The site is located in an area of mixed commercial, industrial and residential development. It was historically occupied by small-scale commercial and industrial uses, including an engineering works, and more recently by a vehicle hire facility.
The site is located in an environmentally sensitive area due to the presence of Principal aquifers and its location within a groundwater Source Protection Zone.
During demolition works, which included the removal of existing hardstanding and relic foundations, an area of residual hydrocarbon contamination was encountered in the shallow soils. It was initially proposed to remove this material and dispose off site. However, given the amount of material that was intended for removal, detailed quantitative risk assessment (DQRA) was undertaken to confirm whether the identified contamination posed a significant risk to the underlying groundwater, and if it could remain in-situ.
CampbellReith attended site to inspect the area and obtain additional soil samples for analysis. Elevated leachate concentrations of hydrocarbons were identified and these were subsequently modelled within the DQRA, in accordance with the Environment Agency’s Publication ‘Remedial Targets Methodology’.
Site specific Remedial Target Values (RTVs) were calculated as part of the DQRA, and the identified hydrocarbon concentrations were several orders of magnitude below these. It was demonstrated that the risk to the underlying aquifers was low and the impacted material could remain on site, thus eliminating the need for unnecessary material removal.