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.

Within Mount Thorley, two small areas in the northern and southwestern extents of the mining lease will reach their final limits during 2020 with remaining reserves to be mined to depth during 2020.

Mineral Processing.
All processing and rejects/tailings disposal activities undertaken in 2019 were consistent with the approved MOP and no changes were made to the processing and rejects/tailings disposal methods.

Currently active tailing emplacements include the Centre Ramp Tailings Storage Facility and Abbey Green South Tailings Storage Facility. Tailings Dam 2 was previously used to receive ash from Redbank Power Station but ceased in July 2014 following the cessation of operations at Redbank Power Station. During 2019 capping works on Tailings Dam 2 continued.