Kestrel Mine, Central Queensland, Australia

The Kestrel mine is an underground operation located 40km north-east of Emerald in central Queensland, Australia. Formerly known as the Gordonstone mine, it is a major provider of coking and thermal coal, supplying close to 4.2Mt annually.

The mine is operated by Kestrel Coal on behalf of a joint venture formed between Rio Tinto Coal Australia (RTCA) and Mitsui Kestrel Coal Investment, a subsidiary of Mitsui Group. RTCA owns an 80% stake in the mine, acquired in 1999 from ARCO. The remaining 20% is held by Mitsui Kestrel.

The mine is undergoing a $1.1bn expansion to extend its resources. As of 31 December 2008, the mine contained an estimated 131Mt of reserves.

The expansion, scheduled for completion in 2012, will increase the mine's capacity to 5.7Mt/y and will extend its life to 2031.

Upon completion, the mine will cover 9,500ha of the mining lease area and 1,800ha of mineral development licences.

Geology

The mine lies within the Bowen Basin, a significant Permian-aged coal basin extending 600km in length and 250km in width. Coal seams hosted within the basin are characterised by significant variations in rank and quality. Coal ranks range from anthracite to low-volatile bituminous along the basin's north-eastern edge that remain structurally disturbed. The deposits in this zone are structurally complex.

The central section of the basin contains medium to high-volatile bituminous coal and high-grade coking coal. Mild structural deformations characterise the deposits in this zone.

Towards the south-west, the coal ranks drop below coking range, followed by a loss of coking properties. The region's significant deposits include low ash non-coking coal that remains unaffected by significant structural deformation besides normal faulting.

Across the basin, coal-bearing horizons are hosted at several stratigraphic levels. Deposits of significant value are, however, limited to four groups belonging to the early to late Permian age. The oldest coal group, hosted largely in the south-western zone of the basin, varies in thickness and lithology. Seams up to 30m thick are found at significant depths in the extreme south-west margin of the basin. The north-hosted seams are thinner and relatively near to the surface.

The second group of coal includes many unconnected deposits along the northern and western edges of the basin. The third group, stretching from the Kestrel mine to the North Goonyella, north of Moranbah, includes high-grade coking coal deposits. The final group consists of late Permian-aged coal formed during the last stage of deposition in the Bowen basin. The widely distributed coal in this group varies in quality and is characterised by relatively low content of reactives and sulphur. The group is a major source of coking, pulverised coal injection and thermal coal.

Mining

The mine uses longwall and continuous mining methods that result in better resource-recovery rates, require less roof-support materials and provide better roof protection to miners compared to other methods. Approximately 375 miners work in shifts to carry out mining at the Kestrel mine, seven days a week.

Expansion

The Kestrel mine expansion will include the construction of two mine access points to extract the underground ore. Surface infrastructure, including a new workshop, administration space, storage and warehouse facilities, will be constructed to support the relocated mining activities. To facilitate coal extraction from the new mining area and the coal handling and preparation plant a rail system will be upgraded with a 7km overland conveyor. A new automated stockpile system will also be built.

The expansion will also involve the construction of a water system including three water management dams with a combined capacity totalling to 575ML.

The initial phase of construction will be carried out over a 30-month period. Underground development will continue for two years. The existing 250m-wide longwall will be replaced by a 375m-wide longwall that will result in reduced unit cost and improved productivity. The longwall operations will begin in 2012 when the existing mine begins ramping down.

Contractors

The construction management contract of the expansion project was awarded to Ausenco, a diversified engineering services and project management company, on 11 May 2010. Valued at $53m, the contract involves managing underground development, constructing the surface infrastructure and upgrading the coal preparation plant.

In addition, a $12m design contract was awarded to AECOM Technology, a global technical and management support services company.