Buncefield pollution minimal, concludes report

The latest report from the ongoing investigation into the explosion at the Buncefield oil depot last December says the environmental impact of the incident is not major.

Despite the fact the blast released an estimated 8,000 tonnes of PM10 particles – around 6% of the UK’s annual emissions of the pollutant in one go – experts looking into the disaster say the ground-level effects were minimal.

The report released this week, the Interim Review of Air Quality Aspects of the Buncefield Oil Depot Explosion, was produced for Defra by consultants Netcen, the Met Office and the Health Protection Agency and was timed to coincide with the release of the third update from the Major Incidents Investigation Board, which looks at the causes of the accident.

The official monitoring shows that despite the unprecedented scale of the Buncefield explosion and fire, ground-level concentrations of a range of pollutants did not deviate from those normally expected at that time of year over local, regional and national scales.

It says that favourable weather conditions and the nature of the smoke led to it being carried upwards, with minimal impact at ground level.

Because of this there was no major public exposure to the cocktail of pollutants, which as well as substantial quantities of particulate matter included harmful nitrogen oxides, carbon monoxide, volatile organic compounds, dioxins, furans, hydrocarbons and polycyclic aromatic hydrocarbons.

Measurements taken from within the plume by a research aircraft operated by the Met Office and Natural Environment Research Council showed that the plume was mainly black carbon-soot.

Concentrations of chemical contaminants, such as polycyclic aromatic compounds and hydrocarbons which would be expected from a fire of this nature, were low.

The Major Incidents Investigation Board has put the cause of the accident down to ‘a failure in the safety mechanisms designed to prevent this type of incident’.

More specifically, it is believed to be a combination of human and mechanical error, with overfilling of a tank allowing unleaded petrol to escape which led to the build up of flammable vapour which then ignited.

The report acknowledges that more work is needed to fully understand the explosion mechanism and how it generated such extreme overpressures, thereby causing so much damage.

Sam Bond

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