Applied Geology
Human Health Risk Assessments

Quantitative Human Health Risk Assessments

Quantitative Human Health Risk Assessments are carried out as a matter of course following all Phase II Investigations where contamination testing has been undertaken and requires to be assessed to establish the potential risk to the end user of the site. Where CLEA SGVs are available, a Tier 1 assessment is initially undertaken based on this data. For contaminants where CLEA SGVs are not available, Applied Geology has developed a series of Tier 1 values which can be used in the absence of CLEA SGVs and additionally has the capability to derive Site Specific Values using SNIFFER and other models.

Where published screening values are available, such as a SGV or GAC, a Tier 1 assessment is initially undertaken based on this data. In the absence of such published screening values or if a site is considered to be a non standard land use then Applied Geology has the capability to derive site specific screening values using appropriate modelling software. 

Applied Geology has a dedicated risk assessment specialist to ensure that it remains at the forefront of the industry, during a time of rapidly changing guidance, best practice and legislation and to ensure that our Geoenvironmental Engineers are fully trained in all aspects of risk assessment.

Applied Geology has specific expertise in the assessment of hydrocarbon based contamination and the derivation of target concentrations which are protective of human health utilising the TPHCWG methodology and data and current Environment Agency best practice.


Case Study 1
Applied Geology was asked to undertake a contaminated land assessment of a site in a village on behalf of the relevant District Council.  The purpose of this assessment was to assess whether the land fell under the definition of ‘Contaminated Land’ as specified under Part IIa of the Environmental Protection Act 1990. Part of this assessment included assessing the risks from the site to human health.

The site, formerly a sand and gravel extraction pit, was land filled with domestic waste in the 1960s-70s. Since this time it has been informally used by the local residents as an area of open space commonly used for dog walking. Part of the eastern end is used as play area for local children. 

Following a ground investigation, the chemical soils data obtained (including the results from an earlier phase of work) were assessed using the guidance given in the Contaminated Land Report (CLR) series of documents produced by DEFRA and the Environment Agency. A Tier 1 assessment was initially undertaken on the data using appropriate screening values. As the site is essentially used as open space it represented a non standard land use. Applied Geology used the ATRISKsoil values for parks as screening values as the ATRISKsoil Conceptual Model for parks most closely resembled the site.

A single data set for the Made Ground was considered appropriate for the site as the borehole logs suggested that the waste material was disseminated throughout.  Where appropriate the two statistical tests – the Maximum and Mean Value Tests, as outlined in the CLR7 publication, were undertaken on the data set for the Made Ground.

The results of the statistical assessment indicated that there were no outlier concentrations present that were above their respective screening values. However, the calculated US95 for arsenic was above its screening value indicating arsenic contamination was present throughout the Made Ground.    

Further investigation and a second tier of human health assessment have been recommended by Applied Geology to further clarify the implications of the elevated arsenic concentrations at the site.