Chronology of events at Buncefield explosion
The investigation of computer data retrieved and analysed after the event revealed that:
10 December 2005
- 6.50pm - Unleaded petrol starts being delivered through the UKOP South Pipeline - one of three into the depot - into tank T912
11 December 2005
- 3.05am - The automatic tank gauging (ATG) system for tank T912 fails to show an increase in levels, despite the tank continuing to fill. The system does continue to show a rising temperature in the tank, indicating that the tank was still filling.
- As a consequence of the flat-lining, the three ATG alarms - User Level, High Level and High High Level - failed to operate, which meant that the control room pipeline supervisor was not alerted that the tank was at a level which needed his intervention.
- 5.37am - Petrol started spilling out of vents in the roof of the tank. Unchecked the level had continued to rise past the Independent High Level System, which failed to operate - neither to sound the audible alarm in the control room nor to shut down the pipeline.
- Drivers along Cherry Tree Lane started experiencing problems with their cars revving, even after the engines had been turned off.
- Tanker drivers report mist/vapour on site, which the investigation later established was caused by the cascading release of petrol from the tank.
- 5.59am - In response to the reports, the pipeline supervisor opened the Fina Line inlet valve to the neighbouring T911 tank, which he wrongly assumed was causing the problem.
- 6.01am - The staff commenced emergency actions.
- 6.01.32 - The vapour cloud explodes. The explosion registers 2.4 on the Richter scale, according to the British Geological society
- It has subsequently been calculated that 250,000 litres of petrol escaped from T912 prior to the explosion.
11-16 December 2005
- Emergency services take control of the scene. The fire takes 5 days to put out.
- Environment Agency staff worked around the clock alongside the emergency services during the incident offering specialist advice on environmental impact.