Workers at Buncefield were under pressure to fill tanks at the oil depot to their maximum in the months before an "almighty" explosion ripped through the site, a court heard today.
Supervisors at the depot were also overworked and did not receive the training they needed, while the device used to measure the levels of the tanks was inaccurate.
St Albans Crown Court heard the explosion at the depot near Hemel Hempstead, Hertfordshire, on December 11, 2005, was similar to an earthquake.
It happened after vapour from 250,000 litres of petrol started to spill out from the top of one of the tanks at the depot.
The environmental damage of the explosion was still not known but could last for decades, a court heard today as three companies went on trial accused of health and safety breaches.
Hertfordshire Oil Storage Ltd (HOSL), TAV Engineering Ltd and Motherwell Control Systems 2003 Ltd are being prosecuted by the Health and Safety Executive and the Environment Agency.
It was alleged HOSL "manifestly failed" in its duty to ensure the site was safe.
Today, the court heard workers didn't receive the support they needed to do the job while they were often under pressure to ensure the tanks were filled to the top.
Under an historical agreement a "commercial fine" had to be paid to the British Pipeline Agency if the depot didn't take a certain amount of fuel from two of the three lines that came in from refineries.
To add to the pressure facing the depot, supervisor Steven Lewis was trying to bring in a new management system to run the site after it was transferred from Fina to Total.
And gauges made by Motherwell Control Systems 2003 Ltd and used to measure the fuel levels in the tanks often became stuck.
Andrew Langdon QC, prosecuting, said: "Supervisors didn't get much help or protection in what they did.
"They didn't get any risk assessments worth their name - pretty essential you might think - how the tanks should be filled, how they should be emptied, what happens with all these considerations."
Turning to the jury, the barrister added: "You might be thinking that if you had a supervisor's job you wouldn't fill the tanks to the high level.
"It is surely less stressful to fill them to a lower level but there was a pressure. The sheer volume that came through this terminal had increased over the years, it may have increased three or four fold over a decade."
The court heard that petrol stored in one tank could fill some 100,000 cars while in 2005 an estimated 400 tankers were visiting the depot every 24 hours. The depot was often busiest between 4am and 6am.
Earlier, the court heard that shortly before 6am on Sunday, December 11, 2005, vapour from 250,000 litres of petrol spilled from the top of a storage tank at the depot.
Shortly after 6am it ignited causing an "almighty" explosion, similar to an "earthquake".
In written evidence read to the court, tanker driver Paul Reed, who witnessed the blast, said: "All of a sudden I felt a whoosh coming from behind me. It was like a strong wind thudding me in the back. Immediately following the whoosh was a massive and loud explosion. The force of this blew me off my feet and on to the floor.
"There was a bright orange-yellow glow which was fire and I can remember breathing became a problem. It was as if all the air had been sucked away and I could see chunks of burnt and twisted metal on the floor."
The court heard it was a "good job" no-one was working at the site at the time of the explosion, which caused severe damage to nearby houses.
Mr Langdon said the accounts of local people painted a "very frightening picture".
He said: "Some of those who lived a short distance from the terminal suffered significant damage to their homes. Windows were blown in, some doors were blown off their hinges.
"For some it felt like an earthquake. At one home about 500 metres away the ceiling collapsed and bricks and beams fell.
"We do in everyday language over-use the word 'miraculous', but here it was miraculous no-one was killed."
There had been widespread environmental damage as the result of the explosion, the effects of which were still not fully known.
The Buncefield site sits on a layer of flint and clay. Below that was chalk, a porous aquifer from which water was supplied from various points within a 10km radius of Buncefield.
Special walls used to protect each of the tanks had failed to do their job and contain the spillage.
Total UK had already admitted three health and safety breaches in connection with the explosion while the British Pipeline Agency Ltd has also admitted two charges in connection with the explosion.
Motherwell Control Systems 2003 Ltd is currently in voluntary liquidation.Reuse content