Tailings Dam Management

Management of Operated Tailings Facilities

GRI 306-1 / 306-2 / G4-MM3

In August 2020, Global Tailings Review (GTR) formulated the Global Industry Standard on Tailings Management (GISTM). The International Council on Mining and Metals (ICMM) is committed to compliance with GISTM, and as a member of ICMM, we are responding to the standard.
Our Group thoroughly implements various measures to prevent significant environmental accidents at closed mines that our Group manages in Japan, and tailings facilities managed by CBNC and Taganito HPAL (THPAL) in the Philippines. We also disclosed information concerning high-risk tailings facilities in accordance with the provisions of the GISTM, established a working group under the Nature Conservation and Restoration Subcommittee, and took measures to ensure compliance with the GISTM.
On August 1, 2024, we formulated the Sumitomo Metal Mining Group’s Tailings Facility Management Policy based on the GISTM in order to clarify guidelines concerning governance and implementation structures, principles, allocation of management resources, collaboration, preparations for and responses to emergency situations, reviews, and disclosures. In this policy, we make a commitment to securing the resources necessary for conducting tailings facility management activities, cooperating with stakeholders, including local communities, mitigating risks throughout the lifecycle from tailings facility planning to decommissioning, and reducing impacts on the environment, as well as providing support for the safety management of tailings facilities at mines and other facilities in which we have invested.
In August 2025, in addition to high-risk tailings dams for which we had disclosed information, we also confirmed that all the tailings dams subject to disclosure managed by the SMM Group (17 facilities) are GISTM-compliant, and disclosed information accordingly.

Rehabilitation

GRI 306-1 / 306-2

CBNC and THPAL produce intermediates for electrolytic nickel and nickel sulfate. At tailings facilities, the slurry remaining after nickel recovery in the production process is treated through neutralization to remove toxins and precipitate heavy metals.
CBNC has three tailings facilities and THPAL has one. The first CBNC tailings facility reached its storage capacity and completed its role, and accordingly, we are rehabilitating the site to establish an independent and sustainable ecosystem. Many local residents and indigenous people are involved in this work, and rehabilitation plays an important role in creating local employment. In addition, we conduct regular monitoring, and safe and effective management of tailings facilities throughout their lifecycles is confirmed by independent organizations and other concerned parties.

Managing Closed Mines

GRI 306-1 / 306-2

We manage nine decommissioned and closed mines and the associated tailings facilities in Japan.
Wastewater from mines, tunnels and tailings facilities, where tailings and other materials are accumulated during mine operations. Such wastewater is primarily acidic and contains heavy metals, and as a result, it is properly treated at a water treatment facility before release.
We conducted assessments of accumulation sites in accordance with statutory management standards, which were revised following the Great East Japan Earthquake in 2011, and through 2018, we invested a total of approximately JPY4.5 billion to strengthen the 11 accumulation sites that failed to meet the standards. As a result, all accumulation sites now satisfy the standards.
In addition, we have responded to the increasing severity of natural disasters in recent years by completing the installation of emergency power generation equipment at each site and taking other measures by FY2023 to prepare for interruption of external power supplies and discontinuation of traffic for up to three days.
In August 2025, we also disclosed information regarding accumulation sites subject to GISTM.
Going forward, we will continue to soundly manage closed mines while also engaging in facility and infrastructure strengthening and improvement.

Management Framework for Closed Mines