Mine water rebound in German hard coal mines – geochemical and petrophysical data support for an integrative monitoring plan

Mine water rebound in German hard coal mine areas operated by RAG AG under the leadership of RAG Foundation is a showcase for post-mining associated research. It is a long-term, cost intensive and multidisciplinary project affecting highly populated urban areas like the Ruhr District. RAG is facing long-term liabilities as regulatory framework for the rebound process. Currently, mine water is pumped from levels down to 1200 meters to be discharged into local rivers. In the vicinity, monitoring water wells were drilled to identify any hydraulic potential changes in the overburden sections in support of the project’s risk assessment. Mine water management issues comprise control and forecast of mine water levels including to determine a financially and environmentally sustainable level. Mine water treatment, evaluating hydraulic barriers, but most importantly, protecting groundwater for domestic use and even more critical, regional drinking water reservoirs are mandatory prerequisites. We identified natural hydrochemical tracers, worked on in-situ processes affecting mine water chemistry and progressed with petrophysical measurements on core material including clay mineralogy screening to deliver a first step towards an integrative monitoring approach to manage such liabilities. A suite of own and literature-based hydrogeochemical and petrophysical data are presented to better describe the regional hydrology and geology.