“A range of construction and design flaws”: the language seems hardly adequate to describe last year’s disaster in Brazil that saw a tidal wave of muddy red sludge explode out of a tailings dam – let alone explain it.
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BHP Billiton, and its partner Vale, have set aside up to $1.3bn (£1bn) to cover costs arising from the fatal accident that occurred at an iron ore mine in Brazil previous year.
The Fundao dam-burst disaster caused a huge mudslide which killed 19 people and polluted a river.
“The panel restricted its work in explaining the physical basis of the failure”, Canadian engineer Norbert Morgenstern, who led the panel, told the newswire, adding that investigators had avoided “any evaluation of alternates related to design or construction”.
A separate police investigation has accused iron miner Samarco of wilful misconduct, which the firm denies.
In a statement, Dean Dalla Valle, BHP Billiton’s chief commercial officer, said the dam failure had “a devastating impact”.
“Given the legal proceedings, it wasn’t appropriate that we actually try to use this process to attribute blame”, he said, adding that “we have no reason to believe that anyone at BHP had any information that indicated that the dam was in danger of collapsing”.
The authors said the original design had to be changed, which used a type of sand created to prevent a process known “liquefaction” – where soil loses its strength and stiffness when pressure is applied to it.
Asked whether cost-cutting since 2012 may have been a factor in the dam’s failure, he said “absolutely not”, with no evidence anyone had prioritised production over safety.
There was increased weight on the tailings as the height of the dam was raised to more than 100m.
A small quake on the day of the dam burst may also have “accelerated” the failure, the report added. “Quite the opposite, it showed the company altered the project in a way that would not have been permitted”.
BHP Billiton said it had reviewed 10 of its biggest tailings dams and found they were stable, but was taking steps to improve risk management.
Analysts say the problems with the tailings dam should have been obvious to management, but BHP insists no one is to blame.
The three companies involved in March struck a $US2.3 billion rehabilitation agreement with government authorities in Brazil to cover clean-up costs and damage from the disaster.
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BHP Billiton said it had learnt from the tragedy. Vale’s shares rose 2.4% on Monday and BHP’s shares rose 1% in early trading on Tuesday.
