OZ Minerals, in its latest quarterly results, has confirmed that Byrnecut Group will sink the Wira shaft at its Prominent Hill copper-gold operation in South Australia.

Byrnecut has extensive experience of shaft sinking in the Asia-Pacific region, according to OZ. It is also the underground mining contractor at its Prominent Hill and Carrapateena mines, which, the miner says, will assist in the integration of activities as it continues to increase production rates from Prominent Hill.

Back in August, the OZ Minerals Board approved construction of a hoisting shaft at Prominent Hill, paving the way for a mine life extension and throughput expansion.

Coming with a pre-production capital expenditure of A$600 million ($449 million), the Wira Shaft expansion project will see the underground production rate increase to 6 Mt/y from 2025. At this point, the average annual copper and gold production is expected to be circa-54,000 t and circa-108,000 oz, respectively, some 23% more than expected in the current trucking operation.

Back then, OZ said sinking of the shaft was expected to commence in the March quarter of 2022. Mining and installation of underground and surface infrastructure was scheduled for completion along with commissioning of the Wira shaft at the end of 2024, with nameplate capacity expected in the first half of 2025.

In an update last week, OZ said the shaft collar construction site works had commenced and were due for completion in January 2022.

“The award of the shaft sink contract followed after a lengthy period of Early Contractor Involvement working through various contractors’ proposals and then selecting the best for project outcome with reduced risk and an effective delivery period at an economic cost,” it said. “The designs for the shaft sinking equipment are progressing well. Orders have been placed on the mill runs for the headframe steel with delivery scheduled for December 2021.”

The shaft design comprises a 1,329-m-deep, concrete-lined shaft with a diameter of 7.5 m. Construction of the shaft will be via conventional strip and line method, with the sinking period approximately two years.

The shaft mine expansion also enables generational province potential with further mine life extensions possible as 67 Mt of resource remains outside the shaft expansion mine plan, OZ Minerals says. Further, an exploration program has also identified that mineralisation remains open at depth beyond the current resource boundary, potentially accessible via the shaft.

Prominent Hill produced 17,565 t of copper and 41,245 oz of gold in the September quarter.