The current systems use a methodology for tailings disposal based on the alternating operation of their reservoirs: in sequential periods of 30 days during the dry season and 60 days during the rainy season. Thus, the drying of tailings in each reservoir is ensured by the combined actions of drainage and evaporation, which results in tailings with at least 60% solid content. This process ensures greater safety by reducing the amount of water in the dams.
The basic principle of the drying process is to allow the sedimentation and thickening of tailings to obtain a material with better mechanical properties. This final characteristic of Mineração Paragominas' tailings favours the stability of the reservoir. This phase makes the operation safer and helps to ensure that the dams are in stable condition and in full integrity, which is verified through constant monitoring and audits by internal and external specialists, as well as regular legal audits. All equipment defined for dam monitoring is installed and operating normally. These include:
Piezometers: used to monitor water pressure in dams.
Water Level Indicators: used to detect the presence and depth of groundwater.
Surface Marker: used to measure any surface displacement in the embankment.
Inclinometer: monitors changes in the internal structural formation of the dam.
Tailing Dry Backfill
Under testing since July 2019, the application of ‘Tailing Dry Backfill’ technology represents the end of the use of large dams for permanent storage of bauxite tailings. The tests are carried out with permanent monitoring and supervision by environmental agencies and in accordance with the technical standards of Conama (National Environment Council). The methodology allows inert tailings from bauxite mining to be returned to areas that have already been opened and mined, instead of being deposited in separate, permanent storage areas. After drying in temporary storage for 60 days, the bauxite tailings are returned to the mined areas before the area is rehabilitated and reforested.
The tailings from bauxite mining are chemically and physically similar to those removed during the mining process. Therefore, it is returned to nature without any impact on the environment.
This significantly reduces the environmental footprint of bauxite mining and increases operational safety. Prior to testing, Hydro conducted technical studies and detailed planning. The tests have been carried out in different climatic seasons, continuously monitored by the project's technical team, and detailed reports are sent to the environmental authorities on a regular basis.
Full-scale implementation may begin after the testing phase and approval of the operating licence by SEMAS (Pará State Secretariat for the Environment and Sustainability).
Audits and inspections
eriodic inspections allow for the assessment of the integrity of the tailings systems, as well as assisting in decision-making, ensuring the integrity and safety of the structures. The operation of the dams at Mineração Paragominas complies with the guidelines established by the National Mining Agency (ANM), the regulatory body responsible for inspecting dams in Brazil, and by the State Secretariat for the Environment and Sustainability (SEMAS), the local environmental protection agency. Both entities supervise the company and may also carry out inspections at any time.
Paragominas Mining conducts daily, weekly and fortnightly inspections:
Daily - routine inspections by the operations team;
Weekly - inspections carried out by the technical team (geotechnical engineers specialising in dam management);
Every 15 days - all data collected during this period is sent via an online system to the National Mining Agency (ANM). This report includes the results of monitoring, inspections and controls on the dams. All internal and external legal reports and analyses validate the current stable condition of Mineração Paragominas' dams, in accordance with Brazilian legislation. The company also uses the support of specialised companies to verify the reliability and safety of the dams..
Declaration of Stability Condition (DCE)
Issued by the National Mining Agency (ANM), this is one of the main documents required for dams. It is a technical certificate issued based on two procedures, also established by the ANM:
1. The periodic review of dam safety, required once every three years, comprises:
- Review of all dam documentation and history;
- Review of dam maintenance and operation procedures;
- Performance of a new geotechnical stability analysis Implementation of hydraulic verification.
In June 2018, periodic reviews were carried out on all Mineração Paragominas dam systems, certifying the current safety condition of the dams.
2. Regular safety inspections must be carried out twice a year, in March and September, issued by a specialised company and reported directly to the National Mining Agency. The inspections are carried out independently by the companies based on various data relating to the condition of the dam.
Emergency action plans
Mineração Paragominas operates with respect for people and the environment, prioritising safety in all its operations. Guided by this commitment, the company maintains processes and procedures aimed at preserving the integrity of people's lives, communities and the environment.
In line with this safety and care policy, Mineração Paragominas has an Emergency Response Plan (PAE) and an Emergency Action Plan for Mining Dams (PAEBM). These documents are complementary and describe scenarios and procedures to be adopted in emergency situations.
Highly trained team
Paragominas has a Geotechnical Management Department (GAGEO) responsible for managing dam systems, as well as tailings disposal and other geotechnical issues.
This team, composed of highly qualified specialists such as engineers and geologists, works to ensure the physical integrity of the dams by following an intense routine of inspections and instrumentation monitoring on all structures.
Updated: September 24, 2025