This dataset indicates the likely susceptibility of groundwater to percolation of MRP and pathogens from Domestic Waste Water Treatment Systems (DWWTS) based on mapped geological information. This dataset was developed as part of A risk-based methodology to assist in the regulation of Domestic Waste Water Treatment Systems (EPA, 2013). http://www.epa.ie/pubs/reports/water/wastewater/dwwtriskranking.html. The aim of the report was to set out a methodology to enable the EPA to adopt a risk-based approach to organising inspections of domestic waste water treatment systems (DWWTSs), whereby the level of inspection would be proportionate to the risk posed to human health and the environment.