Specialist Technical Support: Oil Spill, West Wales

Details:

Kerosene heating oil leaked from a buried oil supply pipe to the ground and groundwater beneath an oil depot in West Wales in 2019.  The site may have been classified as Contaminated Land under Part 2A of the Environmental Protection Act 1990 without intervention. The oil spill was investigated and remediated and the site owner submitted an insurance claim for the costs.

We were commissioned as experts to review the available information on the original oil spill, and subsequent investigation and remediation, and prepare a technical report for them to consider and assess the insurance claim and agree an appropriate financial settlement.

We reviewed thirty technical reports and other documents on the spill and subsequent claim, including several with over 1,000 pages of laboratory test results, and fifteen monthly monitoring reports on completion of the main part of the remediation works.  We initially prepared a comprehensive and extended Conceptual Ground Model for the site considering the geological and hydrogeological conditions, in particular detailing the nature and thickness of the shallow soils present, including an assessment of the extent and thickness of ‘fill’ (Made Ground), and the depth and flow direction of groundwater which was variable due to local hydrological conditions.  From this, the potential soil receptors and pollution pathways were identified, and each was assessed for impact from contamination.

In our technical report, at the request of the client, we concluded with assessment of the following:

• The likely original cause of the oil spill
• The composition of the soils beneath the site and their origin: the extended, comprehensive Conceptual Ground Model. For this particular claim, the lateral extent and depth of the fill (Made Ground) beneath the site was critical.  We assessed the nature, extent and depth of fill in considerable detail via a number of lines of evidence including the soil descriptions provided by third parties on exploratory holes records, the historical setting of the site, the Conceptual Ground Model generated by us for the site, and the local topography (including clear evidence that one side of the depot had been cut into the existing valley side).  As part of the claim, we also considered and responded to the site owners suggestion that the extent of fill was greater than suggested by the exploratory holes records.
• The possible impact of the oil spill on the former buildings and structures: these structures had been demolished as part of the remediation works; however, we were able to provide an assessment of the likely impact on the shallow soils, including fill materials, and the possible impact on buildings and structures.
• The efficacy of the remedial works undertaken on behalf of the site owner: we reviewed the numerous monitoring reports to assess the success of the remedial works undertaken.

We also reviewed and provided comments on the technical content of claim documents submitted separately to the insurer.

Our technical assessment was provided as a comprehensive report, with a non-technical executive summary, which enabled the insurer to settle the claim.