Dubbed "the most serious U.S. refinery incident in recent years" by a top U.S. Chemical Safety Board official, an Aug. 6 flammable vapor explosion at a Richmond, Calif., refinery is under investigation by that agency.
CSB chairperson Rafael Moure-Eraso said the fire was a near-disaster for refinery personnel.
"The circumstances warrant a full and independent federal investigation to determine the root causes," Moure-Eraso said. "Although fortunately no workers were killed, the overall impact of the incident ranks it as among the most serious U.S. refinery incidents in recent years."
According to the CSB, the fire occurred when a combustible hydrocarbon liquid known as "gas-oil" leaked from an eight-inch pipe connected to a crude oil distillation tower in the refinery's crude unit.
Workers initially noted the leak and were in the process of attempting repairs on piping connected to the still-operating crude oil distillation tower when the leak suddenly intensified. Due to the high temperature of the material in the tower, in excess of 600 degrees Fahrenheit, the gas-oil immediately formed a large flammable vapor cloud.
An initial report by the refinery owner filed with the Contra Costa County Department of Health Services states that the fire occurred at the refinery's No. 4 crude unit at about 6:30 p.m. Preliminary information indicates the fire was near P-1149 (C-100 Atmospheric Column No. 4 Sidecut pump). This unit was not operational.
Five minor injuries were reported by employees, three of them associated with the incident, the report states. These employees received first aid at the refinery and returned to work on the same shift.
The refinery fire brigade was on scene at the time of the explosion, the report states. The CSB subsequently released photos taken by investigators showing a fire truck consumed by flames.
According to the Associated Press, investigators are looking at heaters and responding emergency vehicles as possible ignition sources for the massive vapor cloud.
"Typically in refineries there are fired heaters that have an open flame. There are a number of (possible) sources of ignition," Holmstrom said.
A CSB team of seven investigators arrived at the refinery on Aug. 8 and has since been conducting witness interviews and reviewing documents at the site.
"Witness testimony collected by CSB investigators indicates that a large number of workers were engulfed in the vapor cloud," said CSB Team Lead Dan Tillema, P.E. "These workers might have been killed or severely injured, had they not escaped the cloud as the release rate escalated and the cloud ignited, shortly thereafter."
The information gathered so far indicates the incident had a serious impact on the community, said CSB Board Member Mark Griffon, accompanying the team.
"Area hospitals told CSB investigators that they attribute hundreds of emergency room visits by community members to reported effects of the release and fire, with symptoms ranging from anxiety to respiratory distress."
CSB structural and industrial safety experts arrived at the site on Aug. 13 to prepare for safe entry by investigators into the immediate area of the fire.
Tillema said important issues in the investigation included understanding why the pipe that later failed was kept in service during a late 2011 maintenance turnaround and what procedures and industry practices exist for responding to a leak of combustible material from a running unit. He said the Board anticipates executing a site preservation and evidence testing agreement with the refinery and other investigative groups and arranging for independent testing of the leaking section of pipe to determine the failure mechanism.
Both the refinery and the United Steelworkers, which represents hourly workers at the plant, have been cooperating with the CSB team, a CSB press release states. The refinery has provided assurances its personnel will freely share their knowledge and investigative information with the Board. Cal/OSHA, Contra Costa County, the U.S. Environmental Protection Agency, and other investigative groups are fully cooperating.
Additional fallout from the refinery disaster came in mid-August when Contra Costa County officials announced their decision to seek proposals to replace the telephone-alert firm that struggled to notify residents about the fire.
According to the San Francisco Chronicle, it took more than three hours for 18,000 people near the refinery to get calls advising them to shelter in place. Nearly a quarter of the initial calls were not picked up by a person or answering machine, tying up the system by forcing a redial of those numbers.
Further problems were caused by a "feedback loop," the newspaper reported. Even when a call was completed, the system sometimes redialed before that registered.
The CSB is an independent federal agency charged with investigating serious chemical accidents. 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.