In Worst-Case Scenario, Chemical Release At Superior Refinery Would Double Evacuation Area

A tank containing hydrofluoric acid at the Husky Energy oil refinery recently forced a temporary evacuation in Superior after a series of explosions and fires there. The highly toxic chemical could have prompted an evacuation of more than 25 miles if that tank had been full.

At the most, that tank can hold just under 78,000 pounds of hydrofluoric acid, according to a 2017 hazardous materials response plan for the refinery. In the worst-case scenario, Douglas County Emergency Management Director Keith Kesler said they would evacuate people up to 26 miles from the refinery. But, he said how many people would be evacuated depends on which way the wind is blowing.

“If it were to go south as it did in this event, the number would be significantly lower than if it were a wind that was blowing it over across the city into Duluth,” he said. “Then, the numbers would be higher.”

Kesler said that’s the largest evacuation requirement of any chemical in the Twin Ports for which they may have to provide emergency response.

The refinery stores a combined roughly 60 million gallons of gasoline, crude oil, asphalt and fuel oils.

The 2017 hazardous materials response plan for the refinery also includes information on other chemicals at the facility, including chlorine, ammonia and sulfuric acid. All those chemicals have evacuation zones, but they don’t extend beyond more than a couple miles from the refinery. A worst-case scenario release of hydrofluoric acid from the refinery would cover the entire city of Superior and much of Duluth, according to the plan.

“This area would extend into rural Douglas, Carlton, and St. Louis counties,” the plan reads. “The use of numerous major road, rail, and water routes would be affected.”

Kesler said county officials conduct site visits of the refinery each year to confirm the amount of chemical on site. They also prepare a document that includes information about facilities that would need to be evacuated, including schools, nursing homes and hospitals. However, he noted the evacuation is not the first line of defense against any release of hydrofluoric acid at the refinery.

“There were many other things in place,” said Kesler. “The first line of defense to protect that tank kept anything really bad from happening to it, and that was the water curtain and the deluge system around it.”

Husky Energy spokeswoman Kim Guttormson said in an email that there are multiple layers of protection around the tank to prevent any release of hydrofluoric acid, which include the water curtain and a pressure safety valve.

“In the event pressure builds in the tank, the safety valve opens and the HF gases flow to a scrubber where they are neutralized and sent on to the flare system for destruction,” wrote Guttormson. “The remaining liquid HF would be drained to the acid neutralization pit and rendered safe.”

Husky has said they’re exploring options for the refinery’s structure moving forward in light of concerns raised over the chemical. Duluth Mayor Emily Larson and Superior Mayor Jim Paine have called on the refinery to end its use at the facility as part of the refining process. Guttormson said the company will be able to properly evaluate options for the refinery once federal agencies have completed their investigations.