Although its only a preliminary report that's part of a larger investigation, the Chemical Safety Board's findings show a number of previous abnormal start-ups in the isomerization unit that was destroyed in March. Other safety issues that could have played a part in the tragedy were employee trailers too close to the unit and at least four previous releases of flammable chemicals into the air. CSB chairwoman Carolyn Merritt says the investigation isn't over. "This is still an open investigation and root causes will be determined and presented to the board and then those root causes will be voted on and accepted or not by the board based on the evidence that is presented by the staff," she says.
Investigators also say they've narrowed down at least one ignition source to a truck that was idling near the isomerization unit. Lead investigator Don Holmstrom says there was likely no single cause for the explosion, but instead a combination of factors. "In our investigations of incidents there's always multiple causes. So in any particular incidents there are multiple things that happened that gave rise to the, in this case, the very serious and deadly results," he says.
The CSB's final report and recommendations are expected sometime next year.