In theory, the installation of retention basins to control rainwater is not illogical. However, in cities, this solution is practically not feasible, because the volumes to be contained are too large. I have observed this myself during certain municipal projects, in particular during a mandate obtained from the City of Quebec, where it was proposed to create such a basin in a new residential complex in order to avoid having to change a pipe located downstream, the latter having to receive the water from this complex and the drainage basin in which it was located. The calculations showed that such a structure took up a disproportionate amount of space to the point of no longer justifying the development project.
In a city like Montreal, it is very likely that a feasibility study would show that the retention of rainwater, as proposed by Ms. Sophie Van Neste (The DutyApril 17, 2021, “Better stormwater management to adapt to extreme events”), is probably not a feasible solution. But such a study should be launched by the Quebec government and should be comprehensive and territorial. It could establish possible interventions in the sewer network to improve the situation and consider the conditions of the river waters in terms of their harmfulness and the significance of the consequences of this on the environment. Such a study would put into perspective the need for interventions both in the network and on the river.
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