Contaminated Land Exposure Assessment - CLEA 2002

The UK Department for Environment, Food and Rural Affairs (DEFRA), previously the Department for the Environment, Transport and the Regions (DETR) have released the first of a new set of guideline values, calculated using the Contaminated Land Exposure Assessment (CLEA) model.

The CLEA 2002 model was (finally) released in March 2002. This is an evolution of the CLEA 1997 model originally developed by the late Professor Colin Ferguson at Nottingham Trent University, and later at Nottingham University (after the entire Land Management Team were headhunted by the latter institution).

In common with other UK strategies, this approaches the problem of contaminated land with the idea of fitness for a particular purpose. It is based on human toxicological data and uses Monte Carlo simulations to model the potential pathways for human exposure, taking into account the intrinsic uncertainties.

Guideline values produced by the model indicate a level below which the site is considered safe. Above the guideline value, further investigation is required. Thus the CLEA guidelines provide an objective basis for decision-making, based on an assessment of risk to human health.

Soil Guideline Values as a Function of Land Use

These are the values published in the SGV series of documents, and are based on the sandy soil described in CLR 10. They will vary according to soil type. It is very important that you refer to the original source documents for full guidance on how to apply these values.

^[A] House with a garden and therefore the possibility of ingestion of home-grown vegetables

^[B] House or apartment with no private garden area

^[C] Open space, often made available by the local authority, for people to grow fruit and vegetables for their own consumption

^[D] Assumes that work takes place in a single-storey building, factory or warehouse where employees spend most time indoors involved in office-based or light physical work. Does not apply to sites with 100% hard cover, such as car parks

CLEA publications

These are the documents originally released. All are available as free downloads from the DEFRA website. The CLEA 2002 modeling software is also available as freeware from the same source.

^§ Source: CLR, TOX and SGV documents, in PDF format, and the CLEA 2002 software model may be downloaded  from the Environment Agency web site at http://www.environment-agency.gov.uk/subjects/landquality/113813/672771/?version=1&lang=_e