Aggregate mining in Ontario is a highly contentious landuse activity between many stakeholder groups. Land use activities, within a watershed, including anthropogenic infrastructure and anthropogenic changes to the natural infrastructure (such as aggregate pits and quarries), may increase susceptibility of an aquifer by modifying contaminant migration pathways, which is an issue of water security. The purpose of this research is to apply the Vulnerability Scoring Tool to test its utility in the field of water security. The methodology is applied to an aggregate extraction site in the Grand River Watershed in Ontario, and presents an example of how changing land use may change exposure pathways. In particular, the case study results indicate an increase in vulnerability once the aquitard had been penetrated, through aggregate excavation. Applying vulnerability and risk models to future aggregate mining sites can be a useful decision-making tool when investigating impacts of aggregate extraction sites on water security. / Canadian Water Network