A former petrol filling station site, due to be redeveloped to make way for a housing development, was believed to have a history of leaks in a number of the Above Ground Storage Tanks and Underground Storage Tanks. A site investigation (SI)showed high concentrations of petroleum hydrocarbons, indicative of the presence of free phase product. The SI results confirmed that the petroleum hydrocarbons had percolated through the unsaturated zone, impacting groundwater in the chalk aquifer at 18m BGL.
It was determined that benzene was the risk driver and a stringent remedial target was derived, including a significant reduction in total petroleum hydrocarbons (TPH).
The consultant designed a remedial strategy comprising the operation of a Pump and Treat (P&T) system, enhanced with PetroCleanze, followed by an application of ORC Advanced in order to accelerate the natural attenuation of the residual groundwater contamination. Down and cross-gradient of the treatment zone, sentinel wells were drilled at the site boundary to monitor the PetroCleanze and abstraction treatment. These were also used for ORC Advanced application later in the project.