Dual Phase Vacuum Extraction

VertaseFLI was employed to design and build a comprehensive remediation system to address a plume of hydrocarbon contamination within the saturated and unsaturated zone. This targeted both free phase and dissolved phase contamination, relating to leakage from the former ASTs associated with St Georges Hospital. Additional site investigations were also undertaken to assess a potential plume of DNAPL (TCE) in the vicinity of the former hospital laundry.

Project Details


Bovis Homes


Stafford, West Midlands

Project Value



12 months

Services Provided

In-situ DPVE, LNAPL & DNAPL removal, groundwater TCE investigation, abstraction well decommissioning, UST removal, additional site investigation & risk assessment works

Further Information

The site was previously occupied by the former incinerator and laundry buildings of the former St Georges Hospital, Stafford. VertaseFLI was responsible for the design and installation of an in-situ DPVE system comprising 24No abstraction wells within the previously identified plume of contamination. The primary driver for remediation was to maximise the recovery of the hydrocarbon contamination and remove the free product. Initial investigations identified a thickness of free product floating on top of the ground water of up to 650mm across the plume. 

The system was operational for 9 months and focused on maximising the rate of contaminant recovery. The system was regularly optimised to enhance the mass recovery rates from the subsurface with over 1,000 litres of free product recovered from the area via the treatment process, removing all the mobile free product with no rebound of contamination noted during the post remediation monitoring. 

In addition to the DPVE work, TCE contamination had been previously identified in monitoring wells along the southern boundary of the site, in the vicinity of the former laundry building.  A series of deep monitoring wells were installed, to the underlying bedrock to assess the level of contamination, including the potential for DNAPL contamination. Monitoring and risk assessment works were successfully completed to demonstrate that the level of TCE in the deep groundwater did not present an unacceptable risk to the wider environment.

In parallel with the remediation works, VertaseFLI also undertook additional works to locate and grout 3No large (>10m diameter) historic groundwater abstraction wells and to remove and validate underground storage tanks (UST's) contained within the adjacent ongoing development site.

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