Saturday 8th of August 2020

extreme risk of causing environmental damage by mining dam failure...


Five dams used to store mining waste are at “extreme” risk of causing environmental damage if they fail, according to a review by BHP, the world’s biggest mining company.

BHP said in a presentation on Friday that four tailings dams in Australia and one in the US were ranked at the highest level of risk, and had the potential to cause serious damage to the local environment and cause scores of deaths in the case of a collapse.

The company revealed the results of a risk assessment into its dams after two high-profile fatal dam failures in Brazil that collectively killed hundreds of people. 

In a presentation to investors, the mining company said 16 of its 67 tailings dams which hold mining byproducts were “high risk”. The risk relates to the damage which would be caused to the environment and to human life if they collapsed.

The company said the “extreme risk” rating given to five of its dams means more than 100 people would be killed and there would be major environmental and economic and structural damage.

In 2015 a dam in Brazil, which was being run with BHP in a joint venture, collapsed killing 19 people and devastating the local environment.

The company said it had a range of controls to manage the risk, including surveillance and monitoring. BHP said in its presentation: “The dam risk review identified no immediate concerns regarding dam integrity. Subsequently we have undertaken dam safety reviews which provide assurance statements on dam integrity.”


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Failure Mechanisms

Forensic analyses of ash pond and tailings dam failures are hindered by the massive destruction that washes away evidence from the failed zone. Nevertheless, forensic investigations of notable dam failures have identified several mechanisms, including overtopping due to water mismanagement (Merriespruit, South Africa, 1994) (6), shear failure of foundation soils (Mount Polley, Canada, 2014) (7), and shear of compressible low-permeability tailings placed near the perimeter of the impoundment (Samarco, Brazil, 2015) (8). These postfailure investigations have often found the convergence of more than one weakness in the design, construction, and/or operation of the dam.

The Brumadinho dam was closely observed, and abundant laboratory tests, in situ tests, and monitoring data were available. Furthermore, it failed 3 years after closure, contrary to the expectation that geotechnical structures become more stable over time. Indeed, an August 2018 audit concluded that the dam was stable (9). That an apparently closely monitored and inactive dam failed catastrophically less than half a year after being audited suggests that there may be gaps in the scientific understanding of waste-storage facilities and of time-delayed triggers of failure. Filling these knowledge gaps will require changes in how coal ash and mine tailings are characterized, improved test protocols, and enhanced physics-informed data interpretation.

Tailings dams and ash ponds experience various time-dependent processes, such as gradual strains associated with pore-water pressure dissipation or creep, internal erosion and piping, and the migration of fine grains that can cause the gradual clogging of internal drainage pathways and the rise of fluid pressure within the impoundment. These processes occur throughout the entire life of the structure, and their effects can take years or even decades to become evident. By contrast, most laboratory experiments conducted on tailings and coal ash samples last from a few hours to a couple of weeks. This discrepancy in time scales points to the need for continuous monitoring of these structures to properly assess their evolution in time.

The large mudflows that follow dam failures imply the presence of loose, water-saturated sediments that want to contract upon shear: Water cannot drain fast enough, and grains become temporarily suspended, forming a dense fluid (liquefaction). However, laboratory studies that attempt to emulate the hydraulic deposition used to deliver ash and tailings to the pond often fail to predict liquefaction under monotonic loading until impoundment depths exceed 15 to 20 m. In other words, these studies suggest that the hydraulic deposition of ash and tailings does not necessarily produce a contractive, liquefiable sediment.


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think steel... think copper...

BHP has launched the second phase of its ‘Think big’ advertising campaign, spotlighting their role as a resource provider and in Australia’s economy.

The campaign has been produced by Big Red, the same agency as the initial phase of ‘Think Big’, launched in 2017.

The first 30-second TV spot focuses on steel, which is produced from iron ore and coal, and its role in growing cities.

“We are continuing to tell the story of how the people of BHP develop and deliver the resources that underpin global development and support Australia’s economy,” says BHP chief external affairs officer Geoff Healy.



Think copper

Electric cars need four times as much copper as standard cars and at BHP we’re proud to be one of the largest producers of copper in the world.

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THINK Steel makes Gus think of the 1960s American guzzlers:





THINK Copper reminds Gus of times when Nixon was in a bind about the escalation of the war in Vietnam...:




Pictures in Gus collection of stuff. 1960s/1970s old American magazines...


Note: according to Gus's discreet long investigation of steel supplies and such, the chinese steel is about 50 per cent substandard. That is to say that in its supplies to the world (including Australia) 50 % of it is as per specification of the order and about 50 % is below specs (in strength and hardness) for the same order. Wholesalers who buy chinese steel though cannot send the "lower quality" stuff back to China — and have to flog it whichever way they can. One wonders if some of this stuff ended up in the construction of say the Opal Tower in Sydney... 


We know that BHP is far more precious about its steel quality specs.

shortage of iron ore...

It's the grim nature of raw economics that when a river of toxic sludge surged down a Brazilian valley killing about 300 people in January, things really looked up for the Australian budget.

The disaster, caused by the collapse of a tailings dam at Vale's iron ore mine, brought a bonanza to Treasury coffers as the Brazilian company's Australian competitors Rio and BHP raked it in.

Iron ore, priced at $72 a tonne at the time of the lethal sludge slide, started steadily increasing as Vale's production slipped, reaching $122 a tonne. It's since dipped to $91 but this is still 65 per cent higher than the $55 a tonne forecast by Treasury for the current financial year.

Now, before your eyes glaze over, just remember this: every $10 over the forecast iron ore price generates a whopping $3.7 billion for the federal budget over the year.

This bumper iron ore story has masked troubles afflicting the economy; it's why the Prime Minister and the Treasurer can boast that while Germany, Britain and Singapore went backwards in the June quarter, the Australian economy continues to grow.

Twenty-eight years of uninterrupted growth is an extraordinary record, even if another's misery has been to our benefit.


But how to keep that growth going is in contention, especially in what Josh Frydenberg described this week as a "new world with low interest rates, relatively low unemployment and low inflation".

Beneath the Treasurer's Pollyanna performance on Wednesday, when he sugar-coated the worst economic data since the GFC, the Government appears to be in hot disagreement with the Reserve Bank.

Key people within the Morrison Government believe the RBA should have cut official interest rates harder and sooner. They also believe Governor Philip Lowe has more slashing to do, despite the cash rate already being at an historic low 1 per cent.

The tension between the coalition and the RBA isn't anywhere near the outright hostility seen in the United States, where Donald Trump has asked whether Federal Reserve chair Jerome H Powell is a "bigger enemy" than Chinese President Xi Jinping.

But the Morrison Government is clearly of the view that the Reserve should be doing more to stoke life into the stuttering economy.


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