How it works

Nexa prioritizes the reuse of materials through new technologies, as an alternative in the treatment of tailings and waste. This proposal is applied at the Morro Agudo Mine, where tailings are a commercially viable by-product.

This proposal is applied at the Morro Agudo Mine, where tailings are a commercially viable by-product.

Some operations may combine one or more disposal methods. At the Atacocha, El Porvenir and Cerro Lindo units in Peru, we adopted the backfill system, whereby 46% of the tailings are returned to the mines at the Pasco Complex (Atacocha and El Porvenir), and 38% is returned to the Cerro Lindo mine, in which part of the waste is filtered, separating water and solids.

n Brazil, we already operate in the Vazante mine, disposing of the tailings in dry stacks, which reduces environmental impacts and risks to the operation.

Backfilling Dry Stacking Dams

Backfilling refers to filling the mine with tailings, inserted into the voids of underground mines, for the purpose of increasing the structural stability of the mine, providing platforms, improving ore recovery, and disposing of tailings.

The underground disposal of tailings in mining pits can only occur when the tailings are considered inert, eliminating the possibility of contaminating water or soil.

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Also called a filtered (or dewatered) tailings stack/deposit, the pulp tailings that remain after processing the ore undergo filtering, drying and handling (whether combined or single method), until obtaining moisture content below 20%.

By extracting water from the pulp (the mixture of liquid plus ore or tailings), the solid part is stored or placed in stacks, ensuring reduced environmental impact.

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A dam is a structure built for the purpose of containing, impounding or storing water, liquid substances, or mixtures of liquids and solids, whether permanently or temporarily.

The term “dam” comprises not only the levee or embankment itself, but also all associated structures, such as: spillways and sluices, reservoir, headrace, diversion structures, tailrace, water intakes, impoundment intakes, saddle dike, among others.

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Status of dams and tailings deposits

The disposal of waste in NEXA for several alternatives, but all of them meet the best practices and technologies available. Below, you can view the status of the structures (dam, pound and reservois) at each site and the construction method used for each one.

Consolidated

Active

22

Inactive

25

Total

47
Brazil Peru

23

Dams and tailing deposits in Brazil

Units

Morro agudo
Vazante
Três Marias
Juiz de Fora
01 2 3 4 5 6 7 8 9 10
Active Inactive

24

Dams and tailing deposits in Peru

Units

Chapi
Sinaycocha
Cerro Lindo
Atacoha
El Povenir
Cajamarquilla
01 2 3 4 5 6 7 8 9 10
Active Inactive

Data and documents

Tailings, Residue, Water and Waste Rock Management System

In order to control and monitor dams and tailings deposits, we apply guidelines from the International Commission on Large Dams and the Canadian Dam Association (CDA). We use processes and procedures that form the Integrated Dam Management System (called SIGBar) and an Integrated Deposit Management System (called SIGDep), permanently monitored by an independent firm, Geoconsultoria, which receives inspection data every 15 and 30 days, respectively, to issue its reports. This Management system is designed based on the routine monitoring of the structures and the monthly issuance of a “traffic light” that is taken to all hierarchical levels in the company, and presented at periodic meetings of the executive board.

Tailings, Residue, Water and Waste Rock Management System

What is SIGBAR?

What are SIGBAR and SIGDEP? SIGBAR is a Dam Management System developed by Geoconsultoria, aimed at ensuring the stability of dams, and SIGDEP is a Tailings Deposit Management System, so that any potential weaknesses are reported in advance, allowing for preventive actions.

MODULES

Each module serves to standardize a single way of acting.

REFERENCES

ICOLD – International Commission on Large Dams
Brazilian Committee of Large Dams

We use processes and procedures that comprise the Integrated Dam Management System (SIGBar).

This system consists of 12 modules that establish the rules and measures for periodic monitoring activities, based on which we control all of the structures. SIGBar establishes guidelines for managing documents, monitoring activities, evaluation, risk analysis, compliance with rules and legislation, training of the workforce, structure operations, and other provisions.

This work is monitored on an ongoing basis by an independent firm, which receives data from inspections performed every fifteen days and consolidates data from all monitoring activity to issue monthly stability reports.

Modules implemented in 2007

PRELIM

Definition of preliminary planning activities

MONITOR

Geotechnical mnitoring activies and records

EVALUTE

Evaluation and records of the behavior and safety.

DOCUMENT

Organization, registration and avaliability of documents.

LEGAL

Analysis of legislation and verification of applicable requeriments.

GVISTA

Provision of key information about dams.

TRAINING

Training of all personnel involved in management.

OPERATIONS

Operation manual for dams and operational controls.

RISK

Risk analysis, identifyng the structure's risk conditions.

EMERGENCY

Emergency Action Plan (PAE) incluing Dam Break and Self-Rescue Zone

Modules implemented in 2007

PLANNING

Tracks the service life of each structure.

ENVIRONMENTAL

Monitors and tracks the environmental function.

Dam management routine
Daily
  • Comply with operational procedures
  • Conduct operational inspections
  • Perform monitoring
Every 15 days
  • Perform onsite inspection of safety conditions
  • Perform monitoring
  • Data sent to Geoconsultoria for evaluation
Monthly
  • Data sent to Geoconsultoria for stability assessement
  • Perform monitoring
  • Issue the sigbar indicator
  • Consolidation of monthly reports and issuance of indicators

Origin of the actions

Recommendations for twice-monthly inspections; recommendations from Geoconsultoria; special or cross inspections; actions for deploying the Emergency Plan; Cross-check; compliance with legal requirements; decommissioning; environmental area; operational life.

The “TRAFFIC LIGHT” is the way for us to monitor the stability of the structures and all associated action plans.

Golden rules

GOAL
Nexa Resources has adopted 7 golden rules in all its operations that aims to ensure the management of geotechnical structures and safety of all employees and third parties, they are:

 

1 – Project

Build geotechnical structures only with detailed projects, and any modification in the project can only be done with the prior approval of the designer/ATO and the awareness of the external consultant, responsible for dams in the unit and corporate.

2 – Licenses

Authorize any construction activity, dam raising, corrective maintenance work and operation only after the necessary licenses have been issued. When applicable, notify the responsible inspection agency.

3 – Nexa management system

Comply, according to the Nexa management system, with the Operation, Maintenance and Supervision (OMS) manual and keep it updated according to the current operation scenario, physical characteristics of the dam/pond and organizational structure. Any change must have the approval of the structure’s technical manager, external and corporate consultant.

4 – Communication and notification flowchart

Communicate, according to the communication flowchart of the geotechnical structure present in the Operation, Maintenance and Supervision manual (EC<=6) or in the emergency action plan (EC=10), the identified anomalies or instrument readings with abnormal levels.

5 – Data Management

Never manipulate, modify or falsify inspection and monitoring data or replicate data from previous months as being from the current month.

6 – Supervision and Auditing

Attend to all recommendations of the monthly safety assessment with priority and high risk, cross checks, legal demands and audits (DCE/DCO/Legal requirements with classification of major or extreme seriousness), on time or if requested new deadline have the awareness of the business and sustainability directors.

7 – Communication of Environmental Accidents

Immediately communicate environmental accidents greater than or equal to level 4 and/or potential severity greater than or equal to 5, infraction and inspection notices, to the pertinent and/or corporate entity, according to the company’s standard.

Application of the golden rules

The non-compliance with any rule, standard, or procedure for dams and deposits must be reported and analyzed by the audit team.

Corrective action will depend on the severity of the violation and other relevant circumstances, determining the appropriate response which may include, but not limited to:

1 – Reinforcing compliance training, education, or coaching;

2- Verbal or written warning;

3 – Suspension; or

4 – Termination of employment contract.

Denunciation and evaluation
The denunciation channel is the ethical line, this channel is impartial and transparent, guarantees the confidentiality of information, and preserves the identity of the people involved.

Through it, it is possible to clarify doubts of interpretation, submit reports of non-compliance with the golden rules for dams and deposits, and follow up on a report that has already been filed.

The sending of a report (anonymous or not) can be done through the link nexaresources.com/pt/ethics-line or by phone:

Brazil

0800 892 0741

Canada

1 855 888 9926 / 1 885 350 9393

Luxembourg

800 201 11

Perú

0800 50 000 / 0800 50 288

USA

1 855 8889926

Áustria

0800 200 288

Reports can also be made directly to the immediate managers to carry out the treatment of the irregularities observed.

Reuse of Tailings

In Morro Agudo, we transformed all the tailings into a secondary product, Agricultural Limestone Powder, from which Zincal200 is derived. The tailings from the mining operation are sedimented, part of which is reused in the plant and part of which is sold as Zincal, a product used in agriculture to decrease soil acidity and increase yields. In 2019, we began selling more Zincal than the volume produced at the unit, which allowed us to reduce the stockpiles of old tailings. Last year, we passed the milestone of one million metric tons of limestone sold, and doubled the reprocessing of old tailings at the plant. Aside from representing revenue on the order of US$ 8.7 million (15% of the unit’s total revenue), the process eliminates the need to build new containment structures such as dams, resulting in economic and environmental gains.

Sirens

In 2019 we installed the most modern siren system in the areas of the Self-Rescue Zone*, with a sound intensity of 70 dB, at all units in Brazil, in the metallurgy and mining sectors. Our mass evacuation system has not only sound alerts but also voice resources (both pre-recorded and live-voice), which offers greater efficiency and eliminates any possibility of confusion, thus minimizing panic, restoring order, and bringing safety to the local populace. We use OMNI-360º sirens, specifically designed for open areas and with completely autonomous operation, powered by a photovoltaic system (solar energy).

Regardless of the wind direction, the sound continues to be propagated in all directions within the area of interest. The sound design includes sirens with 360° propagation, and the system’s robust performance has been proven throughout the last 35 years, with more than 20,000 sirens installed in 50 countries around the world. The system is STI-certified (SPEECH INTELLIGIBILITY INDEX) and meets the International Standard ISO 9921-2003 (ERGONOMICS – ASSESSMENT OF SPEECH COMMUNICATION), which is one of the world’s best known standards regarding clarity of voice emission.

Our system is called SI TEST® which is activated automatically once a day, without disturbing the communities in the protected areas. In this test, each amplifier, speaker driver, battery charger, battery bank, and radio signal are checked individually, being indicated by an alarm registered in the Control Center. Additionally, an audible test is performed daily, as a second test to verify system operation. The sirens are in accordance with the requirements of the latest Brazilian legislation, which provides for a range within a radius of 10 kilometers or a flood wave equal to 30 minutes. We are currently in the process of automating the geotechnical instrument monitoring process. In addition to the online monitoring required by law, we conduct onsite inspections every 15 days.