Managing Decommissioned and Closed Mines

The SMM Group appropriately manages the top soil, waste rock, tailings, sludge, and other mining waste generated in accordance with our resource business. Rock (waste rock) containing sulfide ores, in particular, can easily result in the production of water that contains heavy metal ions as well as acidic water due to sulfate ions from oxidation, and accordingly we appropriately treat effluent at a water treatment facility prior to discharging it.
As shown in the map of closed mines managed by SMM, we operate 42 slag storage facilities in Japan.
Legal standards regarding the stability of storage facilities were revised after the Great East Japan Earthquake in 2011. After assessments were conducted based on these revised standards, 11 sites were found to be insufficient, and by 2018 we had finished construction to strengthen these sites, investing a cumulative total of approximately ¥4.5 billion.
Tailings and other mining waste generated by mines accumulate at storage facilities. The breach of an accumulation site could potentially cause significant damage. Accordingly, going forward, we will continue to soundly manage closed mines while also engaging in facility and infrastructure strengthening and improvement.

■ Decommissioned and Closed Domestic Mines
(as of July 1, 2023, dates in parentheses are closure/suspension dates)