Remediation of a fuel spill in chalk Wiltshire Downs

Remediation of a fuel spill in chalk Wiltshire Downs

FLI QDS were commissioned by a fuels distribution company to recover a volume of fuel from chalk below the Wiltshire Downs. The fuel had leaked from a distribution pipeline in a remote area of the downs close to two sites of Special Scientific Interest and a National Trust site.

A solution feature in the chalk was identified immediately adjacent to the spill location. Six boreholes were installed to evaluate the extent of impact in and around the solution feature. Photoionisation detector headspace readings indicated the solution feature provided a major contaminant pathway and had retained a significant proportion of the contaminant mass. We were contracted to treat the 25m deep solution feature and surrounding unsaturated chalk soils.

Project Details

Remediation method

We built and installed a flexible soil vapour extraction system to recover vapour phase hydrocarbons from the unsaturated chalk and solution feature. Extracted vapour was treated via granular activated carbon (GAC) filters. Our treatment system was fully automated and operated on a 24-hour basis. Real time mass recovery data was collected by telemetry from an in-line Flame Ionisation Detector (FID).

Remediation outcome

Our treatment system was successful in abstracting and treating over 4 million cubic metres of vapour. Over 13 months more than 2,750kg of hydrocarbons were recovered (2,000kg within the first six months). The system was switched off when asymptotic levels of recovery were reached.

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The site manager led an effective team that progressed the works in a diligent and effective manner

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