The diapir, dome shaped, Permian age salt deposit WAPNO, oval in horizontal cross section /900 × 400m/ has got gypsum cap outcrop. The deposit was being worked out as the gypsum quarry in years 1828–1931. After the gypsum reserves were depleted water filled the quarry and the reservoir occured to be hydraulically connected with salt mirror. Exploitation of the salt deposit was carried out in years 1920–1977 and 11.5 mil. tones of rock salt was mined using room and pillar stoping. The exploitation was started on 4-th level/depth 405m/going down to 9 th level/depth 544m/. In years 1952–1967, in order to increase the salt production, the 3rd level was also mined. This was located above 4th level, mined out previously and in which some cavings and moistness were stated. The direct cause of the flooding of mine was influx of surface water into mined out chambers of 3rd level through the horizontal sill pillar along easily soluble potash salt streaks and bands, which had got their outcrops on the salt mirror. As the result of leaching of the surface of salt mirror the karst trough were eroded and filled with saturated brines and saline. In these places the width of protection sill pillar was considerable reduced. One of such troughs, from which the outflow of brines and saline occured, was located in the direct vicinity of the mined out chamber 36 on the 3rd level of the mine. The main initial importance for the future safe mining in diapir dome shaped salt deposits is the adequate, detailed geological survey of the upper part of the deposits, the cap of the dome, salt mirror and the hydrogeological conditions, before the mining is started.
The salt diapir dome WAPNO consists of Permian /Zechstein/ salt formations, which is known on the about 60% of the area of Poland, on considerable depth of several thousand meters. As the result of halokinetic prosesses in certain places the salt masses were uplifted, creating the specific salt structures. Thrusting through overburden the salt masses took shape of salt diapir domes. One of them, WAPNO, is the smallest from the numerous known in central part of the country. The discovery of the salt diapir dome WAPNO is connected with qurrying of the gypsum cap, commenced in 1828,when the saline outflows were stated. The salt deposit below the cap was intersected by borehole MOSZCZENNO in 1869. Results of extensive geological survey and here especially geophysical and hydrogeological exploration and drillings indicate the structual concept of the salt deposit, which is given below. The salt diapir dome WAPNO in the vertical cross section is an upper branch of bigger salt structure, which roof was stated on the depth of 1500 m. These formations being caverneous and fissured are highly water bearing. The gypsum cap located directly on the salt dome and the surrounding Mesozoic formations are covered by younger deposits, i.e. Tertiary and Quaternary formations, which being clay and sandy rocks are mostly also water bearing.
