Those of you involved in contaminated land issues, either for the purposes of land redevelopment or clean-up where human health is a consideration, will probably be aware the Environment Agency (EA) have been tinkering with their CLEA (Contaminated Land Exposure Assessment) model and have made some "significant" changes.

These changes have resulted in the withdrawal of the Soil Guide Values (SGVs) used in the assessment of the risks to human health which were published prior to August 2008. This means that new SGVs need to be derived for all contaminants of concern based on the EA's modified CLEA approach and by running their new version of the software.

The new version of the software is now a deterministic model as opposed to the probabilistic previous versions. This means that the CLEA model calculations are based on single value inputs for each parameter; these have been selected based on being either an average or conservative value or on the basis of expert judgment.

The new software still requires the input of a considerable amount of information for each potential contaminant. As usual the EA have provided a wealth of guidance on the use of the model and appropriate input values to digest.

However, this overhaul of the model is still underway, and whilst toxicological information can still be obtained from the old TOX (Toxicological) Reports, in the longer term the EA are updating the TOX reports and will withdraw them as their new replacements are issued. Currently they are still available and the EA believe that much of the information contained in the existing TOX reports will not change.

Additionally, the EA indicate that specific values for certain parameters used in the software, such as "soil to dust transport factors" and certain "correction factors", etc, will be made available in the new Soil Guideline Value (SGV) Reports as and when they are issued.

Although published in 2004, before the update, the EA document "Review of the Fate and Transport of Selected Contaminants in the Soil Environment - Technical Report P5-079/TR1" appears to remain a useful source of chemical parameters for the CLEA model - use the EA website's publication search facility to find it here - http://publications.environment-agency.gov.uk/epages/eapublications.storefront.

The new software and handbook are available on an evaluation basis until the end of November 2008 - version 1.03 (beta). The EA are inviting comments on the new version which should be sent by e-mail to cleacomment@environment-agency.gov.uk. We are in the process of trialing the new version and will keep you informed. The CLEA software, handbook, publications (including TOX Reports) and guidance can be found on the Environment Agency's website here - http://www.environment-agency.gov.uk/subjects/landquality/113813/2021813/2021831/2023822/?version=1&lang=_e.

News article Sept/2008/03/SHB