Corrected: Brazil dam collapse reignites debate over storing mining waste

Seabridge Gold

19/11/2015 23:52

(Corrects paragraph 20 to Porgera mine "once considered", not 
is "working on", mixing tailings with coarse waste rock and mud 
to create a product that can be stored on the surface in dumps, 
and adds current technology. Corrects paragraph 21 to "a 
different" wet and dry disposal technology to make clear that 
Teck Resources does not use the same system as considered at 
Porgera.) 
    * Disposing of ore waste big global safety, environmental 
issue 
    * Alternative engineering known as "dry stack" often put 
forward 
    * Cost, climate can make alternatives costly, unviable 
 
    By James Regan and Susan Taylor 
    SYDNEY/TORONTO, Nov 19 (Reuters) - A deadly mud slide at an 
iron ore mine in Brazil has reignited calls for safer ways to 
dispose of millions of tonnes of ore waste held back by man-made 
dams.   
    The disaster at the Samarco iron ore mine is only the latest 
in a series involving tailings - waste in mining parlance - that 
have devastated the environment, and in the case of Samarco, 
killed at least 11 people and left another 12 missing. 
    Tailings are typically a mud-like material and their storage 
and handling has become a major safety and environmental issue, 
since they can be toxic and may need to be kept isolated. 
    The Nov. 5 disaster has been termed an "environmental 
catastrophe" by Brazil after sending waste across two states and 
liability could fall on Samarco's joint owners Vale  VALE5.SA  
and BHP Billiton  BHP.AX   BLT.L . 
    BHP Billiton's chief executive said the miner was reviewing 
all of its dam facilities and that the companies involved in 
Samarco would set up an inquiry with submissions from a wide 
range of experts, including on the history of tailing dams.   
    "That is why we will be entirely open with the findings of 
this report to hope that regulators and companies around the 
world benefit from that learning, so that something like this 
never happens again," Andrew Mackenzie told an analysts call.  
    In Brazil, at least, the industry could face tougher rules 
after a congressman said a proposal for a new mining code would 
include stricter regulations for tailings dams and could make 
dry processing obligatory. urn:newsml:reuters.com:*:nL1N13516V 
    Alternative engineering known as "dry stack" is often put 
forward as a way to mitigate disasters such as Samarco. 
    The process removes water from spent ore using vacuum or 
pressure filters, allowing tailings to be stacked and better 
controlled. 
    Advocates say it can also curb waste seepage into 
groundwater that risks extending environmental liability for an 
operator long after a mine has run its course. 
    But partly due to cost it is rarely employed, meaning that 
thousands of wet tailing dams have been built with more planned. 
    There are 839 tailings dams in the United States alone and 
some 3,500 worldwide, according to the U.S Army Corps of 
Engineers and the United Nations.   
     
    DRY STACKING ECLIPSED 
    A tailings dam rupture at the Mount Polley copper mine in 
British Columbia, Canada, 15 months ago led experts to recommend 
that mines in the province use the best available technology, 
including dry stacking.     
    "Mount Polley started this big cry for dry stack, which is 
an entirely different form of tailings deposition but it often 
doesn't work for any number of reasons," said Lindsay Newland 
Bowker, a policy advisor and consultant on mine tailings waste. 
    Toronto-listed Seabridge Gold  SEA.TO  this year rejected 
dry stacking for a new mine in British Columbia, concluding it 
wasn't feasible in wet, mountainous regions.  
    Even so, some are using the technology.  
    The Greens Creek gold mine in Alaska was among the first to 
use it. The La Coipa mine in Chile's Atacama Desert and Hudbay 
Minerals'  HBM.TO  proposed Rosemont copper mine in the U.S  
state of Arizona also plan to employ dry stacking. 
    A drying process at Australia's Karara iron ore mine leaves 
a chemically inert material that is stacked on a patch of 
outback desert before being returned to the soil. 
    "Where we are seeing dry stack technology being more 
embraced is in areas where water is scarce," said Dirk Van Zyl, 
professor of mining engineering at the University of British 
Colombia.  
         
    "COMES DOWN TO ECONOMICS" 
    The Porgera mine in Papua New Guinea, which is jointly owned 
by Barrick Gold Corp  ABX.TO  and China's Zijin Mining Group 
 601899.SS   2899.HK , once considered mixing tailings with 
coarse waste rock and mud to create a product that can be stored 
on the surface in dumps. This was never implemented and instead 
a plant at the mine removes coarser content from tailings, which 
is then mixed with cement and pumped underground. The finer 
tailings mix is then discharged in a river.  
    A different wet and dry disposal technology is already being 
used by Canada's Teck Resources Ltd  TCKb.TO  at its Elkview 
coal mine, while the Silvertip lead mine in British Columbia 
will use a combination of dry and underground storage. 
    John Werring senior science and policy advisor with the 
David Suzuki Foundation, a Canadian environmental group, said 
more mines might use dry stacking if governments stopped 
approving conventional tailings dams and pushed companies to 
come up with alternatives. 
    "But it always comes down to economics," Werring added. 
    Nonetheless, failure to contain mine waste can be costly.  
    During construction of Papua New Guinea's OK Tedi copper 
mine the tailings dam failed and waste was directly discharged 
into the creeks running into two rivers, destroying thousands of 
hectares of forest and inundating villages and vegetable 
patches. 
    In 1996, then-owner BHP Billiton agreed to a $400-million 
out-of-court settlement for the land holders near the mine and 
five years later divested its majority interest. 
 
 (Editing by Ed Davies) 
 ((jim.regan@thomsonreuters.com; +612 9373-1814; Reuters 
Messaging: jim.regan.reuters.com@reuters.net)) 
 
Keywords: BRAZIL DAMBURST/TECHNOLOGY