A hole in a valve was cited as the source of an explosion at a Husky Energy refinery in northwestern Wisconsin last spring that injured 36 people and required the evacuation of a large part of the city of Superior.
The latest findings of the U.S. Chemical Safety and Hazard Investigation Board were shared Wednesday at a town hall meeting in Superior.
According to the update erosion created a hole in the slide valve, allowing air to mix with hydrocarbons. The resulting blast sent debris hurtling into an asphalt storage tank. The puncture spilled about 15,000 gallons (12,490 imperial gallons) of hot asphalt, which later ignited. The fire raged for more than 4 hours, spewing a variety of pollutants into the air.
The blast forced the evacuation of many Superior neighborhoods, and led to $83,000 in OSHA fines.
A spokesman for Husky Energy says the Canada-based company will continue working with the board to understand the cause of the explosion.
"It was clear that the events of April raised serious concerns about refinery operations and the evacuation order," said Kristen Kulinowski, CSB Interim Executive Authority. "The CSB is committed to a transparent investigation, so that you can all understand what happened here and how it can be prevented from happening again."
The next step in the process is releasing a final public report. At this time there is no indication when that will happen.
