Oil company Chevron will pay a £5 million fine after a refinery explosion killed four workers and seriously injured another in West Wales.
Dennis Riley, 52, Robert Broome, 48, Andrew Jenkins, 33, and Julie Jones, 54, died, while Andrew Philips suffered major injuries after a storage tank exploded at the site.
The five workers had been emptying the tank in the Amine Recovery Unit when the blast and subsequent fire took place shortly after 6pm on June 2 2011 in Pembroke Dock.
The explosion resulted in a fireball that severed the five-tonne tank roof, which was thrown 55 metres into a storage sphere containing Butane.
An investigation by the Health and Safety Executive found the explosion was most likely caused by the ignition of a highly flammable atmosphere within the tank, during what should have been a routine emptying operation ahead of cleaning and maintenance.
It also found there had been long-standing failures regarding safety management systems.
The refinery was operated at the time by Chevron Limited before it was sold to Valero Energy UK LTD in August 2011.
On Thursday at Swansea Crown Court, Valero was fined £5 million and ordered to pay costs of £1 million, after it pleaded guilty to two breaches of the Health and Safety at Work Act.
Chevron will pay the fine and the court costs after coming to an agreement with the company.
Specialist cleaning firm B&A Contracts Ltd was also fined £120,000 and ordered to pay costs of £40,000 after it also pleaded guilty to breaching two sections of the Health and Safety at Work Act.
Speaking after the hearing, HSE inspector Andrew Knowles said: “This incident, which had devastating consequences for all of those involved, was entirely preventable.
“Many opportunities to take action to control risk were missed, that would have prevented the incident from occurring.
“It is important to realise that the incident could have had even more serious consequences had the butane sphere or pipe track been damaged by the flying tank roof.
Detective Superintendent Anthony Griffiths from Dyfed Powys Police said: “We hope that the lessons learned ensure that a tragedy of this nature doesn’t happen again.
“Our thoughts remain with all the families involved.”