At the time the fire was ignited, the workers were performing annual inspection work on motor-operated valves.
Investigators found that odourless sweet natural gas was leaking due to the failure of two stem seal O-rings, and that the structure the workers were in had not been checked for flammable gas before they started work. The electrical spark that started the fire would likely have happened when the motor-operated valves’ close button was pressed during maintenance.
The TSB adds that work permits were not consistently done before the start of work, which increases the risk of workplace accidents. For instance, when a leaking valve is found, a tag should be placed at the structure’s entrance to let workers know about the potential danger.
Since the incident, Spectra has enhanced gas leak inspections and identified and repaired any leaks.