Officials in Calgary aim for ‘lowest’ repair timeline after pipes arrive from San Diego

Officials in Calgary aim for ‘lowest’ repair timeline after pipes arrive from San Diego
Officials in Calgary aim for ‘lowest’ repair timeline after pipes arrive from San Diego

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.

Officials with the City of Calgary are now reporting that repairs could happen sooner 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 – specifically the excavations and uncovering of the five pipe sections – we can now share that we are targeting the lowest point of our original three to five week timeline, which is July 5 ,” 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 Wednesday morning, Mayor Jyoti Gondek thanked the Southern California Water Authority and said a local shop is sandblasting the pipe and coating it with epoxy to ensure it is ready for use so crews can get to work on five “hot spots” along the main that need repairs.

“As we heard yesterday, these hotspots are not leaks, but parts of the power line that needed immediate repairs,” Gondek said.

Wednesday marks two weeks since the Bearspaw southern feeder main — which is 7 miles long and up to 7 feet wide in some places — suffered a breach. Since then, Stage 4 water restrictions on outdoor water use have been introduced, in addition to a city-wide fire ban.

One of the locations 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 being shipped in from San Diego rather than sourced from somewhere closer, Gondek said the city first considered local options, but the size of the pipeline posed a significant challenge.

“This is generally not the size of pipe used in oil and gas operations,” she said.

“When this type of component is available, it’s usually because an organization that delivers water to residents has it on hand. And that’s why the San Diego County Water Authority is such an important partner for us.”

Gondek says the city chose the option that would speed up repairs.

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, specializing in the repair of large diameter pipes.

In an interview with CBC Radios The current On Tuesday, Bell explained that Bearspaw’s southern feeder 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:

“Over time, these steel wires developed some metallurgical problems. In particular, the tubes produced between approximately 1960 and 1980 are experiencing greater problems than the other tubes produced outside that period.”

What happened to those pipes?

Bell says that around that time, some parameters were changed during the manufacturing process, making the pipes “less robust.”

“What we’re dealing with now is these pipes are 40 to 50 years old, they’re aging and they’re interacting with the environment, they’re deteriorating and they have problems,” 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 on Wednesday Calgary eyeopener.

He says these high-voltage wires are brittle and don’t have much play.

“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, broke on June 5. (Municipality of Calgary)

He says that there were some changes in standards in the 1970s, but that this has not been a problem since the 1980s, after that was corrected.

Bell said he has been involved in a number of studies involving PCCP and is aware of about 600 examples of catastrophic failures that have occurred since 1968.

“They’re actually found anywhere that preload has been applied,” he said.

“It just depends on the production, how much was used. It’s not all pipes, not all wires that are bad.”

He says the challenge with PCCP is to repair the damaged wires before it becomes a problem. He calls it a difficult process.

LISTEN | Researcher explains production issues behind some water infrastructure:

As repairs continue, officials are still urging Calgary residents to remain water-conscious. Gondek said 450 million litres were used in the city on Tuesday, meaning usage has remained relatively consistent this week.

According to the mayor, 600 Olympic swimming pools of water have been saved in the past two weeks.

Gondek thanked Calgarians for “holding the line” and staying below the safe usage threshold of 480 million litres.

River diversion options

On Tuesday, the provincial government issued two temporary diversion permits to the city of Calgary, which now allows 200,000 cubic meters (200 million litres) for non-potable industrial use through diversion points from the Bow River.

This means the City of Calgary can now track and manage water withdrawals from the river throughout the life of the permits.

The first water main break has been repaired. Now officials are focusing on five hot spots in the feeder main. (Terri Trembath/CBC)

Ryan Fournier, the press secretary for the provincial Ministry of Environment and Protected Areas, said it is an effort to relieve pressure on the drinking water system due to the critical main break in the supply line.

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 it will be the responsibility of the end user 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 necessary to move this program forward quickly.”