Remediation and monitoring for a tar-polluted industrial site, Belgium  

Two centuries of industrial use left a brownfield site in Belgium heavily contaminated with tar. The site developer wanted to turn the area into a small, modern business site for local companies. However, as soil is contaminated at both surface and deeper levels, remediation and long-term monitoring are necessary.

The site is polluted with low- and high-viscosity tar, and the main contaminant is a relatively light tar with low levels of volatile aromatics and phenols. As tar is denser than water, it sinks through the water-saturated soil where small droplets become trapped in the soil pore spaces and become dense non-aqueous phase liquid (DNAPL). DNAPL tar products are difficult to detect and treat. On the Belgian site, DNAPLs reached 18 m depth and contaminated groundwater over a 40,000-m2 area.

RSK conducted an extensive risk assessment and considered best-available techniques to create a remediation action plan. The plan aimed to minimise the source contaminants as much as possible and remove the DNAPL. The plan proposed several remediation techniques including excavating source contaminants, removing DNAPL by pump-and-treat methods, and geohydrological control.

Site redevelopment is ongoing, with a major remediation goal of removing the dispersion risks caused by DNAPL and preventing a widespread groundwater plume. Even though the planned DNAPL removal is expected to take 10 years, RSK is committed to removing the health and safety risks posed by this tar pollution.