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By Christinne Muschi
MONTREAL, Nov 11 (Reuters) - Montreal, Canada's second-largest city, began dumping untreated sewage into the St. Lawrence River on Wednesday, 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.
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.
"It's surprising, disgusting and outrageous that the city of Montreal took this path, which is the least costly alternative for them," said Lee Willbanks, from advocacy group Save the River, based in the riverside town of Clayton in New York state. "If Montreal does it, others municipalities might do the same."
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.
"As I have repeatedly said, if there were better options we would certainly have considered them," he said. "But the reality is that the option we have chosen is the one with the least environmental impact."
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.
The U.S. state is well upstream of Montreal and so is very unlikely to see any effects of the city's dump. Nevertheless, politicians there were worried about it.
"It shows poor judgment and it doesn't just affect Canadian waters - we share this water with Canada," said Phil Reel, a legislator in New York's Jefferson County, which borders the eastern edge of Lake Ontario and the head of the river. "It's a resource vital to both communities."
'DIAPERS,CONDOMS AND SYRINGES'
The operation was delayed until after Canada's federal election in October. The new environment minister, Catherine McKenna, imposed extra conditions including monitoring, improved clean-up plans, and regular reporting of water quality through mid-2016.
Still, there was consternation among some in the city of 1.6 million, and surrounding areas.
Parti Quebecois provincial legislator Mathieu Traversy said several municipalities feared their riverbanks would be polluted with "diapers, condoms and syringes."
"Who will pay for the cleanup?" the Montreal Gazette quoted him as asking.
The city has said the dump will have little effect on the river's fish population and will not affect drinking water quality for residents.
Alexandre Joly, head of a non-profit group devoted to improving the quality of water in St. Lawrence and access to it, called on Montreal residents to avoid putting some items such as condoms and tampons down the toilet during the wastewater dump.
"You have to remember that whatever you put in the toilet for the next week is going to go directly into the river," Joly told the Canadian Broadcasting Corporation. (Reporting by Alastair Sharp in Toronto, Randall Palmer in Ottawa, and Pete DeMola in Plattsburgh; Editing by Frances Kerry)
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