Canada's environment minister has signed off a contentious plan in Montreal to dump 8 billion liters of raw residential and industrial sewage into the St. Lawrence River, as long as certain conditions are met.

Calling the plan "less than ideal" and noting she was not "not thrilled to be in this situation," Catherine McKenna none-the-less called her approval "an example of evidence-based decision making."

"We looked at the risks associated with an unplanned discharge versus the risks associated with a planned discharge," the newly-minted minister of environment and climate change said on Monday from Paris, where she is attending talks related to the upcoming climate change conference.

"We could mitigate the risks if the city had a planned discharge, with conditions," she concluded. The conditions include monitoring the discharge, reviewing the dump afterwards, and a review of the effects on the nearby community.

The drama over the controversial dump, which will see Montreal dump the untreated wastewater into the major body of water that links the Atlantic Ocean to the Great Lakes, has been stretching out for weeks. The city announced its plan in September, then backtracked, then reinstated it, until the federal agency Environment Canada stepped it and issued a order blocking the move. The city has said it has no choice but to execute the dump, which is part of construction work on a highway.

It expected to last seven days and will flush the equivalent of 2,600 Olympic-sized pools of sewage from the Montreal boroughs of LaSalle, Verdun, and Notre-Dame-de-Grace into the river. The city says the sewage represents less than 1 percent of the average volume handled by the main water treatment plant in the area.

"I wish there was a magic bullet, here," said McKenna on Monday. "I wish there were other options given the short timeframe we have ... If we have this review, we will ensure that everyone will have their chance to give their two cents on what they can improve. The city, the province, there's things they could have done better."

She also said the government is "very interested" in hearing from affected indigenous communities that live in the area of the dump. McKenna said the officials had consulted the Kahnawake reserve, which is southwest of Montreal, but she did not indicate if they supported the plan