DNAPL Dual Phase Vapour Extraction

VertaseFLI was employed to design and build an appropriate remediation scheme to address TPH contamination within the unsaturated and saturated zone including LNAPL, and a trichloroethene (tce) plume present as DNAPL on a different part of the site.

Project Details

Client

Segro

Location

Hounslow, London

Project Value

£460,000

Duration

9 months

Services Provided

Dual phase vapour extraction, bioremediation, LNAPL and DNAPL removal

Further Information

The site was previously a tool manufacturing facility, VertaseFLI undertook removal and processing of all hardstandings and obstructions beneath. The resultant recycled aggregate was placed across the site as a piling mat. These works also included the identification and removal of comprehensive buried infrastructure and services including two underground fuel storage tanks.

TPH impacted soils in the unsaturated zone were excavated and subjected to ex-situ bioremediation. These excavation works allowed access to the shallow groundwater where free product removal was undertaken by skimming and dissolved phase TPH was addressed via pumping and treatment via our groundwater treatment plant. All voids were re-instated with recycled aggregate produced by the slab processing and treated soils. Because TPH contamination extended beyond the site boundary, a clay stank was installed along one boundary keying into the underlying London Clay to prevent re-contamination of the subject site. Excavation of the TPH impacted soils was complicated by the known presence of localised cement bonded asbestos. Due the relatively small quantities, this was subjected to handpicking for subsequent export from site.

The main driver for remediation was a significant TCE plume which was present on a different part of the site.  TCE was present as both dissolved phase and DNAPL resting on underlying London Clay approximately 8m deep.  VertaseFLI designed appropriate treatment well construction and spacing to facilitate effective vapour, dissolved and DNAPL recovery including ensuring an appropriate zone of influence extended beyond the site boundary.  This design and build work was undertaken in-house within our own workshops.

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