Expert report: proposed gold mine in Brazilian Amazon presents unacceptable risk | Interamerican Association for Environmental Defense (AIDA) Skip to content Skip to navigation
17 June 2020

Altamira, Brazil. An expert study released today reveals serious deficiencies in the environmental impact assessment submitted to Brazilian authorities by Canadian mining company Belo Sun. The analysis exposes an unacceptable degree of risk that the tailings dam at the proposed Volta Grande gold mine will fail, contaminating the Xingu River and harming nearby indigenous and other communities.

The report’s author, Dr. Steven Emerman, explains that despite the presence of geological faults at the mine site, the company has not produced any seismicity studies. Nor has the dam been designed with seismic safety in mind, in violation of Brazilian tailings dam regulations. 

Dr. Emerman also raises concern about the company’s use of its tailings reservoir to capture water. Industry best practice is to prevent the flow of surface runoff into tailings ponds in order to minimize the risk of dam failure. Moreover, the report reveals that Belo Sun has provided contradictory information regarding its tailings storage plan to investors and Brazilian regulatory authorities. Dr. Emerman recommends that the project’s licence be revoked.

Brazilian courts suspended Belo Sun’s installation licence in 2017 because the company failed to study the project’s impact on indigenous and other traditional communities, or to consult these populations.

Belo Sun has been criticized for publishing misleading statements to bolster sagging interest in the project among potential investors, amidst growing evidence of social, environmental, financial and reputational risks.

Last week local movements Rede Xingu+ and Xingo Vivo para Sempre submitted Dr. Emerman’s report to government agencies responsible for project licensing. These organizations demand that additional studies be undertaken, which they argue are “indispensable to assess the social and environmental viability of Belo Sun’s mining project considering the grave risk to indigenous and other river-dwelling communities located next to the project and its tailings dam.”   



From conflicting information to the absence of seismic safety criteria, Dr. Emerman's opinion highlights eight main points that support the recommendation to reject the Volta Grande project:

  1. The tailings dam was not designed under any seismic safety criteria, violating Brazilian regulations in this regard. Any tailings dam should be designed to withstand events such as floods and earthquakes. Contrary to the Brazilian standard, the company did not include in its studies an analysis of local seismicity nor did it simulate the response of the structure to a hypothetical seismic acceleration.
  2. Although geological faults have been mapped at the tailings dam site, no local seismicity studies have been done, which also violates Brazilian tailings dam regulations. Seismic activity is responsible for causing the dissolution of saturated debris into water, one of the most common causes of tailings dam failures. 

    In Brazil, in 2019 alone, there were three dam failures, including the rupture of the Vale dam in Brumadinho (Minas Gerais), which caused at least 250 deaths. Cases like these demonstrate the need for and importance of local seismicity studies and are indispensable for the proper assessment of the risk of failure of a tailings dam.

  3. No risk analysis has been made of the geological faults mapped in the vicinity of the project site. Three of these faults, which are structures present in rocks and which can promote seismic movements, intersect at the exact site of the proposed tailings dam.
  4. The official simulation of the rupture assumes, without justification, that the flow of the waste would be interrupted when it reaches the Xingu River, ignoring the capacity of the toxic elements to travel tens of kilometers along the Volta Grande. The conclusions of the EIA also support the hypothesis that the tailings flow would take 97 minutes to reach the Xingu, but without mentioning the details of the calculation used.

    According to the modelling presented in the opinion, considering the volume of tailings stored on the order of 35 million cubic metres and assuming a spill of approximately 25%, under a conservative scenario the flood would cover an initial distance of up to 41 kilometres along the river. At a speed of 20 km/h, the flooding of Belo Sun's dam would reach the Xingu in only seven minutes, covering the distance of 41 km in only two hours, reaching the Volta Grande Indigenous Land. After the rupture of the Vale Dam in Brumadinho, the tailings flow reached 120 km/hr, 100 km/hr more than the more conservative scenario proposed in the report.

    In the worst case, with the release of 100% of the stored tailings, the initial flow would cover 98 kilometers along the Xingu River and could reach the Amazon River and the Atlantic Ocean.

  5. There is a high risk of toxic water spillage into the Xingu. The project provides for the recycling of cyanide leachate, a substance used to separate gold, which can result in waste water that is highly enriched with toxic elements such as arsenic and mercury. The result, whose analysis is absent from official documents, could be the spillage of a waste-water mixture that is highly toxic to aquatic organisms into the Xingu River in the event of a dam failure or spill.
  6. There is no plan in the EIA to close the mine or tailings dam, a key issue for the social and environmental viability of the mining project. The document contains a promise by the business group to find out, after the event, how to permanently stabilize the tailings dam.
  7. The waste storage system adopted at the time is not viable and runs counter to good mining practice. Part of the solution to reduce the probability of tailings dam failure is to reduce the water content in the tailings tank. But the Belo Sun project envisages that all the waste will be saturated and under seven metres of free water, above the surface of the solid waste.
  8. Aware of the issue raised in the previous point, the company seems to have decided that the current plan to flood the waste is not feasible. The Chief Executive Officer of Belo Sun Mining stated o MiningWatch Canada that he would abandon the current plan for a filtered tailings storage facility, which should have a significantly lower water content. However, the company provided conflicting information to Brazilian organizations and regulatory authorities: in a presentation to FUNAI in October 2019, the company described the same wet waste storage plan as the EIA.

"The provision of contradictory information to different audiences by Belo Sun Mining and its Brazilian subsidiary is very serious in terms of the reliability of the information provided in the administrative processes," the opinion reiterates.

Rede Xingu+ is an articulation of indigenous, riverine and partner organizations that work in the Xingu River basin.

Movimento Xingu Vivo para Sempre is a collective formed in 2008 by local, national and international civil society organizations; threatened indigenous and non-indigenous communities; and social, human rights and environmental movements that oppose the construction of hydroelectric dams on the Xingu River and that fight in defence of the rights of local people.


Dr. Steven Emerman, Malach Consulting, +1-801-921-1228 (Utah, USA)

Brent Milikan, Amazon Program Director, International Rivers, +55-61-98153-7009 (Brasilia, Brazil). Mr. Milikan can connect journalists to representatives of Rede Xingu+ and Movimento Xingu Vivo para Sempre.

Karyn Keenan, Director, Above Ground, +1-613-791-7532 (Ottawa, Canada)


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