The direct cause of the explosion was the ignition of a heavy hydrocarbon vapor cloud which emanated from raffinate liquids overflowing from the top of a blowdown stack.

[10] A very serious explosion affected the complex in July 1979, when hydrocarbons at 265 psi (1,830 kPa) were released from a failed 12 inches (30 cm) elbow in the depropanizer overhead condensing system of the sulfuric acid alkylation unit.

[18] An internal BP audit conducted in 2003 found that a "checkbook mentality", blame, and status culture eroded HSE as well as general performance; the condition of assets and infrastructure was poor; management had not created meaningful action plans; and that there were insufficient resources.

The tolerance of these kinds of risk "distracted" people from routine safe practices at the task level, or made them feel skeptical about the commitment to safety at the plant.

[27] In early March 2005, mere weeks before the explosion, an internal e-mail warned, "I truly believe that we are on the verge of something bigger happening and that we must make some critical decisions [...] over getting the workforce's attention around safety.

Because plant start-ups are especially prone to unexpected situations, operational practice requires the application of a controlled and approved pre-start-up safety review (PSSR) procedure.

During the morning meeting on March 23, it was discussed that the heavy raffinate storage tanks were nearly full and, therefore, a second day-shift supervisor ("B") was told that the start-up procedure should not continue, but this information was not passed on.

Pressure started to build up in the system as the hydrocarbon vapors and the nitrogen remaining in the tower and associated pipework from when it had been put back in service became compressed with the increasing volume of raffinate.

No emergency alarm sounded, and at approximately 1:20 pm, the vapor cloud was ignited by a backfire, as observed (by nearby witnesses) to be originating from the overheating truck engine.

Technical failings included the use of a blowdown drum that was both insufficiently sized and outdated, a lack of preventive maintenance on safety-critical systems, and inoperative alarms and level sensors in the ISOM process unit.

[78] A team of experts led by John Mogford, the senior BP Group vice president for safety and operations, examined the technical aspects of the explosion and suggested corrective actions.

[73] It identified four critical factors without which the explosion would not have happened or would have had a lesser impact: "loss of containment; raffinate splitter start-up procedures and application of knowledge and skills; control of work and trailer siting; and design and engineering of the blowdown stack.

"[81] Furthermore, five critical underlying cultural issues were identified:[82] The Mogford final report did not, however, find evidence that anyone intentionally made decisions or took actions that put others at risk.

[83] Among the issues "preventing the successful execution of some key work processes", the team singled out: leadership factors, including failure to hold people accountable for safety and silo mentality, among other issues; risk awareness, indicated by complacency and repeated failure to heed recommendations arising from previous accidents; measures for control of work, which was found to be both insufficient and unadhered to; negative workplace conditions, as shown by poor housekeeping and insufficient plant maintenance; and a contractor management philosophy lacking diversity and inclusion values.

[74][85][86] It further noted that management responsibilities within BP Group were unclear, and that the poor state of the plant equipment and the insufficiency of spending on maintenance were contributing factors to the accident.In sum, the Texas City Refinery had a culture of risk taking coupled with a failure to understand the process safety implications of prior incidents [...], a long tradition of failure to comply with simple procedures, the desire to avoid conflict within its organization, and a penchant for placing persons in key roles who lacked adequate professional training.

[76][99] A figure of this stature and curriculum was specifically selected by BP to publicly show to U.S. opinion-makers that the company was eager to learn the lesson and make strides to change.

[104][105] It further stressed that worker fatigue and a system that encouraged overtime had detrimental effects on safe plant operation,[106] and that the company had failed to deal with deficiencies arising from known incidents, risk assessments and audits.

The survey results also showed that managers and white-collar workers generally had a more positive view of the process safety culture at their plants when compared with the viewpoint of blue-collar operators and maintenance technicians.

[113][114][115] One of the key findings of the CSB was that the blowdown system used at the ISOM unit was antiquated and totally inadequate, being located as it was amid the plant and liable to spew unignited heavy vapors down into normally manned areas.

Merritt highlighted that the studies were shared with key executives in London, but BP's response was inadequate, with the little investment made not addressing the real issues in Texas City.

[103][i] The CSB also issued a recommendation for the American Petroleum Institute (API) and the United Steelworkers (USW, the trade union representing refinery workers) to work together to develop a guideline for understanding, recognizing and dealing with fatigue during shift work, as well as to create performance indicators specific to process safety in the refining and petrochemical industries,[135] since measuring safety purely based on eminently occupational indicators such as lost-time incidents was seen as insufficient in the context of preventing major process accidents.

[139] The CSB judged that the Amoco–BP merger had negatively impacted the ability of the organization to deal with process hazards, because organizational changes occurred without getting assessed in terms of their consequences on safety.

[144] The report further negatively compared OSHA's available resources with those of other agencies, like the British Health and Safety Executive or the Contra Costa County, California hazardous materials programs, that were much more prepared in spite of their smaller scope of oversight.

[159][163] BP also said that it would eliminate all blowdown drums/vent stack systems in flammable service, of which there were 11 at Texas City, and install new flares in line with their new policy prohibiting atmospheric venting of-heavier-than-air light hydrocarbons.

[168] CSB chairman Carolyn Merritt said there were striking similarities between the accidents of Texas City and Prudhoe Bay, including "long delays in implementation, administrative documentation of close-out even though remedial actions were not actually taken, or simple non-compliance" as well as "flawed communication of lessons learned, excessive decentralization of safety functions, and high management turnover.

[173] By this time, BP had already taken a markedly apologetic stance over recent accidents, especially Texas City, with their executives and technical experts giving presentations about what went wrong and how they were working to prevent that from happening again.

[174] However, only three years later, the 2010 Deepwater Horizon explosion and oil spill occurred, causing a very serious impact on the company on a global scale, again stemming from BP's operations in the U.S. As a result, Hayward resigned, and his role was taken over by American-born Bob Dudley.

[175] Under Dudley, BP announced in 2011 that it was selling its Texas City refinery as part of its divestment plan to pay for ongoing compensation claims and remedial activities following the Deepwater Horizon disaster.

[193] On February 4, 2008, U.S. district judge Lee Rosenthal heard arguments regarding BP's offer to plead guilty to a federal environmental crime for two violations of the Clean Air Act (CAA)[194] with a $50 million fine.

[241] OSHA also issued an internal memorandum[242] to address the CSB's recommendation on updating the PSM regulation to include requirements for hazardous process facilities to extend their management-of-change procedures to capture organizational changes.