The largest of three mills at BHP Billiton’s Olympic Dam processing operations in South Australia suffered an electrical failure in late January and was shut down for maintenance. A diagnostic review revealed damage to the motor stator coil. A repair and remediation plan was being developed, and the company said the mill would be out of service for approximately six months.

BHP Billiton plans to use this period to bring forward some of the maintenance activities and preparatory work required to support a planned extension of the underground Olympic Dam mine’s southern mine area.

The mill is the largest of three mills at Olympic dam. The two smaller grinding mills will continue to operate at full capacity. However, as a result of the suspension of the primary mill, other processing activities on site are being scaled back.

As of mid-February, BHP Billiton was estimating a loss of copper production of between 60,000 and 70,000 mt, with the majority of the loss anticipated before the end of its financial year to June 30. A return to full production is anticipated by the end of the September.