Case Study
Incident Investigation - Buncefield Oil Storage Depot
The Client
The Problem
The Buncefield Oil Storage Depot was comprehensively damaged by
a series of explosions and fires which started at approximately 6am
on Sunday 11th December 2005. This was the largest event of its
type in Europe since the 2nd World War. Several people were injured
but none fatally. Many of the surrounding industrial premises were
destroyed and windows were shattered at 1 km distance.
What We Did
HSL was called in
immediately by the Health Protection Agency to collect air samples
and perform analyses as soon as possible. A scientist was "blue
lighted" to the scene within a few hours of the request being
received.
Subsequently HSE asked HSL to carry out a wide-ranging
investigation to establish the cause of the incident. The
Environment Agency requested damage surveys and mapping of all the
tank bunds
The investigation covered the following principal areas:
- Examination and photography of site damage
- Interrogation of site CCTV images
- Investigation of control and alarm systems
- Fire and explosion studies
- Human factors issues: control room layout and shift
working
The primary cause of the incident was found to be the
overfilling of a tank containing unleaded petrol, resulting in the
escape of 250,000 litres of fuel. There was little or no wind at
the time and a vapour cloud, consisting of air and hydrocarbon
vapour, was formed. This cloud spread around the site, following
the natural topography, until it encountered a source, or sources,
of ignition. The malfunction of the tank control and alarms systems
was the key factor in explaining the release.
A series of experiments was carried out on the Buxton site using
two full-scale models of sections of the storage tank in order to
study the fuel release. The overpressure generated during the
explosion was deduced from damage to buildings and cars; in the
case of the latter, a number of vehicles were subjected to various
explosive overpressures in a blast chamber at HSL in order to
"calibrate" the damage observed in vehicles on the Buncefield
site.
Outcome/Benefits
HSL's findings were presented in a series of incident reports to
HSE. Our staff will be required as expert witnesses in any legal
proceedings.
The magnitude of the overpressure generated during the explosion
could not be explained by conventional wisdom relating to
unconfined vapour cloud explosions. HSL is therefore collaborating
with industry on a joint research project to study this
phenomenon.
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