Calgary officials aiming for ‘low end’ of repair timeline after pipes arrive from San Diego

Two critical pieces of pipe needed to repair a burst water main that triggered citywide water restrictions arrived from San Diego Tuesday evening and are being prepared for installation.

Calgary city officials now say repairs could progress faster than previously expected.

On Wednesday afternoon, the city's general manager of infrastructure services, Michael Thompson, provided an update on the repair schedule.

“Looking at the work completed to date – particularly the excavation and exposure of the five pipe sections – we can now report that we are targeting the lower part of our original schedule of three to five weeks, which is July 5,” Thompson said.

“There are still many risks ahead, but with each passing day that we work on this complex repair, we are more confident about our schedule.”

During the city's Wednesday morning meeting, Mayor Jyoti Gondek thanked the Southern California county's water authority and said a local shop was in the process of sandblasting and epoxying the pipe to ensure it was ready for use, while workers went to work to eliminate five “hot spots” along the main line that need to be repaired.

“As we heard yesterday, these hotspots are not leaks, but sections of the main line that needed to be repaired immediately,” Gondek said.

Wednesday marks two weeks since Bearspaw's southern supply line – which is 11 kilometres long and up to two metres wide in places – ruptured. Since then, Level 4 water restrictions have been issued for outdoor water use, as well as a citywide fire ban.

Calgary officials aiming for ‘low end’ of repair timeline after pipes arrive from San Diego

One of the sites where digging is taking place to repair hotspots is seen at 16th Avenue NW and 46th Street. (Monty Kruger/CBC)

When asked why the infrastructure was sourced from San Diego rather than a closer location, Gondek said the city initially considered local options, but the size of the line posed a significant challenge.

“That’s not generally the size of pipe used in oil and gas production,” she said.

“When a part like this is available, it's generally because it's provided by an organization that provides water to residents. 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 will speed up repairs.

All this has drawn attention to the water infrastructure and one expert says the break may have something to do with the material of the main water supply line.

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 at Structural Technologies, a company specializing in large diameter pipe repair.

In an interview with CBC Radio's “The Current” on Tuesday, Bell explained that Bearspaw's southern main pipe is a prestressed concrete cylinder pipe (PCCP), a composite pipe made primarily of concrete.

“Most of our pipes were made of a single material, like cast iron or steel or maybe slightly reinforced concrete, until around World War II when we needed steel for the war effort,” Bell said.

To explain the layers of this PCCP, he says that first, concrete is poured with a thin steel cylinder inside it, and that steel cylinder acts as a membrane to keep the water in the pipe. Then it is wrapped with incredibly high-strength steel wires, which Bell says are “about four to five times stronger than the steel can inside.”

It is these steel wires that determine the structural load-bearing capacity of the pipe.

LISTEN | A lesson on prestressed concrete cylinder tubes:

“These steel wires developed some metallurgical problems over time, and in particular the pipes produced between 1960 and 1980 have more problems than the other pipes outside this [time period].”

So what happened to these pipes?

Bell says that at that time, some parameters were changed in the manufacturing process that made the tubes “less robust.”

“We are now dealing with pipes that are 40 to 50 years old, they are aging and interacting with the environment, they are deteriorating and causing problems,” he said.

“This is not unusual for pipes of this era.”

PCCP problems?

City officials say the broken section of Bearspaw's south main was installed in 1975, but they have not yet confirmed the cause of the June 5 break.

“They generally don't leak before they burst,” Bell added in an interview with the Calgary Eyeopener on Wednesday.

He says these high-voltage lines are brittle and don't allow much play.

“They break, and that leads to the catastrophic failures that you see and experience.”

A rupture occurred in Bearspaw's southern water main, which is 11 kilometers long and up to two meters wide in places, leaving hundreds of homes and businesses in the northwest of the city without water.A rupture occurred in Bearspaw's southern water main, which is 11 kilometers long and up to two meters wide in places, leaving hundreds of homes and businesses in the northwest of the city without water.

On June 5, Bearspaw's south water main, which supplies about 60 percent of the city's water supply, broke. (City of Calgary)

He says there were some changes to the standards in the 1970s, but since the 1980s, after that was corrected, there has been no problem

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

“They basically occur anywhere where prestressing has been used,” he said.

“It just depends on the manufacturing process, how much was used. Not all pipes, not all wires are bad.”

He says the challenge with PCCP is to repair damaged lines before they become a problem, describing the process as difficult.

LISTEN | Researcher explains manufacturing problems of certain water infrastructures:

While repairs continue, authorities continue to urge Calgary residents to use water sparingly. Gondek said 450 million litres were used across the city on Tuesday, meaning usage has remained relatively consistent this week.

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

Gondek thanked the people of Calgary for “holding up” and not exceeding the safe consumption limit of 480 million litres.

Options for river diversion

On Tuesday, the provincial government granted the City of Calgary two temporary diversion licenses that now allow the city to divert 200,000 cubic meters (200 million liters) of water from the Bow River through diversion points for industrial use as non-potable water.

This means that the City of Calgary can now track and manage water withdrawals from the river for the duration of these permits.

Officials said repairs to the first burst pipe were completed on Sunday and the site is now being filled with soil.Officials said repairs to the first burst pipe were completed on Sunday and the site is now being filled with soil.

The original water main break has been repaired. Officials are now focusing on five fires in the main line. (Terri Trembath/CBC)

Ryan Fournier, spokesman for the provincial Ministry of Environment and Protected Areas, said it was an attempt to relieve the pressure on the drinking water system caused by the critical rupture of the main supply line.

During a press conference Wednesday afternoon, Coby Duerr, deputy director 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 domestic water for construction work.

“The water is free and it is the responsibility of the end user to ensure that the water is suitable for the intended use,” Dürr said, adding that the city could provide more information in the coming days.

“We would like to thank the provincial government for expediting the necessary approvals to move this program forward quickly.”

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