Potash mining waste pile Sollstedt (Thuringia):: Investigations of the spreading of waste solutes in the Roethian Karst

The Sollstedt potash waste pile has been deposited without a basement layer on the Middle Bunter and Roethian. Therefore, a part of the salts dissolved by meteoric water infiltrates into the groundwater. The strongly mineralized waste pile seepage water spreads not only into the Middle Bunter but also into the Roethian, which is generally considered an aquitard, because in this area the Roethian is strongly karstic. This study demonstrates that there is a relationship between the seepage water and the strongly mineralized springs surrounding the stockpile. In particular, the strong mineralization of the Silze spring, which is situated in the supposed direction of groundwater flow, can be attributed to mixing with the seepage water. From the calculated water and salt balances, it is concluded that the major part of the seepage water which previously infiltrated in the Roethian infiltrates directly into the Middle Bunter. This suggests a preferential but locally limited permeability of the Roethian in the horizontal and vertical directions.