Phase 2 - Site Investigation

A site assessment may end at the Phase 1 stage if it is found that neither the site or the surrounding area are thought to pose a potential risk to end users or the wider environment. If further investigation is required this is generally undertaken as a Phase 2 - Site Investigation, in accordance with BS10175:2001, incorporating the following:-

Intrusive Investigation

An Intrusive Investigation may comprise the following aspects:-

  • Excavation of exploratory holes using a range of techniques depending on the site, including window sampling, trial pits, cable percussive and rotary drilling techniques
  • Logging of profiles in accordance with BS5930:1999
  • Recovery and analysis of groundwater and soil samples for site specific range of potential contaminants identified within the CSM
  • In-situ gas and groundwater monitoring if required

Tier 1 Risk Assessment

This comprises a generic assessment of the results generated within the Intrusive Site Investigation, through comparison of the measured contaminant concentrations against appropriate assessment criteria.

Current guidance within the UK policy framework for assessing potential risks to human health from contaminants in surface soils are contained within the Contaminated Land Reports (‘CLRs’) and the Contaminated Land Exposure Assessment (‘CLEA’) model produced by DEFRA & the Environment Agency (2002).

CLR7 sets out a statistical basis for the assessment of the results of chemical analysis of representative samples obtained from a ground investigation. The premise is to review the entire data set, as opposed to comparing individual results to a given Soil Guidance Value (‘SGV’). The method is designed to reflect uncertainty within a limited number of samples obtained.

A range of generic criteria is used to assess the potential risks to other sensitive receptors, such as controlled waters.

Tier 2 Detailed Quantitative Risk Assessment

From a Tier 1 assessment contaminants of concern are identified as requiring further investigation. This commonly involves the assessment of risks to human health and/or controlled waters through some form of contaminant fate and transport modeling using complex risk assessment models to determine the level of risk present. These may include:-

  • Environment Agency Remedial Target spreadsheet (R&D Publication 20)
  • CLEA 2002
  • GSI RBCA Toolkit
  • RISC Workbench 4.0
  • RISC Human 3.1
  • SNIFFER

At Terragen our consultants have a wealth of experience in designing and implementing Phase 2 Site Investigations including undertaking appropriate risk assessments. If you would like further information on any of the techniques discussed above, or would like to discuss a particular project, please contact us at info@terragenenvironmental.co.uk