Montreal, Canada's second-largest city, began dumping untreated sewage into the St. Lawrence River on Wednesday, November 11 angering environmentalists with a repair operation that could release as much as 8 billion liters (2.1 billion gallons) of wastewater into a major waterway, according to Reuters.

The city has said the dump, expected to last up to a week, is necessary while work is carried out to replace ageing parts of the waste treatment system that could create a greater environmental hazard if it unexpectedly broke.

The action prompted outrage from cities and citizens downstream - worried about raw sewage in the water and the possibility of detritus such as condoms washing up on riverbanks. Even some upstream were concerned because of the precedent it was setting.

Signs advising against touching the water were posted on the banks of the river directly opposite Montreal's main port area. Despite the large size of the dump, waste will likely be quickly diluted and swept away by the huge volume of the river and there was no odor or physical signs of the operation, which has generated the Twitter hashtag #flushgate.

In full-page ads in Quebec's main newspapers on Wednesday, Montreal Mayor Denis Coderre defended the operation as vital to protecting the river in the long run.

The river runs for almost 1,200 kilometers (745 miles) from Lake Ontario to the Atlantic Ocean, and features migratory birds and a variety of whales. It forms much of the border between New York state and the Canadian province of Ontario.