The remediation of an arsenic-contaminated site has successfully paved the way for new commercial uses.
When the Department of Environmental Affairs decided not to approve off-site disposal as a default remediation strategy, an alternative in situ methodology needed to be adopted in remediating a section of industrial land in Durban. The chosen approach was to use ferrous sulfate to stabilise the contaminated soil.
“Our conceptual site model had identified potential risks to human receptors, as well as groundwater and surface water resources,” explains Richard O’Brien, principal environmental geochemist, SRK Consulting.
“The human health risk meant that any action plan had to ensure that impacted soil would be capped with hardstanding paving to mitigate the exposure of workers to arsenic impacted soil.”
The remedial strategy focused on protecting the groundwater resource, occurring at a depth of 7 m to 13 m below surface. The risk assessment involved site-specific geochemical analysis of arsenic mobility and partitioning within the soil – an uncommon approach in this part of the world, says O’Brien, but one that proved effective in assessing groundwater risks.
Eastern and western zones
Results from the initial soil assessment delineated the site into two in terms of soil arsenic concentrations. In the western portion, the concentration was usually over the soil screening value for industrial land use of 150 mg/kg; the eastern portion was primarily below this level.
