In 2011, SoBRA established a number of sub groups to work on specific topics with the aim of providing guidance and tools of potential benefit to land contamination practitioners. The sub groups operate in accordance with SoBRA’s procedure document.

Our currently active sub groups are listed below. If you would like to become involved in a sub group then please email: [email protected]


Following the Control of Asbestos Regulations 2012 and SoBRA’s 2013 summer workshop on asbestos in soil the sub group is now active. The group is writing up the summer workshop and is also developing the exposure scenarios that were commenced in the summer workshop. Once the workshop is written up the group will continue to develop these scenarios and other risk assessment techniques to support the JIWG chapter on risk assessment of asbestos in soil. The group would particularly like to hear from anyone with asbestos in soil, dust and asbestos in air concentrations so please get in touch via [email protected].

Please see the Terms of Reference for further details.

Vapour Intrusion

Following the SoBRA 2017 Summer Workshop, several recommendations for further research/advice were made relating to vapour intrusion which were documented in the workshop publication and we have formed the vapour intrusion (VI) sub group to consider these.  The VI sub group has been tasked with delivering several outputs, initially the preparation of four technical guidance summary notes covering: conceptual site model (CSM) development for VI linkages; identifying when soil gas sampling is beneficial; data collection methods; and modelling tools.  It is intended that these guidance notes will be followed by the development of GACsoilgas for the standard CLEA land uses (i.e. vapour phase GAC for comparison with soil gas/vapour data), identification of a screening distance process consistent with UK guidance, and advancement of the competency of practitioners regarding the selection and implementation of vapour phase mitigation measures.  

Members were invited to be part of a sub-group in 2018. 

Please see the Terms of Reference for further details.

Non-Aqueous Phase Liquids

The evaluation of contaminated land risk relies on understanding sub-surface processes. Non-aqueous phase liquid (NAPL) can be difficult to measure, meaning conceptual site models (CSM) may be data deficient.  Following several requests from our members, SoBRA has created the NAPL sub group. The aim of the NAPL sub-group are to support technical excellence in the assessment, estimation and evaluation of risks associated with NAPL, and to encourage best practice by delivering practical advice to support decisions regarding the appropriate management of NAPL risks.

The sub group aims to avoid reproducing the wealth of existing NAPL guidance but instead provide clear practical advice that can be applied to the various stages of site assessment: including introductory context for the UK approach and regulatory signposts, development of a solubility spreadsheet, a NAPL mobility screening tool, information on options for monitoring and their respective pitfalls, interpreting results from bail down tests, NAPL transmissivity and residual saturation, and a guide to remedial options for NAPL.

Members were invited to be part of a sub group in 2019.  Please see the Terms of Reference for further details

Ground Gases

The focus of the ground gas sub group is to improve the quality ground gas risk assessments delivered by the industry. Currently many assessors only consider gas monitoring results with little attention given to other equally important data. Members are currently working on three projects that have been prioritised by the group:

  • a road map or tool box of the guidance on ground gas investigation and assessment;
  • advice sheet on developing and using conceptual site models for gas; and,
  • advice sheet on how to calculate gas mass flux rates and to screen out “no risk sites”.

Anyone with an interest in ground gas is welcome to join.
Please see the Terms of Reference for further details.