New 2014 DEFRA Soil Screening Levels - Clean or not?

2014 has seen the publication by DEFRA of the new and long-awaited 'Category 4 screening levels' (C4SLs) for soil contamination. However, whilst the majority of contaminated land is remediated through development, the new C4SL have been derived to demonstrate that land is not contaminated.

It was DEFRA's intention that the C4SLs could be of use in the planning regime. However, policy responsibility for the National Planning Policy Framework falls to the Department for Communities and Local Government and DCLG have not made the role of C4SLs clear. As a result, there is uncertainty in the industry as to the status of the C4SLs in the planning regime.

The Good News and the Bad - benzo(a)pyrene and lead

The new C4SLs are based on a slightly higher acceptable level of risk. Therefore, you would expect the C4SL screening levels to be generally higher than the old SGVs or GACs.

This is indeed the case for the widespread contaminant, benzo(a)pyrene, which is found on the majority of brownfield sites and is frequently the driver for remediation. Adoption of the new C4SL, which is five times higher than the previous standards, could potentially remove the requirement for remediation in a large number of residential developments.

For lead, however, the new C4SL is less than half of the previously accepted screening criterion. There is some scope to adjust the screening level on the basis of background lead in soils, and a clear understanding of how to apply the standard is necessary. It is, therefore, increasingly likely that lead will become the new driver for clean-up on many brownfield sites. It will also be interesting to see how regulators view sites that have previously been remediated to the old standards for lead, however, it is unlikely that it could be proven that these represent a significant risk or that further remediation is justified.

In the absence of a clear government steer on use of C4SLs in the planning regime, it will be necessary to test out Local Authorities' perceptions and requirements with respect to environmental risk. The planning regime requires that developers ensure a 'safe' development - but the question remains - how do you define 'safe'?

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