A trail derailment in New Brunswick last October that spilled 2,000 litres of methanol into the ground was caused by an “undetected” rail issue, federal officials say.
The Transportation Safety Board (TSB) said Tuesday that the CN Rail derailment, which happened on Oct. 30, 2023, near Dunsinane, N.B., was caused by a section of rail that broke off while the train was over a small bridge.
“The rail broke as a result of an internal fatigue defect that likely originated from fine cracks in the surface of the rail, known as head checking,” it said.
On that day, the TSB said the CN Rail freight train was travelling on the Sussex Subdivision when a train-initiated emergency brake application occurred. The conductor inspected the train and found that the last four cars had derailed.
Roughly 2,000 litres of methanol leaked from one of the derailed cars, which was later cleaned up along with any contaminated soil, the TSB said.
Inspection records revealed the rail section that broke had undergone third-party ultrasonic rail flaw detection (RFD) testing using a hi-rail vehicle three times within the five months before the derailment, the TSB said.
“Each of the tests were unable to obtain valid results. The operator then used an ultrasonic hand tool, which did not identify any internal defects. The head checking on the surface of the rail likely affected the reliability of the ultrasonic testing in identifying the internal fatigue defect within the rail that broke,” it added.
The investigation determined that, if rail surface conditions that affect the reliability of the ultrasonic RFD testing are not required to be reported to a railway operator, internal rail defects can remain undetected and mitigation measures may not be implemented, increasing the risk of a derailment due to an in-service rail failure.