During investigation of a previous gasoline spill, an area in the southern part of the Tank Terminal showed elevated levels of BTEX compounds and Hydrocarbons in soil and groundwater exceeding the criterias set by “Svenska Petroleum och Biodrivmedel Institutet” – SPBI. The leak created a growing risk of migrating contamination flowing into the neighboring marine environment. Due to pipelines and entrance settlements in daily use, the source of the contamination was difficult accessible for treatment. In 2017, the client sought an effective treatment of the contamination not causing greater business intervention or closing of facilities.
The solution
Circle K signed up a fixed price contract with Ejlskov regarding remediation of the contaminant flux and plume hot spot. Due to area complexity, Ejlskov’s approach comprised the installation of a permeable reactive barrier combined with targeted in-situ ‘hot-spot’ treatment using innovative Trap & Treat® BOS 200® bioremediation technology. The treatment immediately brought the contamination plume in control and initiated an ongoing biodegradation process eliminating over time underground LNAPL concentrations. Only 6 months later contamination inside the barrier location was reduced to levels safely below SPBI criteria. The remediation works were carried out over a 2-week period and were completed successfully without disrupting every-day activities at the facility.
Services provided by Ejlskov
Full-scale application of Trap & Treat® BOS 200® in-situ remediation, including:- Trap & Treat® BOS 200® in a combined hotspot and barrier design application, preventing contaminant migration to neighboring property
- Full-scale in-situ remediation of the contaminated area
- Groundwater monitoring programming
Remediation process and results
An evaluation of the existing relevant soil and groundwater data showed that there was approximately 1,650 kg of contamination in the soil at the outlined barrier location. Ejlskov proposed a plan that would clean the soil inside the remediation area to safe levels below the standards set by SPBI within 3-5 years gradually reducing the downgradient contamination meanwhile maintaining full production at the terminal.
Flexible drilling equipment and technical expertise enabled Ejlskov to optimize the remediation design with some unique approaches making use of a triangular injection grid pattern with vertical offset injection levels, high pressure top-down injection techniques and inclined injection holes along a part of the containment wall.
By means of in-situ Trap & Treat® BOS 200® technology, Ejlskov was able to perform 80 high pressure precision-drilled injections in a 160 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 6 months of monitoring after ended injection showed that the levels of total hydrocarbon and BTEX compounds in the groundwater was already reduced to below the standard set by the SPBI. Xylene was the only parameter still above the criteria after these first months, but steadily declining concentration levels showed that the process continually performed as planned.