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Becancour River and St. Lawrence Watershed - Wastewater Treatment Systems Assessment

Watershed of the Bécancour River and the Saint-Laurent zone - Evaluation of wastewater treatment systems

An initiative of a citizens' committee, which extended to the watershed of the Bécancour River and the Saint-Laurent area

In order to support the Bécancour zone watershed consultation group (GROBEC) in updating its water master plan, the Fondation Rivières carried out a performance evaluation of municipal wastewater treatment systems throughout the Bécancour area. This decision follows a project carried out for the Irish Trout Lake Protection Association (APLTI), which demonstrated the Foundation’s rigorous approach to GROBEC.

The objectives: identify sanitation issues between 2014 and 2018 and produce a summary report intended for municipal decision-makers, interest groups and the public. Support was also provided to target intervention locations for a green infrastructure implementation project.

Bécancour River. Credit: Pierre Gagné/Green Week


Progress report

  • Data compilation Monitoring system for municipal water sanitation works (SOMAE)
  • Interpretation of diagrams and tracking data


Diagnosis and action plan

  • Telephone interviews with many water sanitation services
  • Production of a summary table of suggested courses of action
  • Support for municipalities wishing to find sources of financing


Partners and collaborators

  • Bécancour area watershed consultation group (GROBEC)
  • The Irish Trout Lake Protection Association (APLTI)
  • All 34 municipalities that responded to our diagnostic questions
  • Adopters of the Bécancour River



Treatment plants
Overflow structures

The raw data from Monitoring of municipal wastewater treatment works (SOMAEU) were obtained from three different sources, namely GROBEC, MAMH and the Ministry of the Environment and the Fight against Climate Change (MELCC). Of the 32 municipalities of interest present in the study area (including 6 without treatment), the representatives of 30 of them participated in a telephone interview (94 % participation). The six study areas correspond to the sub-watersheds of the Chêne and Gentilly rivers, the Nicolet river, the St. Lawrence River as well as the basin of the Bécancour River. The performance diagnosis is divided into two main sections: the performance of the wastewater treatment plants and the performance of the networks and overflow structures.

Duration of the study

This project to evaluate wastewater treatment systems covers the years 2014 to 2018. It was divided into two phases between June 2018 and March 2020.



None of the priority files which required the construction of wastewater treatment works will be able to be completed in 2020, as required by regulation.


The main polluting sources identified upstream of the basin could be significantly reduced in 3 to 10 years.


Eight of the 32 municipalities have carried out work over the past two years to reduce wastewater overflows and phosphorus emissions.

Among the 36 systems studied, almost three quarters need to improve their sanitation performance at their treatment plant and/or on their network.

How is the water quality in the Bécancour area?

The Bécancour River is strongly affected by the sanitation performance of the City of Thetford Mines, which is located upstream of the watershed. A lack of disinfection of treated water and frequent spills during rainy weather are to blame. On a broader scale, many small stations encounter phosphorus removal difficulties, especially downstream of the Bécancour River. Six municipalities in this territory are in the process of building wastewater treatment plants at the end of their existing networks. The vast majority of spills in the territory occur in the Bécancour River and the Petite rivière du Chêne.

Our mandates for evaluating wastewater treatment systems

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