Material Issue
Water

GRI 103-1, 103-2, 103-3

For our operations, water is also a subject of great importance and, therefore, the bolstering of water resources management in line with the company’s sustainable action policy is part of our strategy. Our water efficiency target is to achieve 75% recirculation in all operations by 2025. Another challenge is the specific use of new water in our processes: the target is to reduce such water collection by 30%.

Our performance in this regard is regularly measured. The following monitoring indicators in 2017 showed that our water recirculation was on the order of 66% in 2017, compared to 67% in 2016. The calculation took into account the volume collected in relation to all the water used in the process. GRI 303-3

Our water management plan is divided into three main stages, which are periodically reviewed and applied in the operations as well as greenfield projects under development. The three stages are:

❯ Diagnosis: consists of water risk assessment and the development of a framework for water accountability;

❯ Control / Mitigation: exercised through audits and a contingency plan;

❯ Development: includes a Measurement Master Plan (flow) for all units, with 14 initiatives that contribute to increase recirculation and reduce fresh water intake.

Evolution

In 2017, we made progress in mapping the water scarcity risk through the development of the Water Risk tool. We applied this matrix in all our units and, today, we can express both the risk exposure and its aspect. We also evolved in terms of water monitoring critical analysis, aligning concepts and standardizing results from outside quality analysis laboratories.

Another important initiative during the year was the standardization of water accounting practices. We now can evaluate the actual cubic meter cost of water used in each unit, including pumping, circulation, treatment and concession costs. These oversight practices will lead to the introduction of a number of managerial improvements into the process, while also helping monitor the largest users of the resource, permitting better planning. For 2018 and 2019, we intend to install internal flow meters in each user area considered most relevant to water management. As a result, we will be able to identify new opportunities for further evolution.

As examples of good water management practices, we can highlight the following initiatives in some units. Cerro Lindo operates the first desalination plant in Peru. With a station composed of storage tanks, pumping networks and reverse osmosis filters, it is possible to operate with 100% of the water taken from the ocean and there is no effluent disposal at the mining unit. The unit also has recirculation and treatment systems that allow the efficient reuse of the water in the production process, minimizing intake losses and costs, maintaining water efficiency at 91%.

Regarding our units in Brazil, we continued the “Clean Water” project at Morro Agudo, which allows the removal of good quality water directly from geological faults, fractures and wells for use in the plant and subsequent return to the environment. Its water reuse process has reached the 78% mark. In Três Marias, also notable has been the reduction of water use by 17% due to improvements in the resource management process initiated in the second half of 2017.

Water use by source17 GRI 303-1

Note 17: The water balance of Nexa is based on the Water Accounting Framework (SMI / MCA, 2014), which incorporates all the volume of water collected and used by the organization. The data are reported considering the abstractions of surface water (river and sea), underground (coming from wells or withdrawal for mine lowering, although not used in the production process) and rainwater stored in physical structures located in the units.

Disposal

Our water recirculation program also contributes to ensuring lower effluent volumes. This reduces both the risk of an adverse impact on the environment and the cost of treatment to ensure that the effluent discharged meets the required quality parameters. In 2017, 40% of the environmental expenses were earmarked for effluent treatment purposes.

With the exception of Cerro Lindo unit, where there is no mining waste disposal, 100% of the effluents from other plants are sent to Treatment Stations (ETSs/ETSi) and submitted to processes according to type. All new projects have the prerogative to start operations with a built-in recirculation ratio of at least 75%.

In Juiz de Fora, we will conclude the installation of the new industrial drainage system in 2018, designed to segregate rainwater in the unit. The works contemplate the construction of new drainage networks, adequately sized and made out of resistant materials; installation of a pumping system for the containment tanks in the industrial area to Barragem da Pedra reservoir, in peak rainfall periods; construction of sedimentation tanks and drainage segregation.

The Santa Catarina river, present in Vazante (northwest Minas Gerais), is one of several Brazilian water sources that suffer from a water scarcity crisis. The soil through which the river flows is karst, whose characteristics are favorable for the appearance of dolines, a proven natural phenomenon. Since 2014, when the lack of rain began to worsen in the region, some of these features appeared along the river, contributing to a reduced flow. The company is conducting studies related to the subject and constantly monitors the river’s movements. In addition, we act as a partner with the community, the municipal government and environmental agencies to minimize the impacts of the water crisis in Vazante through dialogue and panel discussions with the community (see more on Community.)

Note 18: The data are calculated based on the Water Accounting Framework (SMI / MCA, 2014), which considers the sum of reused water / sum of water used and the GRI base, where the sum of reused water / sum of used water withdrawn.