Thousands began returning to their homes; cause unknown?

The refinery explosion and massive asphalt fire that injured 13 people and caused entire neighborhoods to flee this Lake Superior city lasted less than a day thanks to thousands of gallons of specialized foam, trained firefighters equipped with the right gear and a fire suppression system that showered portions of the refinery in water.

It was a close call, Superior Mayor Jim Paine said at a Friday news conference. Exactly how close is spelled out in a 2011 industry report.

Under the worst-case scenario, up to 180,000 people in the region surrounding this working-class port community of 27,000 residents could have been hurt or killed if the blast had compromised a tank of hydrogen fluoride that sat within 200 feet of Thursday’s fire at the Husky Energy, Inc., refinery, according to a report by the Center for Public Integrity, a nonprofit news organization.

“We’re talking about a dense, cold, killing cloud,” said Fred Millar, a Virginia-based environmental consultant and activist on chemical safety. “The serious evacuations in Superior indicate that they were worried about something that could have much more serious consequences than a burning tank of asphalt.”

Nobody was killed in the initial blast or explosions that followed at the refinery south of town. By Friday morning, the mayor had given residents who had evacuated the day before the all clear to return to their homes and firefighters had scaled back their emergency response after a harrowing 24 hours. The U.S. Environmental Protection Agency (EPA) also was on the scene to monitor air quality and to help oversee the beginning of the cleanup.

Hydrogen fluoride is a fast-acting acid that can cause deep, severe burns. Exposure can occur through inhalation and skin contact. The chemical can permanently damage the eyes, skin, nose, throat, respiratory system and bones, according to a 2013 report issued by the United Steelworkers union, which represents many refinery workers.

Paine acknowledged Friday that the fire had the potential to be “absolutely catastrophic,” but said the evacuation zone was large enough to contain any release of the chemical, and that the city had adequate medical transport and supplies to treat exposures. As an added precaution, an industrial sprinkler system was triggered to spray the hydrogen fluoride tank with water, said Superior Fire Chief Steve Panger.

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