Workers at Buncefield oil depot were overworked and did not receive the training they required ahead of an explosion in 2005, a Crown Court has heard.
The court heard evidence that staff at the Buncefield site were not given the support they needed to do their job while they were often under pressure to ensure the tanks were filled to the top, the Independent reported.
The allegations were made as Hertfordshire Oil Storage, TAV Engineering and Motherwell Control Systems 2003 faced prosecution by the Health and Safety Executive and the Environment Agency for their roles in the explosion, near Hemel Hempstead, Hertfordshire.
The prosecution lawyer, Andrew Langdon, 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."
He 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."
Total UK had already admitted three health and safety breaches in connection with the explosion while the British Pipeline Agency has also admitted two charges in connection with the explosion.