The FRAC-WECO project elaborates a framework for the assessment, at the regional scale, of the risk posed by contaminated sites on water resources and ecosystems. The general methodology developed in the project relies on several key research and tools developments, on the one hand, process studies contributing to a comprehensive assessment and modelling of water and contaminant fluxes at the scale of interest and of biogeochemical properties and toxicity of contaminants, on the other hand, regional indicators of water quality deterioration and ecotoxicity, so as to propose management tools and indicators for contaminated sites ranking in terms of risks and costs. It consists in evaluating the level of water degradation at the scale of the groundwater body as a referential for decision-making in terms of water resources management in the perspective of the EU Water Directive (trend assessment and reversal) and for an objective socio-economic analysis evaluating, in monetary terms, the damages related to water resources deterioration and the costs for restoration.