The use of Geographic Information System (GIS) for regional scale groundwater contamination risk assessment by chlorinated solvents in the Permo-Triassic sandstone aquifer
The long term contamination of groundwater resources by dense non-aqueous phase liquids (DNAPLs) such as chlorinated solvents is an increasing problem being faced throughout the industrialised world. The transport and eventual fate of these compounds in the subsurface is controlled by the nature of the chemical spillage, the hydrogeological characteristics of the aquifer media and physiochemical properties of the particular contaminant. Geographic Information System (GIS) based risk assessment tools are developed for use with the UK’s Permo-Triassic Sandstone aquifer in order to assist stakeholders make informed decisions on the best use of groundwater in high risk areas and assess the value and management options for resources that are coming under increasing pressure from chlorinated solvent DNAPL contamination. Both semi-quantified and quantified probabilistic methods are presented with associated case studies using the best available data for regions of the UK where high densities of chlorinated solvent users industries combine with valuable groundwater resources. However, attempts at validation of the methodologies are hindered by availability of information on a regional scale, in particular the difficulties in collection and collation of historical land-use data is seen as a major hurdle to the accurate prediction of areas and resources at risk. Nevertheless the tools are potentially useful for guiding regulators and decision makers in the water industry to prioritisation of sites for site specific studies.