Husky Energy Superior Refinery Explosion and Fire

On April 26, 2018, at approximately 9:58 a.m., an explosion and subsequent fire occurred at Husky Energy’s Superior Refining Company LLC refinery in Superior, Wisconsin (“Husky Superior Refinery”).a The incident occurred during a planned maintenance event, called a turnaround, with approximately 800-900 people on site, including employees and contractors. As a result of the explosion and fire, 36 refinery and contract workers were injured and sought medical attention, including 11 people who suffered Occupational Safety and Health Administration (“OSHA”) recordable injuries. In addition, the chemical disaster caused approximately $550 million in property damage. Husky Superior Refinery reported that it released 39,000 pounds of a flammable hydrocarbon vapor mixture during the event.b The explosion occurred while the refinery was shutting down its fluid catalytic cracking (“FCC”) unit for the turnaround.c Two FCC unit vessels, the primary absorber and the sponge absorber, exploded at approximately 9:58 a.m., shaking buildings up to a mile away and propelling over 100 metal fragments, some several feet long, up to 1,200 feet from their original location into the surrounding operating areas. Explosion debris punctured a nearby asphalt tank at the refinery, spilling hot asphalt that flowed outside of the tank’s containment area. Approximately 17,000 barrels of hot asphalt spread through the refinery and ignited at approximately 12:00 p.m., causing fires to erupt at multiple operating areas of the refinery. The City of Superior evacuated 2,507 residents within 2 miles north, 3 miles to the east and west, and 10 miles south of the refinery. To protect its residents, the City of Duluth, Minnesota, issued a shelter-in-place advisory at 8:00 p.m. The fires were extinguished before midnight. The shelter-in-place and evacuation orders were lifted at 6:00 a.m. the next day. In addition to concerns about smoke from the fires at the refinery, the City of Superior evacuation was based on the potential risk of a release of highly toxic hydrofluoric acid (“HF”), which was stored at Husky Superior Refinery and used in the refinery’s HF alkylation unit.d Although the HF storage tank was not damaged by debris from the explosion and no release of HF occurred, the asphalt tank punctured by the explosion debris was located farther away from the point of the explosion than the refinery’s HF storage tank. Debris from the explosion could have punctured the HF storage tank, given its closer proximity to the point of explosion.e The Superior Fire Department, the City of Superior, the U.S. Coast Guard, the U.S. Environmental Protection Agency (“EPA”), and the Wisconsin Department of Natural Resources (“WDNR”) responded to the incident. Additionally, OSHA and the U.S. Chemical Safety and Hazard Investigation Board (“CSB”) investigated the accident.