Report unveils safety failure caused UK depot blast

An oil depot blew up after safety systems failed, investigators said. A gauge on a tank got stuck, allowing hundreds of tons of unleaded petrol to spill out, a report into the explosion at the Buncefield terminal, UK, in December concluded.
High-tech systems which should have automatically stopped fuel being piped into the tank also failed, the report added. But investigators refused to blame anyone. An investigation board -- set up after the explosion -- said it could not be specific about failures at the site for fear of prejudicing any criminal prosecution or civil legal action.

Taf Powell, who is heading the investigation into the explosion at the Buncefield depot in Hemel Hempstead, Herts, on December 11, said all his findings would be made available to prosecuting authorities. But he said there were certain aspects he could not discuss for fear of prejudicing potential court proceedings.
Mr Powell said investigations had shown that unleaded fuel was spilling out of a storage tank on the Buncefield site for 40 minutes prior to the explosion at 6.01 a.m. He said the tank had started receiving unleaded petrol through a pipeline at 7 p.m. on December 10. At 3 a.m. on December 11 a gauge on the tank had stuck and wrongly showed that fuel was no longer being pumped in. At about 5.20 a.m. the tank began to overflow out of breather holes on the roof. A cloud of vapour gathered over the site and exploded at 6.01 a.m.

Mr Powell said investigators were not sure what had caused the vapour cloud to ignite. He said the likelihood was that a spark had been generated either from a pump-house on the site or from a generator in a nearby car park.
Investigators did not believe that the explosion had been triggered by a driver flicking a switch on a fuel tanker on the site or by anyone using a mobile phone nearby. Later, separate reports from the Health and Safety Executive, the Health Protection Agency and Defra found that, despite the scale of the explosion and the later fire, there was no long-lasting damage to air quality or the water supply.

Fears that the water table would be polluted by a potentially lethal chemical used to douse the oil tank flames have, so far, proved unfounded.
A Defra report into air quality at ground level following the blast found that there was no change on the levels of pollutants over local, regional and national scales. This was in part thanks to the high plume of the hot smoke meaning most of the smoke dispersed at high altitudes. Measurements taken from within the plume by a Met Office aircraft showed that the plume was mainly black carbon soot.