Could the Buncefield disaster happen again, 20 years on?

When the Buncefield oil depot exploded on 11 December 2005, sending a fireball into the sky, it was declared the largest explosion in peacetime Europe.

More than 40 people were injured and thousands were forced to evacuate. The fire on the outskirts of Hemel Hempstead burned for five days.

The official investigation found the cause was an overfilled fuel tank and failed safety systems, leading to a vapour cloud that ignited with the force of up to 30 tonnes of TNT.

Twenty years on, the site in Hertfordshire is quiet but the risk has not disappeared.

With new housing estates in the vicinity of the depot, it raises the question whether Buncefield, or any similar site, could explode again.

Des Collins, a Watford-based litigation lawyer who represented hundreds of victims in their quest for compensation, warns against complacency.

“It’s largely been forgotten about because it was just a one-off and people think it’ll never happen again, but it could,” he says.

He points to government housing targets as a driver for development near high-hazard sites.

“The impetus behind the present government to build houses goes right across the board. And the present government will build on brownfield land. Now there’s a huge impetus on local authorities to allow this to happen.”

But Ian Travers, a safety consultant who had a spell as the Health and Safety Executive’s (HSE) deputy director of chemicals regulation, says the chances of a similar accident happening again have been greatly cut due to improvements made by the fuel storage and refinery sector.

“However, whenever significant hazards, such as large-scale storage of flammable liquids or other hazardous substances, are present, the risk of harm can never be zero,” he says.

“In the UK, the law does not require zero risk but that risks are reduced so far as is reasonably practicable.”

Before the explosion, Buncefield was the fifth largest oil depot in the country. It was connected by pipeline to Humberside and Merseyside as well as to both Heathrow and Gatwick airports.

An independent board set up by the HSE published a report on the disaster.

It pulled together findings from three earlier progress reports by the HSE and the Environment Agency.

Investigation manager Taf Powell recalls the stark findings.

“The board of inquiry found that there were systemic failures in the design, the operation and the maintenance of the site – and in the end the owners were prosecuted with, at the time, the largest health and safety fines that had been handed down in the UK,” he says.

Five businesses were ordered to pay almost £10m between them in fines and costs for their roles in the explosion.

The HSE introduced development proximity zones to restrict building near large-scale petroleum storage sites, and the Control of Major Accident Hazards (COMAH) Regulations were strengthened.

They apply to sites such as fuel depots and chemical plants where large amounts of dangerous substances are stored, and they require operators to show how they keep people safe, maintain reliable equipment and plan for emergencies.

But Mr Powell says the risks remain.

He adds that risk assessments at the time suggested equipment failures could trigger a chain of events thought to be almost impossible. There was also a chilling revelation uncovered.

“When we did our experimentation on full-size equipment in our own laboratories, we found that it would happen several times a year.”

The risk is not confined to Hertfordshire. The UK has dozens of COMAH sites storing millions of litres of fuel. From Teesside to Southampton, these installations are essential to the economy – but they bring with them inherent dangers.

HSE guidance on land-use planning makes clear that local authorities must consult on developments near major hazard sites.

The Major Incident Investigation Board set up after the explosion issued 78 recommendations covering safety systems, emergency planning and land-use policy.

However, 18 recommendations on land-use planning were not adopted at the time, says Mr Powell.

The Tank Storage Association (TSA) represents companies engaged in the storage of bulk liquids, including transport and heating fuels.

It describes the Buncefield explosion as a “defining moment that continues to inform and drive ongoing improvements within high-hazard industries”.

After the incident, the TSA played a role in the Buncefield Standards Task Group, which in 2007 published a report recommending improvements on how high-hazard industrial sites should store fuel.

Among these were suggestions that walls and floors should be designed to better retain water, and at high-risk sites be made from stainless steel.

The TSA tells the BBC it had worked to insure the “implementation of the investigation’s recommendations”.

A spokesperson adds: “The Tank Storage Association remains steadfast in its commitment to continuous learning and to working closely with peers, regulators and government to manage risks and foster a healthy, resilient sector for the future.”

The Buncefield depot was operated at the time by Hertfordshire Oil Storage, which was a joint venture between Total and Chevron.

In a statement, Chevron said: “[Our] first priority is safety. We remain grateful that there were not more serious injuries as a result of the incident.”

Total UK, which has also been approached for comment, said in 2010 following court proceedings: “We fully accept our responsibilities for the events that took place at Buncefield in 2005 and recognise the devastating consequences that the incident has had on the surrounding communities and businesses.

“This was an unprecedented incident from which we and the industry have learnt many lessons.”