A crack was identified as the cause of a pipeline rupture that triggered a wildfire in west-central Alberta in 2024, according to a report released on Thursday by the Transportation Safety Board of Canada (TSB). The TSB disclosed its findings on the rupture of a natural gas pipeline near Edson, Alberta, approximately 200 kilometers west of Edmonton.
The incident occurred at around 10:45 a.m. on April 16, 2024, when a 36-inch pipeline carrying sweet natural gas ruptured about 36 kilometers northwest of Edson. The pipeline, owned by Nova Gas Transmission Ltd., a subsidiary of TC Energy Corp, ruptured due to stress corrosion cracking induced by a combination of soil conditions, deteriorated protective coating on the pipeline, and increased internal pressure.
Soil tests conducted at the site revealed microbiological activity capable of corroding the pipeline’s steel. Additionally, the compromised external coating of the pipeline exposed its steel to external elements, leading to potential corrosion.
According to the report, the pipeline’s pressure was escalated to its highest operating level on the morning of the incident, causing the crack to fully rupture.
Despite the crack being detected two years prior in a 2022 in-line inspection, it was classified as non-reportable by analysts. The report highlighted that a potential crack identified at the site was wrongly downgraded to a non-reportable “metal loss” feature by analysts from the inspection service provider, Baker Hughes. Consequently, the crack was not considered in TC Energy’s inspection analysis or risk assessment for the pipeline.
In response to the findings, TC Energy stated its commitment to working with its in-line inspection vendors to fortify their processes and enhance integrity management practices. Baker Hughes also acknowledged the seriousness of the TSB report and pledged to leverage the findings to improve its inspection technologies and services.
The report also provided new insights into the aftermath of the rupture and ensuing wildfire. Following the rupture, the natural gas ignited, causing an explosion that resulted in a seven-meter-deep crater. Approximately 20 meters of the pipeline was expelled due to the blast, with the largest debris piece launched 200 meters away. The escaping natural gas burned until it self-extinguished at 1:45 p.m. on the same day, releasing nearly six million cubic meters of gas. The incident sparked a wildfire that consumed over 60 hectares, but fortunately, no injuries were reported. The ruptured pipeline section was replaced and resumed operation under reduced pressure on May 27, 2024.
