The potash district in Alsace near Mulhouse was created in 1904, when potash was discovered for the first time.
The search for usable minerals and rocks in the Upper Rhine Graben using the drill core method or seismic methods has led to the discovery of large quantities of potash in the Wittelsheim Basin. Tertiary formations at the edge of mountains and also in the Upper Rhine Graben suggest gravel, gypsum, limestone and oil (in small quantities). On an area of 2,000 ha of land, at a depth of 460 to 1,000 metres, the raw material potash could be mined. A similar, but much smaller deposit was mined east of the Rhine between Buggingen and Heitersheim. The potash salt deposits in the southern Upper Rhine Graben were formed in the Tertiary period and are much younger than the potash salt deposits of the Upper Permian in northern Germany and south of the Harz Mountains. They are formed here from alternating deposits of sylvin and halite (sylvinite), magnesium salts are absent (no carnallitite or magnesium salt-containing hard salts). The extraction of potassium chloride from sylvinite was simple, but energy intensive: hot saturated aqueous sodium chloride solution dissolves potassium chloride from the ground sylvinite, but hardly any other sodium chloride. After separation from the rest of the crude salt and cooling, potassium chloride crystallizes.
Extraction in the salt mines became unprofitable in the Alsace plants at the end of the 1990s because potash salt could be mined much more cheaply in Canada. Even with transport from Canada to Alsace, extracting the salt was cheaper than mining it on site
After the mining of potash was no longer profitable, attempts were and are still being made to use the industrial wasteland for other purposes. For example, the open-air museum Écomusée d’Alsace was built on the industrial wasteland in Alsace in Ungersheim, directly at the former potash mine Mine Rodolphe. A visit to the former mines Mine Rodolphe and Joseph-Else is occasionally possible. Numerous miners’ settlements bear witness to the once large workforce. The large spoil heaps are characteristic of the landscape.
Otherwise, brownfield sites are also used as landfills or to attract new businesses. In order to bring new jobs to the region, the vacant flat areas are sold cheaply for subsequent use by other industrial companies. Since 2002 and the global economic crisis in potash mining, the upheaval in Alsace has taken place with the cessation of potash mining.
The potash basin near Mulhouse and groundwater salinisation on the Upper Rhine
The spoil heaps at the large mines, not only in Wittelsheim and Pulversheim, formed grandiose, scenically fascinating erosion landscapes, however, the local hills consist of up to 90 % salt. In recent years, the spoil heaps have been cleaned up. The leaching of the “potassium sandjars” in the south of Alsace, caused by the rain, salinates large parts of the groundwater of the Alsatian Rhine plain as far as the Sélestat area. In the sedimentation basins on the Fessenheim Rhine island, more than a million tonnes of salt have seeped into the groundwater, polluting the groundwater on the Baden side of the Rhine as well. One hundred years of industrial history have resulted in an important part of the groundwater of the Rhine plain no longer being usable for drinking water production.