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A leaking valve had caused an oil spill at a pipe cross section at the Danish Shell refinery. An injunction had been issued from the authorities, and from previous remediation attempts using traditional methods it was clear to Shell that to meet the economic and technical requirements set for the task, and to prevent migration of the oil contaminant plume, all while maintaining daily operation at the refinery, alternative solutions had to be found. This was the challenge Shell presented to Ejlskov.

The solution

Ejlskov applied our Trap & Treat BOS 200® technology, which reduced the levels of total hydrocarbon in the groundwater to below the standard set by the Danish Environment Authority over a period of just 18 months. A full remediation of the contamination was completed with no disruption to the daily operations of the refinery, and at a price less than 30% of the cost for traditional solutions, such as excavation.

Services provided by Ejlskov

Full-scale application of Trap & Treat® BOS 200® in-situ remediation, including:

  • high resolution site investigation to identify contaminant mass distribution in soil
  • unique 3D-mapping and planning software for precise and efficient remediation
  • fast and dynamic installation around and under pipes, leaving the production facilities untouched

Remediation process and results

An evaluation of the site by Ejlskov showed that there was approximately 1.600 kg of oil contamination in the soil. Ejlskov proposed a plan that would clean the soil to safe levels below the standards set by the Danish Environmental Authority after 3-5 years, and remove the contamination at the same time as maintaining full production at the refinery.

Ejlskov carried out two surveys using MIP (Membrane Interface Probe) and soil sampling that delineated the extent of the contamination over 350 m2 and to depths of 10 m below ground level. The site presented challenges both in the subsurface, with a complex geology, and on the surface with obstacles from oil refinery structures and utilities. Flexible drilling equipment and technical expertise enabled Ejlskov to optimize the remediation design with some unique approaches: a triangular injection grid pattern with vertical offset injection levels, high pressure top-down injection techniques, inclined injection holes, and adjustment of the lateral and vertical injection spacing in relation to the utilities.

By using in-situ Trap & Treat® BOS 200® technology, Ejlskov was able to perform 170 high pressure precision-drilled injections in a 350 m2 area. Trap & Treat® BOS 200® is a proven technology effective at remediating oil contaminated soils. It works by trapping the contaminants via carbon absorption and then removing the contamination by biological degradation. The initial 18 months of monitoring after the injection showed that the levels of total hydrocarbon in the groundwater was already reduced to below the standard set by the Danish Environmental Authority.