Ongoing investigations at the devastated Buncefield fuel depot have revealed possible problems with safety instrumentation and raised the issue of human factors in the management of major hazard sites.
Ongoing investigations at the devastated Buncefield fuel depot have revealed possible problems with safety instrumentation and raised the issue of human factors in the management of major hazard sites.
Commenting on the publication by the Buncefield Major Incident Investigation Board of its Initial Report into the December 2005 blast, investigation manager Taf Powell said: “Evidence continues to be gathered from different sources and the emerging information contributes to a greater understanding of the underlying root causes. This allows the investigation team to refine its enquires further and to bring into focus elements such as wider management systems and organisational factors.”
The Initial Report essentially summarises information from three previously published progress reports (see SHP News February, May and June) but it also includes significant new findings that emerged since publication of the third progress report on 9 May. These relate to the functioning of the systems used to shut down fuel delivery when a tank is full; the likely composition of the fuel released from Tank 912; and the ongoing monitoring of the environmental impact of the incident.
In relation to the instrumentation systems, the ultimate high-level override switch has now been recovered and examination revealed that the position of a test lever fitted to it would have been critical to continued effective operation. It has yet to be determined whether this feature is relevant to the Buncefield explosion but the discovery prompted the HSE to issue a safety alert on 4 July requesting fuel depot operators using the same switch as that used at Buncefield to carry out immediate checks of their equipment.
Also since the third progress report the pattern of fuel dispersal and vaporisation has been confirmed. Further sampling found that the released fuel “probably had a butane content of 10 per cent”, meaning it would have had a high vapour pressure and thus been able to evaporate rapidly to produce a flammable vapour.
As for the environmental impact, further work is needed to determine the full extent of groundwater contamination. However, detection of perfluorooctane sulphanates (PFOS) has prompted the Environment Agency to launch a targeted national groundwater sampling exercise to investigate the wider prevalence of these and related compounds (PFOS are bio-accummulative and toxic to mammals).
There was a great deal of speculation in the wake of the third progress report on the role of human error in the incident but as yet, there have been no concrete findings on this issue. The Initial Report does, however, state that the Investigation Board will, when the investigation is further advanced, wish to offer further advice on “the human and organisational factors that contribute to the safe operation of a major hazard site”. Such factors include “job organisation, management of organisational change, monitoring and supervision, training, and control-room layout”.
The Initial Report has been endorsed by the EA and the HSC, whose chair, Bill Callaghan, commented: “The report indicates that good progress has been made in identifying the root causes of the incident. . .It is of paramount importance to ensure that all the lessons of Buncefield are learned to prevent reccurence of such an incident, and to ensure the maximum effectiveness of emergency arrangements if an incident does occur.”
Safety minister Lord Hunt added: “Work being carried out by a cross-government group to determine the implications of new information being gathered by the HSE about major hazard sites has been underway since before the Buncefield incident but will take account of information arising from the investigation. Once clear conclusions emerge, the work will be the subject of consultation with stakeholders.”
www.buncefieldinvestigation.gov.uk
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