Mitsui Kinzoku has started mine operations in Kamioka area, Gifu prefecture in 1874, and ever since, we have been in the mining business for over 140 years. In Republic of Peru, we currently have our own developed mines in operation: the Huanzala Mine and the Pallca Mine operated by Compania Minera Santa Luisa of Mitsui Kinzoku Group. It has been over 50 years since the Huanzala mine started its operation in 1968. The Pallca Mine was developed as a branch of the Huanzala Mine in 2006.
In Japan, most of the mines have already suspended or terminated operation due to resource depletion.
Management of mines in operation
The Huanzala Mine is situated in the Andes at an elevation of about 4,000 meters, and it has been producing zinc, lead and copper concentrates, contributing to a stable supply of metal resources.
In Peru, the Environmental Law promulgated in 1993, which prescribes PAMA (the Environmental Adjustment and Management Program) as an obligation to existing mines in operation. The Huanzala Mine was the first mine in Peru to acquire PAMA in 1997. The mine completed environmental measures based on PAMA in 2008, and minimized impact on the environment.
In addition, the mine acquired the certification of ISO14001 and OHSAS1800 in 2008, and completed a transition from the 2014 version to the 2015 version of ISO14001.
Items listed in PAMA
- Acidic pit water treatment
- Recycling of wastewater
- Stability evaluation of tailings dam
- Dust collection equipment of crushing process
- Treatment of living wastewater and solid waste
- Regeneration of Contaicocha lake
- Polluted soil treatment
Contaycocha is a lake located downstream of the Huanzala Mine, and it was unable for living things to inhabit because of the acid water discharged from the mine. In addition to water quality improvement through acid water treatment, Minera Santa Luisa worked on environment restoration such as water sealing of acid sediment by raising the embankment and soil covering and tree planting. As the result, trout and waterfowls have returned to the lake as the water quality and the surrounding environment have been restored.
Mine closure plan
Since mineral resources are limited, environmental management after mine closure is indispensable for maintaining the surrounding environment. However, quite a few mines had been abandoned and affected the environment in history. In Peru, the Law of Mine closure was promulgated in 2003, which required mines in operation and mine development projects to submit a closure plan and to accumulate the closure costs based on the plan. The Huanzala Mine conducted voluntary pre-survey in 2004 prior to the law enforcement, and carried out some closure works that were identified as necessary in the survey ahead of the plan. The works include removal of acid waste rock which generates acid water, closure of inflow passage of surface water, separation of mine water into clean water and polluted water, and soil-covering/planting of waste rock storages. In 2009, both Huanzala mine and the Pallca mine obtained government approvals for the closure plan and have started accumulating closure costs in 2010.
We implement works for mine closure in advance at the Huanzala Mine and the Pallca mine. We work on removal of waste rock generated in the past operation and soil-covering/planting at the Huanzala Mine
left：Before soil-covering/planting（Huanzala, 2007） right：After (Huanzala, 2019）
Management of suspended and closed mines
Mitsui Kinzoku continues environmental management of suspended and closed mines, in accordance with the Mine Safety Act, and applicable laws and regulations. Contact of rainwater with waste rock and metal containing rocks may generate acid water containing heavy metals. In order to manage acid water and to prevent mine pollution, we conduct inspection tours and the checking of managed site, water quality monitoring in neighboring areas, and water purification by acidic water treatment equipment.
We patrol suspended and closed mines on a regular basis to confirm that there is no hazardous spots, such as new caved-in hole in which people may fall.
In the underground of the Huanzala Mine, acid water generates due to an abundance of sulfide of iron in ore. Applying mine pollution prevention technology in Japan, Minera Santa Luisa built a mine-attached neutralization plant in 1998 that was the first one in Peru. The mine continued to improve the plant by increase of settling tanks, betterment of lime addition pumps and enlarging air agitation blowers, and keep processing stable acid water treatment.
A 24-hour monitoring system of mine drainage water is put into place, thus it is consistently ascertained that the pH level of the water released into the river is below the required environmental standard value.
Furthermore, we voluntarily conduct survey every three days in order to check the concentration of heavy metals within the drained water. In addition, water samples are collected from locations around the Huanzala Mine once every month to check the water quality in accordance with related laws. The flotation plant at the Huanzala mine is also advancing efforts to recycle water and striving to reduce water consumption.
The neutralization plant of Huanzala. After neutralization, the supernatant water is discharged into the river with pH level below the required environmental standard value and the sediment is stored in the tailings dam. The processing capacity of the plant is 18 m3 / min.
Tailings dams management
In the smelting process, slurry type wastes called tailings are generated. The facility to storage “tailings” is called “tailings dams”. In recent years, a series of dam collapses occurred in Brazil and Canada and they have been considered as significant environmental and social issues. Mitsui Kinzoku group regards the management of tailings dams as one of the major risks in the mining business and manages them in accordance with applicable technical guidelines and manuals.
In Japan, there were leakage incidents at a number of tailings dams caused by the Great East Japan Earthquake in 2011. Then in 2012, the ministry of Economy, Trade and Industry revised the Technical Policies of the ministerial decree defining technical standards of mining facilities (called "Technical Policies" hereafter). We recognize that the Technical Policies is an important guideline for ensuring the safety of tailings dams in Japan, which have relatively high risks of earthquakes, and we manage tailings dams in accordance with these Technical Policies.
In 1995, we conducted voluntary stability evaluations of the top three tailings dams out of 13 dams managed by Mitsui Kinzoku after the Han-Shin Awaji Earthquake disaster in 1995. As a result, we confirmed these three dams would remain stable even in the event of a massive-scale earthquake (Level 2 earthquake).
We also evaluated the stabilities of five dams in line with the revision of Technical Policies from 2012 to 2015 that were subject to Technical Policies requirements, and ascertained they have extremely low risks of major collapse in the event of Level 2 earthquake. Furthermore, we have been evaluating five dams since 2017 that were not subject to the Technical Policies, and have confirmed four of them have the earthquake resistance. We are still collecting the data of the remaining one, and we plan to implement countermeasure constructions by 2021 in case if it is judged that they are necessary.
In stabilization surveys of a tailings dam, we dig observation well and measure the groundwater level to check seepage into dam embankment.
In Peru, Minera Santa Luisa designs, manages and conducts stability evaluations of tailings dams in accordance with the technology guidelines and manuals defined by the Ministry of Energy and Mines.
Peru is a country with a relatively high risk of earthquake like Japan. As a result of stability evaluation, it has been confirmed that the tailings dam of the Huanzala mine has no problems and will remain stable, even if the area is hit by a major earthquake of a level that only happens once every 500 years. In order to ensure the safety, in-house engineers conduct monitoring of the seepage level in the levees every month. External specialists also check the seepage level in the levees and perform tilt measurement every three months.
Chuspi, the tailings dam of the Huanzala Mine. We evaluated the stabilities again in 2017 and confirmed that it would remain stable, even if a major earthquake hit the area.
The list of tailing dams managed by Mitsui Kinzoku Group
In June 2019, Mitsui Kinzoku disclosed information about abandoned tailings dams based on requests from the British Church Pension Committee and the Swedish National Pension Fund Moral Committee.
Information Concerning Tailings Dam management
Relationships with the local communities
Compania Minera Santa Luisa strives to establish relationships of co-existence and mutual prosperity with the local communities. The Huanzala mine and the Pallca mine have concluded regional assistance agreements with local governments in order to support local governments and residents. Santa Luisa has provided various community supports such as direct support for local communities and indirect support through infrastructure investment.
|Local community support
Free supply of electricity from company-owned hydroelectric power stations.
- Donation of school supplies, PC and books
- Job training and employment supports
- Constriction of schools and children's parks
Livestock industry support
- Construction of clinics
- Donation of medical implements
- Free examinations and vaccinations
- Improvement of the breed of domestic animals
- Distribution of seedlings
- Instructions on livestock industry
- Construction of irrigation canals
|Investment in infrastructure
Construction of roads
Development of local communities’ infrastructure
- Catac road（from Pacific coast to Huanzala mine）
- Pallca-Chiquian road（from Chiquian town to Pallca mine）
Improving housing for local residents
- Construction of bridges, water and sewage facilities, and administrative offices, etc.
- Support for the relocation of residence in landslide area
Construction of a bridge in a neighboring village. Infrastructure investments create jobs in local communities and revitalize the local economy.
The supports for the agriculture and livestock industry are important measures to revitalize the local communities; We provide technical supports by specialists and veterinarians. Domestic animals such as sheep, llamas and cattle propagated in our own farm are given to the local farmers.
The Integrated Report “Mining business”[PDF：199kb]