Quebec City is forced to dump hundreds of millions of liters of wastewater into the St. Lawrence River due to a breakdown in one of its water treatment plants overnight from Saturday to Sunday.
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21,000 cubic meters per hour of wastewater were sent into the river. This represents 21 million liters every hour.
A wall valve in the western water treatment plant broke in the closed position, thereby preventing water from entering the infrastructure.
“It’s a valve that controls the flow brought to the station which has a part that broke in the closed position. Our water, since 2 a.m., has been diverted entirely to the St. Lawrence River,” explains Valérie Tremblay, director of water treatment operations.
To give an idea of the size of the spill, the manager specifies that the current volume diverted to the river is 5.7 m3 per second, while the total flow of the watercourse is 12,000 m3/s.
“The percentage of the discharge on the flow of the river is 0.043% of the volume. […] It’s still minimal, ”Ms. Tremblay puts it into perspective.
Hard work as a diver
To achieve a solution to the problem, the city must replace the part directly at the bottom of its accumulation tunnel, at a depth of 30 feet. To achieve this, a team of specialized divers was dispatched from Montreal for a complex dive.
“We are talking about raw wastewater. It is very loaded with organic matter. They don’t see us. They work almost blind,” explains Valérie Tremblay.
Since the city already had the spare part, the initial plan is to get it fixed quickly. On the other hand, if the maneuver proves unsuccessful, alternative plans have already been established to put an end to the spill.
“If that doesn’t work, we will certainly be able to use a crane to force the valve open. Otherwise the divers can take a torch to cut out the door to let in a certain volume of water”, indicates the director.
Both of these scenarios, however, involve another repair operation “when the volume will be shrunk after melting.”
Appeal to citizens
At the end of the day on Sunday, the teams had managed to open the valve to 60% of its capacity. “The operations are bearing fruit,” says Ms. Tremblay.
Until the problem is resolved, the city is forced to divert the sewage inlet usually heading for the west plant directly to the river.
In order to prevent harmful objects from being discharged into the St. Lawrence, the city would like the cooperation of citizens, asking them not to “throw wipes and sanitary napkins down their drains”.
The City of Quebec indicates that it will take stock of the situation on Monday morning.