By Sally Heathcote
The mining fraternity – including those in Broken Hill – have been keenly watching events unfold at Australia’s largest underground mine, Cadia East, following an evacuation due to ‘instability’.
The temporary closure of the gold and copper mine, owned and operated by Newcrest, has seen some workers redeploy to Broken Hill to temporarily fill shortages in the industry here.
Cadia East is 25km south-west of Orange and 900km east of Broken Hill in central western New South Wales.
Cadia Valley Operations includes the Cadia East block cave mine, the Cadia Open Pit, the Ridgeway Mine – which is on care and maintenance – and the processing plant.
Cadia East produces more than 10 times the amount of ore mined across Broken Hill each year.
But on July 22 the mine was evacuated when a new ventilation rise hit an underground aquifer, creating instability. The potential for water inrush was an immediate concern.
The Environmental Protection Agency (EPA) and the NSW mining regulator immediately began investigations and confirmed that water had flowed into the ventilation shaft.
A road bordering the mine was closed as a precaution. Newcrest’s site general manager, Aaron Brannigan, said that initial assessments using remote camera technology were used to visually assess the situation and ensure safe access procedures were followed.
Drill rigs and grout pumps have since been mobilised to install a grout curtain around the rise to minimise the water inflow. The rise is also being backfilled with inert rock material to stabilise it. The recovery plan is on track to allow the mine to start operations again in late August.
While underground mining remains suspended since the incident, surface stockpiles have kept the mill running and could do so until September.
According to industry sources there have been no job losses, with highly skilled staff who are in short supply across the industry redeployed to other mines in Newcrest’s portfolio.
Some of Cadia’s shotcrete and cable bolting workers have been redeployed temporarily to Broken Hill which has assisted the mines here which have also suffered labour shortages during Covid.
Over the years Broken Hill miners have successfully overcome their own geotechnical hurdles.
So-called ‘creep’ events have resulted in extensive surface subsidence on the old BHP mining blocks a number of times in the past but extensive backfill of tailings using waste rock,is used in Broken Hill today to avoid subsidence issues.