The November 2005 Buncefield oil storage incidentIntroduction Incident statisticsThe Buncefield oil cloud explosion incident occurred at 06:02:32 Hours on Sunday, eleventh, December 2005 through series of fuel-cloud explosions (Buncefield MIIB 2005:5-7). The incident occurred in a Buncefield oil storage and transfer depot in Hemel Hempstead. The incident caused minor injuries to 43 people but no incident related fatalities were reported. The incident resulted into evacuation of at least 2000 residents. The fire was brought down by effort of at least 1000 firefighters who consumed 750, 000 liters of foam concentrate and 55 million liters of water.
The incident disrupted operations of 630 businesses and affected jobs of 16,500 employees (Buncefield MIIB 2005:22-30). Cause of the incidentTo-date, the cause of the incident has not been established. Oil specialists on BBC NEWS indicated the incident was caused by fuel-air explosion following failure of ‘leak detection system’ to detect fuel leakage resulting into built up of explosible fuel concentration in bunds and dense vapor-cloud formed due to frost conditions at ground level. While BBC NEWS 24 reported a security guard who had detected smell of fuel and requested an oil tanker driver to switch off the tanker engine that might have might have caused ignition of the fuel-air cloud.
Mechanism of fuel-air explosionFuel-air explosion, a type of BLEVE (Boiling Liquid Expanding Vapor Explosion) normally results when ignition of a gas-cloud occurs in a confined volume (Advisory Group report 2007:2). The flame propagation after ignition produce gaseous combustion products whose pressure buildup increases as heat of combustion increases leading into explosion when the confining structure fails (Advisory Group Report 2007:2). This explosion mechanism doesn’t provide guideline for the Buncefield oil incident whose greater percentage of explosion was not confined.
Unconfirmed reports indicate the incident was a terrorist attack according to Italian television who described features on ‘July 2005 terrorist bombings’ citing a videotape that had been released by al-Qaeda who are alleged ‘had four days before the incident released threats on attack on fuel depots and refineries that contained oil ‘stolen’ from Muslim countries. Forensic analysis for source of ignitionFlame modeling and numerical simulation proposed the ignition was initiated in the emergency pump house which conforms with witness statements and CCTV coverage as the emergency fire alarms were activated (MIIB Third progress report 2006 (figure 1)Forensic analysis for explosion propagationForensic analysis indicated that the explosion was a function of hydrocarbon aerosol explosion (figure 3) that was characterized by stratified explosion as a subset of multiple ignition sources resulting into multiple detonations that was propagated by self-sustaining episodic explosion.
The initial overpressures from numerical flame simulation and flame modeling using ethylene indicated that initial explosion generated overpressures of 1000 kPa with shock waves at 10-20ms.
The mechanism of propagation was sustained by ignition of suspended debris and forward radiation from the flame front. Effects of Buncefield incident to the environmentFollowing ignition of the fuel-air mixture, the explosion resulted into release of combustion products into the atmosphere that affected balance of atmospheric gaseous constitution thus creating imbalance of air quality. The incomplete combustion resulted into a smoke plume that was visible from far (Bower & Targa, 2006). Some of the gaseous products included Nitrogen IV oxide whose mass was 37.3 metric tones, Carbon monoxide 1712.7 metric tones, Benzene (Toluene, Xylene and Trimethylbenzene) at 58.3 metric tones, PM10 at 8249.5 metric tones, PM2.5 at 4949.7 metric tones, Dioxins at 1.32 metric tones while B[a]P at 284kg.
The high heat energy from the exothermic process killed soil micro-organism. The heat energy resulted into ‘soil caking’ and calcification of soil hence negatively affecting the stability of the soil. The ‘shock waves’ following initial explosion which generated overpressures above 1000 kPa affected soil stability (Steel Construction institute, 2009).