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Section 1: Cleanup of contaminated land and groundwater |
1 Centre for Research into the Built Environment, The Nottingham Trent University, Burton Street, Nottingham NG1 4BU, UK
2 The Environment Agency, Steel House, 11 Tothill Street, London SW1H 9NF, UK
In recent years the UK Department of the Environment has, with others, developed a framework for contaminated land risk assessment, including the derivation of new Guideline Values. These are an important component in an integrated procedure for site-specific risk assessment which combines consistency of approach with flexibility to ensure that local circumstances are taken into account.
Guideline Values are derived using the Contaminated Land Exposure Assessment model (CLEA) which calculates human exposure via ten different exposure pathways. The relative contributions of the pathways vary according to site use, and hence the Guideline Values may also vary. This is consistent with the UK Government's ‘suitable for use’ policy. Guideline Values may also vary as a function of soil pH, soil organic matter, etc., reflecting the influence of such parameters on contaminant partitioning between soil solids and soil solution. The research described here is underpinned by complementary work to choose the most appropriate toxicological criteria for each contaminant.
Where Guideline Values are exceeded, the intention is that either a further phase of risk assessment or remedial action is triggered. If the former is chosen the emphasis will be on establishing whether exposure conditions differ significantly from the generic conditions assumed in CLEA. This is expected to be more cost-effective in general than site-specific risk assessment procedures. It does, however, require that the exposure assumptions and data values used in deriving the Guideline Values are understood by the risk assessor so that the necessary comparisons with site-specific conditions can be made.
