Several factors caused the feeder’s main line to fail: City of Calgary

The city late Friday afternoon released preliminary findings from an investigation into the failure of the Bearspaw South supply line, indicating there are a number of factors behind its failure.

The aim of the investigation, which was overseen by Associated Engineering and Pure Technologies, was to better understand what led to the pipe’s deterioration until it failed on June 5, 2024.

Researchers isolated three possible factors in their Friday statement:

• Microcracks of the outer protective layer of the pipe;
• High chloride levels in the soil at various locations; And
• Wires that snapped due to corrosion and hydrogen embrittlement.

They concluded that there was no single factor that led to the main failure in June.

“The Bearspaw South Feeder Main is a critical piece of infrastructure and is responding well to the rehabilitation work completed between June and November and now stabilized,” said Michael Thompson, general manager of infrastructure services for the City of Calgary.

“Thanks to our acoustic monitoring, we only registered two wire breaks on the main supply between October and November. In July and August there were 23 wire breaks.”

The preliminary assessment of the pipe design and its operation confirmed that the original design was in accordance with the guidelines of the time.

The performance of the pipe was found to be well within the design parameters of the pipe.

What’s next

The final report will be presented to the city’s infrastructure and planning committee on December 11.

Construction of two other segments of pipe, one along Parkdale Boulevard. NW between 26 Street and 27 Street NW and the other at the northbound Memorial Drive exit to Crowchild Trail are both nearly complete.