OZ Minerals has announced plans to build a second decline to expand the underground production capacity of Prominent Hill copper-gold mining operation in northern South Australia.
The second access decline will connect existing underground development with the open-pit.
With the new decline, the company will be able to increase the peak capacity of the underground mine by around 30% to about 3.5Mt-4.0Mt per year and decrease unit operating costs.
By reducing unit costs, the company can further minimise cut-off grades.
OZ Minerals managing director and CEO Andrew Cole said: "Prominent Hill's underground mine is proving itself to be an excellent asset and we want to invest in its future.
"Prominent Hill has amongst the lowest C1 costs... and, even on its own, the underground mine is within the bottom quartile of C1 cost producers."
Construction of the second decline will require $12m and is expected to be complete in the next two years. It will increase truck efficiencies underground.
OZ Minerals said that the additional capacity will allow the company to bring forward underground production during 2018-22.
The company also plans to spend around $4m in 2016 to target resource to reserve conversion.
Prominent Hill consists of Malu open-pit mine, and Ankata and Malu underground mines.
The operation came on stream in 2009, and currently produces more than 100,000t of copper every year.
Image: By building the new decline, OZ Minerals can increase the peak capacity of the underground mine by around 30%. Photo: courtesy of OZ Minerals Limited.