The Australian miner also blamed previously announced geotechnical difficulties at its Rocglen mine for the reduction. Company representatives also said costs incurred at Narrabri are not expected to be material, adding that controls have been implemented to stop a recurrence.

Mining in Narrabri’s third longwall panel began in March with a different configuration from the first two longwall panels. Two extra roof supports, meanwhile, were added to the tailgate end of the longwall to improve safety and reduce costs, according to Whitehaven officials.

However, floor horizon controls at the longwall face-line’s tailgate end were lost, officials added, culminating in a differential between floor levels in the mine, which led managers to cease production. Whitehaven has since implemented a timetable, which would affect output, according to officials.