Ca­dia shut­down af­ter dam col­lapse

The Australian Mining Review - - NEWS - EL­IZ­A­BETH FABRI

NEWCREST Min­ing will fall short of its pro­duc­tion guid­ance in FY18 af­ter a tail­ings dam wall col­lapse at Ca­dia gold mine last month forced op­er­a­tions to a stand­still.

While it was too early to pro­vide an in­di­ca­tion of dam­ages, the miner said the dam col­lapse would “ad­versely im­pact guid­ance for FY18”.

The tail­ings wall breach on 9 March in­volved a lim­ited break­through of ma­te­rial at the north­ern dam em­bank­ment, which was con­tained in the ad­ja­cent tail­ings dam to the south.

Newcrest said cracks were iden­ti­fied ear­lier that day dur­ing a reg­u­lar in­spec­tion be­fore the dam failed later that even­ing.

“When such cracks were no­ticed the site team quickly en­gaged an in­de­pen­dent geotech­ni­cal con­sul­tant to as­sist Newcrest’s geotech­ni­cal en­gi­neers at Ca­dia with an in­spec­tion and pre­lim­i­nary as­sess­ment of the em­bank­ment,” it stated.

At the time, Newcrest con­firmed there were no in­juries or fur­ther threats to safety, but as a pre­cau­tion it would sus­pend all min­ing and pro­cess­ing op­er­a­tions at the mine un­til fur­ther no­tice.

On 27 March, af­ter a two and a half week break, Newcrest recom­menced min­ing op­er­a­tions at Ca­dia East with mined ore to be stock­piled at sur­face un­til pro­cess­ing re­sumes.

Newcrest said it was un­der­tak­ing work on mul­ti­ple re­cov­ery sce­nar­ios, in­clud­ing al­ter­na­tive tail­ings lo­ca­tions such as the old Ca­dia Hill open pit.

“Newcrest con­tin­ues to work with the NSW reg­u­la­tors on per­mit­ting the Ca­dia Hill open pit tail­ings op­tion and has com­menced pro­cure­ment of some of the nec­es­sary equip­ment to al­low this pos­si­bil­ity to be utilised if ap­proved,” Newcrest stated.

“A pro­hi­bi­tion no­tice is­sued on de­posit­ing tail­ings in the north­ern tail­ings fa­cil­ity re­mains in place.”

Newcrest man­ag­ing di­rec­tor and chief ex­ec­u­tive San­deep Biswas said the miner did a group wide review of all of its tail­ings fa­cil­i­ties fol­low­ing BHP’s Sa­marco tail­ings dam dis­as­ter in Brazil in Novem­ber 2015, with Ca­dia’s dams re­viewed in­de­pen­dently in 2016 and 2017.

“This was a to­tal sur­prise to us given all of the re­views of the dam and cer­ti­fi­ca­tion that we’ve got so we will have to do a lit­tle bit of soul search­ing there clearly,” Mr Biswas said.

This wasn’t the first time Ca­dia pro­duc­tion has taken a hit.

In April 2017, a mag­ni­tude 4.3 earth­quake near Ca­dia forced the mine to shut for three months, which re­sulted in a 48 per cent drop in prof­its for Newcrest.

Newcrest pre­vi­ously de­clared it would pro­duce be­tween 680,000 and 780,000 ounces of gold and about 70,000t of cop­per out of Ca­dia in FY18; in the first half, Ca­dia pro­duced 300,737oz of gold and 30,459t of cop­per.

The North­ern and South­ern (fore­front) tail­ings dam at Ca­dia.

Im­ages: Newcrest Min­ing.

An aerial view of the fail­ure zone.

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