'Stress corrosion cracking' found to be cause of 2018 pipeline explosion in Prince George

Cause of 2018 pipeline explosion released by TSB The Transportation Safety Board has released its findings into the cause of a natural gas pipeline explosion near Prince George.

Vancouver — A 2018 pipeline explosion near Prince George, B.C. was the result of "stress corrosion cracking," the Transportation Safety Board has found.

On Oct. 9, 2018, a natural gas pipeline operated by Enbridge ruptured near Prince George, which resulted in a significant fire and 125 people being evacuated.

In the days following the explosion, FortisBC asked residents to turn down their thermostats and reduce the amount of gas they were using, warning customers that they could lose gas supply. While no FortisBC infrastructure was damaged in the rupture, the utility used the pipeline to supply natural gas to its customers province-wide.

Now, nearly a year and a half later, the TSB said it found the rupture was caused by stress corrosion cracks on the outside surface of the pipeline and that the polyethylene tape coating that was put on the outside surface to prevent corrosion had deteriorated.

"This allowed soil moisture to come into contact with the pipe surface, leading to corrosion and cracking," the TSB said in news release about its findings. "Growing and merging over time, the cracks reduced the load-bearing capacity of the pipeline at normal operating pressures."

While the operator had a hazard management plan in place, the corrosion wasn't identified and an inspection of the pipeline segment that was originally scheduled for 2017 was delayed until the fall of 2018.

"As such, the existing cracks remained undetected," the TSB's statement said.

In a response to the board's findings, Enbridge said its reviewing the report closely and has completed a "pipeline integrity program" on its system throughout B.C.

"We know this incident has caused concerns and disrupted the lives of many people in the area. For that, we apologize," said Michele Harradence, senior vice president and chief operations officer, gas transmission and midstream for Enbridge in a news release.

"We commit that we have learned from this incident and have taken steps to ensure the safety of our natural gas system."