Germany will quit from black coal mining in 2018, the last two operating mines in the federal state of Northrhine-Westphalia are going to stop production by then. Nevertheless, post-mining operations will have to be continued endlessly (in the foreseeable future). The maybe most important of these so called “eternity tasks” is the handling of large amounts of ascending mine water: in the Ruhr mining district alone, about 120 million m³ of mine water per year have to be pumped from depths of several 100s of metres to the surface and discharged to adjacent receiving water courses to avoid flooding of former and still active mining drifts. This water has temperatures of up to 50° C and may contribute to a future geothermal energy supply of the region. On the other hand, the mostly saline waters also partly contain unwanted trace substances of potential environmental concern. These include radionuclides (esp. ²²⁶Ra and ²²⁸Ra) and polychlorinated biphenyls (PCB). The former are probably geogenic contaminants while the latter are suspected to derive from anthropogenic remnants left in the galleries. These substances´ sources, mobility and distribution in surface waters and sediments are hardly understood, associated social consequences of their occurrence in this densely populated area have not yet been discussed. The proposed interdisciplinary young researchers group “Dealing with an Eternity Task in the Ruhr Area” (DETRA) aims at addressing suchlike questions from natural scientific and social scientific points of view. In summary, we will address interdependencies of geoscientific findings and social consequences around a water-related environmental problem in a densely populated urban area, and contribute to understanding the impacts of a transforming water and energy landscape in the region.