The city released the preliminary findings of an investigation into the Bearspaw South power grid failure late Friday afternoon, suggesting a number of factors were behind its failure.

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

Investigators isolated three possible factors in his statement Friday:

• Microcracking of the outer layer of protective mortar of the pipe;
• High levels of chloride in soil at various locations; and
• Wires that have broken due to corrosion and hydrogen embrittlement.

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

“The Bearspaw South Feeder Main is a critical piece of infrastructure and is responding well to the rehabilitation work that was completed between June and November and is now stabilized,” said Michael Thompson, City of Calgary’s General Manager of Infrastructure Services.

“Through acoustic monitoring, we recorded only two wire breaks on the power line between October and November. During the months of July and August, there were 23 wires.

Preliminary review of the pipeline design and operation confirmed that the original design was consistent with the guidelines of the time.

Pipeline operations were found to be well within the pipeline’s design parameters.

What’s next

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

Construction on two other pipeline segments, one along Parkdale Blvd. NW between 26 Street and 27 Street NW and the other at the Memorial Drive exit ramp onto northbound Crowchild Trail are nearly complete.