Macarthur's coal shipments fell 23.1% during the December quarter from the same period last year to 955,000 tonnes.
The company blamed the fall on construction works at Dalrymple Bay Coal Terminal, which is in the throes of expanding.
Macarthur said shipments out of Dalrymple Bay were at their lowest level in four years. The port shipped 40.3Mtpa during the December quarter against forecasts of 50.1Mtpa.
Shipping delays also hurt Macarthur in demurrage costs, the Queensland producer averaging $A5.95/t during the December quarter.
Despite this the company managed to export some coal through Abbot Point terminal, reducing the impact from the Dalrymple cutbacks.
The Coppabella open cut produced 497,000t during the December quarter, down on the corresponding period. Macarthur attributed the fall to rainfall, an eight day shutdown over Christmas and high stockpiles.
From early December to January 21, 678mm of rain fell on Coppabella - more than the annual average.
Macarthur said a significant amount of water had accumulated in the pit which it would need to remove via pumping prior to resume coal mining.
At Moorevale production levels were better - the mine produced above budget and 60% higher than the same period last year. This was despite a minor failure in the advancing highwall.
While rainfall at Moorevale was much lower than Coppabella, water had still entered the pit.
Pumps are removing the water and while overburden mining had resumed, the company expected delays in accessing coal.
Despite all the rain, Macarthur said it still expected to reach projected sales of 4Mtpa in the 2008 financial year.