Covering the Hattorf and Wintershall tailings piles

There is no potash mining in the world without residues. At the Werratal potash plants, a large part of the residues is disposed of in tailings piles, as is customary worldwide. Rainfall on the tailings piles generates saline water, which in turn has to be disposed of. K+S sees the greatest leverage for minimizing the impact of salt piles on people and the environment in the future in covering and greening them. Ideally, this will ensure that precipitation no longer comes into contact with the salt body of the tailings pile, thereby minimizing the amount of mineralized tailings pile water. Since the summer of 2022, the plateau areas of the tailings piles in Hattorf and Wintershall have been covered and then landscaped. Beginning in the early 2030s, the slopes are also expected to be progressively covered and revegetated using a system specifically designed to meet the unique requirements of these structures.

The tailings consist of the residues from the production of fertilizers and other valuable mineral products in the surface plants. Rain or snow dissolves salts from the tailings piles. The resulting saline tailings water is collected in trenches around the pile, stored in basins, and then, in accordance with the relevant permits, discharged into the Werra river or used for the prescribed flooding of former mines. K+S and, therefore, also the Werra plant are pursuing the goal of reducing the amount of saline tailings pond water to the technically possible minimum in the future by covering the tailings piles and, therefore, minimizing the discharge into the Werra, for example. At the same time, the covering system also reduces the tailing piles impact on groundwater.

Four reasons form the basis for the measures to cover the tailings piles at the Werra plant:

The K+S Werra plant is aware of the importance of its long-term responsibility for people and the environment in the region. Covering the tailings piles is an expression of this commitment. The greening of the tailings is intended to make an active contribution to improving the quality of life in the region. The goal is to create sustainable solutions that address both environmental and social issues. The commitment extends beyond the environment. We work closely with the local communities, listen to their concerns, and jointly find solutions to the benefit of all.

As a major employer and provider of training in the Werra Valley region, K+S wants to secure the jobs of the approximately 4,400 employees at the Werra plant in the long term. The continued existence and maintenance of the production sites is only possible if the disposal of production residues is secured. Sustainable management of residues and the covering of tailings piles ensure that K+S is a reliable partner for the people and the economy of the region, not only today, but also in the decades to come.

By covering and subsequently revegetating the tailing piles, rainwater infiltration is gradually reduced and ultimately prevented. This significantly decreases the generation of saline seepage water. Covering the tailings piles makes a significant contribution to reducing the amount of saline water and improving the ecological condition of the rivers. The goal is to create a sustainable future in which industrial activities and environmental protection are in harmony. Reducing the salinity of rivers is an important step in this direction and demonstrates a responsible attitude and commitment to preserving natural habitats.

The Werra plant is firmly committed to giving something back to nature and having a positive impact on the environment. One of the aims of covering the tailings and planting vegetation on them is to reintegrate the tailings into the landscape. By greening the tailings piles, K+S is creating new habitats for plants and animals and enabling the resettlement of native plant species. This increases biodiversity and strengthens the resilience of local ecosystems.

The implementation of an integrated tailings pile covering system is intended to achieve several key benefits:

1. Reducing the environmental footprint of Werra Plant as a production site.
2. Restoring the land surface, reintegrating the tailings piles into the surrounding landscape and creating new habitats for plants and wildlife.
3. Supporting the river basin management plan of the Weser River Basin Community (FGG Weser), with the medium- and long-term objective of achieving a good chemical and ecological status of the Werra and Weser rivers.
4. Maintaining the production capacity of Werra Plant and thereby helping to secure jobs in the region for the long term.

The covering of the tailings piles in the Werra Valley consists of two distinct sections: the flat plateau areas and the long, steep slopes. In 2022, we began covering the plateau areas of the tailings piles at our Hattorf and Wintershall sites. The system consists of a durable, tear-resistant synthetic liner that is placed on the prepared surface of the tailings pile. On top of this, a drainage layer and an approximately one-metre-thick soil layer are installed. The soil originates from the preparation of new tailings pile areas and can therefore be reused locally in a sustainable manner. The soil layer provides the foundation for vegetation establishment. The plants subsequently return a large proportion of precipitation directly to the atmosphere through evapotranspiration. The synthetic liner prevents rainwater from infiltrating the tailings pile, thereby preventing the formation of saline wastewater. Covering of the Hattorf tailings pile plateau was largely completed by the end of 2024 (approximately 6.8 hectares). Covering of the Wintershall tailings pile plateau is progressing steadily and is expected to be provisionally completed by the end of 2026.

Based on the positive experience gained with the surface covering already established on the tailings pile plateaus, as well as the numerous advantages of this system, plans are in place to extend the covering to the tailings pile slopes in the future. A prerequisite for this is the regrading of the steep slopes to allow the soil layer to be placed permanently and in a stable manner. The required reshaping will be carried out using tailings salt. Existing slope sections will be partially regraded, with the resulting material being selectively reused to reshape and flatten other areas of the tailings pile.

The standardized design of the low-profile covering system and the use of tailings material for slope regrading significantly reduce the need for external construction materials and, consequently, the volume of transport on public roads. Construction times are also shorter compared to other covering systems used on tailings piles, such as soil and demolition waste covers, which require large quantities of material. Overall, this approach reduces impacts on the surrounding environment and minimizes disturbance to local residents. At the same time, the technically sealed system prevents the formation of contaminated saline seepage water.

This system is ideally suited to both sites, as it requires only a limited amount of material and enables rapid implementation through to completion of the entire slope covering project. Although covering the slopes will result in an increase in the footprint of the tailings piles, the further developed concept enables the implementation of a fully sealed system, preventing the future generation of saline seepage water. To conserve natural resources and support sustainable practices, tailings material from our own production processes, as well as material generated from the selective regrading of existing areas, will be used primarily for reshaping purposes. As part of the permitting process, K+S demonstrates that only suitable and environmentally safe materials are used. As with the plateau areas that have already been covered, the soil applied above the sealing component originates from the surrounding region. In this way, we make an important contribution to further reducing the environmental impact of our tailings pile sites. The multi-phase permitting process began in 2023 with the so-called scoping phase, during which the scope of the required investigations was defined. These investigations cover all relevant aspects, ranging from the quality assessment of the materials used and the long-term stability of the covering system to its impacts on people and the environment. A large proportion of the required studies has already been completed. The results are currently being incorporated into the application documents and prepared for submission. We will continue to provide regular updates on the progress of the permitting process and the covering project itself through our News section.

In the long term, the covering of the tailings piles will make a significant contribution to improving the ecological condition of the sites, creating new habitats for plants and wildlife, and transforming the currently white mountains of the Werra Valley into green hills.