Buncefield five await penalty fate (VIDEO)

Five companies will be sentenced on Friday for their part in the explosions at the Buncefield fuel depot, which caused the largest fire in Europe since the Second World War.

The investigation
In what turned out to be the most complex joint investigation they had ever undertaken, the HSE and Environment Agency managed to retrieve computer data from the site to piece together the events leading up to the explosions. The investigation deduced that on the evening of 10 December 2005, unleaded petrol began to be delivered through the UK Oil Pipelines Ltd South Pipeline – one of three feeding into the depot – into tank T912.

Just after 3am, the automatic tank gauging (ATG) system for T912 failed to show an increase in fuel levels, despite the tank continuing to fill. The system continued to show a rising temperature in the tank, indicating that it was still filling.

Three ATG alarms failed to operate, which meant that the control-room pipeline supervisor was not alerted that the tank was in danger of overflowing.

At 5.37am petrol started spilling out of vents in the roof of the tank. The level had continued to rise past the independent high-level system, which failed both to activate an audible alarm in the control room and to shut down the pipeline.

Speaking at a pre-sentence media briefing today, HSE deputy chief executive Kevin Myers explained that “the air was so saturated with petrol it created a mist, a highly-flammable vapour”, which, “in some places, was up to four metres thick”. He added that drivers passing nearby the site at the time reported experiencing problems with their cars revving uncontrollably, even after they had turned off their engines.

In response to reports he was receiving, the pipeline supervisor opened a valve to a neighbouring tank, which he wrongly assumed was causing the problem. The control room commenced emergency actions at just after 6am, but less than a minute later the vapour cloud ignited, causing an explosion that registered 2.4 on the Richter scale. It was calculated that 250,000 litres of petrol escaped prior to the explosion.

The safety failures
Bob Woodward, lead inspector for the Buncefield investigation, told SHP that overall site operator HOSL had “failed to monitor the performance of the site or the systems of operation, and failed to provide the necessary expertise. It also relied on audit management systems that concentrated on personal safety rather than process safety.”

Total UK Ltd, which was responsible for day-to-day operations, didn’t have proper systems in place for tank-filling arrangements, and operators were effectively working blind, as they couldn’t see what was happening in two other pipelines feeding into the depot.

“The gauge had stuck 14 times in the last three months [prior to the incident],” said inspector Woodward. “But the management had no system to show that this was an issue.”

He added that site supervisors also felt isolated owing to a lack of engineering support from head office.

Motherwell Control Systems 2003 Ltd, which installed the gauges and independent high-level system, failed to do anything to rectify the gauges, which kept sticking during operations. Tav Engineering Ltd, which designed the high-level switch, had not passed on information about its operation to the users, and British Pipeline Agency Ltd, which was responsible for the UKOP pipelines, had failed to undertake a proper survey of a separate tank, which, owing to a design failure, leaked more liquid than it should have done.

The investigation was also critical of the shift system that was operating in the control room, with some staff working long hours, and shift handover instructions lacking detail. Inspector Woodward added that staff were under severe pressure, as the volume of fuel handled by HOSL had leaped by 50 per cent since the previous year.

Summing up the lessons from the incident, inspector Woodward said: “For major-hazards industries, it is important to identify safety-critical control systems and then to have systems in place that will monitor and test these to make sure they are working.”

The environmental impact
The fire took five days to put out, during which time Environment Agency staff worked around the clock alongside the emergency services, providing specialist advice on the environmental impact. Howard Davidson, the Agency’s Thames regional director, explained that samples of fuel and oil from the site were gathered for forensic fingerprinting – a technique that allowed the Agency to match the substances found on the site to computer records.

He said that large quantities of petrol and firewater had escaped into the environment, although there has been no lasting impact on local river water quality, while computer modelling has helped the Agency understand how the pollution will travel through the groundwater. Nevertheless, he stressed that “once groundwaters get polluted, it is very difficult to remediate them, and evidence suggests that they will be polluted for decades to come”.

A legacy of Buncefield, added Davidson, has been the creation of the Air Quality Cell – a national, multi-agency group of technical experts chaired by the Environment Agency with the Health Protection Agency, Met Office, Health and Safety Laboratory and Food Standards Agency. It was first deployed in May when it advised the local health community, police and fire service on air-quality issues after a blaze broke out at a chemical processing site in West Yorkshire.

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