Australian mining firm Newcrest Mining Ltd has confirmed there was a ‘limited breakthrough’ of tailings material at the Cadia northern tailings dam embankment in New South Wales on 9 March, with the breakthrough contained within the southern tailings dam.
Newcrest said it is monitoring the impact carefully and has observed no environmental damage. There were no injuries as a result of the event and
Newcrest believes there is no ensuing threat to personal safety.
Geotechnical analysis has commenced on possible repair options of the failure zone. Work has also commenced on multiple recovery scenarios including alternative tailings locations such as the old Cadia Hill open pit, which is already the subject of a prefeasibility study to assess suitability for tailings disposal.
An area of the embankment slumped late Friday 9 March 2018 following the identification of cracks earlier in the day in the dam wall during a regular inspection. When the cracks were noticed, Newcrest said the site team quickly engaged an independent geotechnical consultant to assist its geotechnical engineers at Cadia with an inspection and preliminary assessment of the embankment.
As a precaution Newcrest stopped depositing tailings into both dams late in the day of 9 March 2018. To allow site management to focus on the evaluation of the event and remediation plans, Newcrest progressively suspended all mining and processing operations at Cadia, fully effective on 10 March 2018.
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 of the wall has been detected since Friday night, said Newcrest.
New South Wales regulators were notified immediately and Newcrest said it is working closely with them until the review is completed, supported by independent geotechnical consultants. Local landowners and residents downstream of the tailing facility have also been kept informed.