The Rivière du Nord winds its way through downtown Saint-Jérôme for around ten kilometers: a true oasis of freshness in an urban environment! However, even in the heatwave, few people dare to swim there and there is currently no public beach. Formerly very popular for swimming, the reputation of the river near Saint-Jérôme is today unenviable. The city's sewer system is known to overflow during rainy weather and contaminate the river, making safe swimming impossible.
On the other hand, a few days after the rain and the overflows, we could expect that the pollution will gradually fade and that swimming will then be possible, even if it means wanting to imagine a beach, and this more and more with recent summers. And you, would you swim in the Rivière du Nord? It is to better answer this question that the City of Saint-Jérôme commissioned us this summer.
On the trail of bacteria
Our first results collected at the urban beach site studied by the City were not very encouraging: there were clearly sources of pollution higher up in the river which made swimming impossible. We were going to have to investigate! How? By following the trail of bacteria of fecal origin such as E.coli!
To do this, we take water from different strategic locations along the river and, when we see a spike in bacteria in our results, we know we are getting closer to the source. Scientific analyzes are therefore our favorite tool in this fecal investigation but I admit that, the closer we get to the source, the more it is the nose that takes over!

No wipes in the toilet!
Our investigation allowed us to discover the kind of disaster that cleaning wipes thrown down the toilet can cause. We have used them a lot since the start of the pandemic, but when they end up in our sewer systems, rather than degrading like toilet paper, they clump together with greasy substances and become a real scourge. A good example is a clogged sewer line that overflows into a stream.

This type of blockage is very unpredictable and poses a real threat to beach swimming and the health of our rivers. Continuous water quality monitoring devices make it possible to detect them and act quickly, but they are still not widely used.
An “underwater” drone near the beach
Of course, the Rivière du Nord is not just brown and foul-smelling. It’s also majestic falls, lush vegetation and captivating morning drizzle. It was to show you all this that my colleague Christian and I went to film images with a drone a few weeks ago.
The morning was progressing well and I was busy collecting my last samples (being careful not to look too much at the camera, in order to look natural). When suddenly, a rustling of leaves, followed by a splash! The drone had been carried away by a gust of wind and got stuck in a tree branch before plunging to the bottom of the river, before our eyes. My colleague will tell you about this incredible adventure shortly…
No beach this year, but there is hope
The summer of 2021 was ultimately not at all conducive to swimming, but our results still made it possible to identify several sources of pollution in the Rivière du Nord. When they have all been eliminated, perhaps one day we will be able to open a beach there without fear. Until then, there's work to be done! Come on, I'm going back!
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About the Author
Philippe Maisonneuve