PRINCE GEORGE (NEWS 1130) – A pipeline rupture and fire near Prince George almost a year and a half ago was caused by corrosion and stress cracking, according to the Transportation Safety Board.
An investigation into the explosion northeast of the city on Oct. 9, 2018 has found soil moisture was able to make it through a protective coating that had deteriorated over time. That led to stress cracking and eventually the failure of the metre diameter, high pressure, Enbridge natural gas pipeline.
“This allowed soil moisture to come into contact with the pipe surface, leading to corrosion and cracking. Growing and merging over time, the cracks reduced the load-bearing capacity of the pipeline at normal operating pressures,” the Transportation Safety Board said in a release.
“The pipeline operator had a stress corrosion cracking hazard management plan in place for this pipeline. However, the extent of the existing cracking on the segment of pipe that ruptured was not identified. The model used to predict crack growth did not take into account all potential uncertainties in the predicted crack growth. This resulted in cracks growing at higher rates than the model predicted. Additionally, an inspection of this pipeline segment scheduled for 2017 was deferred until the fall of 2018. As such, the existing cracks remained undetected.”
The rupture resulted in a months-long natural gas shortage in B.C., but no injuries were reported and impacts to the environment were minimal.
“Although emergency response activities were successful in mitigating the impacts of the occurrence, the investigation determined that during periodic emergency response exercises in the 4 years prior to the occurrence, not all nearby communities and operators of nearby pipelines were included,” the Transportation Safety Board said. “If pipeline emergency response exercises are not conducted periodically with all potentially affected stakeholders, gaps in emergency response plans may not be identified, thereby increasing the risk that all parties will not be sufficiently prepared to respond to a pipeline emergency.”
The TSB has advised Westcoast Energy to improve its inspection and pipeline management practices. Shortly after the pipeline failure, the National Energy Board, now named the Canada Energy Regulator, issued new safety orders in an effort to protect people and the environment in the event of such an event.
In a release, Enbridge says it has done work to prevent future incidents like this from happening.
“We know this incident has caused concerns and disrupted the lives of many people in the area. For that, we apologize,” says Michele Harradence, Senior Vice President and Chief Operations Officer, Gas Transmission and Midstream for Enbridge. “We commit that we have learned from this incident and have taken steps to ensure the safety of our natural gas system.”
The 2,900-kilometre pipeline extends from just beyond Prince George, in Fort Nelson, to the U.S. border.
-With files from The Canadian Press