Noting that the Texas City refinery is owned and operated by BP Products North America Inc. and not its London-based parent company, BP on May 17 released an "interim fatal accident investigation report" that concludes that the March 23 explosion occurred because BP unit managers and operators in the isomerization unit "greatly overfilled and then overheated" the unit's raffinate splitter, a tower that is part of the isomerization unit. The fluid level in the raffinate splitter tower at the time of the explosion was nearly 20 times higher than it should have been, according to the report.
As a result of the mistake, flammable hydrocarbons were forced into the adjacent blow down stack, the report says. Officials from BP and the U.S. Chemicals Safety and Hazard Investigation Board (CSB) believe that the flammable liquid and vapor -- which shot like a geyser from the 100-foot blow down stack just seconds before the explosion, according to eyewitness accounts -- ignited, possibly from an idling truck nearby, although the source still is unknown.
The presence of water or nitrogen in the tower at startup also may have contributed to a sudden increase in pressure that forced the hydrocarbon liquid and vapor into the blow down stack, according to the report.
The report also concludes that the presence of mobile trailers near the blow down stack and the failure to evacuate personnel when it became apparent that pressure was building within the isomerization unit and that flammable vapors were being vented to the atmosphere "greatly increased the number of deaths and injuries."
BP investigators believe that the use of a flare system instead of a blow down stack would have "reduced the severity of the incident."
"The mistakes made during the startup of this unit were surprising and deeply disturbing," said Ross Pillari, president of BP Products North America. "The result was an extraordinary tragedy we didn't foresee."
The investigation of the March 23 tragedy was conducted by a team of BP executives, BP refining and safety experts and salaried and union employees of the Texas City refinery. Tasked with determining the cause of the explosion and making recommendations for preventing similar accidents in the future, the team published the interim report because the remaining work that needs to be done "is not expected to change the root causes or the recommendations" in the interim report, according to BP.
In response to the recommendations made in the 47-page report, Pillari said management at BP's Texas City refinery has "clarified and reinforced roles, responsibilities and expectations around startup, operating and evacuation procedures." The facility also has prohibited the occupancy of trailers within 500 feet of blow down stacks and flares, while "non-essential personnel are being moved out of process areas."
The company says it will commission a third-party-led study to recommend the safe placement of temporary structures.
"Our goal is to eliminate or reduce the need for temporary buildings at the refinery by limiting the work force in process areas to operators and people involved in hands-on maintenance," Pillari said. "We are assessing space needs for workers whose jobs require them to be located at the refinery. We are also looking at options for securing leased space in the community for workers whose duties can be performed away from the refinery."
Among other actions BP will take, the company will "modify or replace all blow down systems which handle heavier-than-air hydrocarbon vapor or light hydrocarbon liquids (gasoline and lighter)," according to the company.
BP also is conducting a facilitywide review of the processes and operations at the Texas City refinery.
"We regret that our mistakes have caused so much suffering," Pillari said. "We apologize to those who were harmed and to the Texas City community. We cannot change the past or repair all the damage this incident has done. We can assure that those who were injured and the families of those who died receive financial support and compensation. Our goal is to provide fair compensation without the need for lawsuits or lengthy court proceedings."
At least one Houston attorney has promised legal action against BP stemming from the March 23 incident.
A spokesperson for CSB said the agency will "review the report in detail and integrate the information into CSB's ongoing investigation."
"With BP's ongoing cooperation in our investigation, we had already been apprised of the key information and issues discussed in the report," said CSB lead investigator Don Holmstrom. "We will be reviewing the report in detail over the next few days. The report's recommendations to change from an open-air vent stack system to a closed system utilizing a flare to burn off any dangerous vapors, and to remove personnel trailers away from potential harm, are prudent ones, in keeping with good refinery design and practice."