We consider an exemplary scenario drafted in the context of the recently started EU-project FracRisk. The setting belongs to six scenarios representing diverse subsurface processes on different scales. A numerical approach considering sources, pathways and targets quantifies the environmental impact associated with this setting. A Global Sensitivity Analysis of properly defined output quantities takes into account uncertain parameters and operational conditions within a FEP-based evaluation of risk and counteractive measures. At this early stage of the project, this showcase of the general modeling workflow addresses migration of frac-fluid through a naturally fractured reservoir (source) to an overlying formation (target).