Freight car structural failure is blamed for a train derailment in Sarnia over four years ago.
The Transportation Safety Board (TSB) released its investigation report into the derailment of 45 rail cars and a locomotive in the CN Paul M. Tellier Tunnel on June 28, 2019.
The train was en route from Sarnia to Port Huron, Michigan when the rail cars left the tracks on the Canadian side of the border.
No injuries were reported, however one tank car released over 45,400 litres of sulphuric acid. The tunnel was closed for 11 days while the scene was cleared.
The investigation determined that the derailment occurred when a bathtub gondola car sustained a structural failure and the leading end collapsed.
The investigation report said the car was built in 1978 and was modified in 2012 for use in scrap steel service.
At the time of its failure, the car had a number of pre-existing defects that contributed to its reduced structural integrity. Visual examination determined that the defects were not recent but had developed over a period of time.
Of the train's 140 cars, 125 were loaded, 12 were empty and three were residue cars.