The Buncefield explosion: Were the resulting overpressures really unforeseeable?

On Sunday 11 December 2005, a severe unconfined vapor cloud explosion followed by several tank fires occurred at the Buncefield oil storage depot in England, near London, causing widespread damage to homes and businesses surrounding the site, hopefully without any victim. The damage caused by the resulting blast wave(s) surprised all the process safety community and explosion experts, as common hazard assessments would have predicted overpressures of only 5 kPa (0.73 psi), instead of 200 kPa (29 psi) as suggested by the data collected onsite. One of the particularities of the Buncefield oil storage depot is that it was surrounded by long and continuous rows of trees and bushes; this singularity is currently considered as a preponderant factor in the resulting high overpressures. Recently, explanations of the resulting overpressures were given by some authors using data from large-scale explosion tests and CFD simulations. The objective of this article is to verify whether application of simple methodologies used in common risk assessments could allow to estimate the severity of the Buncefield explosion. (C) 2011 American Institute of Chemical Engineers Process Saf Prog 31: 55-71, 2012