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Defra’s Category 4 Screening Levels Assessment Faces Challenges

Defra has released its provisional C4SLs for the assessment of land affected by contamination under Part 2A of the Environmental Protection Act 1990, but the new screening levels face some challenges when it comes to assessing land under the Town & Country Planning Act.

The Category 4 Screening Levels represent the concentration of a contaminant in the soil below which a site is definitely not classed as ‘Contaminated Land’ as defined by Part 2A of the Environmental Protection Act. Soil screening levels have been derived for arsenic, cadmium, chromium, lead, benzo(a)pyrene and benzene.

Defra’s report described C4SLs to be useful when a simple test is needed to decide if land is definitely not contaminated land.

The challenge is that C4SLs are conflicting with existing Generic Assessment Criteria (GAC), which represent the “minimal risk” level. GAC is designed to be so safe that if the recorded soil concentration is at this level, there is no risk of harm. This is particularly important when it comes to achieving a successful planning application under the Town and Country Planning Act.

In general C4SL values are higher than the soil guideline values, but developers are advised to caution the expectation that soil can have greater levels of contamination for sites they are developing. In reality, C4SLs are not designed for this purpose, and many local planning authorities will not recognise them in this way.

agb Environmental has had planning decisions influenced by the C4SLs already and will continue to use them as another ‘line of evidence’ when it comes to assessing whether a site is suitable for use or not.

It is thought that C4SLs will be used as a screening criteria that can be used within a generic quantitative risk assessment. Defra hopes that the C4SLs will prove effective in eradicating the need for unnecessary remediation or taking sites out of the “grey area” between definitely not contaminated and potentially contaminated.

For further information about all contaminated land issues, call agb Environmental on 01638 663226.

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