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The former Ascham Street works were originally identified by The London Borough of Camden under its duty under Part 2A of the Environmental Protection Act 1990 for investigation as potentially contaminated land due following complaints from local residents in relation to the former metal plating works. The Ascham Street Chemical Works site was remediated and redeveloped in 1998 and a nursing home built over the main electroplating workshop. However gardens and brickwork of 29 of the 42 surrounding residential dwellings were found to be contaminated with lead and cadmium from the works requiring the removal of contaminated hotspots within the upper 500mm of garden soil of each of the dwellings.
Cognition was contracted by the London Borough of Camden to identify and segregate all contaminated soil and brickwork from the gardens and reinstate them to the residents individual requirements. The work was carried out under the watching brief of the project consultant with validation sampling carried out to ensure residual soils met the Site Specific Assessment Criteria (SSAC) for lead and cadmium, 1170mg/kg and 29mg/kg respectively. The site had very restricted access, requiring entry to all gardens via a single property for both disposal of contaminated soil and import of clean materials. Careful coordination with residents and local authority was vital to ensure each garden was reinstated to an agreed specification. The objective of the remediation strategy was to minimise excavations in garden areas to 300mm wherever possible and deepen only those areas where absolutely necessary to comply with the regulatory regime. Field measurements of soil contamination were carried out using a hand held XRF analyser, enabling large amounts of data to be quickly assimilated across the gardens and target deeper excavations to only those zones where absolutely necessary. The key elements of the works included;
The application of the latest assessment techniques during verification, combined with the close collaboration between client, consultant, contractor and the residents, successfully bought to a close over three decades of concern for stakeholders, and delivered significant project savings for the benefit of central government, the local authority, residents and the environment. The initial cost estimate for remediating all 42 properties would have exceeded £1M with the removal of more than 2000m3 of soil. Delineation and testing meant that only 600m3 of contaminated soil needed to be removed at a cost of approximately £220k. The project won a Brownfield Briefing Award for the innovative approach to contamination segregation and verification.