Geosyntec has been retained by a client who has been required under IPPC to address contaminated soil and groundwater issues at their manufacturing site in Ireland. The project objectives have migrated from providing peer review to leading a detailed site characterisation study and risk assessment in addition to performing laboratory and field based remedial trials. These are being used to develop designs and implement full-scale corrective action over a two year period.

Geosyntec’s initial involvement in the project comprised a peer review of the work undertaken by another consultant and we were subsequently retained to take the project forward.

The facility has handled a broad range of organic solvents over a 50 year operating history. Numerous potential source areas were identified from a Source Audit exercise reflecting changes in the chemical storage and production facilities used at the site during its lifetime. A review of the groundwater flow regime coupled with water quality data from their IPPC monitoring network were used to establish areas of potential concern and gaps in the current understanding of potential pollutant linkages. This work identified some areas on on-going losses which were rectified and the installation of interim containment measures where appropriate.

The main contaminants of potential concern at this site are dichloromethane, xylenes, toluene, cresols, MTBE and THF. The fate and transport of this contamination is complicated by the presence of in-ground structures, preferential migration pathways in the drift and fractured bedrock. Parallel studies of six source areas at the site have been completed and involved delineation and detailed risk assessments. The delineation studies include detailed quantitative soil gas surveys/borehole installation for source areas delineation and multilevel well installations in the drift/bedrock to assess the flux of contaminants to the adjacent river and wider groundwater quality. Numerical groundwater flow models were developed to parameterise the risk assessment and aid in the remedial design.

A remedial options assessment was undertaken and this identified a blend technologies for inclusion in the treatment train. Remedial pilot and bench-scale treatability trials have recently been completed for Dual Phase Vacuum Extraction (DPVE), In-Situ Chemical Oxidation (ISCO) and Enhanced In-Situ Bioremediation (EISB) of the main contamination source areas. Stage 1 of the remedial response is currently being installed.

The investigation works have enabled a clear understanding of the key areas of concern at the site in terms of the type, magnitude and distribution of contamination present. They have also facilitated the identification of the principal risk drivers for corrective action to protect human health, an adjacent river and impacts to wider groundwater quality thereby minimizing the scope of remedial works required. The investigation findings have also informed site staff tasked with reviewing addressing integrity issues for their current containment measures.