CGL has recently completed supervision of the initial phase of remediation and groundwater treatment at the Brunel Street site in east London. The site is proposed to be redeveloped for mixed residential and commercial land use with apartment blocks of up to 26 storeys.
CGL has previously undertaken a data review and site investigation and produced a Detailed Quantitative Risk Assessment (DQRA) for Controlled Waters to assess the impact of the contamination encountered at the site on local receptors. The findings of the site works and DQRA were utilised to provide a remediation strategy which includes excavation of a hydrocarbon impacted hotspot where soil contamination was affecting the groundwater and causing high ground gas readings. The impacted material was selectively excavated; however, analysis of the groundwater indicated no elevated concentrations present and further dosing was not required.
Post-excavation monitoring indicated that concentrations of ground gases had reduced to low risk levels and that ground gas protection measures would not be required. The groundwater remediation consisted of in-situ treatment of chlorinated solvents using Regon-Ox to increase dechlorination in the groundwater. The dosing of the groundwater was followed by a 12-week monitoring programme which indicated that concentrations of the chlorinated solvents had reduced to below limits of detection.
Further remediation in the form of a vapour barrier is proposed for this area of the site and capping layers are required in soft landscaping. However, this next phase of remediation will be undertaken later in the construction programme.