It could be worse. And there’s a good chance it is — or will be soon. At any minute, in fact.A third party review into the integrity of Calgary’s water system will ultimately be looking for signs of what could potentially be systemic structural weakness across the entire water network.That’s because the design flaws in the type of concrete pipe that failed have been well documented across North America and Europe — and China — for at least the past two decades. .The particular cement and rebar construction that has been used since the 1970s is prevalent all through Calgary as well, officials confirmed.“The pipes have been used across North America and are used in many jurisdictions. When we do the review, we'll be looking at this specific incident to understand what the causes work and to take lessons from that and then we'll be applying those lessons across the entire network,” Infrastructure Services general manager Michael Thompson said at the city’s daily media briefing on Tuesday..Sooner is better.According to the Water Research Foundation, extensive water main failures using this particular construction have been widely documented since at least 2006.The condition had been in a National Research Council of Canada (NRCan) report as far back as 2008.Presently, more than 32,600 km (20,300 mi) of concrete pipes had been installed in the United States and Canada, according to the American Concrete Pressure Pipe Association, and over 20,000 km (12,427 mi) had been installed in China by the end of 2019.The problem is particularly acute in China, which coincidentally shares similar geology as Alberta.A 2019 study sponsored by WaterRF revealed statistically that for a total of 5 million pipes produced between 1940 and 2006, one rupture and 66 other failures occurred for every 13,200 pipes, or approximately every 80 km (50 miles) of pipeline.Luckily, in Calgary asbestos cement pipes were used for water distribution mains only make up about 1% or 67 kilometres of the water main network. In a nutshell, the outer concrete layer is particularly susceptible to interaction with chemicals in groundwater that essentially render it into talcum powder.Indeed, a photo supplied by the city of Calgary shows the damaged section with the exposed steel reinforcement bars that are meant to be encased in cement.The irony is that typical water systems can leak as much as 30% of produced water volumes without being noticed until they catastrophically fail..The loss of this prestress due to wire breakage depends on the number and location of broken wires and the maximum pressure likely to occur in the future. The report said “the most common failure scenario… is that the thin cylinder is exposed to internal water through cracks in the concrete core as a result of both stress redistribution and stress release with an increase in the number of broken wires under a combined load.”In other words, what happened in Bowness on June 5, cutting off 60% of the city’s water supply.The good news is that public and private water service lines, which deliver drinking water from the main to homes and businesses, do not have asbestos cement, which was largely discontinued decades ago.But statistically speaking, that means there is a strong likelihood of the review uncovering similar hotspots along the entire Calgary mainline, especially considering there are now five problem areas along just the 11 kilometre length of the Bearspaw main..Thompson said the scope of the review will include, but not be limited to, understanding the factors that contributed to the original pipe failure, current practices for inspection and asset sustainability and recommendations for specific actions to “improve water supply resilience.” .The review will be guided by an expert panel from academia, the water industry, water utilities, management and engineering and government entities focused on infrastructure, he added.Presumably — but without saying it directly — the worst case scenario is that it will all eventually have to be ripped out and replaced with steel. That’s exactly what the City of Denver did after a catastrophic water main break in 1997.“The hotspots we mentioned are not leaks. There are sections of pipe that are in need of more immediate repair,” Thompson said.
It could be worse. And there’s a good chance it is — or will be soon. At any minute, in fact.A third party review into the integrity of Calgary’s water system will ultimately be looking for signs of what could potentially be systemic structural weakness across the entire water network.That’s because the design flaws in the type of concrete pipe that failed have been well documented across North America and Europe — and China — for at least the past two decades. .The particular cement and rebar construction that has been used since the 1970s is prevalent all through Calgary as well, officials confirmed.“The pipes have been used across North America and are used in many jurisdictions. When we do the review, we'll be looking at this specific incident to understand what the causes work and to take lessons from that and then we'll be applying those lessons across the entire network,” Infrastructure Services general manager Michael Thompson said at the city’s daily media briefing on Tuesday..Sooner is better.According to the Water Research Foundation, extensive water main failures using this particular construction have been widely documented since at least 2006.The condition had been in a National Research Council of Canada (NRCan) report as far back as 2008.Presently, more than 32,600 km (20,300 mi) of concrete pipes had been installed in the United States and Canada, according to the American Concrete Pressure Pipe Association, and over 20,000 km (12,427 mi) had been installed in China by the end of 2019.The problem is particularly acute in China, which coincidentally shares similar geology as Alberta.A 2019 study sponsored by WaterRF revealed statistically that for a total of 5 million pipes produced between 1940 and 2006, one rupture and 66 other failures occurred for every 13,200 pipes, or approximately every 80 km (50 miles) of pipeline.Luckily, in Calgary asbestos cement pipes were used for water distribution mains only make up about 1% or 67 kilometres of the water main network. In a nutshell, the outer concrete layer is particularly susceptible to interaction with chemicals in groundwater that essentially render it into talcum powder.Indeed, a photo supplied by the city of Calgary shows the damaged section with the exposed steel reinforcement bars that are meant to be encased in cement.The irony is that typical water systems can leak as much as 30% of produced water volumes without being noticed until they catastrophically fail..The loss of this prestress due to wire breakage depends on the number and location of broken wires and the maximum pressure likely to occur in the future. The report said “the most common failure scenario… is that the thin cylinder is exposed to internal water through cracks in the concrete core as a result of both stress redistribution and stress release with an increase in the number of broken wires under a combined load.”In other words, what happened in Bowness on June 5, cutting off 60% of the city’s water supply.The good news is that public and private water service lines, which deliver drinking water from the main to homes and businesses, do not have asbestos cement, which was largely discontinued decades ago.But statistically speaking, that means there is a strong likelihood of the review uncovering similar hotspots along the entire Calgary mainline, especially considering there are now five problem areas along just the 11 kilometre length of the Bearspaw main..Thompson said the scope of the review will include, but not be limited to, understanding the factors that contributed to the original pipe failure, current practices for inspection and asset sustainability and recommendations for specific actions to “improve water supply resilience.” .The review will be guided by an expert panel from academia, the water industry, water utilities, management and engineering and government entities focused on infrastructure, he added.Presumably — but without saying it directly — the worst case scenario is that it will all eventually have to be ripped out and replaced with steel. That’s exactly what the City of Denver did after a catastrophic water main break in 1997.“The hotspots we mentioned are not leaks. There are sections of pipe that are in need of more immediate repair,” Thompson said.
