Who is contaminating the Rivière du Nord? For several summers, investigators armed with sampling bottles and rubber overalls have been investigating to find the culprits.
Municipalities crossed by this important Laurentian watercourse have entrusted biologists from the Fondation Rivières with the task of increasing water quality analyzes. Objective: precisely locate the places where it degrades, in order to identify the sources of contamination.
The bloodhounds follow the trail of fecal coliforms, the proliferation of which prevents swimming on most of the river. After decades of industrial activity on this river following the colonization of Curé Labelle, it is now the toilets in the surrounding area that are polluting.
“ These are either municipal water discharges that are poorly treated, overflows after heavy rains or non-compliant septic installations,” explained biologist Philippe Maisonneuve while preparing his next sampling.
Pinned to his hunting board in recent years: in Saint-Jérôme, “a commercial office that was not connected to the sewer network. Every time someone flushed the toilet, you basically saw the leftovers of your meal going into the river.”
In the same municipality, “we went up a stream that we knew was contaminated without knowing where it came from,” relates the young expert. At one point, a brownish-white mass was seen. » It was “a manhole which overflowed at high pressure” directly into a tributary of the river, due to a blockage caused by wet wipes put in the toilet by citizens.
Another example: the Sainte-Adèle wastewater treatment plant, the water from which sometimes still came out contaminated. “Disinfection was done with UV lamps, but there was no cleaning done,” explains Philippe Maisonneuve. Sometimes something as simple as that…”
A suspicious stream
Standing in the water of the river, in Val-David, the biologist follows a new trail. A stream coming from Gold Lake, just upstream, “comes out with contamination thresholds that are continuously above the swimming threshold,” he explains. “It could contribute to the contamination that we see as far as Val-Morin. »
Work has already been done by the municipality of Val-David to investigate, without success. So we try to take other samples to find out from which sector the contamination begins.
Philippe Maisonneuve, biologist
When laboratory analysis reveals a problem at a specific point in the Rivière du Nord, biologists increase the number of samples taken in this sector in order to try to locate as precisely as possible the place where the water quality is falling.
However, the task is not easy: the concentration of fecal coliforms can vary greatly over time, particularly due to the weather. The heavy rain this summer has also made the task of the Rivières Foundation particularly complicated, since no sampling is possible after substantial precipitation: sewer overflows – and therefore coliforms – are so numerous that biologists cannot can no longer locate other problems.
However, certain sources of contamination are well known, and have been for a long time, but solutions are slow. This is the case near the Sainte-Agathe wastewater treatment plant, where a contaminated water pipe from the municipal network flows into the Rivière du Nord. Citizens and associations have been trying for years to correct the situation, without success.
“We have to be responsible”
It was the mayor of Prévost who had the idea of commissioning the Rivières Foundation for this project. The region contributes to the financing.
“The ultimate dream? », evokes Paul Germain. “Perhaps, one day, bring swimming back to our territory. »
The elected official says he is satisfied with the work done so far, particularly because the solutions to many of the problems identified are in the hands of the municipalities themselves. “It gives us a portrait. From that, we can start working,” he said. Prévost also has its own challenges: “a problem of occasional overflow”.
“What is a bit paradoxical in these issues is that often the installations are at the southern limit of the city, so when you work on your water quality, it is the lower municipality which benefits, said Mr. Germain. But at some point you have to be responsible. »