Mount Thorley Warkworth (MTW) is located within the Sydney Basin of New South Wales (NSW), a world–class export thermal coal mining district.

The Sydney Basin is a north-south trending basin, containing generally flat lying Permian Triassic sequences, approximately 250 km long, averages 100 km in width, ranges from 2km to 4km in depth and covers an area of approximately 37,000 km2 onshore and 15,000 km2 offshore.

Sedimentation in the Sydney Basin can be divided into many distinct depositional episodes, related to marine transgression and regression an terrestrial sedimentation. In the Sydney Basin the total thickness of the sedimentary package ranges on average from 2 to 3 km over much of the basin, based primarily on drill-hole records and deep seismic profiles.

Coal bearing formations in Permian aged sediments are extensive in the Sydney Basin and range in depth from near the surface to over 1 km. The Sydney Basin is divided into five major coalfields; Southern, Central, Newcastle, Hunter and Western, and comprised of black anthracite coal bed of a few centimetres to several meters, interbedded with sandstones, shales, tuffs and claystone. During coal bore drilling in the late 19th Century a number of bores encountered flows of natural gas.

The Late Permian coal measures show sources of both oil and gas, with the offshore basin possibility more prone to oil Fine grained sediments deposited during the brief marine incursions that took place during the Late Permian may also have some potential as oil sources.

-West Pit: Normal mining operations continued throughout 2014 with Truck and Shovel pre-strip on the upper and mid benches and Dragline operations on the lower two benches. MTW commenced a transition to an offset Dragline digging method during 2014 by taking a 120m wide strip on the BFA Dragline bench. .

-North Pit: Normal mining operations continued throughout 2014 with Truck and Shovel pre-strip operations on the upper and mid benches and single bench Dragline operations at the basal seam. North Pit remains a steady state mining area with adequate highwall offsets in place resulting in good working room for mining equipment.

-South Pit: Normal mining operations continued throughout 2014 with Truck and Shovel pre-strip operations on the upper and mid benches and double bench Dragline operations on the lower 2 seams.

Warkworth CHPP has a nominal output capacity of 7.2 million washed saleable tonnes per annum and a bypass capacity of approx 3 million tonnes of ROM. Coal is transferred from the active working areas of the mine to the CHPP by truck. The raw coal is screened into two sizes and then washed via the use of dense medium cyclones, spirals and flotation circuits, as follows:

-Coarse coal is treated in two-stage dense medium cyclone circuits. These circuits involve the use of a magnetite and water mixture (dense medium) from which the heavier, non-coal material sinks and is subsequently removed leaving the coal in solution;

-Fine fraction is washed in a two-stage spiral process;

-Flotation and centrifugal techniques are used to remove very fine non-coal particles from the tailings of the main plant. Separated coal is dewatered in centrifuges prior to sending to Redbank Power Station as Beneficiated Dewatered Tailings (BDT) or to clean coal stockpiles.