Telluric slider Groundwater Remediation London

Free product recovery and in-situ chemical oxidation on a development site in London

Client: Developer
Location: Southwark
Contract period: 12 weeks

The site, covering an area of approximately 0.25 ha, was historically occupied by an iron foundry, warehouse, and builders yard with nine underground fuel storage tanks (USTs) and an electrical sub-station.  Previous investigation work had shown that the USTs had leaked resulting in two soil and groundwater plumes contaminated with diesel and white spirit.  Telluric Land Remediation was recommended to the Client as a specialist contaminated land remediation contractor experienced in the in-situ chemical oxidation of soil and groundwater.

Following excavation and removal of the nine USTs, thirty six remediation boreholes were installed to a depth of 7.0 m.  Extensive groundwater monitoring was undertaken daily using an interface meter to determine the presence and location of any light non-aqueous phase liquids (LNAPL).  Before undertaking in-situ chemical oxidation (ISCO) it was necessary to remove this gross free phase hydrocarbon product . This was done by periodically pumping from the network of installed remediation wells and, once substantially removed, was followed by injection of chemical oxidants to the deeper Kempton Park Gravel formation. 

Prior to chemical injection, remedial target concentrations were exceeded for the hydrocarbon bands aliphatic C6-C8, C8-C10, C12-C16 and aromatic C12-C16. However, following completion of treatment, very low residual hydrocarbons were present, with none of the samples exceeding the agreed remedial target concentrations.

In-situ groundwater and gas monitoring were undertaken during and after the remediation work. Groundwater monitoring, including temperature, pH, conductivity, oxidation-reduction potential (ORP) and dissolved oxygen (DO) showed sub-surface conditions returning to their normal background levels after chemical treatment.

Following three months of remediation work, the site was redeveloped for domestic housing.

telluric bullet Our solution

  • Design of remediation system
  • Installation of groundwater monitoring boreholes
  • Removal of free phase hydrocarbon product from groundwater
  • Treatment of residual contamination by in-situ chemical oxidation
  • Progress reports and compilation of final validation report

This site was remediated to the requirements of the regulators over a contract period of 12 weeks to allow cost effective residential redevelopment.

A pdf version of this groundwater remediation case study is available here.