Local Authority Case Study
Chorley Part 2A Investigation
Ground Investigation and Detailed Part 2A Ground-Gas Assessment
Ground-Gas Solutions (GGS) partnered with the LK Group were engaged by Chorley Borough Council to carry out spot sampling, high-frequency bulk gas monitoring, trace gas analysis and a ground-gas risk assessment for a potential Part 2A site in Chorley. The site currently comprises residential housing with associated driveways and private gardens. Potential receptors were identified as site users, adjacent residents and buildings. The site was considered to be potentially contaminated by virtue of its previous use as a former reservoir (now infilled), complaints of gas odours by local residents and lack of any clear documentation confirming appropriateness of remediation prior to its redevelopment.
The conclusions of the investigation will help the Council decide whether the site should be determined as contaminated land under Part 2A of the Environmental Protection Act 1990.
The intrusive investigation comprised 10 No. window sample boreholes and excavation of hand auger holes, installation of monitoring wells, ground gas monitoring (spot sampling and high frequency), and gas sampling. Laboratory testing included landfill trace gas suite and isotopic analysis.
Of specific project interest, GGS GasClam instrumentation was deployed to capture infrequent ground gas events, with simultaneous monitoring conducted in monitoring well installations and within residential property.
Risk Assessment and Conclusions
A detailed Part 2A ground-gas risk assessment with advice and recommendations for the Local Authority is still ongoing. The information obtained during the ground investigation and monitoring programme have proved to be extremely useful in development of a detailed site specific conceptual model and determination of gas regime and driving environmental conditions at the site.
Bulk and trace gas results are being used to carry out quantitative and qualitative assessment of ground-gas contamination risks to the existing site users and building receptors.
The reporting will be meet Part 2A requirements and the project complies with CLR11 Model Procedures.