The water main that burst last Friday in Montreal may have been rated A, the highest, but this data did not allow us to determine its real condition, maintains the City of Montreal. Degradation had been observed during an inspection in 2017, but this main should have been able to hold up until 2030, according to the authorities, who are still trying to understand the reason for the premature corrosion of the infrastructure.
On Tuesday, the Water Department wanted to clarify the rating system given to all pipes. The segment that suffered a break had an A rating, the highest according to the methodology established by the Ministry of Municipal Affairs, which is based on the number of breaks and the age of the pipes.
The city uses these ratings to develop its interventions to be carried out on secondary pipes, but it does not rely on them for large-diameter main pipes, because other criteria must be taken into account, explained Chantal Morissette, director of the City of Montreal’s Water Department. “Our 84-inch pipe had never broken and it was only 40 years old. So, this pipe was category A. But that’s not the category we use to make our decisions,” she said.
Broken cables
Electromagnetic inspections carried out in 2007 and 2017 on the water main that burst last Friday showed deterioration of steel cables encircling the 2.1-metre diameter pipe. The inspection carried out in 2007 on the 6.1-metre segment of the pipe under René-Lévesque Boulevard, near De Lorimier Avenue, showed that 15 of the 510 cables had failed. By 2017, that number had climbed to 35 for the same segment. However, the City considered that this rate was not a cause for concern in the short term, as the threshold requiring intervention was 65 broken cables.
Thus, according to an analysis carried out to determine the deterioration curve of the pipe, the City had a period of 12 to 15 years before intervening. According to the standards of the American Water Works Association, which provides for inspections every six or seven years, the City planned to repeat the inspection later this year.
“It is clear that the pipe deteriorated much more quickly than what was anticipated in the degradation curves. This pipe will be the subject of an in-depth diagnosis so that we can understand what could have caused this deterioration and caused a breakdown that we could not have foreseen,” indicated Chantal Morissette.
Criticized by the opposition for its lack of transparency, the Plante administration defended itself from having hidden information concerning the state of the pipeline following the 2017 inspection. “We were in a hurry. We wanted to keep people safe,” argued Maja Vodanović, head of the water file on the executive committee. “We give you the information as quickly as we have it.” […] We did not want to give incomplete information.”
“Zero risk does not exist”
The City intends to maintain the pace of monitoring operations every six or seven years in the main pipes, especially since this is a costly and complex operation that requires the pipe to be taken out of service so that a robot can circulate in it. Chantal Morissette points out, however, that the City could use new technologies in a monitoring contract that will be awarded soon.
She added, however, that if the diagnosis the city obtains for the pipe that burst on Friday allows it to believe that other major pipes are in the same situation, practices could be revised. “Zero risk does not exist,” the official stressed, however.
The pipe that burst is a C301 type pipe, made of steel and concrete. C301 pipes are known to be susceptible to corrosion. That is why, since 1988 and 1989, the City has required that they be coated inside and out to protect them from rust. However, only 40 of the 150 kilometres of C301 pipes in Montreal are protected by these coatings, indicated Chantal Morissette.
The opposition at City Hall is criticizing the administration for refusing to disclose all available information to Montrealers. “It is certain that on Friday morning, Mr.me Morissette gave a report to the mayor,” said Ensemble Montréal leader Aref Salem.
He is also concerned about the condition of the other C301 pipes dating from the same period and is demanding that the City carry out more frequent inspections of these pipes. “Montrealers must be reassured today about the condition of the water system.”