There is “little likelihood” that dumping eight billion litres of sewage into the St. Lawrence River will affect fish production, if it’s done before winter and properly monitored, Environment Canada has confirmed.

The report into the controversial sewage dump concluded that a planned dump is better than an unplanned dump, which is a possibility considering the state of Montreal's sewage system network. Experts have said unplanned dumps happen frequently when it rains. The report also says if Montreal goes ahead, it should do so before January.

Fish in the river are currently being affected by chemicals and pharmaceutical drugs not filtered out by the current sewage treatment process, but scientists don't know how much aquatic life will be effected if the city goes through with the dump, explaine Daniel Cyr, co-author of the study

“There of been very, very few studies anywhere really where people have looked at raw sewage,” said Cyr, adding that the city will have to monitor spawning areas between Nuns’ Island and Montreal.

“The risks to reproduction is minimal, but the immune system is definitely a risk. I mean the immune system has been shown with the treated effluent to be affected,” said Cyr.

First nations communities have been vocal against the proposed sewage dump.

The Kahnawake council has met with Environment Canada and has concerns over the long-term impacts of plant life along the river banks.

 “We fish, we like to go paddling, we have a canoe club right here, and there are people who still go and pick medicinal plants along the water we don't know what kind of effect that's going to have,” said Joe Delaronde, spokesperson for the Mohawk Council of Kahnawake.

Montreal has dumped raw sewage into the river two other times over the past 15 years and heavy rains often lead to untreated water flowing into the river.

Cyr says the dump is the least risky option, but the city and province must study the impacts more closely.

“If we're going to do this and we know we're going to have to do this again. I think it would be beneficial that we really establish exactly what the consequences are, hopefully there's nothing dramatic that will happen, but establish the consequences to that next time we plan differently,” he said.

The report delivered to Environment Canada Friday stopped short of endorsing or rejecting Montreal's plan to dump untreated wastewater into the St. Lawrence River for a limited time, saying instead the city should consider implementing more measures to mitigate the dump's environmental impact.

The report comes after a trio of environmental experts were appointed Oct. 19 to analyze the plan.

Cyr from the Universite du Quebec co-authored the study alongside McGill's Viviane Yargeau, and Robert Hausler of Ecole de Technologie Superieure, delivering their report to Environment Canada Tuesday Nov. 3.

On Monday Nov. 9, a federal order not to dump the 8 billion liters of raw sewage into the river expires.

Environment Canada spokesperson Caroline Blais pointed out Friday that the experts' mandate wasn't to approve the plan, but to analyze it.

The experts recommend the city implement measures such as using a tanker to collect some of the sewage and installing temporary pumps to divert the wastewater from one of the city's interceptors.

The city of Montreal came up with the plan about 18 months ago, saying it was a regrettable necessity to dump eight billion litres of sewage into the river during a seven- to 10-day period.

During that time construction crews would be moving a snowmelt collector near the Bonaventure Expressway that feeds into a sewage treatment facility.

The city says it would be impossible to work on the sewage lines while they were still conveying wastewater, and so instead the sewage would flow into the river from emergency overflow outlets at several points on the southern and eastern parts of the island.

Montreal said it had planned the sewage work for a colder part of the year to minimize the environmental impact, because fewer people would be using the water for recreation and because the colder temperatures would inhibit bacterial growth.

Environment Quebec approved the plan after analyzing all options and deciding that Montreal had no other choice but to dump the sewage.

With a file from The Canadian Press