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.