Potential risks to controlled waters and future users of the site were identified and qualified through the formation of a preliminary risk assessment. The overall recommendation was that no further investigations were required.
We understood the client’s wish to proceed quickly so that the development could commence and responded by issuing a final report within five days of being commissioned.
As with most of our phase 1 desk studies that are required for planning conditions, the Contaminated Land Officer at Reading Borough Council was contacted to establish any particular concerns and pick up on any additional information they may hold. This ensures that when the report is submitted our recommendations are well informed and address any specific issues.
A range of data was collated to draw together an overall picture of the site and the surrounding environment, so that a conceptual model could be produced. This enabled the risks to local sensitive receptors of concern to be identified and qualified.
A study of historical maps was undertaken to identify past uses at the location in order to assess the likelihood of historical contamination having occurred. A residential garden and former greenhouse were identified to have been present within the site boundary dating from the 1940s.
A review of a commercial data set highlighted the presence of two former landfills present within 500 m of the site. One of these landfills had already been identified through consultation with the Contaminated Land Officer at Reading Borough Council.
The Council confirmed that the landfill was producing methane gas and was being investigated under Part IIA of the Environmental Protection Act 1990. The Council had established that the gas was migrating off-site at least 20 m, with the potential to migrate for up to 1 km from the former landfill site.
Our contaminated land consultant discussed the issue with the regulator and this, combined with a review of the underlying superficial geology, allowed the real risk to be assessed. The presence of overlying impermeable glacial till prevented the methane from rising to the surface and thus posed little risk to the site.
However, as a precaution gas protection measures were recommended and were subsequently developed into the design of the new buildings.
An overall risk assessment was produced qualifying the contamination risks posed, and the sensitivity of the receptors of concern. The conclusion was that the site was low risk, leading to a recommendation that no further assessment (including any intrusive investigations) of the site was deemed necessary in relation to the proposed development.
Instead, the use of gas protection within the proposed building design would provide conservative mitigation against any landfill gas risk.
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