The analysis of destructive water infiltration into the Wieliczka Salt Mine – a unique UNESCO site

The Wieliczka Salt Mine has been inscribed in 1978 on the first UNESCO list of World Cultural and Natural Heritage as a unique monument in the world scale. During more than 700 years of its operation, the inflow of outside water into the underground excavations constituted the biggest threat to the mine. Infiltration of water into the salt deposits can cause flooding of the mine and have a destructive influence on the state of the bedrock and the excavations through uncontrolled leaching of NaCl. The analysis of the geological structure and natural hydrogeological conditions in the area is one of many concerns in attempting to determine the water infiltration routes. Cluster analysis conducted for the different ions, and the correlations calculated, indicate that it is difficult to identify significant associations between the various ions other than the obvious and expected associations between, e.g., mineralisation of, Na and Cl, and Ca, Sr and SO4, Similarly, the spatial distribution of the different ions in the analysed effluents does not allow to determine groupings of several effluents with characteristic changes in the content of one or more ions. Furthermore, no regularities are revealed by sample graphs of ion associations. Such considerations motivated focusing the work on the interpretation of ion concentrations which depart from the average, based on the analysis of the origin and location of the effluents, the geological structure, the operation time span for each region, the presence and accessibility of old chambers and galleries, and also the occurrence of chamber subsidence which reach the surface. It is possible to identify water migration routes and interpret the chemical composition of mine effluents only through a comprehensive analysis of the causes of water phenomena encountered in the mine which has operated since the thirteenth century.