Project members: Timm Reisinger, Thomas R. Rüde

The dissertation project "Mass transport of underground stored non-nuclear waste materials in adjacent aquifers" refers to the current topics of expiring coal mining in Germany, associated mine flooding and the problem of stowed metal-containing residues.

From the mid-1980s to 2006 large amounts of residues were used for stowing in hard coal mines of the Ruhr Area, Germany. A mixture of water and fine-grained residues were pumped directly into the goaf, i.e. into the collapsed material of the hanging wall beyond the shield. Due to mine flooding, highly mineralized groundwater with several tens of grams per litre of sodium chloride can come into contact with the residues. In case of a contaminant release of these residues the transport initially takes place via flow in fractures.

A major challenge is to find out whether metals can be released from the stowed materials and, in case they were released, the country rocks are able to retard or even hinder their transport. Without retardation or barrier function of the country rocks there is a risk that pollutants reaching the surface via mine water drainage. For this purpose, laboratory tests such as column tests, single fracture experiments and flow cell experiments with typical country rock samples and waters of differing chemical composition were carried out. To enable reviews and predictions of mass transport into adjacent aquifers - based on the experimental results - a modeling of contaminant transport for a single fracture was performed.