2005 Hertfordshire Oil Storage Terminal fire

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Hemel Hempstead in the UK
Hemel Hempstead in the UK
In this satellite photo the pollution from the explosions, appearing black, is spreading in two main streams from the explosion site at the apex of the inverted 'v'.   The orange dot is a marker not the actual fire.
In this satellite photo the pollution from the explosions, appearing black, is spreading in two main streams from the explosion site at the apex of the inverted 'v'.
The orange dot is a marker not the actual fire.
The fire seen from a vantage point between the Northgate and 3Com buildings.
The fire seen from a vantage point between the Northgate and 3Com buildings.
Smoke from blasts, six hours after and twenty five miles away in Buckinghamshire.
Smoke from blasts, six hours after and twenty five miles away in Buckinghamshire.
The smoke plume from Dunsmore, Bucks (about twenty miles away).
The smoke plume from Dunsmore, Bucks (about twenty miles away).
Smoke is visible from the banks of the Thames in Fulham, West London (about twenty two miles away).
Smoke is visible from the banks of the Thames in Fulham, West London (about twenty two miles away).

The 2005 Hertfordshire Oil Storage Terminal fire began after a series of explosions early on the morning of 11 December 2005. The terminal, generally known as the Buncefield Depot, is an oil storage facility located near the M1 motorway on the edge of Hemel Hempstead in Hertfordshire, England. These were some of the largest explosions ever to occur in the country, and the incident has been described as the biggest of its kind in peacetime Europe. The tank fires were extinguished by the afternoon of 13 December 2005. However, one storage tank re-ignited in the evening, and the firefighters left it to burn, rather than attempting to re-extinguish it.

The incident

Explosion and fire

The first and largest explosion occurred at 06:03 UTC near container 912. From all accounts, it seems to have been an unconfined vapour cloud explosion. An inversion layer permitted people to hear it from a hundred miles (160 km) away; there are reports it was heard as far away as France and the Netherlands. The British Geological Survey monitored the event, which measured 2.4 on the Richter scale. People were woken in their beds even in South London. Subsequent explosions occurred at 06:27 and 06:28. Witnesses observed flames hundreds of feet high from many miles away, with the smoke cloud visible from space, and as far north as Lincolnshire.

Damage from the blasts, ranging from broken windows and blown-in or warped front doors to an entire wall being removed from a warehouse, occurred more than half a mile (800 m) away. Buildings in neighbouring St Albans also suffered: for example, Townsend School had serious blast damage, and a window was blown out of St Albans Abbey (both c. 5 miles (8 km) from the site). Several nearby office blocks were hit so badly that almost every window, front and back, was blown in as the explosion ripped through them. Had this happened during the working day, these offices would have been full of people; there is no doubt that this would have caused dozens of deaths. Reports also indicated that cars in nearby streets caught fire. The roof of at least one house was blown off. Buildings in the vicinity were evacuated by police, not only because of the smoke and possibility of more explosions but because of the danger of structural damage making the buildings unstable.

There were 43 reported injuries; two people were deemed to be seriously injured enough to be kept in hospital, one in Watford General Hospital, with breathing difficulties, and another in Hemel Hempstead Hospital; they were not in a life-threatening condition. Some early media reports spoke of eight fatalities, but these may have been persons missing. All members of staff from the terminal were accounted for.

Hertfordshire police and fire services and the MP for the area, Mike Penning, have made clear that there were seven fuel tanks on the site which, as of 14:00 on 12 December, had not been affected; these tanks were at risk of exploding if the fire were to spread.

Tackling the blaze

Around 150 firefighters began to tackle the blaze at 08:20 on the morning of 12 December, putting in containment measures before applying a large quantity of foam. Plans had been in place to start using foam at midnight on 11 December, but were delayed by last-minute concerns over possible pollution of local rivers and underlying water sources from contaminated water used to fight the fires. Six high volume pumps were used to extract 25,000 litres of water per minute from a reservoir 2.4 kilometers from the fire, with six more high volume pumps deployed at various locations to serve as boosters. 32,000 litres of aerated foam per minute were directed against the fire for just over four hours, after which the pumping rate was reduced. Half the 20 individual fires were reported extinguished by midday. By 16:30 it was reported that a further two tank fires had been extinguished, but that one of the earlier extinguished tanks had ruptured and re-ignited, and was now threatening to cause the explosion of an adjacent tank. This led to the M1 motorway being closed again, the public exclusion area being widened and firefighters being temporarily withdrawn until the risk from the threatened tank could be determined.

Firefighting operations were resumed at about 20:00 and it was still anticipated that all fires could be extinguished during the night. Further damage occurred to one of the storage tanks in the early hours of the morning, causing firefighters to be withdrawn once more, but operations resumed at 08:30. By midday on the 13 December, all but three fires had been extinguished, although the largest tank was still burning. The smoke plume had been considerably reduced and was more grey, indicating the amount of vapourised water now joining the smoke. Firefighters were confident that the remaining fires could be extinguished during the day. It was reported at 16:45 that all tank fires were now extinguished, although some smaller fires remained. 75% of firefighters for Hertfordshire were involved in fighting the fire, together with support from 16 other brigades.

A further fire broke out during the early morning of 14 December. Firefighters were of the view that extinguishing it would leave the risk of petroleum vapour re-igniting or exploding, so it would be better to allow the fire, which was well contained, to burn itself out.

Hertfordshire Fire Service's deputy chief Mark Yates stated that escaping petroleum vapour was the most likely cause of the original explosion and fire.

Some chemical components of firefighting foams may present considerable risks to water resources and various ecosystems, particularly those in riverine environments.

Smoke cloud

The black smoke cloud, which was clearly visible from satellite photographs, drifted at high altitude (around 9,000 feet, 2750 m) towards Reading and Swindon, and could be seen across much of South East England. The small particles in the smoke, which contained hydrocarbons, can be an irritant but had low toxicity and were not expected to cause any long-term harm. The Met Office issued warnings that the smoke in the atmosphere could come down in rainfall during the night of 11 December.

For the first two days of the fire, the high thermal energy made the plume highly buoyant; this, together with settled weather conditions, allowed the plume to rise to a great height with little cross-mixing. When the fire was reduced in intensity it was reported to be possible that the plume would be less buoyant and that ground-level smoke concentrations could then rise significantly.

By 12 December, it was reported that the smoke cloud had reached northern France; it was expected to arrive in northern Spain by the weekend.

To investigate the smoke cloud the Facility for Airborne Atmospheric Measurements, a research aircraft operated jointly by NERC and the Met Office, made two flights on the 12th and 13 December. In the first flight the edge of the plume was followed along the south coast of England. Carbon monoxide, nitrogen oxides and ozone concentrations were found to be low with soot particles being the major component in the cloud. The second flight went into the centre of the plume to obtain data to help forecasting and emergency teams.

Reactions and responses

Evacuations and closures

Around 2,000 people from the Hemel Hempstead area were evacuated from their homes, and emergency services asked residents of the smoke-affected areas to close their windows and doors and stay inside. Hertfordshire Constabulary advised people who had houses with smashed windows to seek refuge with friends or family nearby if possible. Some people whose homes were damaged by the blast were placed in hotels, while others stayed in a nearby shopping centre. Total, the operator of the Buncefield depot, set up a helpline for people whose properties had been badly damaged by the explosion, and called in local authorities and the Salvation Army to provide accommodation or other help for those affected by the explosion.

About 227 schools across Hertfordshire and Buckinghamshire as well as libraries and other public buildings were closed on December 12 and December 13 for public safety. Police and local authorities advised residents to consult the "Hertfordshire Direct" website for up-to-date information. The University of Hertfordshire campus located further afield in Hatfield remained open. Meanwhile, 78 schools in Luton Borough were closed on 13 December and a limited number of schools in Bedfordshire. These were closed on the advice of Hertfordshire's Health Protection Agency that all schools should be closed in a 10-mile radius of the incident site due to concerns of the smoke plume and children's health. They reopened as normal on 14 December. (ref)

Transport disruption

The incident occurred close to junction 8 of the M1 motorway. The motorway was shut between junctions 12 and 6a (about eighteen miles or 29 km) shortly after the incident. Other roads in the vicinity, including the short M10 motorway, were also closed.

Some local petrol stations reported long queues as people started panic buying. A spokesman for the Department for Trade and Industry gave assurances that no petrol shortage was likely to result from the incident.

The Oil Terminal supplied 30% of Heathrow Airport's fuel, and because of the fire, the airport had to start rationing aircraft's fuel. Some long-haul flights to the Far-East and Australia had to "pit-stop" at Stansted Airport or other European airports to refuel, while short-haul operators were asked to fuel their planes for the round trip before flying to Heathrow. Fuel shortages continued for months after the explosion.

Business disruption

A number of companies were affected by inability to reach premises used for distribution, even where the premises themselves were largely unaffected by the blast.

The worst hit of the buildings were the Northgate Information Solutions headquarters and the Fujifilm building, both of which were totally devastated. Northgate is an IT company, one of the directors of which is Stephen Lander, former head of MI5. As of December 13 their building was completely unusable, and it may have to be demolished if it is found to be unsafe. The Fujifilm building was rendered unsafe, and demolition began soon afterwards. By June 2006 it had been completely removed from the site.

The Northgate and Fujifilm buildings were closest to the blast, although the surrounding Catherine House (to the north), Keystone Distribution building (to the west), and 3Com Corporation and RO buildings (to the south), were also extensively damaged. As a result of the destruction of the equipment in the Northgate building several websites they host were briefly inaccessible — including that of the Labour Party. Addenbrooke's Hospital in Cambridge was also affected with the IT system dealing with admissions and discharges needing to be replaced for several days by a manual system.

Local criticism

Criticisms were expressed by local citizens and the local MP that originally the depot had been constructed away from other buildings, but that developmental pressures had led to both houses and commercial premises being built near to the depot.

Legal actions

A total of 2,700 claims have been filed by residents, businesses and insurers. A group of 146 claimants is hoping to bring a class action against Hertfordshire Oil Storage Ltd. On 17 March 2006 a High Court official, Senior Master Turner, adjourned a hearing on whether to permit the class action until October 2006 at the earliest.

Groundwater pollution

In May 2006 Three Valleys Water announced that it had detected the fire retardant perfluorooctane sulfonate ( PFOS), used in fire fighting foam, in a ground water bore hole close to the Buncefield site. It stated that no water from this well entered the public water supply and that a nearby well and pumping station had been closed since the fire as a precaution. The chemical is a known health risk and the UK government had been about to ban its use. However just prior to the announcement the Drinking Water Inspectorate announced that it was increasing the safe level of the chemical in drinking water. This prompted the Hemel Hempstead MP, Mike Penning to accuse the government of changing the rules to suit the situation in which PFOS levels in drinking water in the area may rise in the future. (ref)


A government enquiry held jointly by the Health and Safety Executive (HSE) and the Environment Agency was started, but calls for a full public enquiry were declined . The Board included Lord Newton of Braintree, Prof Dougal Drysdale, an authority on fire safety and Dr Peter Baxter, a medical expert. Environment Agency and HSE staff were also on the board. The board's aim was to identify the immediate causes of the explosion, rather than consider who was to blame for any deficiencies, so as not to prejudice further legal proceedings. An initial progress report by the Major Incident Investigation Board on 22nd February 2006 did not go into the causes of the explosion, but looked at the environmental impact.

A further announcement was made on 9 May 2006 about the sequence of events which enabled the explosion to occur. Starting at 19:00 on the evening of 10 December Tank 912, towards the north west of the main depot, was filled with unleaded petrol. At midnight the terminal closed, and a check was made of the contents of tanks which found everything normal. From approximately 03:00 the level gauge for Tank 912 began indicating an unchanging level reading, despite filling continuing at 550 cubic metres per hour. Calculations show that the tank would have begun to overflow at about 05:20. 40 minutes later, an estimated 300 tonnes of petrol would have spilled down the side of the tank onto the ground inside bund A, a semi-enclosed compound surrounding several tanks. There is evidence suggesting that a high level switch, which should have detected that the tank was full and shut off the supply, failed to operate. CCTV footage shows a cloud of vapour from 1-2 metres deep flowing away from the tank. By 06:01, when the first explosion occurred, the cloud had spread beyond the boundaries of the site.

The extent of the damage meant it was not possible to determine the exact source of ignition, but possibilities include an emergency generator and the depot's fire pump system. The investigators did not believe that it was caused either by the driver of a fuel tanker, as had been speculated, or by anyone using a mobile phone.

It was felt unlikely that the explosion had a widespread effect on air quality at ground level.

The terminal

The Hertfordshire Oil Storage Terminal (HOSL - Hertfordshire Oil Storage Ltd), generally known as the Buncefield complex, was the fifth largest oil-products storage depot in the UK, with a capacity of approximately 60 million Imperial gallons (273 million litres) of fuel, although it was not always filled. This was approximately 5% of UK oil storage capacity. It was a major hub on the UK's oil pipeline network (UKOP) with pipelines to Humberside and Merseyside and is an important fuel source to the British aviation industry, providing aircraft fuel for local airports including London Gatwick, London Heathrow and Luton airports. Approximately half of the complex is dedicated to the storage of aviation fuel. The remainder of the complex stores petrol and diesel fuel for petrol stations across much of the South-East of England. The terminal is owned by TOTAL UK Limited (60%) and Texaco 40%.

The seat of the fire, and the worst damaged section, was "HOSL West", used by Total and Texaco to store a variety of fuels, and the neighbouring British Pipeline Agency area.

Initial speculation on causes

The police issued a statement saying that they were treating the incident as an accident as opposed to a terrorist attack. Rumours of a deliberate attack, in the form of an aeroplane deliberately crashed into the site, spread in the initial aftermath of the explosion as a result of the distinctive noise the event made. They may have been given some credence because of the proximity of Luton airport to the site of the incident, and the fact that numerous flight paths crisscross the area.

Italian television stations early on the morning of the fire described the event as a possible terrorist attack and went to the extent of showing features on the July 2005 terrorist bombings. Speculation about the possible terrorist nature of the blasts was prompted by the fact that a videotape allegedly released by al-Qaeda four days previously had called for attacks on fuel depots and refineries containing oil "stolen" from Muslim countries. However, the cause of the blasts will likely not be known until a full investigation is completed.

An oil industry specialist speculated on BBC News that a vapour leak could have built up to explosive concentrations because of the ground frost in the area keeping vapour concentration at ground level. This would have resulted in a fuel-air explosion. It is industry practice for detection systems to be in place to reveal leakages. In order for this scenario to be fulfilled, there must have been a leakage that was not picked up by the leak detection system.

A BBC News 24 interview with a petrol tanker driver, who was about to load his tanker at 06:00, reported a cloud of mist rolling in from the tank farm area behind the loading bay. All electric lights were turned off and they were ordered to leave the site on foot. As he was doing so, the blast blew him off his feet. In another interview, a security guard in a nearby office building reported an unusual smell of petrol inside his building before the explosion. Hertfordshire police reported speaking to a tanker driver concerned that switching the engine cut-off on his tanker might have triggered the explosion.

Other safety experts spoke of a known "Weekend effect" in industry, in which weekend maintenance creates an unsafe condition.

A retired military explosives safety officer submitted his published paper on this explosion to HSE's in-house Inquiry. The paper was designed to help those who lived close to petrol storage depots and who were worried about the risks they and their buildings faced. It held views different from those of other experts whose opinions had been voiced publicly. It was critical of HSE's general safety culture and showed that in the UK the severities and frequencies of explosions like that at Buncefield were unacceptably high.

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