Our investigation of a former industrial site in Dagenham concluded that the previous storage of oils and lubricants had locally impacted soil and groundwater quality in one area, requiring remediation of local soil and groundwater. Impacted soils were rapidly identified, characterised and excavated, and groundwater was treated in order to achieve the defined remedial targets for petroleum hydrocarbons.
We were commissioned to undertake a supplementary site investigation of a site, located in Dagenham, which had previously been used for concrete casting, maintenance of vehicles and equipment associated with a railway construction project and storage of materials.
It was concluded that the storage of oils and lubricants, during a period when the site was leased, had locally impacted soil and groundwater quality in one area of the site. Leakage or spillages of these substances had subsequently migrated to ground through joints in the concrete surface of a storage area.
Remediation of impacted soils and groundwater in the vicinity of the storage area was recommended. The objective of the remediation works was to ensure petroleum hydrocarbons in this area were reduced to appropriate levels and hence remedial targets were defined on this basis. An appraisal of potential remediation options identified that the excavation and off-site removal of soils and treatment of impacted groundwater was the best practicable technique.
The remediation works were supervised by our suitably qualified personnel. On-site testing of petroleum hydrocarbon concentrations within soils was performed using the PetroFLAG system. This system is a rapid and portable method for the determination of hydrocarbon concentrations in soil. It was used to help confirm the likely extent of the material which was contaminated above the remedial target concentration. This helped to inform decision-making during the excavations without having to wait extended periods for the results from laboratory analysis.
Impacted groundwater encountered within the excavation was pumped and passed through a groundwater treatment plant (which included passing the groundwater through an oil/water separator and granular activated carbon to adsorb dissolved contamination) prior to appropriate disposal.
Once the impacted soils had been satisfactorily identified and excavated and groundwater had been treated, validation samples were collected and submitted for formal analysis at an accredited laboratory to confirm that the defined remedial targets for petroleum hydrocarbons had been achieved.
ESI, now part of Stantec, is recognised as a UK centre of excellence for contaminated land assessment and remediation, and is contracted by both public and private organisations to carry out similar work.