January 29, 2019 / 7:04 PM / 3 months ago

Vale eyed dam design changes in 2009 that may have prevented disaster

    By Marta Nogueira and Ernest Scheyder
    RIO DE JANEIRO/HOUSTON, Jan 29 (Reuters) - Brazilian miner
Vale SA            identified concerns around its tailings dams
in 2009 and studied but did not implement several steps that
could have prevented or lessened the damage from last week's
deadly disaster, according to a corporate presentation seen by
Reuters.
    A tailings dam, used to store the muddy detritus of the
mining process, collapsed on Friday, killing at least 65 in one
of Brazil's largest industrial accidents on record.             
    The Brumadinho disaster, coming just over three years after
a similar incident at another mine partially controlled by Vale,
has fueled calls for a management overhaul and erased more than
70 billion reais ($18.61 billion) in Vale's market
value.            
    But a decade ago, the world's largest iron ore miner was
considering ways to use fewer tailings dams, including
alternative uses for the waste rock, according to the 73-page
presentation.
    The presentation pointed to the rising volume of tailings
produced at the company's mines, with some locations producing
hundreds of thousands of tonnes of tailings daily.
    The report suggested Vale make building materials from
tailings, including bricks, a step that would give the company
another revenue source and lessen the volume needing to be
stored using dams.
    The 2009 Vale report had recommended the company undertake a
project to be called "Zero Dams" that would have involved drying
out tailings, among other steps. It was not known whether the
report reached the top levels of Vale management nor why it was
not implemented.
    Vale declined to comment. The report's author, Paulo Ricardo
Behrens da Franca, left Vale a year after submitting it and now
works as an industry consultant. Reached by Reuters, he did not
comment.
    
    'INHERENTLY DANGEROUS STRUCTURES'
    Vale's Brumadinho facility was built using the cheapest and
least-stable type of tailings dam design, a commonly used
structure in mining known as "upstream construction." 
    Chile, Peru and other earthquake-prone countries ban the
design, in which tailings are used to progressively construct
dam walls the more a mine is excavated. Brazil is not as
earthquake-prone as its western neighbors, but even small
seismic activity has been shown to affect tailings dams.
    Because these types of tailings dams are waterlogged, they
are easily susceptible to cracks and other damage that can cause
bursts like the one that occurred last week near Brumadinho.
    "A tailings dam may look safe, but it's still retaining a
lot of moisture behind it," said Dermot Ross-Brown, a mining
industry engineer who teaches at the Colorado School of Mines.
"They're inherently dangerous structures."
    Tailings dams tend to be shorter in height than conventional
water dams, but often are far wider in span.
    The disaster's cause remains unknown. Vale said the dam had
not received tailings for about two and a half years and was in
the process of decommissioning, a step that should have lessened
risk, engineers said.
    "It's really puzzling to me this happened as the (dam) was
closing," said Cameron Scott of SRK Consulting, a mining
engineering firm. "This disaster will make future mine
permitting harder."
    The dam had passed a September 2018 inspection by the German
firm TUEV SUED AG and Vale Chief Executive Fabio Schvartsman
said equipment had shown the dam was stable on Jan.
10.            
    On Tuesday, Brazilian state prosecutors arrested three Vale
employees and two TUEV SUED employees.                
    
    RISK
    Brazil has nearly 4,000 dams that are classified as having
"high damage potential" or being at high risk, with 205 of those
dams containing mineral waste, the country's Regional
Development Minister Gustavo Canuto said.             
    Analysts and engineers said that the Brumadinho disaster
will hopefully push the industry to stop storing wet tailings
and instead move toward the more-expensive-but-safer process of
storing dry tailings. 
    That process requires drying the tailings and storing them
on-site, abrogating the risk of a dam burst. The approach is
becoming more popular in Canada and other countries with
stricter mining regulations.    
    "The industry doesn't yet fully realize the risk its taking
on with those type of wet tailings dams," said Matt Fuller of
Tierra Group International Ltd, a tailings engineering
consulting firm. 
    Officials in Brazil's Minas Gerais state, where the disaster
occurred, say they are now going to push for legislation
requiring dry mining and forcing miners to tear down tailings
dams when they are located above communities.
    A similar proposal failed last summer, with its defeat
attributed by the bill's sponsor to lobbying pressure from
mining companies.
    Brazil is still reeling from the 2015 collapse of a larger
dam, owned by the Samarco Mineracao SA joint venture between
Vale and BHP                 , that killed 19 people.
    After Samarco, the International Council on Mining and
Metals (ICMM) issued updated guidelines for its members to try
to safeguard tailings dams used to store waste left over from
mining operations.
    The ICCM said on Saturday that the mining industry still has
"lessons to learn" from Samarco and similar events.            
    Mining companies typically hire engineering firms that
specialize in tailings dams to build the structures, not
necessarily dam contractors themselves, a step that some
industry observers hope changes soon.     
    "The mining companies are not placing dam safety at the
forefront of their preoccupations," said Emmanuel Grenier, a
spokesman for the International Coalition of Large Dams (ICOLD),
a non-governmental organization focused on dam engineering.
    The group "is recommending that dams, especially large dams,
be built by dam professionals, but it is too rarely the case for
tailing dams," Grenier said.
($1 = 3.7614 reais)

    
 (Additional reporting by Barbara Lewis in London, Christian
Plumb in Santiago, Gram Slattery in Belo Horizonte and Maria
Carolina Marcello in Brasilia
Writing by Ernest Scheyder; Editing by Amran Abocar and
Marguerita Choy)
  
0 : 0
  • narrow-browser-and-phone
  • medium-browser-and-portrait-tablet
  • landscape-tablet
  • medium-wide-browser
  • wide-browser-and-larger
  • medium-browser-and-landscape-tablet
  • medium-wide-browser-and-larger
  • above-phone
  • portrait-tablet-and-above
  • above-portrait-tablet
  • landscape-tablet-and-above
  • landscape-tablet-and-medium-wide-browser
  • portrait-tablet-and-below
  • landscape-tablet-and-below