In January, the Perth-based miner projected completion of the plant for end of March 2012 but has since cited “throughput and yield issues” as cause for the delay.

In a statement released Tuesday, Wesfarmers said the delay in commissioning the plant would see an increase in Curragh’s unwashed high-ash pulverised coal injection coal sales on the spot seaborne PCI market.

“Sales mix for the 2012 financial year is now forecast to be 39% hard coking coal, 21% semi-hard coking coal and 40% PCI,” the company said.

While a Wesfarmers spokesperson was quoted in the Australian Financial Review saying the company was restrained by commissioning requirements and bad weather, managing director Stewart Butel was upbeat about maintaining performance despite the delay.

“Curragh’s metallurgical coal sales are forecast to be in the previously announced range of 6.8 to 7.2 million tonnes for the 2012 financial year, subject to satisfactory commissioning of the new coal preparation plant, no significant wet weather and satisfactory rail and port operations,” he said.

Second quarter metallurgical coal prices for most of Curragh’s customers have been cut by 11% compared to the first quarter 2012.