The Arley Consulting Company Limited was commissioned by a development company to undertake a comprehensive ground investigation and contaminated land assessment at a former fuel station in Wigan. The site included a transport café and HGV park as well as re-fuelling facilities.
This phase of the study included the review of all available information associated with the site, including a previous site investigation undertaken during the decommissioning of the underground storage tanks (USTs). A preliminary conceptual model was derived to identify potential constraints to the proposed residential development to assist site investigation design.
A detailed site investigation was designed based on the findings of the preliminary conceptual model and the previous site investigation. The investigation comprised trial pits and cable percussion boreholes and was designed to assess the nature, distribution and thickness of made ground and ground contamination across the site and to assess the underlying natural strata for potential contamination migration. In addition, gas monitoring probes were installed. Soil and groundwater samples were collected using strict quality assurance procedures and selected samples were analysed for specific chemical contamination. A routine gas monitoring programme was implemented to monitor the six probes installed.
An assessment of all site investigation information identified significant possibility of significant harm with respect to human health and the proposed residential end use due to the presence of elevated concentrations of PAH and DRO. Remedial measures were recommended to remove the areas affected by the organic contamination. In accordance with the planning condition, the report was submitted to the local planning authority.
TACCL undertook all remedial supervision for the excavation and removal of approximately 1,500 m3 of hazardous waste. Validation testing was undertaken following excavation works and a completion report was produced detailing the compliance of the remedial works to the method statement.