RIO DE JANEIRO—Brazilian mining firm Samarco Mineração SA was alerted to “severe” structural problems in one of its dams a year before it collapsed but didn’t take appropriate measures to fix them, an engineer who worked on the dam said.
Dam engineer Joaquim Pimenta de Ávila said he was consulting for Samarco when, in September 2014, he inspected a crack in its Fundão waste-storage facility. He believed it indicated the beginning of a break and said he recommended that Samarco step up monitoring and reinforce the Fundão dam with a buttress.
About 14 months later, the dam collapsed, releasing an avalanche of sludge that buried a rural village, killed at least 17 people and traveled more than 400 miles.
Considered one of Brazil’s worst environmental disasters ever, the Nov. 5, 2015, incident has triggered a criminal investigation and a roughly $5 billion civil lawsuit by authorities against Samarco and its parent companies, mining giants Vale SA and BHP Billiton Ltd.
Samarco disputed Mr. Pimenta de Ávila’s account and said it followed his recommendations. In an interview Sunday, company lawyer Maurício Campos Júnior said it never received any warning of an “imminent” rupture from any of its consultants.
“Cracks or surges can occur in any dam,” Samarco said. “The operator’s duty is to report them, evaluate them and treat them adequately, with reports, technical recommendations and contracted projects, as Samarco always did.”
The company didn’t say whether it constructed the buttress Mr. Pimenta de Ávila says he recommended, but Mr. Campos said Samarco was in the process of strengthening the dam at the time it failed.
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