Copper-gold miner Newcrest has suspended operations at its Cadia mine after a tailings dam embankment slipped on March 9.
Newcrest has advised the market its FY18 will not meet earlier guidance because of the shutdown.
Cracks were observed early on March 9, during a regular inspection of the dam wall. In the late afternoon, a “limited breakthrough of tailings material” took place. The breakthrough is currently contained to the lower, southern tailings dam, and there were no injuries recorded.
Newcrest has been forced to stop depositing tailings in both dams, thus has been forced to temporarily close the mine, which makes up a significant amount of Newcrest’s annual production.
“When [early on March 9] cracks were noticed the site team quickly engaged an independent geotechnical consultation to assist Newcrest’s geotechnical engineers at Cadia with an inspection and preliminary assessment of the embankment,” the company said.
“The area around the tailings dam has been secured, and a comprehensive geotechnical monitoring system has been implemented, involving radar and cameras, to allow real time assessment of ground movement of the dam wall.”
No further movement has been detected since March 9, the company said.
Communities downstream of the tailings dam have been kept up-to-date since the incident.
“The tailings material is a slurry of finely ground rock, water and a low level of benign processing reagents,” the company said. “Cadia does not use a chemical reduction process to recover gold – that is, the gold extraction process does not involve the use of substances such as mercury, cyanide and arsenic.”
Newcrest closed on the ASX on March 9 at $21.59. The next day of trading, March 12, it dropped to a close of $20.60. It declined again on March 13 to $20.20.
The company has not yet given an estimated date for the re-opening of Cadia.