collaborators

  • City of Repentigny

Our methodology

Regular tracking sites
Testing sites
counts of E. coli

Surface water samples were taken by the Fondation Rivières team and counts ofE.coli were carried out by the Eurofins EnvironeX laboratory located in Longueuil. The 4 regular monitoring sites targeted by the in-depth water quality assessment were sampled at least twice a week for 9 weeks. Screening tours were also carried out in order to precisely locate contaminated discharge points.

Duration of the study

The project lasted from July to September 2022.



For 2 of the 4 sites studied, the water quality was most of the time of sufficient quality to allow the practice of nautical activities.


The water quality threshold for swimming was frequently exceeded, even in the absence of heavy rain.


Among the identified sources of contamination are cross-connections and wastewater overflows, but these are not adequately measured.

The City of Repentigny could speed up access to swimming by prioritizing the correction of cross connections by potential swimming sector and by equipping itself with electronic overflow recorders (EED) on all overflow structures. 

Identify sources of contamination to address problems

To better measure overflows as well as problematic structures, the City of Repentigny would benefit from installing EEDs. Only half of the works currently have one. EEDs capable of measuring the frequency and cumulative daily duration of overflows have been required since 2014 according to article 9 of the Regulation respecting municipal wastewater treatment works (ROMAEU).

Then, to optimize the City's efforts to replace cross connections, the Foundation recommends that it prioritize areas that could be used for swimming and other water activities. All that remains is for the City to implement our recommendations so that we can one day swim there!

Do you make decisions within your municipality?

Consult the guide to opening an urban swimming site to find out how the Fondation Rivières can help you.

Plage de Verdun
Verdun beach in summer 2021

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