Remediation of a high profile retail site in Denmark

A retail site outside Copenhagen (a high end retail site selling between 6 and 7 million litres of fuel per year and offering a large car wash area) suffered an undetected spill from a fuel line, leading to gasoline pollution over a protracted period, which mixed together with older contamination caused by historical spills at the site. Over a period of approximately 10 years, more than 30 monitoring wells were installed to assess the situation both within the upper moraine clay/weathered limestone aquifer and the primary aquifer within the competent limestone formation. Regular reports to the regulator were required to provide evidence of the plume containment achieved by use of a Pump & Treat system. Between 2012 and 2014 a crucial phase of the project took place involving the shift of the remediation strategy by performing a full scale high resolution site investigation and the pilot test of an in-situ bioremediation solution aimed at replacing the use of the P&T system. During this phase GWSDAT was widely used to model the development of the plume within the upper and primary aquifer together with the local improvements of the groundwater conditions in the pilot test area. The GWSDAT analyses supported amongst other factors the approval of the 3M € full scale in-situ remediation conducted between Q3-Q4 2014 and Q2 2015. At completion of the remediation works, quarterly groundwater performance monitoring was conducted as part of the Performance Remediation Based contract in place with the client. All the generated groundwater data analysis was conducted in GWSDAT. This clearly established the stability of the situation (supporting the approval of discontinuation of any P&T activity) and that levels of benzene (driver of the remediation) were dropping significantly. In June 2018 the site was signed off for no further action allowing the O&G client to regain full value of the high-end piece of land within the area.

Gabriele Giorgio Ceriani, In-Situ Remediation Services Team Leader and Senior Site Manager for Ejlskov A/S in Aarhus, Denmark, was a key person in the analysis. Giorgio commented: “GWSDAT has proved to be an invaluable tool, not only in the high profile project described above but in many other projects where a large series of groundwater data is available. The use of the tool (in the right conditions) allows a proper overview of the data and when presented along with the right explanation of the site specific conditions to end-clients and regulators, can definitely help in supporting solid and rational decisions. In the specific case of our company (where we have an in-house software used to model high frequency soil and MIP data), GWSDAT can be used as a support tool to generate GW plots and level contours using a different interpolation method and providing a QA/QC role in the overall evaluation of a site. By being easy to use and available for free online, the personal recommendation is to use it (along with the right data) to gain a better understanding of the site conditions developing or that have been developing historically at your site”