The accidental detonation of vapour from some 300 tonnes of leaked petrol at the Herefordshire Oil Storage Terminal was the largest land-based non-nuclear explosion since the Second World War. Jon Herbert looks at a new report examining how continuous safety improvements have helped turn good practice into common practice.

The extent of the Buncefield oil storage depot blast was monumental. On Sunday 11 December 2005, a simple equipment failure resulted in an explosive boom that was loud enough to be heard 125 miles away, stretching as far as Belgium, the Netherlands and France.

Post-event investigations found that a measurement gauge had become stuck. As a result, the level of petrol in a storage tank rose until it overflowed. At the time, it was an accident waiting to happen.

Fortunately, of the 43 injured, only 2 were detained in hospital; there were no fatalities. Medical aid was given to 244 people.

Ten years on, the Health and Safety Executive (HSE) remains determined that history should not repeat itself.

A new report from the HSE’s Control of Major Accident Hazards (COMAH) Strategic Forum, The Buncefield Major Incident: Ten Years On, recognises that Buncefield not only triggered a detonation but also a determination that continuously improving industrial safety would ensure that similar circumstances are extremely unlikely to happen again.

Those who learn from history don’t have to repeat it

The lessons learned have translated far beyond the oil and gas sector to wider industry, and in many cases far beyond UK shores. One of the most significant changes has been the way in which large high-hazard plants, such as oil refineries, storage depots and chemical plants, are laid out and operate.

The Buncefield site, close to the M1 motorway, was the UK’s fifth largest oil production depot. Owned jointly by Total UK Limited and Texaco, it could hold 60 million gallons of fuel. After what was thought to be have been an initial fuel-air explosion of unusual strength, 20 large storage tanks were engulfed in the inferno.

It is estimated that 41 minutes after the failure of the high-level switch that should have closed off the fuel flow, 300 tonnes of petrol would have spilled through roof vents and down the side of the first tank on to ground inside a bund wall. There it quickly formed a rich fuel-air vapour.

The British Geological Survey reported that the event registered 2.4 on the Richter scale. One theory is that rows of deciduous trees may have played a role in propagating the flame front such that its pressure wave caused the detonation of remaining fuel.

Not unexpectedly, subsequent investigations pointed to the need for safety measures to stop future fuel leaks from tanks in the first place. Further steps would then be needed to prevent any fuel that should escape from forming flammable vapour. There was also a need to prevent pollutants from poisoning the environment.

The high thermal energy of the incident, combined with settled weather, created a highly-buoyant plume that drifted over several counties. Within a day, this was reported to have reached northern France, with expectations that it would be in Spain within a week.

Soot particles were found to be the major component of the cloud, with low levels of carbon monoxide, nitrogen oxides and ozone.

Locally, some 2000 people had to evacuate their homes; other residents were asked to stay indoors with closed windows and doors. In the Borough of Luton, 78 schools were closed for a day following county protection agency advice that all schools within a 10-mile radius should not open for fear of smoke plume effects on pupil health.

Another environmental consequence was that the bio-accumulative and toxic fluorosurfactant perfluoraoctane sulfonate (PFOS) used as a fire-fighting foam was found in adjacent water boreholes; no water from this source was allowed into the public supply.

In addition, some 18 miles of the M1 were closed. Petrol stations reported long queues of panic buyers. Heathrow Airport was also forced to introduce fuel rationing since Buncefield supplied 30% of its aviation needs. Long-haul flights to Australia, the Far East and South Africa were affected. Fuel shortages continued for months.

Thankfully, as 11 December was a Sunday, no employees were present in a number of surrounding business properties that were damaged to the extent that 6 had to be demolished. It was noted at the time that although the original depot was intentionally sited away from property, development pressures had subsequently led to both homes and commercial premises being built too near to the terminal.

Regime changes

The changes that have been introduced since are not just technical. High leadership standards are now seen as essential to the effective control of major hazard risks.

As such, a set of core principles were established by the newly-formed Process Safety Leadership Group and used to define the organisation and resources needed for a transition into practice.

This was seen as a major achievement of regulators, the industry and trade unions all working together. One of the main lessons coming out of Buncefield is that effective major hazard risk management comes from pooling experience and insights.

Chair of the COMAH Strategic Forum, Ken Rivers, emphasises today that the challenge of translating “good” practice into “common” practice is relevant to many industries across national boundaries. The consequences of getting it wrong can turn major hazard incidents into “enterprise ending events”, he says.

A Major Incident Investigation Board (MIIB) was formed to investigate the incident and subsequently issued a number of recommendations, many related to safety and environmental standards at fuel storage depots.

One area identified for improvements was emergency response, with a series of recommendations made for emergency planning and how industry and regulators should work with the emergency services and civil response organisations. Guidance notes are available for COMAH sites.

The COMAH Competent Authority (CA), regulators, industry and trade unions together formed the Buncefield Standards Task Group (BSTG), followed by the Process Safety Leadership Group (PSLG) to address MIIB recommendations. Details can be explored on the HSE website.

Wider implications

The main aim of the group was to set minimum standards for “in-scope” tanks, reinforced by good practical guidance on any additional measures needed to contain leaks.

Publication of the PSLG report was followed by 50 other sites which used similar “in-scope” tanks analysing their plants and operations against the new guidance provided.

The CA used their findings to set action plans for upgrades and modifications needed, in some cases with significantly higher standards. Installation required detailed planning during major maintenance shut-downs.

Operators were also given guidelines for re-evaluating the risks associated with overfilling large petrol storage tanks, plus automatic protection systems, based on work at the Health & Safety Laboratory.

All risk assessments must now be documented, and in higher-risk cases have to include the operator’s COMAH Safety Report. This is reviewed and revised regularly.

Another innovation is the planned maintenance of storage tanks for fitness for use and mechanical integrity. In addition, to cope with any possible leak, operators must complete hazardous area assessments against Dangerous Substances and Explosive Atmosphere Regulations 2002, followed by an equipment review.

CCTV and gas detectors could play a greater future role. Additional guidelines have been provided by the Chemical and Downstream Oil Industries Forum (CDOIF).

Another priority has been improvements to managing any spill, including sealing gaps and improving the integrity of concrete bund wall joints, with fire-proof steel plates were necessary.

The CA subsequently published a (now archived Containment Policy) and supporting guidance. Since then, it has inspected fuel storage terminals with improvement plans to meet appropriate standards.

A report entitled Environmental Risk Tolerability for COMAH Establishments has also been developed to assess environmental risks and pinpoint any further measures needed.

Steps to ensure that site personnel, from operators to managers, understand their roles and responsibilities have led to the chemical industry working towards embedding Competency Management Systems. On-site communication has also been improved.

In addition, “leading” and “lagging” indicators have been introduced to monitor when something is about to go wrong, or has already gone wrong in a process system. Safety performance indicators are also used widely.

Finally, measures have been taken to ensure that the human factor in the form of leadership is not neglected; the PSLG publishes its Principles of Process Safety Leadership up to board level.

In applying these principles, the industry now works with a range of related organisations where training is a priority.

Ken Rivers believes it important that as many people as possible read the new report, reflect on its lessons and, if relevant, identify how risks can be managed more effectively.

Delivering the recommendations for Buncefield is not about setting an end point, he says, but about continuous review, learning and ensuring on-going improvements in good practice.

Published by Croner-i on 18 January 2016