Montreal's big dump has exposed an ugly secret about the St. Lawrence River: cities and communities throughout Quebec routinely flush their untreated sewage into waterways, letting their problems be carried downstream for someone else to deal with.

In 2013 there were 45,000 occasions when cities and towns in Quebec dumped waste directly into the St. Lawrence.

That same year Toronto dumped 1 billion litres of raw sewage into Lake Ontario when a treatment plant lost power.

Just decades ago Montreal routinely dumped all its sewage into the river, and even after it built a sewage treatment plant the city still found itself dumping untreated sewage on occasion. 

In 2003 Montreal dumped nearly 18 billion litres of sewage into the river, and in 2005 another 770 million litres of wastewater went into the St. Lawrence.

One week of untreated sewage

As of midnight Montreal shut down a massive sewage and snowmelt collector near the Bonaventure Expressway in order to make necessary repairs. Internal supports in the tunnels that carry wastewater to the city's treatment plant are rotting, and falling into the sewage flow.

The decision was greeted with a protest that shut down the Mercier Bridge and with people making last-minute use of the river to kayak and fish.

"Instead of putting $166 million on the Olympic stadium, instead of putting $11 million on baseball fields that no one cares about, instead of a new Aquapark, instead of decorating the Champlain bridge with lights for the 350th anniversary, that money could have been used to create biomethane plants that would solve this long-term. If you believe there's nothing else that we can do, you've been duped," said one protester at the Mercier Bridge.

The city of Montreal began working on a solution for wastewater treatment in 2008, but it won't be ready for another three years.

Earlier this year, Montreal awarded a $100-million contract to build a new ozonation plant to treat sewage, but that plant is not expected to be ready until 2018 at the earliest.

The current facility only deals with phosphorus and solid matter, with workers removing diapers, condoms, and other assorted trash flushed down drains and toilets and putting it in a landfill.

The new treatment centre will eliminate 95 per cent of chemicals, including hormones and medication, making the water much better for the fish and other animals that depend on the river.