Pipe leak spilled 150 million litres of sewage into Calgary’s Bow River

The City of Calgary says a wastewater leak discovered on Friday has been contained and crews are now investigating the cause.

The city provided an update on the pipe leak that happened near the Bonnybrook Wastewater Treatment Plant on Friday, giving an estimate for how much sewage was missing from the plant.

“There is no way to know this exactly, but we do have an estimate of how much wastewater we expected to receive at the treatment plant,” said Doug Morgan, City of Calgary general manager of operational services.

The leak is currently contained, and there is no threat to the public.

The potential issue was first noticed on March 19, when crews noticed the plant’s wastewater levels were lower than normal.

Crews began looking at potential causes.

During the investigation, crews noticed levels continued to drop but did not notice anything wrong with the plant or “large industrial customers that have changed their process.”

Crews were able to identify the pipe that was the source of the leak and turn off valves leading to it before diverting wastewater flows to two other pipes in the area.

Morgan says the Bonnybrook plant typically receives about 365,000,000 litres of water each day.

City records show it received seven million litres of water less on March 19 and the following seven days.

By Thursday and Friday, it was receiving 52 million litres less than it typically would.

The city estimates up to 150 million litres of wastewater leaked over a 10-day period.

“The flow at the leak site would have been approximately 1.3 per cent of the total flow in the river. We also know from modelling and other similar incidents in other cities that the material would have diluted quickly, minimizing effects downstream,” said Morgan.

Kerry Black, an assistant professor and Canada Research Chair in the Schulich School of Engineering, echoes that there isn’t much to be concerned about regarding the leak.

“It’s a pipe that has a leak, and that’s pretty commonplace in municipal infrastructure,” said Black.

“This is nothing that’s really going to hurt anybody. The biggest issue it usually causes is to the surrounding water body where it might be leaking.”

Mayor Jyoti Gondek says she and other senior staff were not made aware of the situation soon enough.

“I can tell you I have made it clear to both CAO (Chief Administrative Officer) David Duckworth and GM Morgan that the communication needs to be stronger in this particular case,” said Gondek.

Similar to the water main break in the summer, the incident has brought attention to the city’s infrastructure.

The pipe was installed in 1972 and had not been inspected over the past 15 years.

“Until we know how the pipe failed, we can’t be sure that an inspection would have prevented the issue,” said Morgan.

Gondek says the city has moved from reactive maintenance of wastewater pipes to proactive after the water main break issues that caused a water crisis in the city over the summer.

“We know that aging infrastructure is a critical issue for municipalities across Canada and North America,” said Gondek.

“Work has begun on prioritizing which pipes need to be checked first. The work is complex, as we have seen this weekend. It involves isolating sections of pipe, gaining safe access and pumping before an inspection can be done.”

Troy Vassos, an adjunct professor at the University of British Columbia, says the city was proactive in having backup pipes while monitoring the water flow amount but says the testing needed to be turned around faster.

“The problem is that if you have to wait 24 hours or longer to get a water quality sample to determine if you’ve got bacteria in it, obviously, that’s not a good situation,” said Vassos.

The city is still investigating what caused the pipe to leak.