Brownfield Assessment and RemediationBiosolids Drying Site, UK

LAND & PROPERTY

Ref: PS0068b

Project Summary Brownfield Assessment and RemediationBiosolids Drying Site, UK

Project Value: £300k

Key Project Elements

Due Diligence

Phase II ESA

Planning Support

Environmental Risk Assessment

Remedial Options Appraisal

Remedial Design, Field Trials and Implementation

Validation Reporting

Regulatory Liaison

CRA was commissioned to assist a large developer with a range of environmental services supporting the redevelopment of a 75 acre Brownfield site, from the initial due diligence to land remediation and the final discharge of planning conditions, with regulatory liaison throughout the project. The initial due diligence stage of the project comprised visiting the site and summarising the environmental risks. After purchase of the site, CRA was commissioned to undertake an extensive Phase II Environmental Site Assessment (ESA) to characterise the soil, groundwater and ground gas conditions at the site. CRA produced a conceptual site model, which identified the various sources of organic and inorganic contaminants of concern, pathways and receptors. The main receptors were the river adjacent to the site and future site workers/occupiers. As a result of the Phase II ESA findings, CRA undertook a detailed quantitative risk assessment, which identified a number of contaminants requiring remedial action to mitigate the risk posed to the environmental and human health receptors. A remedial options appraisal found on-site solidification/stabilisation to be a feasible, sustainable and cost effective method of remediation of the (approx) 100,000 m3 of biosolids. Field and laboratory trials were undertaken to determine whether the solidified/stabilised biosolids were suitable both environmentally and geotechnically. It was proven to be an effective remedial method and was implemented at the site prior to construction under supervision of CRA. In addition to on-site solidification/stabilisation, a groundwater collection trench was installed down-gradient of the biosolids lagoons, to provide protection to the adjacent river from the historically impacted shallow groundwater. Prior to the construction of site buildings, CRA undertook a ground gas assessment to determine the requirement for gas protection measures. CRA also undertook regular groundwater monitoring to provide evidence that the solidification/stabilisation had prevented further leaching of contaminants into the shallow groundwater. On completion of site works, CRA prepared a remediation validation report for submission to the Environment Agency in pursuance of discharge of the environmental planning conditions relating to the site redevelopment.