City says Calgary’s most critical water main needs repairs due to ‘wire snaps’ — but what are they?

August 9, 2024 Canuck

This summer, Calgary was forced to cope with water restrictions after the city’s largest water feeder main ruptured on June 5.

The critical artery’s catastrophic failure brought with it a horde of water supply issues, forcing residents of Calgary and all of the surrounding municipalities that rely on its supply to use much, much less.

Now, Calgary is set to re-enter a state of constant water conservation later this month, with Stage 4 outdoor water restrictions — the most restrictive — coming back into play. It’s because more urgently needed repairs along the feeder main were identified during a complete analysis of the 11-kilometre long pipe.

In response to the water crisis, city officials have been flooding citizens with information through updates on the status of the pipe for most of the summer. This included an alarming number of new “wire snaps” being detected along the feeder main as crews worked to gradually restore it to full service.

The messaging around wire snaps comes across as ominous. But perhaps more context is needed for non-engineers to make sense of it all.

So what is a wire snap? And what does any of this mean for the future of some of Calgary’s most indispensable infrastructure?

What ‘wire snap’ means

One expert says that in order to understand what these wire snaps are, it’s important to understand what material makes up the Bearspaw south feeder main.

According to the city, that particular feeder main is a prestressed concrete cylinder pipe (PCCP). Basically, layers of concrete encase a steel cylinder with tensioned steel wires that wrap around the pipe, and it’s all encased in mortar. PCCP is the only pipe type in Calgary’s water system that uses prestressed wires for structural reinforcement, the city confirmed to CBC News.

“That high-strength wire under tension provides the structural capacity for the pipe to withstand the pressure forces inside of it,” said Graham Bell, a research associate professor with the University of Tennessee at Knoxville, in the civil and environmental engineering department.

“Over time, due to operations and corrosion and a lot of other things, wires get reduced in strength, and eventually they’ll break.… With the prestressed concrete cylinder pipe, where that wire is under a lot of tension, you will actually hear the wire break. You’ll hear it snap.”

a chart with various pipe construction materials measured in kilometres. — A graphic from the City of Calgary shows what materials make up the city’s water pipes. (City of Calgary)

Bell added that the acoustic monitoring devices that Calgary has deployed along the feeder main can track those audible wire snaps.

“It’s an early warning system, and it’s a really good thing to do when you have to get a pipe back into operation,” said Bell.

“They know how many more wires broke and where those wire breaks are so they can associate the wire snaps that they hear with the previous damage. At some point, you will go past the tipping point of a critical number of wires where it can no longer maintain the pressure.”

two images. top image shows a large pipe with water coming out. bottom image is a diagram detailing parts of a PCC pipe. — The area of the Bearspaw south feeder main that ruptured on June 5, top, and a diagram displaying the components of a prestressed concrete cylinder pipe (PCCP), bottom. (City of Calgary)

Since bringing the Bearspaw south feeder main gradually back online, a spokesperson for the City of Calgary said its monitoring devices have picked up 17 wire snaps in various locations along the length of the pipe as of Aug. 8.

During a July 11 update, Francois Bouchart, director of capital priorities and investment with the City of Calgary’s infrastructure services department, said the wire snaps didn’t mean another catastrophic failure was imminent.

“These snaps did not mean another break is imminent. The wire coils around each 16-foot (4.8-metre) segment of pipe approximately 350 times,” he said, adding that the snaps were also spread across various locations along the feeder main.

Bouchart said that when water crews discovered five “hot spots” along the feeder main in mid-June, each section of pipe that was replaced had approximately 50 individual wire snaps per segment of pipe, which surpassed the threshold for failure concerns.

Why PCCP?

Calgary has two water treatment plants: the Bearspaw Water Treatment Plant, which draws water from the Bearspaw Reservoir on the Bow River, and the Glenmore Water Treatment Plant, which draws water from the Glenmore Reservoir fed by the Elbow River.

Built in 1975, the Bearspaw south feeder main — which is 11 kilometres long and as wide as two metres in parts — is Calgary’s most important water main. It feeds water directly from the Bearspaw plant to the rest of the city’s water mains, transporting roughly 60 per cent of the city’s treated water supply. Glenmore is responsible for the other 40 per cent.

According to the city’s website, the majority of Calgary’s water system is made up of polymer pipes. The system includes 187 kilometres of PCCP and 331 kilometres of other concrete pipes.

News of wire snaps along Calgary’s most critical water main likely makes one wonder why PCCP is used at all.

Kerry Black, assistant professor and Canada Research Chair with the University of Calgary’s Schulich School of Engineering, in the department of civil engineering, says “it’s way too premature to point fingers at different types of material, different types of pipe.”

Speculation around the reliability of PCCP built between certain decades has been widespread since the June 5 rupture. Large-diameter pipe experts like Bell have discussed some of the known issues with that specific pipe material.

LISTEN | Graham Bell discusses PCCP problems:

The Current19:29Which cities use the same kind of pipe that burst in Calgary?

The water main that failed in Calgary was a prestressed concrete cylinder pipeline, a type of infrastructure that has ruptured in other places, too. What other Canadian cities rely on these pipes?

Even the City of Calgary’s 2019 handbook on standard specifications and design guidelines for feeder main construction noted that PCCPs are “prone to accelerated mortar deterioration” from soil corrosion. It also flags that these are resource-intensive, difficult to repair pieces of infrastructure.

Black, who studies municipal water engineering, says she’s excited citizens are talking more about utility infrastructure and what makes up a city’s pipes. However, she believes in the integrity of the methods and materials used in Calgary for transporting water and wastewater, adding that PCCP has been used for decades and still is today.

“I don’t have concerns about that pipe, but I do have concerns, as a nation, on how we monitor the integrity of our water and wastewater infrastructure, and how much money we’re investing in it,” she said.

“We’re still well below what we need to be investing in it.”

Water ‘not valued’ the way oil is

Since the water crisis began, Black says she’s been receiving emails from people with concerns about civic water infrastructure. The No. 1 question asked in those emails, she says, is why water pipes are so vulnerable to suffering breaks, but the oil and gas industry seems to have pipelines figured out.

“What you’re transporting is really important in this conversation,” she said. “The reality with water is because it’s not valued the way that oil is, we allow it to leak out of our pipes and we’re OK with that. We have a different kind of relationship with it.”

“When you pay more for something, you value it more, and so you’re not letting a drop leak out of your pipes, you’re spending a ton of money on pipeline integrity. And we’re not doing that for municipal infrastructure.”

When asked if she believes this crisis will disrupt the concrete water pipe industry as a result of eroded public confidence in PCCP, Black says she’s more interested in how this conversation will push funding for better water infrastructure to the forefront.

“I don’t think you’re going to see major changes in how we deliver water, truthfully, unless we pay more. The reality is, the more expensive pipes are just that — they cost more. And that money can only come from one place, right?”

WATCH | Calgary mayor says feeder main will be shut down again:

City provides update on Calgary’s water system

2 days ago

Duration 27:58

The City of Calgary provides an update on the June 5 water feeder main rupture that affected its treated water supply.

In light of Wednesday’s announcement, Black believes this situation will continue to place a hard-to-ignore spotlight on the importance of infrastructure. With more severe water restrictions returning on Aug. 26 while the feeder main undergoes repairs, Black says she’ll be watching public reaction to water infrastructure budgets in the future.

At least $20-25 million in costs

Maintaining and inspecting water infrastructure — especially large-diameter pipe, like feeder mains — is a costly process.

During Wednesday’s press conference, Calgary Mayor Jyoti Gondek told reporters that city council “has made a very clear commitment to funding the medium- and long-term maintenance work that is needed for our water system.”

Repairing the initial feeder main break is expected to cost Calgary between $20 million and $25 million, according to the city. However, this figure doesn’t factor in costs associated with any of the upcoming repair work, nor does it include any lost revenue associated with the break.

A drone shot of a water main break. — A drone shot of the spot where the original June 5 rupture broke ground, next to a plaza on 16th Avenue N.W., just west of Home Road. (Monty Kruger/CBC)

It’s important to note that civic engineers have not confirmed what caused the near 50-year-old feeder main to prematurely deteriorate, according to the city, though some industry experts are drawing parallels to similar instances of feeder main failures in Calgary’s past.

Roy Brander was a senior infrastructure engineer for Calgary Waterworks — the former name of the city’s water services department — until he retired in 2016. During his career, he oversaw the aftermath of the 2004 feeder main rupture that left about 100,000 residents without water and flooded McKnight Boulevard.

That catastrophic failure triggered the launch of the city’s feeder main inspection program, according to a case study paper from Pure Technologies, the city’s water industry partner. Brander says that when the PCCP feeder main along McKnight ruptured 20 years ago, the city took proactive steps to mitigate the problem in the future.

In an email to CBC News, the city said it also has acoustic fibre optic monitoring — the same technologies that detected new wire snaps in the Bearspaw south feeder main — in place for the McKnight feeder main, running along McKnight Boulevard N.E. between 36th Street and 52nd Street.

a sandwich board sign on green grass reads "mandatory outdoor water restrictions in effect" — Calgary will remain under Stage 1 outdoor water restrictions until Stage 4 is initiated on Aug. 26. (Helen Pike/CBC)

Brander echoed Black’s thoughts about water being less valued than oil, leading to lower-cost infrastructure. Still, he believes these processes — including regular maintenance and monitoring, coupled with properly funded infrastructure — are vital for municipalities.

When the initial break occurred about two months ago, the city inspected just over four kilometres of the pipe. Once back in service, a tool known as a PipeDiver — which can move through the pipe and inspect it while it’s in service — was sent in from the Bearspaw treatment plant, inspecting the full length of the pipe.

The results of that analysis are what has triggered the newly scheduled maintenance at the end of the summer, after it found that 16 new areas of the pipe needed urgent repair.

In an email to CBC News sent Friday morning, the water services department said it used data from its acoustic monitoring and PipeDiver analysis to develop the feeder main rehabilitation plan.

When asked if the analysis found more wire snaps, a spokesperson for the department said “it was revealed that several sections of the Bearspaw south feeder main are approaching the threshold for the number of wire snaps that are considered acceptable at an operational level.”

16 new problem areas discovered

Brander says citizens are witnessing the benefits of pipe monitoring technologies.

He used the Titanic as an analogy for the June 5 feeder main rupture, comparing the proactive repair technologies for civic water systems to the safety measures that were initiated by the 1912 mega ship disaster.

“You can take comfort in all the lives the Titanic deaths saved,” he said.

“There’s no question that this [feeder main break] is going to mean that we are far less likely to have another break in the future, because we’ll be looking for them harder and repairing more proactively.”

Sections of the pipe are being triaged, and areas along 33rd Avenue N.W., Parkdale Boulevard and 16th Avenue N.W. will be prioritized beginning Aug. 28. Officials estimate that this repair work will take until Sept. 23, but the timeline is subject to change.

A map of a portion of Calgary highlighting various locations in which repairs to its water system is needed. — Sixteen new hot spots were detected along a key Calgary feeder main. Planned maintenance will be carried out over the coming weeks, city officials say. (City of Calgary)

“In June, we actually replaced several segments of the feeder main with new pipe. This time we are planning to take a different approach,” said Gondek, adding that the city is planning to address the urgent repairs through the reinforced concrete encasement method.

“This is the type of repair that we completed earlier this summer when we found the thrust block and we reinforced the existing pipe instead of removing and replacing it. This work includes exposing the pipe through excavation, building an exterior reinforcing steel cage, pouring concrete and then backfilling the excavation.”

Plans to create redundancy in the system

During a Friday afternoon news conference, Calgary’s general manager of infrastructure services, Michael Thompson, said the city has learned a lot about the pipe since it ruptured in early June.

“We know we will need a medium- and long-term rehabilitation plan,” he told reporters.

“We’re looking at a number of options, including replacing individual segments of pipe, externally reinforcing segments of pipe, installing a liner through the pipe and constructing a new pipe adjacent to this existing pipe.”

City officials discussed creating more redundancy in Calgary’s water system during the Friday update, adding that plans to construct other feeder mains are already in the works.

“These are projects that have been on the books for some time,” said Gondek.

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