Assessment of Land Contamination
The UK approach to contaminated land is set out in Contaminated Land Report No. 11 (2004) “Model Procedures for the Management of Land Contamination”. The approach is based upon risk assessment, where risk is defined as the combination of the probability of occurrence of a defined hazard and the magnitude of the consequences of the occurrence.
In the context of land contamination, there are three essential elements to any risk: (1) a contaminant source, (2) a receptor (eg controlled water or people) and (3) a pathway linking the (1) and (2). Risk can only exist where all three elements combine to create a pollutant linkage. Risk assessment requires the formulation of a conceptual site model (CSM) which supports the identification and assessment of pollutant linkages.
Lithos adopt a tiered approach to risk assessment, consistent with UK guidance and best practice. The initial step of a contaminated land risk assessment (or Tier 1) is the comparison of site data with appropriate screening values.
In the context of redevelopment within the planning regime, Lithos have derived Tier 1 Screening Values for four different land use scenarios:
- A - Residential with gardens, but no cover (or only up to 300mm)
- B - Residential with gardens and 600mm ‘clean’ cover
- C – Residential apartments with landscaping (i.e. no home grown produce)
- D - Commercial/industrial with landscaping.