SoBRA held a workshop on vapour Intrusion to Support Sustainable Risk Based Decision Making June 2017. The workshops aims were to: provide high quality speakers who could outline the challenges faced for their topic area that affect the evaluation of the vapour intrusion pathway, including CSM, site investigation, modelling and installation of mitigation measures; and to break out into workshop groups to discuss issues pertaining to a topic area in more detail and identify how such issues might be resolved. The four topic areas were CSM, site investigation, development of alternative risk assessment techniques based on scientific studies and the evaluation of mitigation measures using quantitative risk assessment.
This discussion paper explores how air quality values can be derived, and how different modelling assumptions can result in different calculated values. It also looks at how available approaches to calculating values compare to existing standards and guidelines, whether commonly adopted guidelines can be supported by the most recent epidemiological evaluations, and what challenges we still face in coming up with health protective and pragmatic guidelines.
Volatile constituents in groundwater have the potential to cause risk to human health via volatilisation and migration of vapours into overlying buildings or outdoor air space followed by inhalation. Where the conceptual site model identifies this contaminant linkage as being of possible concern it is usually necessary to assess the risks further in order to determine whether they are acceptable or not. One method that can be used is to compare measured concentrations of volatile constituents in groundwater with conservative generic assessment criteria (GAC) protective of human health via the inhalation of groundwater-derived vapours pathway. This helps the assessor determine the level of risk associated with this particular contaminant linkage. A working group of the Society of Brownfield Risk Assessment (SoBRA) has developed a methodology and derived GAC for 64 commonly analysed volatile constituents in groundwater. The methodology utilises the Environment Agency’s (England and Wales) CLEA model to estimate the average long-term concentration in shallow groundwater (the GAC) that would lead to tolerable/minimal risk to site occupants from vapour migration and inhalation in indoor and outdoor air from chronic exposure. Screening values have been derived for residential and commercial land-use scenarios. The generic screening values are intended to complement other screening methodologies (such as exclusion depths and distances) for assessing the groundwater vapour contaminant linkages.
This SoBRA funded project creates a new methodology for identifying local sources of contamination and relationships between historical urban development and groups of potentially toxic elements (PTEs) in urban soils. The Belfast Tellus data is used to create the methodology, which is then tested on Sheffield using GBASE data. Eleven PTEs are considered within this research; arsenic (As), cobalt (Co), chromium (Cr), copper (Cu), molybdenum (Mo), nickel (Ni), lead (Pb), antimony (Sb), tin (Sn), vanadium (V) and zinc (Zn). These elements are expected to be related to different geogenic and anthropogenic sources within the study areas.
Rebekka McIlwaine, Siobhan Cox, Rory Doherty and Mark Cave (2016)