Two major sections of pipe needed to repair a water main that burst, causing citywide water use restrictions, arrived from San Diego Tuesday evening and are now being prepared for installation.
City of Calgary officials now say repairs could proceed faster than previously expected.
On Wednesday afternoon, the city’s general manager of infrastructure services, Michael Thompson, provided an update on the repair timeline.
“Looking at the work completed to date – particularly the excavations and uncovering of the five pipeline sections – we can now say that we are targeting the lowest point of our original timeline of three to five weeks, which is July 5 would be,” Thompson said.
“There are still many risks ahead, but every day we complete this complex repair, we become more confident in our timeline.”
During the city’s briefing on Wednesday morning, Mayor Jyoti Gondek thanked the Southern California Water Authority and said a local workshop is sandblasting the pipe and coating it with epoxy to ensure it is ready for use so teams can work on five ‘hotspots’ along the main pipeline that need to be repaired.
“As we heard yesterday, these hotspots are not leaks, but parts of the main pipe that needed immediate repairs,” Gondek said.
Wednesday marks two weeks since the Bearspaw Southern Feeder Main — which is seven miles long and up to six feet wide in places — suffered a rupture. Since then, Stage 4 water restrictions on outdoor water use have been put in place, along with a citywide fire ban.
One of the sites being excavated for hotspot repairs is pictured along 16th Avenue NW and 46th Street. (Monty Kruger/CBC)
In response to questions about why the infrastructure was moved out of San Diego and not somewhere closer, Gondek said the city did consider local options first, but the size of the pipeline posed a major challenge.
“This is generally not the size of pipe used in oil and gas operations,” she said.
“When this type of part is available, it’s usually because an organization that delivers water to residents is the one that has it on hand. And that’s why the San Diego County Water Authority has been such an important partner for us.”
Gondek says the city chose the option that would make repairs faster.
All of this has focused attention on the water infrastructure and one expert says the rupture may be related to the material the water supply pipe is made of.
Graham Bell is an associate professor in the Department of Civil and Environmental Engineering at the University of Tennessee. He is also vice president of technical services for Structural Technologies, which specializes in large-diameter pipe repair.
In an interview with CBC Radio The current Bell explained Tuesday that the Bearspaw south supply line is a prestressed concrete cylinder pipe (PCCP), a composite pipe material composed primarily of concrete.
“Most of our pipes were made of a single material, like cast iron or steel, or maybe lightly reinforced concrete, until about World War II, when we needed steel for the war effort,” Bell said.
To explain the layers of this PCCP, he says that concrete is first poured with a thin steel cylinder inside of it, and that steel cylinder acts as a membrane to keep the water inside the pipe. Then it’s wrapped with incredibly strong steel wires, which Bell says are “about four to five times stronger than the steel can that’s inside.”
It is those steel wires that determine the structural capacity of the pipe.
LISTEN | A lesson on prestressed concrete cylinder tubes:
“Those steel wires developed a number of metallurgical problems over time, and in particular the pipes manufactured between about 1960 and 1980 have a greater number of problems than the other pipes outside of that.”
What happened to those pipes?
Bell says that around that time, a number of parameters in the manufacturing process changed, making the pipes “less robust.”
“We are dealing here with pipes that are 40 to 50 years old. They age and impact the environment. They deteriorate and problems arise,” he said.
“That’s not unusual in this pipe era.”
Problems with PCCP?
City officials say the ruptured section of the Bearspaw South Supply Line was installed in 1975, though they have not confirmed the cause of the rupture that occurred on June 5.
“They generally don’t leak until they break,” Bell added in an interview with the Calgary eye opener.
He says these high-voltage wires are brittle and don’t yield much.
“They snap and that leads to the catastrophic failures you see and experience.”
Bearspaw’s south water main, which is responsible for about 60 percent of the city’s water supply, suffered a break on June 5. (City of Calgary)
He says there were some changes to the standards in the 1970s, but once that was corrected there haven’t been any problems since the 1980s.
Bell said he has been involved in a number of studies involving PCCP and knows of about 600 examples of catastrophic failures that have occurred since 1968.
“They’re actually found everywhere that preload was used,” he said.
“It just depends on the production, how much was used. It’s not all tubing, not all wire is bad.”
He says the challenge at PCCP is fixing the wires in distress before they become a problem, calling the process difficult.
LISTEN | Researcher explains production issues behind some water infrastructure:
As repairs continue, officials are still urging Calgarians to remain water conscious. Gondek said 450 million liters were used in the city on Tuesday, meaning usage has remained relatively consistent this week.
According to the mayor, the water consumption of 600 Olympic swimming pools has been saved in the past two weeks.
Gondek thanked Calgarians for “holding the line” and staying below the safe usage threshold of 480 million gallons.
River diversion options
On Tuesday, the provincial government issued two temporary diversion permits to the City of Calgary, allowing up to 200,000 cubic metres (200 million litres) of water for non-potable industrial uses to be discharged through diversions from the Bow River.
This means the City of Calgary can now monitor and manage water withdrawals from the river for the life of the permits.
The first break in the water pipe has been repaired. Now officials are focusing on five hotspots in the feeder main. (Terri Trembath/CBC)
Ryan Fournier, spokesman for the provincial Department of Environment and Protected Areas, said it is an attempt to relieve pressure on the drinking water system caused by the main line break.
During the briefing on Wednesday afternoon, Coby Duerr, deputy chief of the Calgary Emergency Management Agency (CEMA), said the city is working closely with the local construction industry to open two sites along the Bow River to provide non-potable water for construction work.
“This water will be free and will be the end user’s responsibility to ensure the water is suitable for the intended use,” Duerr said, adding that the city could provide more information in the coming days.
“We would like to thank the provincial government for expediting the permits needed to quickly implement this program.”
