Alsace Subsoil: 42,000 Tons of Toxic Waste Threaten the Region’s Drinking Water Reserve

In Wittelsheim, thousands of tons of industrial poisons lie underground for a quarter of a century. Yet this former promise of temporary storage has now become a definitive geological trap. The drinking water of millions of residents is now subjected to this heavy environmental uncertainty.

The StocaMine site houses 42,000 tonnes of toxic compounds beneath Europe’s largest freshwater aquifer

At more than 500 metres deep, the former Wittelsheim potash mine hides a dangerous chemical cocktail. The Alsatian subsoil thus sequesters asbestos, mercury, arsenic, and cyanide. These dangerous industrial wastes occupy the galleries of an abandoned mining operation.

In 1999, the state approves this technical project to neutralize these unwanted substances. Nearly 42,000 tonnes of residues are transferred into the deep cavities. The engineers envisioned the facility as a modern storage site capable of permanently protecting the surface from direct pollution.

However, the toxic deposit sits directly beneath Europe’s largest groundwater aquifer. This vast reserve of fresh water crosses borders and supplies millions of households as far as Germany. Consequently, the slightest seepage would threaten the sanitary safety of a cross-border region.

The official pledge of reversible storage collapses after a toxic underground fire at the bottom of the galleries

Initially, the government defended the principle of reversibility. Authorities promised residents that the toxic substances could be extracted if technically necessary. Accordingly, the operation presented the site as a mere temporary stopover. Local officials even accepted the facility on the basis of this formal commitment.

But a severe underground fire abruptly erupted in 2002. This major incident permanently halted the arrival of new chemical shipments. From that moment, the site abandoned its original purpose and shifted to emergency management. The project lost any operational coherence in the face of the risks of toxic emissions.

The natural subsidence of the underground galleries pushes the state to opt for a definitive sealing of the site

Underground, the rock keeps moving incessantly. Indeed, the salt caverns suffer a very powerful natural geological subsidence. The walls slowly close in on the poisoned containers. This constant mechanical compression tightens the margin for maneuver and makes any human descent overly perilous.

Yet, a glimmer of hope arose in 2017. The administration then authorized the extraction of 93 % of the mercury waste, regarded as the most dangerous. Workers brought these highly toxic drums to the surface without incident. This technical success suggested a full removal of the remaining residues for the neighboring residents.

Nevertheless, in 2021 the government took a complete flip. The ministers decreed the permanent confinement of all remaining stocks. According to public experts, there is not enough time to extract all materials before the wells are crushed. The State thus chose to seal these galleries to permanently close the file.

The administrative court approves the definitive sealing despite strong opposition from Alsatian groups

This decision sparked the anger of the Destocamine collective and ordinary citizens. Regional elected officials also called for the removal of the most harmful products before full closure. However, the Strasbourg Administrative Court dismissed their appeals in June 2025. The ruling thus grants legal clearance to the projects.

Now, the Ministry of Ecological Transition is accelerating the underground works. According to state engineers, geological movements will block any human access by the end of the decade. This hotly contested dossier thus leaves a heavy legacy for future generations facing the underground residues.