The two studies now running are the Sulphide Expansion Project (SEP), an examination of the viability of a “super pit” concept involving the mining of low-grade sulphide mineralisation below the oxide zone and a proposed increase in mill throughput up to about 20Mtpa, and the I Series Project (ISP), an underground evaluation based on bulk mining methods.

In December, Newcrest approved a $29.6 million investment for the next stage of ISP, which involves developing a decline down to the underground orebody at around 1000m below the surface.

Granny Smith control room ... "The big challenge is to maintain cashflow ... between the decline in production from Sunrise and bringing Wallaby up to speed." - Bill Plyley, resident manager.

Greeff said the decline should reach the deposit by the end of this year, with a final go-ahead decision expected in 2001. “The reef is a higher grade and thicker than we are currently mining,” he said. “It should average 10-15gpt, with the thickness ranging up to a couple of metres.”

Meanwhile, the SEP pre-feasibility study should be finished by mid-year. Brokers estimate a capital cost in the order of $US200 million.

“It would involve fairly conventional treatment, but the ore is relatively low-grade at around 1gpt,” Greeff said. “However, keep in mind that Cadia is around 0.7gpt gold, and they only get around 70% recovery. We are looking at 1gpt, 30% more gold, and 90% recovery. It certainly looks economically attractive compared with Cadia, but you still have to line up all your ducks.”

At the envisaged throughput rates, the SEP could double Telfer’s production to around 600,000ozpa. However, the expansion — if approved — is still three or four years away, while existing open cut reserves are sufficient for only two years.

“There may be a year or two of lower (open cut) production or no production — we don’t know at this stage,” Greeff said. “Obviously we are doing what we can to fill in that gap. Like Boddington, we have been stretching it out for a few years, and it looks like it might go for a bit longer.”