Downtown water main burst | Good rating, poor condition

The pipe that burst last Friday in downtown Montreal had the best possible condition rating, but its steel reinforcement was compromised, the City of Montreal revealed Tuesday. Other sections could be in the same situation.

An inspection in 2018 revealed that 35 of the 510 steel cables were broken in the six-metre-long concrete pipe that collapsed, said the city’s water department director, Chantal Morissette, at a press briefing. However, the structure only dated back to 1985 and its expiration date was still far away.

This finding led to additional analyses being carried out on the pipeline, which concluded that replacement work would need to be carried out within 10 to 15 years.

“It is clear that the driving deteriorated much more quickly than anticipated,” said the official. “This driving will be the subject of an in-depth diagnosis so that we can understand what may have caused this advanced deterioration.”

Ten years earlier, in 2007, a previous inspection revealed that 15 reinforcement cables had failed.

The pipe that gave way on Friday actually had an “A” deterioration rating, as The Press reported it on Tuesday morning, Mr.^me Morissette. But this indicator only takes into account the age of the structure and the number of ruptures it has suffered. C301 prestressed concrete pipes (like the structure that gave way) are particularly subject to corrosion and are all “under surveillance” by municipal engineers.

No “magic number”

The City of Montreal argued that there was no absolute threshold of broken cables above which an emergency replacement was automatically carried out. The analysis must take into account several factors, including the water pressure received in the pipe.

“The 35 broken cables is really not a magic number,” continued Mr.^me Morissette. “Rest assured that if we have auscultation results that show us that there is a risk of breakage – no matter the number of cables [rompus] –, we stop driving immediately.”

After the two inspections carried out in 2018, the pipeline was placed back on the normal pipeline reinspection schedule. It was also due to be subject to new inspections starting in the fall, assures the City of Montreal.

Maja Vodanović, the elected official responsible for water on the executive committee, reiterated the Plante administration’s confidence in civil servants and their decisions. “The City of Montreal’s Water Department is incredibly rigorous and competent,” she said. “I hope that reassures the population.”

The elected official also stressed that the prevention work of civil servants has now allowed the entire east end of Montreal to continue to have drinking water despite the failure of this important pipeline.

Opposition worried

Montreal has 110 kilometres of pipes identical to the one that broke on Friday, with a greater or lesser number of broken cables depending on the sector. A burst like the one that occurred on Friday, “we are doing everything we can to prevent that from happening [à nouveau]but zero risk doesn’t exist,” said Chantal Morissette.

Aref Salem, the leader of the opposition on Montreal city council, said he was “very concerned” about the possibility of another pipeline rupture occurring on a similar line. Citizens, “if it’s not nature that’s flooding them, it’s the City of Montreal that’s flooding them,” he said. We’re going to have to change the standards, we’re going to have to shorten [les délais entre] auscultations. […] Montrealers must be reassured today about the state of their water network.”

The elected official also denounced the fact that crucial information about this conduct was revealed only five days after the incident.

An investigation is underway and the section that gave way will soon be sent to a laboratory to be analyzed in detail. The lessons learned from this event will be useful to the service’s engineers, assured his boss. As for the repair of the pipeline, it will not be able to begin for several weeks, due to a lack of parts.