Montreal's sewage dump plan reveals common misconceptions

Theglobeandmail.com
Nov. 10, 2015
By Les Perreaux

The prelude to Montreal’s sewage dump was roiling in controversy. The event itself, which was to begin at midnight with the flip of a few switches at the city’s main sewage plant, is likely to pass imperceptibly, at least at first.

At 12:01 a.m. Wednesday morning, workers at the Jean-R. Marcotte waste-water filtration plant were to engage a series of automated valves and gates to divert about one-third of the city’s waste water from households, storm sewers and factories into 24 pipes leading straight into the heart of the St. Lawrence River.

Recent news coverage has featured stock images of sewer pipes spilling into waterways. The discharge will show nothing that dramatic, with each of the outlets reaching 15 metres to 30 metres from shore and several metres below surface.

The discharge is large - an average of 793 cubic metres per minute - but will be whisked away quickly by the river’s flow of 7,000 cubic metres per second. Urine, excrement and even toilet paper will quickly disperse. In some spots near the city, coliform counts from feces will likely rise to levels unsafe for drinking directly or recreation. But a few kilometres downstream, experts say, evidence of extra human waste will be difficult to detect.

What happens to other items - from litter on the streets that washes into storm sewers, to the dental floss, wipes, condoms and tampons people insist on flushing - is less predictable. Teams equipped to scoop up debris and set up collection booms will patrol the shores and waterway.

One of the first and largest discharge points is behind a high school in the neighbourhood of Verdun, southwest of downtown. A nearby small bay is nicknamed Baie des capotes (capote is slang for condom) for what floats up during the occasional discharges that take place during rainstorms.

Most will look first to the bay to see what unpleasant sights and smells surface.

“You should have no odour,” said Richard Fontaine, the sewage plant’s director. “You are unlikely to be able to see anything. It won’t look different than what you see today.”

Fourteen hours after the diversion begins, the 30-kilometre sewage interceptor - wide enough in places for two car lanes – will be empty and workers will descend into it 35 metres underground.

Some workers will dismantle a downtown snow chute that must be moved for a road project. Others will remove rusting steel rails along the network. The rails had threatened to break loose and wreck the filtration plant.

When the work is complete in about a week, eight billion litres of Montreal sewage will be flowing toward the Atlantic Ocean - at least the material not settled onto the riverbed or hung up on shore.

Mayors from Trois-Rivieres, Becancour and other downstream cities have accepted the discharge with resignation.

“If they don’t do the repairs, it’s a ticking time bomb,” Louiseville Mayor Yvon Deshaies said. “What are we supposed to do?”

Denis Landry, the chief of Wôlinak, an Abenaki community whose people fish in the river, said he will try to force Montreal - which has conducted planned dumps several times in the past 15 years - to find a new way in the future.

The sewage dump revealed common misunderstandings about such systems. Almost every major Canadian city occasionally releases sewage into the nearest major waterway.

Sometimes systems are overwhelmed by rainfall; sometimes repairs are needed. Some cities, such as Victoria, don’t even have treatment. Even good systems are built to fail, and when they do, the waste goes into the water. Other backups are rare.

Montreal’s system filters litter and solid human waste when it works, but metals, chemicals, hormones, viruses and bacteria go straight into the river.

Even mayors downstream were surprised to hear how little normally gets filtered. “When I heard hospitals routinely send human medical waste from operations into the river, I jumped out of my chair,” Mr. Deshaies said. “These are things I didn’t know.”

Montreal is making a $250-million addition to its system to treat waste with ozone to kill off germs, and adding retention ponds so the system will overflow less when it rains. The systems should be ready in 2018.

But until then, every big rainfall will flush city sewage into the river. And the next time a sewage main needs to be emptied for maintenance, the waste will go to the St. Lawrence, unless billions of dollars are spent setting up an alternative.