By Brazil Stock Guide – Brazilian prosecutors have called for a review of Eletrobras’ (ELET3.SA) Colíder hydropower plant, citing structural flaws at the dam and extensive environmental damage. The recommendation stems from a technical report by the Public Prosecutor’s Office of Mato Grosso (MP-MT), which found drainage failures and “a considerable environmental and social liability” at the site.
The report urged a comprehensive study that includes the possibility of decommissioning or altering the plant’s structure. Colíder, with an installed capacity of 300 megawatts, has been operating since 2019 and is part of the Teles Pires hydro complex in northern Mato Grosso, according to Valor Econômico.
Structural Failures
A field inspection conducted between Aug. 22 and 27 found critical weaknesses in the dam’s drainage system. Of 70 drains analyzed, 14 lacked piezometers, 55 were missing turbidity screens, and 18 showed material leakage. Five drains had ruptured, while three were sealed for safety reasons. Prosecutors said the frequency of these incidents indicates progressing internal erosion, known as “piping,” a leading cause of dam failure.
Environmental Impact
The MP-MT report also detailed widespread fish mortality caused by reservoir drawdown and oxygen depletion. More than 22,000 fish were rescued, while over 1,500 were found dead — weighing a total of 212 kilograms. “Species such as carás, tuviras, mussuns and lambaris were found in an advanced state of decomposition in isolated pools with high temperature and low oxygen,” the report said.
Water quality tests showed dissolved oxygen levels dropping below 2 mg/L in parts of the reservoir, considered critical for aquatic life. The presence of unsuppressed vegetation in the flooded area — authorized by the state’s environmental agency against federal water authority guidelines — further degraded water quality.
The environmental damage has also hit the local economy, with tourist and fishing businesses reporting cancellations and reduced access to the reservoir. In the self-rescue zone, meant to be evacuated in case of an emergency, 131 of 181 buildings were unoccupied during inspections, undermining emergency readiness. The reliance on mobile sirens for warnings was deemed fragile.
Company Response
Eletrobras, which took full control of Colíder from Copel (CPLE6.SA) in May 2025 after a R$365 million asset swap, acknowledged the issues in an August market filing, raising the dam’s safety status from “attention” to “alert.”
In a statement, the company said: “All actions undertaken prioritize the safety of people, the environment, and the facility. Eletrobras will continue working closely with regulatory and oversight bodies, including the Public Prosecutor’s Office, with which it has cooperated since the start of operations.”
The company said multidisciplinary teams are working in the region to minimize social and environmental impacts while seeking to restore the dam’s normal operating condition. Copel did not respond to requests for comment.
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