The mine is still under a Prohibition Notice from the NSW Mining Inspectorate, which bans the extraction of ore in Panel Cave 1 and Panel Cave 2.
Damage to the Cadia East underground mine infrastructure was minimal.
The majority of work being undertaken relates to increasing the dynamic ground support capacity around known fault structures and rehabilitating ground support in areas hit by the seismic event.
Newcrest has 10 trucks conveying about 65,000t of ore to the processing plant each day from the low grade Cadia Hill stockpiles. That equates to about 24 million tonnes per annum.
This ore has about 0.35 grams per tonne gold and between 0.1% and 0.12% copper.
It is being processed at a recovery rate of 70%.
Newcrest has about 20Mt of economically viable stockpile material available for processing, which should be enough to see the mine through to the reopening of PC1 and PC2 production.
Subject to the lifting of the Prohibition Notice the expected outlook for gold production in the 2017-18 is between 650,000 ounces and 750,000oz.
PC1 has been inspected and the rehabilitation plans on remediating and improving ground support, where required have been made. Work on rehabilitating ground support has started.
An assessment of the crusher chamber and associated infrastructure was conducted and ground support rehabilitation work in the crusher chamber started with resin injection. That will be followed with the installation of additional conventional cables and bolts to restore dynamic capacity using long reach drilling equipment.
Subject to the lifting of the Prohibition Notice, production from PC1 is expected to restart in the first quarter of FY18. Material will initially be trucked to the PC2 crushers. When access to PC1 crusher becomes available ore production is expected to increase.
In PC2 work has continued on rehabilitating and upgrading the ground support there.
Subject to the Prohibition Notice being lifted it is assumed PC2 ore production will restart in the first quarter of FY18.
Work has been prioritised to resort PC2 production safely and as quickly as possible while the remainder of the ground support upgrades are completed in PC1 and other areas of the mine.
Moves are also being made to recommission the Ridgeway sub-level cave. First ore is expected to be available in June.
It is estimated there is about 600,000t of accessible ore at 0.35gpt gold and 0.3% copper.
The Ridgeway sub-level cave has a material handling system that can deliver ore directly to the processing plant.
The feasibility study on the proposed expansion of the Cadia processing plant has been completed, however, approval of the study is pending while the team at site is focused on finalising the remediation work.
According to Geoscience Australia the seismic event at about 2.30am on April 14 had a magnitude of 4.3 on the Richter Scale with an epicentre about 4km from the Cadia operation.
No injuries were sustained in the incident.
Newcrest has its own systems to record seismic events. Its sensors indicated a quake of 3.1 local magnitude scale seismic event. Those recordings indicate there was a fault slip about 200m from the southern end of PC1.
Newcrest’s technical teams are trying to fully understand the seismic event and its impacts.
The level of upgraded ground support required has been reviewed by independent geotechnical experts and deemed to provide sufficient capacity to manage the impact of future local and regional seismic events.
