Project Description

Brownfield Redevelopment,  United Kingdom

Project Details

CLIENT:

CONFIDENTIAL

brownfield remediation
brownfield remediation

The Challenge

In 2018, our Client became aware of this former manufactured gas site and planned to undertake an assessment of the site to identify whether any significant risks exist to human health or the water environment. Following closure of the gasworks, and a phase of partial demolition, the remaining gas works buildings were converted for residential use.  The Client approached IKM with a view to preparing an initial strategy document to assist with initial consultations with home owners 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 and 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 was 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 investigation. Stage 1 comprised the development of the site investigation scope and the 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 a number of shallow boreholes, laboratory testing and one round of soil gas, vapour, and groundwater monitoring. Indoor and outdoor vapour monitoring was undertaken 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.

From the outset, 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.

Having the completed the quantitative risk assessments from the available data, IKM is now in consultation with the Client regarding the next steps; both parties have acknowledged the need for additional data to inform the revised CSM and assess all potential credible pathways where current and future site users could be at risk. Any unacceptable risks will then be included in a Remedial Options Appraisal, in line with current UK guidance.

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