November 24, 2017

Moral from Brazilian dam disaster: the perils of compromising design

An inquest into the November 2015 disaster at Samarco mine tailings dam co-owned by Vale SA and BHP Billiton in Brazil has highlighted, once again, the often ignored significance of proper design in mine development. Indeed, this is an area which mining companies should pay close attention to.

A technical report commissioned by the co-owners has singled out design flaws as one of the possible causes of the collapse of the tailing dam which claimed lives of nineteen people nearby village. The accident, in which 19 people from a nearby village were buried in toxic waste, has been described as the “worst environmental disaster” in recent memory.

However, the 76-page report by an expert panel, headed by Canadian geotechnical engineer, Norbert Morgenster, did not apportion blame to anyone but elected to focus on the root causes.

“It is a very detailed, technical report 10 months in the making,” BHP’s chief commercial officer, Dean Dalla Valle, was quoted by AFP describing the report. He said BHP Billiton did not believe that anyone was culpable from the company was culpable.

The report says the original dam design was robust. But design changes, which had to be made to accommodate construction difficulties eventually caused “liquefaction”, rupturing the dam. Liquefaction is a process where sediments lose their strength and act like a liquid.

The report underlines: “Together with the revised design there was a fundamental change in the design concept whereby more widespread saturation was allowed and accepted.”

“This increase in the extent of saturation introduced the potential for sand liquefaction.”

In the intervening time, Samarco is facing billions of dollars in legal claims for clean-up costs and damages.

Work at the Samarco mine has been halted since the disaster and both BHP and Vale have ruled out operations resuming this year.

Source: AFP via Inetbridge and adapted for African Mining Brief Online

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