Everyone living in our neighborhood had something of a rude awakening early one Sunday morning a couple of months ago. At 6.03 a.m. on December 11, what turned out to be the biggest fire in Europe since World War II was set off by an enormous explosion at the Buncefield oil storage and distribution depot in Hemel Hempstead, U.K., some 20 miles north of London and just three miles from our house.
The explosion itself, which was equivalent to a quake measuring 2.5 on the Richter scale, was heard up to 50 miles away and devastated the surrounding industrial park and nearby houses. Fires engulfed 20 tanks and raged on until finally being brought under control nearly 60 hours later. Amazingly, no one was killed and only two people out of 43 casualties had to be hospitalized. Had the blast occurred on a normal working day, there would have been nine staff on site (versus only two on Sunday) and all the neighboring businesses would have been fully occupied. As it was, around 2,000 people living near the depot were evacuated.
Fortunately, I really was an “editor at large” that weekend, not being at home but 100 miles away in the Midlands — ironically though, just three miles from another, almost identical facility at Kingsbury in Staffordshire, which is fed by the same cross-country pipelines as Buncefield. These pipelines carry refined product from the U.K.’s oil refineries to regional distribution terminals like Buncefield and Kingsbury and on to major airports such as London’s Heathrow and Gatwick.
The four major lines feeding Buncefield carry 2.37 million metric tons a year of fuel, including all grades of gasoline, diesel, kerosene, aviation fuel and gas oil, into a tank farm with a capacity of around 60 million gallons. The terminal was only about half full when the explosion erupted on the part of the site operated jointly by Total and Texaco. BP, Shell and their joint-venture operation, the British Pipeline Agency, also have facilities on the site.
What caused the explosion is still under investigation by the U.K. government’s Health and Safety Executive (HSE), but the consequences of all that fuel going up in flames was plain to see — even as far away as France, as the smoke plume gradually spread across Southern England before dispersing without any apparent environmental impact once the last of the fires had been extinguished.
With memories of the 1974 Flixborough disaster in mind, first thoughts turned to an unconfined vapor cloud explosion. But as there were no pressurized storage tanks on the farm (no LPG, no LNG, just ordinary liquid fuels), any cloud large enough to cause such an explosion on ignition probably would only have formed over some time from an evaporating spillage, either from a leaking tank or from one of the pipelines — either of which should have been picked up by the site’s gas-detection monitoring systems.
The site, which is regulated under the U.K.’s Control of Major Accident Hazards (COMAH) scheme, certainly was considered potentially dangerous. However, the main danger anticipated was fire, not explosions of such magnitude. Only a few weeks before the incident, the HSE had carried out a regular review and cleared fire safety measures on the site. And over the years since the site’s opening in 1968, successive authorities have allowed construction that has brought business and housing developments to within a couple of hundred yards of the perimeter fence — decisions that are now naturally being questioned.
Meanwhile up at Kingsbury, the surroundings remain mainly rural, but I’m sure the same questions will be asked there, as they now should at any major tank farm storing hazardous products. Can it happen here? Why did it happen there? As with Flixborough, the answers could help shape the future safety policies of the industry.