The U.S. Chemical Safety Board (CSB) investigation team that deployed to the April 26, 2018, explosion at the Husky Energy oil refinery in Superior, Wisconsin. This is a brief update of the CSB’s ongoing work:

• The CSB investigation team arrived in Superior the evening of April 26 and to date has photo-documented a large percentage of the refinery. The investigation team has also conducted interviews with approximately 50 Husky Energy employees and contractors who were working at the facility on the day of the incident. 

• Husky Energy has worked cooperatively with the CSB to provide access to the site and relevant information.  Facility employees are represented by the International Union of Operating Engineers and contract employees are represented by various building trade unions that are also cooperating with the investigation.

• The refinery was preparing to enter a 5-week maintenance turnaround, during which time equipment is shut down so that it can be opened, inspected, and repaired as needed.  The explosion occurred at approximately 10 a.m. CDT.  The initial explosion caused property damage and loss of containment of an asphalt tank. The contents of the tank spilled out and the material combusted.

• The initial explosion took place within the refinery’s Fluid Catalytic Cracking, or FCC, unit. The FCC unit “cracks” heavy, high boiling point hydrocarbon molecules into smaller molecules with lower boiling points. The main product produced by the FCC unit is gasoline. The CSB investigation team is currently narrowing its focus to equipment within unit to determine the cause of the initial explosion. The investigation team is requesting and reviewing documentation pertaining to the FCC unit.

• Metallurgical testing will be conducted in order to determine the cause of the initial explosion. The CSB has retained a metallurgical expert to help identify the testing necessary and will work with Husky and other agencies to determine the protocols for the testing.    

• The explosion created a large amount of debris which was scattered in and around the refinery complex.  This debris is being collected and stored for future analysis as needed.

The CSB will continue to provide updates to the public as the investigation unfolds.

The CSB is an independent, non-regulatory federal agency charged with investigating serious chemical incidents. The agency's board members are appointed by the president and confirmed by the Senate. CSB investigations look into all aspects of chemical accidents, including physical causes such as equipment failure as well as inadequacies in regulations, industry standards, and safety management systems.

The Board does not issue citations or fines but does make safety recommendations to facility management, industry organizations, labor groups, and regulatory agencies such as OSHA and EPA. Visit our website, www.csb.gov.

Source: US Chemical Safety Board www.csb.gov