Preliminary findings of Bearspaw feeder main investigation indicate multiple factors for failure

A new length of feeder main pipe sits at the ready for city crews to put into place, nearly a week after the old water main broke, flooding a section of northwest Calgary.

The city released preliminary findings of an investigation into the failure of the Bearspaw South feeder main late Friday afternoon suggesting that there were a number of factors behind its failure.

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

Investigators isolated three possible factors in its Friday statement:

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

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

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

“Through our acoustic monitoring, we have recorded only two wire snaps on the feeder main between October and November. Throughout July and August, there were 23 wire snaps.”

The preliminary review of the pipe’s design and its operation confirmed that the original design was consistent with the guidelines of the time.

Operations of the pipe were 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 Dec.11.

Construction on two other segments of the pipe, one along Parkdale Boulevard. N.W. between 26 Street and 27 Street N.W. and the other at the off-ramp from Memorial Drive onto Crowchild Trail northbound are both almost complete.