Site Background & History
The site was previously an operational gas works owned by British Gas Properties, manufacturing town gas between approximately 1859 and the mid 1970. The site is located adjacent to the River Eden and is approximately 0.6 hectares. Site Investigations identified significant concentrations of BTEX compounds, PAHs, phenol, heavy metals and Ammoniacal Nitrogen. During the late 1990’s remedial works took place on site which are believed to have involved the excavation and removal of significant volumes of contaminated material, however, this methodology resulted in residual contamination remaining at depth on site.
Remediation Strategy
In order to protect the identified surface and groundwater receptors, i.e. the River Eden and address the contamination pathway issues Envirotreat carried out the installation of an E-Clay Permeable Reactive Barrier along the line of the River.
A groundwater modelling program (MODFLOW) was utilised in order to confirm there would be minimal effect on the natural groundwater regime whilst effectively intercepting and treating the contaminated groundwater.
Remediation Works (PRB Installation)
Envirotreat developed a site specific design and formulation for the PRB based on the maximum identified contaminant loading.
The PRB installation was carried out over a 3 week period, incorporating the installation of both the passive and active sections. Passive sections of barrier are designed to ‘funnel’ migrating groundwater towards the active section of the barrier system, where the contaminants are immobilised within the E-Clay matrix.
The E-Clay PRB installation on site was carried out using a Continuous Flight Auger (CFA) by the production of overlapping soil mixed columns.
Post installation groundwater and River monitoring confirmed the efficacy of the remedial solution.
