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Ensuring the safety of hydraulic structures

The organizational structure of NLMK Group includes dedicated services and units responsible for the safety of hydraulic structures. Continuous measures are undertaken to monitor and control the state of the environment throughout the entire life cycle of deposits and tailings. All deposits exploited by the company are currently in commercial development or exploration. The explored reserves of iron ore are estimated to last for 150 years. Mine closure is not planned. In 2021, a comprehensive survey of Stoilensky TMF hydraulic engineering structures (Tailing Management Facility) was conducted together with specialized government agencies, a general design bureau and expert organizations. The survey assessed the safety level of the Stoilensky TMF hydraulic engineering structures as “normal” (the best possible level).

The Group duly informs the local communities about the existence of the tailing dam and holds regular public hearings regarding the development of the complex. All development projects of the company are agreed with stakeholders. Built in 1984, Stoilensky’s tailings dam is NLMK’s only TMF. No environmental incidents related to the tailings dam systems and structures have been recorded throughout its operation.

A local alarm system operates on site and its operability is checked monthly by Stoilensky employees and Rostekhnadzor specialists. A Contingency Plan for Hydraulic Structures at the Tailings Dam has been designed and receives updates every year. Staff training is administered at least once a month. In September 2021, scheduled training sessions were held with the involvement of employees of the EMERCOM of Russia. According to the determination of a specialized state committee, monitoring of seismic activity for the area of ​the tailings dam is not required.

Stoilensky’s tailings dam uses an efficient and environmentally friendly treatment process for treatment of waste rock from beneficiation. It involves liquid extraction followed by forced transfer of thickened tailings into storage. This allows for savings in natural resource management: 80% of process water used for transportation is returned into the beneficiation process. Additionally, better weathering stability of thickened tailings significantly reduces the dust levels at the tailing dam. In order to eliminate the risks of dusting on the tailings dam beaches, the development of spraying and dust suppression systems was continued in 2024, and the beaches were treated with environmentally safe binder solutions in spring and autumn. The Company coated over 150 hectares of dry beaches thereby enabling the effective restraint of dust vortex formation at the facility, even during the dry summer and autumn periods.

Eliminating excess water flow from the beneficiation tailings into the tailings dam mitigates the overflowing risk and reduces pressure on the dams. Given the tailings thickening and the safety measures taken to ensure the safety of hydraulic structures, the risk of tailings dam failure at the Stoilensky is manageable and remains at a conditionally acceptable level.

The water level in the tailings dam compartments is maintained at more than 2 meters below the dam crest, which meets current safety criteria.

Additionally, better weathering stability of thickened tailings significantly reduces the dust levels at the tailing dam. For over five years, the site employs and continuously develops an integrated approach: a mobile irrigation system and treating beaches with a special reagent that binds dust particles together to form a wind- and moisture-resistant crust. Over 150 hectares of dry beaches are treated annually.

The mobile irrigation system currently extends eight kilometers, covering the waste protection dam, the head dam, and Rubezhny Log area. It can operate with 25 sprinklers, but even with 10-12 sprinklers, it covers approximately 1,200 meters of beach, consuming 800 cubic meters of water per hour. The irrigation system, combined with treating the beaches with a special reagent reduced dusting at Stoilensky tailings dam by 75% in dry and windy weather. The system is actively used from late March until October-November, depending on the weather. In the future, Stoilensky’s team plans to extend the system to cover the entire tailings dam.