The city repaired the root of the major flooding on Monday evening, which was a ruptured water main break. But on Tuesday water continued to flow on the university's campus from a second damaged pipe.
The university reported city workers blocked the leak at 2 a.m. Wednesday. The school said crews can now focus on the cleanup.
Michael Di Grappa, the McGill vice-principal, said the flood has had a major impact on thousands staff and students.
He said it will take weeks, or possibly months, before things get back to normal on campus. He estimated the damages could cost as much as $100,000.
City spokesman Jacques-Alain Lavallée said water main breaks are not unusual in the city, especially with recent weather shifts.
He said the water main that broke was 88 years old, and given the temperature drop and the vibrations created by the high number of cars and trucks driving downtown, the break does not come as a surprise.
City workers have excavated the area surrounding the pipe and are using cameras to inspect the pipe and search for any more weak spots.
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