Disused filling station, Radstock. How a robust investigation and risk assessment saved a clients tens of thousands of pounds.
Our client requested a quotation for the remediation of a former filling station. Site investigation works had been carried out previously, but some crucial data was missing. A proposal had been put forward for a remediation scheme to the previous site owner, but on review we identified that the recommended method would not be effective and would high cost implications. We were requested to put together a package that would identify the best remedial option in terms of cost and efficacy.
The data that was available indicated that site was located on a minor aquifer and that the main receptor of concern was a stream that was situated to the north west of the site. Abricon assessed the data and advised the client that a quantitative risk assessment would indicate whether remedial works would be required and if so their scope. A network of monitoring wells was installed to augment those on site as well as providing off site locations to sample groundwater and measure depth. Trial pits were also advanced to assess contamination in shallow soils and depth to rock head.
The data that was gained enabled us to produce a revised conceptual model and carry out a detailed quantitative risk assessment for groundwater using the Environment Agencies P20 methodology. This was submitted to the Environment Agency who agreed that the site was unlikely to pose a risk to controlled water resources. As a consequence, remediation was not required. This not only saved a sum approaching 10 times that of carrying out the site investigation, but it also meant that the delays that would have been associated with remediating the groundwater were avoided.
Site investigation and remediation of a former filling station Avebury, Wiltshire
Abricon were commissioned to carry out a desk top study and because of the potential for contamination with petroleum hydrocarbons, carried out an intrusive investigation to characterise the site. Whilst perched water was encountered on the site, strata below this was dry and the main groundwater body which formed a major aquifer was not encountered despite drilling to 12 m. Groundwater samples were recovered from the perched water for subsequent analysis. The main contaminated areas were in shallow soils where an above ground storage tank had been located, and within the area of the tank farm itself. Perched groundwater was impacted immediately adjacent to the tank farm only.
A Remediation Options Appraisal was carried out that concluded that the most effective way to bring about remediation of impacted soils and groundwater was to use Oxygen Release Compounds (ORC). This was applied by injection and also placing a slurry into the tank excavation area. Targets for groundwater cleanup were derived using the Environment Agency’s P20 methodology. Following application of the ORC and monitoring of the groundwater, the target concentration was achieved enabling discharge of the planning condition.
Contact Abricon to discuss your personal requirements and for free initial advice.