Remediation: it’s all in the technique

Site investigation

The site investigation performed by Inex produced a clear understanding on how

the contaminants were present, where they were located and in what concentrations.

The survey produced a three dimensional map of the contamination on the Oakfield

site. The digging of trenches also produced information on the level of waste

disposed of in the landfill area.

Fed by the information from the site survey, Inex engineers started their work

on the design of the remediation proposal. Several tests were conducted on site

to investigate the geophysical and geohydrological situation, to establish groundwater

flow patterns, soil structure and ground bearing capacity.

Remediation techniques

The remediation techniques used by Inex included the excavation, sieving and

removal of solid waste from the site. Hydrocarbon contamination in the soil

was dealt with by biopiling and land farming, and active barrier treatment was

used to deal with contaminants in the groundwater and perching water.

Finally, a clean ‘living’ layer with a special subsurface protective layer

between the remediated ground and the clean living layer was applied. The active

barrier was installed to deal with long term residual hydrocarbon and heavy

metal contaminants, present in low concentrations, that could dissolve into

the groundwater of hanging water and migrate from the site to the adjacent brook.

To make the site suitable for housing development, it was relevelled and equipped

with a clean living layer of one metre which was installed on top of the old

soil. In between the old soil layers and the new topsoil layer a special protective

zone was installed. This zone was charged with zeolites, a natural mineral with

high absorbing and fixing capabilities.