The City of Calgary was “very proactive” in tackling the feeder main break that has forced residents and businesses to limit their water use for more than one month, according to an American pipeline expert.
Water is now flowing at 55 per cent capacity through the Bearspaw Water Treatment Plant’s south feeder main, a critical line carrying water to about 60 per cent of the city that burst on June 5.
In the weeks since the break, the city has been relying on water from the South Glenmore Treatment Plant, which already supplies water to the other 40 per cent of the city.
Officials from the City of Calgary confirmed Saturday that the repairs and inspection of the 11-kilometre feeder main are now complete. Maintenance work at the Glenmore plant also wrapped up on Friday.
Francois Bouchart, Calgary’s director of capital priorities and investments, told reporters that the inspection results should be available in three to four weeks.
After assessing the results, he said the city will use the data to determine whether further investigation or repair work is needed.
“We learned a lot about this feeder main during this response and it requires a medium to long-term rehabilitation plan,” Bouchart said.
“Depending on what the inspection results indicate, there might be some individual replacement of pipe, but that is premature in terms of truly identifying what we need to do.”
Emergency officials also used Saturday’s update to announce their decision to move from stage four water restrictions to stage three restrictions.
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Under stage three restrictions, residents are allowed to fill watering cans or other containers with potable water to tend to lawns, gardens, shrubs and other outdoor plants.
Businesses can also use water for construction purposes, such as dust control, grading and compaction.
Graham Bell, a research associate professor at the University of Tennessee’s Department of Civil and Environmental Engineering, said he’s worked with the City of Calgary on pipeline projects.
He said prestressed concrete cylinder pipe (PCCP), produced in the 1970s, like the Bearspaw feeder main, presented problems.
“Occasionally, failures do occur even though you’re trying to be as proactive as you can, but you can’t do everything at once, so you end up doing what you can with the budget that you have,” Bell said.
“It’s not a case where you can just decide to shut a main down and do exactly what you want. You have to keep delivering the water people need.”
Bell said the PCCP design is used across North America and is known to be vulnerable to major failures, but noted its engineering has improved since the late 1970s.
He said the City of Calgary was “very proactive” in dealing with the situation at hand because it had installed a PCCP acoustic fibre optical monitoring system upstream of where the failure occurred.
Using that technology shows the city was on the right path, Bell said.
“It’s not like you can just say, ‘I want to replace all this pipe’ because that would be a case where 96 per cent of what you spend, you don’t need to spend,” he said.
“It would almost be worse because you’d be wasting the money.”
Bell estimates that in a few more weeks, the city would have found the bad pipe by inspection and would have had monitoring installed that would allow for an intervention prior to failure.
“One of the things people need to understand is that it’s only about three or four per cent of these pipes have these types of problems,” he said.
“So you’re looking not quite for a needle in a haystack, but you are looking pretty hard through an important wood pile to try to find a few sticks that you want.”
City officials said the next milestone will involve moving from stage three to stage two water restrictions. Progress relies on gradually increasing the system’s supply without compromising the pipe.
“Some level of outdoor restrictions will be in place for some time yet,” Bouchart said.
— with files from Aaron Sousa, Global News
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