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.

Mining Method
Overview
The proposed mining method within MTW is the same as that currently employed. Large electric face shovels, hydraulic excavators and front-end loaders are utilised to load haul trucks to remove pre-strip and parting material. Draglines are used to expose lowest coal seams. Ancillary equipment in the form of drills, graders, rubber-tyred dozers and water carts will provide the mining equipment with support as required. Coal is extracted by front-end loaders and/or excavators loading haul trucks.

The current mining equipment will continue to be used. In general, changes may occur due to replacement or as technology changes.

Overburden and Interburden Material
Overburden removal at MTW is centred on shovel pre-stripping methods and dragline “stripping”. Multiple bench pre-stripping is used to expose shallower coal seams with a combination of dragline and shovel operations to remove lower interburden. Overburden removal operations generally proceed as follows:

- Tree clearing and timber harvesting is carried out under contract. Topsoil removal is carried out under contract using small earthmoving equipment such as a D6 bulldozer with a loader and trucks.

- Overburden is drilled. Generally holes stop short of the coal seams to reduce blast damage to vthe coal. Hole diameters range from 200mm to 270mm. Drill patterns depend on hole depth and hole diameter but pattern sizes will generally range from 5m x 6m to 10m x 12m.

- The overburden material is blasted according to design parameters specific to the geology, the presence of water, and the type of machine intended to dig the material. Overburden and interburden greater than 2.0m in thickness require fragmentation by drill and blasting.

- Overburden/interburden removal is performed by one of three basic methods:

- Shovel / Truck Fleet: The majority of the uppermost seams in the sequence are exposed using an electric shovel loading 240 and 320 tonne trucks. Overburden waste is hauled to dumps located across the site.
- Dragline: Single or double pass removal of loose overburden into previous strip, leaving a thin layer of material overlying the coal seam.
- Dozers: Dozers will be used to remove thin layers of interburden by directly pushing blasted overburden material into the previous void.

Coal
If the coal seam was uncovered by dragline, the thin layer of rock will be cleaned by tracked and wheeled dozers and graders. The coal seams may be blasted, ripped by dozers or free-dug by loaders depending on the nature and thickness of the coal. FrontGend loaders will operate with 180 tonne capacity trucks which haul the raw coal to either the North or South CPPs.

Mineral Processing
Coal will be washed in both the North CPP and South CPP in accordance with market requirements.

North CCP
The North CPP has a nominal capacity of 6.6 million washed saleable tonnes per annum, additional capacity is available through the North CHPP’s bypass facility. This system has not been tested to its maximum capabilities, however historically around 6% of the Run-of-Mine (ROM) coal has been bypassed annually or as high as 1Mt per annum.

The North CPP is a two module plant, each capable of a raw feed rate of 800tph. Raw coal is screened into two sizes, with coarse coal of diameter > 1.4mm treated in a single or two-stage dense medium cyclone circuit and the fine fraction washed in a two-stage spiral process.

The coarse coal circuit relies on relatively simple gravity separation, with coal particles floating in a magnetite and water mixture known as dense medium. The heavier non-coal material sinks while the coal floats ........