Development rates at Carrapateena surpassed expectations for the sixth consecutive month, reaching 5.5km in total.
"It's encouraging to see the rate of development of the decline gain momentum," OZ managing director and CEO Andrew Cole told investors on a teleconference.
Around 60% of the project capital costs have been spent or committed.
The company announced that Downer EDI had been awarded the $660 million Carrapateena underground mining services contract.
The contract starts on July 1 and runs for six and a half years.
Downer replaces Pybar Mining Services, which had been doing an "exceptional job", according to Cole.
Cole said the company was always going to conduct a review at this stage of development, and while it was a close c...