A week before billions of litres of sewage is slated to be dumped into the St. Lawrence River, dozens of protesters on kayaks and paddleboards glided through Montreal’s Lachine Canal on Sunday to symbolize the importance of the waterway.

Dressed in tuques and life jackets, the small group aimed to demonstrate how essential the river is for recreation, fishing and drinking water in Montreal.

“We have to respect the St. Lawrence River,” said paddler Antoine Bonicalzi. “It’s something we have (that) I want people to cherish.”

Montreal’s plan to dump 8 billion of litres of raw sewage in the St. Lawrence has alarmed many in Quebec, but officials say it is a safe and necessary step in a larger infrastructure plan.

The week-long dump is set to begin on Oct. 18.

Montreal Mayor Denis Coderre has supported the massive sewage purge, which he says is a necessary step in a larger plan to move a snow chute before demolishing the downtown Bonaventure Expressway. He also says the plan is safe, and that oxygen in the water will help dissolve bacteria.

City officials have weighed other options, Coderre said, but they were either too expensive or simply not possible.

In a statement published last Tuesday, Environment Minister Leona Aglukkaq asked the mayor for more time to consider the proposal.

"The proposed plans by the City of Montreal to dump billions of litres of untreated raw sewage into this important river is very concerning -- as many citizens have noted publicly... I ask that (Montreal) Mayor (Denis) Coderre halt his plans while a proper assessment is done," Aglukkaq said.

Coderre quickly fired back at the ministry, suggesting that it had known about the project since September 2014 and that the Conservative government is “playing politics behind the backs of Montrealers.”

It is unclear if a resolution will be met by the date of the dump. The city says it expects to hear back from Environment Canada by Wednesday, but the federal agency says it has not agreed to a timeline and must thoroughly review the proposal before making a decision.

Quebec Environment Minister David Heurtel agrees with Coderre’s stance and says that Montreal’s sewage treatment plant could be “at risk” without the dump.

"If the treatment plan goes down, the impact would be far greater than anything that could be caused by this situation," said Heurtel.

An environmental engineer who reviewed the plan said that, considering the high cost of alternative options and the short-term nature of the plan, dumping the waste makes sense.

“You wouldn’t invest in that kind of technology to deal with something that is so temporary,” Sarah Dorner, an environmental engineering professor with Ecole Polytechnique, told CTV News.

But according to a research scientist, so much raw sewage at once will undoubtedly have a negative impact on local fish – and possibly people, too.

“It’s wrong to think it’s just fish,” said Daniel Cyr from the National Institute of Scientific Research. “We’ve gone out and we’ve done sampling in summer, and there are people who run in and out of the water even when it says no swimming.”

A Green Party candidate for the Quebec riding of Pierre-Boucher-Les Patriotes-Vercheres has said the party plans to file an injunction and is working with lawyers to halt the proposal because “the environmental impact is going to be disastrous.”

Instead, the Greens offered another solution: avoid demolishing the snow collector, put the snow somewhere else for the winter and gradually release small amounts of sewage into the river in February. Then, they say, the frigid temperature will neutralize most of the harmful bacteria in the water.

Protesters paddling on the canal Sunday said they don’t support any sewage dump, and that keeping the environment safe is their chief concern.

“We’re not the only ones on the planet,” said protester Jonathan Busby.

Montreal isn’t the only city to dump raw sewage into local waterways. In Victoria, B.C. 130 million litres of sewage is dumped into the Juan de Fuca Straight each day, drawing criticism from environmental groups and government officials in neighbouring Washington state.

According to Environment Canada figures, wastewater is the main source of water pollution in Canada, with more than 150 billion litres of untreated and undertreated wastewater released into Canadian waters each year.

With files from CTV’s Vanessa Lee and CTV Montreal