The Challenge
IKM assessed a former gasworks to identify whether any significant risks existed to human health or the water environment as a result of contaminated land. Following the closure of the gasworks in the 1890’s, and a phase of partial demolition, the remaining site buildings had been converted for residential use. Our client approached IKM intending to prepare an initial strategy document to assist with initial consultations with homeowners on the site.
As the first stage in assessing risks, IKM recommended that a Phase 1 desk study and site visit be undertaken to understand the layout of the former gasworks site, the ground conditions and the scope for undertaking future intrusive ground investigation works. During the site visit, several potential
concerns were identified, including evidence of tar contamination in the area of suspected gas production and storage. Demolition material and evidence of ash were noted within garden areas. This culminated in a Phase 2, intrusive investigation followed by a period of vapour monitoring, and quantitative
risk assessment.
The Solution
The Phase 1 desk study, which included a review of historical and geological maps, a site walkover, and the preparation of a preliminary Conceptual Site Model (CSM), was followed by a five-stage contaminated land investigation.
Stage 1 comprised the development of the site investigation scope and preparation of the contract and specification for the proposed works. An initial phase of hand excavated trial pits and a programme of laboratory testing for soil and leachate samples for a suite of determinants typical of a gas works site was also completed.
Stage 2 comprised the installation of several shallow boreholes, laboratory testing and one round of soil gas, vapour, and groundwater monitoring. Indoor and outdoor vapour monitoring was completed in Stage 3, informed by the initial set of results, and utilising a combination of VapourPins and passive diffusion tubes.
This scope was extended in Stage 4 to provide supplementary indoor vapour monitoring, soil gas monitoring and groundwater sampling to inform the risk
assessment process.
Stage 5 comprised the preparation of the interpretive report, which detailed the site investigation works, generic and detailed quantitative risk assessments, findings, revised CSM, and recommendations.
IKM considered the conditions at the site and developed a pragmatic staged approach to the contaminated land assessment process, ensuring that the
Client was engaged and included at each stage in the process.
The scope of each stage was informed by the findings of the previous stage(s). This measured approach not only offered best value to our Client but also permitted collaboration, taking cognisance at all stages of the sensitive nature of the site and the emotive issues surrounding contaminated land.
