Validation of contamination control measures

Following torrential rain in 2014 an 80 metre stretch of rail embankment was severely damaged by a landslide which blocked the line between Eastleigh and Fareham.

Unfortunately a failure of a diesel tank supplying the repair works led to a spillage of between 500-900 litres of diesel. Immediate remediation works included excavation and disposal of hydrocarbon impacted soil. Although a  number of samples had been taken and analysed, no formal remediation verification strategy or verification report was provided.

The Environment Agency was notified and it raised concerns on the potential impact on a stream approximately 250m from the spillage. The EA also recommended a site risk assessment be carried out to formulate a remediation strategy in accordance with CLR11 framework (Model Procedures for the Management of Land Contamination).

CGL undertook sampling to validate the remediation works to confirm the extent of the contamination and provide background environmental conditions. In-situ analysis and confirmatory laboratory analysis as curtained the spillage hotspot had been sufficiently removed.

Stockpiled arisings from the excavations were also tested and found to be safe to use with clean imported material to reinstate the site.

Leachate testing was completed and hydrocarbon concentrations were found to be well below the relevant assessment criteria.The nearby stream was also sampled upstream and downstream of the site and analyses of hydrocarbon concentrations confirmed the spillage had made no impact to the stream.

With laboratory and engineers’ reports as evidence CGL validated the cleanup as having sufficiently removed all soils impacted by the spill and no water treatment was required.