Mayor Denis Coderre has announced that Montreal will go ahead with its controversial sewage dump at midnight tonight.

The city has met conditions imposed by the new federal government for the city to proceed with its plan to dump eight billion litres of raw sewage into the St. Lawrence River.

Coderre and other city officials held a news conference to talk about the plan Tuesday morning at Montreal's city hall.

"If we could have avoided this choice, we would have done it," Coderre said.

He reiterated that the project is needed so the city can complete essential infrastructure work, including repairs to a key sewer interceptor.

Quebec mayors blast Montreal, Environment Canada

A group of Quebec mayors held their own press conference Tuesday morning to express their dismay with the decision, saying the City of Montreal did not consult enough with other municipalities.

"It's the best of the worst situations," said Bécancour's Jean-Guy Dubois.

The five mayors from Quebec regions asked that Ottawa appoint someone to oversee the St. Lawrence River. They also said their municipalities should be financially compensated if the sewage dump has negative consequences.

City to monitor closely

If the work is not done, the interceptor will continue to deteriorate and eventually break, the mayor said.

"Know that this decision, as unpopular as it is … was taken in a responsible manner," he said.

Montreal will perform frequent tests of the water before, during and after the seven-day sewage dump.

The city will also monitor 156 industrial companies and implement measures to reduce their discharge.

During the dump, there will be a cleaning crew that will be there the entire time.

The measures will cost the city close to $2 million, said Coderre.

On Monday, federal Environment Minister Catherine McKenna said the city could proceed with its plan once it meets the federal conditions for monitoring and minimizing the environmental impact.

What residents are asked to do

The city is also asking residents in affected areas to reduce their water consumption over the next week.

Precautionary measures also include not flushing items such as cigarettes, condoms and medication.

Any activity that involves direct contact with water will be prohibited from in Montreal's Southwest borough for nine days. The same restriction applies to the King Edward Quay sector for an undetermined amount of time.

Environment Canada conditions

Calling the city's plan "far from ideal," she agreed with the findings of an independent panel of scientists that the city's planned release this fall was preferable to an accidental release of wastewater caused by Montreal's decaying sewer system.

McKenna said Montreal could proceed with the dump under these conditions, up until Dec. 5:

Improvements to the city's emergency management plan for the dump.

Improved visual surveillance of the discharge plume.

A more comprehensive cleanup plan for affected areas.

Monitoring of the discharge's impact on the river's ecosystem before, during and after the discharge.

A comprehensive review of the process leading up to the city's decision to dump the raw sewage.

The decision came down after an independent panel said the city should only proceed if it looks further into the environmental impact.

On Monday, Coderre said he agreed with the conditions, and was confident city planners could meet them and proceed with the dump.

Why the sewage dump?

The city has asked residents to reduce their water consumption during the sewage dump. (Charles Contant/CBC) The city announced plans to dump the untreated wastewater into the St. Lawrence River earlier this fall, as a part of construction work on the Bonaventure Expressway.

Montreal says it needs to shut down an interceptor — a major sewer that collects the effluent from a network of other sewer lines on its way to the water treatment plant — for maintenance and to link it to a new snow dump site.

Raw sewage that would normally flow into the interceptor will be diverted directly into the St. Lawrence River as a result.

Both Coderre and Quebec Premier Philippe Couillard have supported the plan since earlier this fall, calling it the best option available.

What areas are affected?

The wastewater from seven different Montreal boroughs and four towns that are directly linked to the interceptor will flow freely into the river.

The boroughs include Lachine, LaSalle, Verdun, the South West, Ville-Marie, Outremont and Mercier–Hochelaga-Maisonneuve.

Montreal West, Cote-St-Luc, Mount Royal and Westmount are also directly linked to the interceptor.

The sewage dump also partially affects five other boroughs and three towns.

Hover over borough or city to see what percentage of the sewage from each is to be diverted.

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