This greenfield site, occupying 2.6 hectares, is intended to be developed to provide a 25-unit residential development. It is located in the Mendip Hills in Somerset where naturally elevated concentrations of heavy metals are present in soils due to mineralisation of the underlying limestone bedrock. Even though it is a result of natural processes, current government guidance requires such “contamination” to be assessed.

The published screening levels that are widely used to determine whether or not soil is contaminated, are derived from scientific literature which tends to be biased towards more hazardous industrial exposure to metals.  This can lead to overestimation of risk from natural soils and unnecessary remediation in the form of clean cover systems is often the outcome.  This is costly financially and in sustainability terms, generating unnecessary vehicle movements, soil disposal and clean soil import.

The client had previously been advised that all topsoil and subsoil would need to be excavated to 0.6 m below finished levels and replaced with clean material. The costs associated with disposing of site soils at landfill and importing clean material from elsewhere meant that the economic viability of the project was in jeopardy.

To avoid unnecessary costs to both our client and the environment, we produced a bespoke and fully justified quantitative risk assessment which demonstrated, to the satisfaction of the regulator, that remediation was not warranted.