All models are wrong – but this workshop will explain when some are useful.  They can be used to probe understanding of the risk at a site.  Any model for vapour intrusion or ground gas risk should consider the specific ground to indoor air pathways that will be present on a site.  This requires a good understanding of different types of floor, foundation, and basement construction and where soil gas migration will occur through them.  Migration of soil gas into basements via groundwater also needs to be considered.  The generic CLEA model for vapour intrusion is not suitable for most UK developments.  This is because of the assumptions that the J&E model it is based on makes, with respect to soil gas flow into the building, not least that there is a basement included as standard.  The Characteristic Situation system used to define ground gas risk is not based on any consideration of building construction or quantified risk assessment.  It is a purely empirical system and if a DQRA is required, gas flow into the building must be assessed.

The workshop will explore different types of building construction in the UK and how to incorporate these into models for vapour intrusion or ground gas risk assessment.  Gas migration models can then be used to assess the effectiveness of different mitigation measures, model the requirements for protection redundancy and provide confidence that the mitigation design will meet risk-based requirements.

Facilitators: Steve Wilson and John Andrews (EPG)

Using a live case study, we will walk through a situation where phthalates — typically considered immobile due to their low solubility and strong adsorption to organic matter — became mobilised in the presence of BTEX (Benzene, Toluene, Ethylbenzene, Xylene).  This unexpected behaviour rendered traditional Remedial Target Methodology (RTM) models unworkable.  The workshop will step through each stage of the risk assessment process: defining the problem, setting objectives, building the conceptual model, testing generic assumptions, and adapting models to reflect real-world conditions.  Attendees will leave with practical insights into data needs, parameter selection, and how to apply sense checks to ensure solutions are robust and realistic.

Facilitator: – Rachel Dewhurst (Stantec)

Imagine your client has a site which is a former firing range but is now open acid heathland.  The site is securely fenced, but forms part of a larger Site of Special Scientific Interest (SSSI).  The client is looking for ways to manage the site to maintain the heathland and has come to you for advice on whether the site would be suitable for livestock grazing.  Limited soil sampling has previously been undertaken at the site and this identified contamination of the shallow soils at the site with heavy metals (lead, copper and nickel).  How would you go about assessing the suitability for the site for livestock?  What site investigation techniques could be undertaken?  How could the risks be assessed?  During this workshop we will discuss how we might develop a conceptual model for various livestock grazing scenarios, consider the approaches we might use for assessing the risks to livestock and to the wider food chain, and the data we might require to support such as assessment, as well as considering ways to sense check our approach. 

Facilitator: Barry Mitchinson (WSP)

QRA is critical to support End of Waste decisions, helping define when a material ceases to be classified as waste, bringing it to the point at which it is recovered and used as a product, helping drive the Circular Economy.  This workshop will look at how to characterise a potential future source (i.e. the ‘waste’) and develop comprehensive CSMs to cover multiple scenarios based on the variety of settings in which the material may be used (i.e. CSM for a potential site as yet undefined). 

Facilitator: Elizabeth Waterfall (Stantec)