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Introduction to Buncefield Incident
Buncefield was a depot located in Hemel Hempstead, northwest of London used for storing and transferring oil. The site was used for the storage of fuel and other commodities before they were transferred to places such as airports and petrol stations. It was one of the largest sites for storing oil in UK. By December 2005, three sites which could store fuel of up to 200000 tonnes had been established at the depot (HSE, 2011).
On December 11th 2005, several explosions that were heard by people 125 miles away from the depot occurred. The explosions caused great damage to property that was in the surrounding areas with more than 2000 people being moved from their homes to save them from the danger they were exposed to. A total of 43 people sustained injuries but no fatalities were recorded.
Basically, petrol over spillage was attributed with the fire that continued burning for five days. The fire damaged most of the tanks and bunds in the depot (HSE, 2011).
Causes of Buncefield incident
The explosion at the oil depot in Buncefield occurred after a large number of gallons containing petrol started overflowing due to failure of the automatic monitoring systems. On 11th December 2005, a fuel gauge that was faulty allowed petrol to get into tank 912. It was then reported that petrol began leaking through a vent situated on the upper part of the tank.
This leakage began 20 minutes after five o’clock in the morning and quickly turned into a cloud of vapor that could catch fire easily as it moved to the sides. By the time the gaseous cloud was set on fire at 6.10 am, it was covering an estimated area of 8 hectares. The source of the fire was suspected to be a pump house or a generator that was near the site.
This incident which was regarded as the largest explosion in the history of European countries since the First World War led to a tremor with 2.4 Richter scale measurements. It caused damage to buildings that were far from the site but no people were injured. Investigations into the incident revealed that the automatic fuel gauge located in tank 912 experienced functional failures at 3 am.
This occurred during a period when the rate at which the tank was being filled was estimated to be 550000 litres per hour (HSE, 2011). By 5.20 am, the tank would have been full but the fuel continued being pumped until the number of litres per hour increased to an unmanageable level. Twenty minutes before the explosion, footages from CCTV cameras indicated that there was a misty cloud coming from the tank (HSE, 2011).
Factors Leading to the Escalation of the Incident
A number of factors led to the escalation of the Buncefield incident. Making an assumption that the bund wall or earthen dykes remained uninterrupted when there was a failure increased the scale of the incident. Estimates made by experts indicated that in case of failures, losses of between 25 and 50 per cent of the contents were possible.
The quantity that could overflow from the secondary confinement could be enormous even when the bund walls were taken into consideration. The earthen dykes and constructed embankments at Buncefield caused a significant loss. Although some experts ignored the fact that there could be catastrophic outcomes as a result of failures, it was discovered that such incidents were possible.
Firstly, the secondary confinement of the bunds at Buncefield were characterized by many mistakes which caused large quantities of firefighting water, fuel and foam to leak from the bunds. The bunds were impermeable and they could not resist fire. As a result, they had no capacity to sustain the large quantities of firewater that were experienced during the incident.
The concrete was effective in dealing with the burning fuels but the bunds caused massive failure at the joints and other points that functioned as penetration points for the pipes. If movement joints between concrete and the slabs had been constructed, expansion and contraction would have been possible hence the scale of the incident would not have escalated. It was also important to ensure that the joints were fire resistant by incorporating metal fire resistants and water stops (HSE, 2011).
Secondly, tertiary confinement at Buncefield was virtually absent and this led to the escalation of the incident. Systems of confinement outside the bunds were only characterized by a drainage pattern that was designed to take care of insignificant spills and rain water. The design of the drainage could not sustain the large-scale releases that took place during the Buncefield incident.
One of the tertiary confinement factors that led to the escalation of the incident was that there was no boundary wall that could restrict the fluids on site and lead them into the drainage systems. As a result, the liquids flowed all over the area once they were released. Another, tertiary confinement factor was that perforation was evident in some drains such that back up liquids escaped through the underground perforations.
The other confinement tertiary factor that escalated the incident was that in the firewater lagoon, the liner could be easily damaged by fire and the debris that resulted from the explosion. These tertiary confinement factors largely contributed towards the escalation and the scale of the Buncefield incident .
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Thirdly, the independent high-level switch was a design failure that escalated the Buncefield incident. An independent high level switch was fitted on tank 20 in July 2004. The designer and manufacturer of this switch was TAV engineering limited.
The intention of this company in designing the switch was to test part of its functionality on a routine basis. However, the design of the switch and its installation presented a false implication of security. Those involved in the installation and operation of the switch at Buncefield were not familiar with its operations thus it was not functional after the test was conducted.
As a result, the defects in the switch and the failure to inform the users of how critical the padlock was caused an escalation of the incident.
In addition, failure of the automatic tank gauging system increased the scale of the incident. The servo-gauge got stuck instead of functioning normally. This was not the first time its failure was observed because it had previously got stuck.
Environmental Implications of the Incident
The Buncefield incident caused serious environmental implications resulting from the fuel and firefighting foam. To begin with, the incident led to the contamination of soil and water in the areas surrounding the site of the explosion. For instance, River Ver which received surface water from the Buncefield site was heavily contaminated.
In addition, other balancing tanks which received water from the Buncefield site and eventually released it to the river were also contaminated after the incident. The fuel and firefighting foam that came from the site was responsible for the contamination.
River Ver which was a source of domestic water for the surrounding people and a habitat for fish suffered great damage. The contamination posed a threat to the existence of fish and people who used water from the river (Sampson, 2010).
The other environmental implication of the incident was the contamination of surface layers of soil. This was as a result of the fuel and firefighting foam that was used to extinguish the fire. Contamination of the surface soil implied interference with agricultural activities since crops could not do well on contaminated soil.
Why the Explosion was Greater than Predicted
Based on known facts and scientific theories, the explosion that took place at Buncefield was greater than predicted. There were different reasons that explained why the explosion was greater than predicted. The first reason why the explosion was greater than predicted was the fact that there was inadequate fault logging.
The fault logging at Buncefield in terms of the working practices and equipment was inadequate. The system of working on shifts made it difficult for short-term strategies of fixing problems to be implemented. In addition, an appropriate overview of why things were going wrong and the possible reasons was lacking.
Consequently, the explosion was greater than predicted (Sampson, 2010). The second reason why the explosion was greater than predicted was the ineffectiveness of the tank filling procedures. It was difficult to observe the status of multiple tanks at any given time thus the high possibility of overflowing.
The third reason why the explosion was greater than expected was the poor control of incoming fuel. There were no proper mechanisms of monitoring the incoming fuel and this made the explosion greater than predicted.
Hiles, A. (2010). The Definitive Handbook of Business Continuity Management. New York: John wiley and sons.
HSE. (2011). Buncefield:Why did it Happen. Available from http://www.hse.gov.uk/comah/buncefield/buncefield-report.pdf .
Sampson, B. (2010). Buncefield five years on. Europe’s largest peactime explosion. Available from https://www.eng-tips.com/viewthread.cfm?qid=274664
Vince, I. (2008). Major accidents to the environment: a practical guide to the Seveso II. London: Butterworth-Heinemann.