The Transportation Safety Board of Canada (TSB) has released its investigation report (P22H0023) into a pipeline rupture that resulted in an explosion and fire near Fox Creek, Alberta in 2022.
Officials say in the early morning of April 7, 2022, a natural gas pipeline operated by NOVA Gas Transmission Ltd. ruptured. Investigators say the escaping gas ignited, resulting in a fire that burned an area of 12,000 square metres. They believe the fire self-extinguished after the flow of gas was stopped by manually closing isolating valves upstream and downstream of the rupture. Officials say there were no injuries reported and no evacuation was required.
Investigators found the pipeline ruptured due to reduced pipe wall strength caused by external corrosion, noting the pipeline’s external coating system had degraded over time, exposing the surface of the pipe to the external soil environment. Investigators believe an impressed current cathodic protection (CP) system that was installed to protect the pipe surface from corrosion in the event of degradation or failure of the external coating, was not adequately protecting the exposed surface of the pipe as intended.
According to investigators, the pipeline’s proximity to a nearby third-party pipeline, combined with degraded pipe coating, low soil resistivity and an incomplete electrical CP bond, contributed to stray current interference, which led to accelerated external corrosion of the pipeline at the occurrence location.
Experts are warning there is currently no centralized system in Canada for consolidating information about pipeline CP system locations and operating characteristics. Experts believe if pipeline operators are not fully aware of the operating characteristics of third-party CP infrastructure in close proximity to their pipelines, CP effectiveness may be compromised, increasing the risk of corrosion. Officials say after the occurrence, NOVA Gas Transmission Ltd. replaced the damaged sections of the pipe and initiated steps to permanently shut down the entire pipeline.
See the investigation page for more information.
The TSB is an independent agency that investigates air, marine, pipeline, and rail transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.
