Metropolitan Coal is located within the Southern Coalfield, within the southern part of the Sydney Basin, which is infilled with sedimentary rocks of Permian age (<270 million years ago) and of Triassic age (<225 million years ago).

Three formally named coal seams of the Illawarra Coal Measures are present in the Southern Coalfield, namely the Bulli, Balgownie and Wongawilli Seams.

Immediately overlying the Bulli Coal unit of the Illawarra Coal Measures are sandstones and claystones of the Narrabeen Group. The Narrabeen Group contains the Newport Formation (sometimes referred to as the Gosford Formation), the Bald Hill Claystone (also referred to as Chocolate Shale and formed as a result of laterite weathering Gerringong Volcanics), the Bulgo Sandstone, the Stanwell Park Claystone/Shale, the Scarborough Sandstone, the Wombarra Shale and the Coal Cliff Sandstone. At the top of the sequence in the area of interest is the Hawkesbury Sandstone (HCPL, 2008).

Many features of the NSW Coalfields surface topography are directly correlated to the basement structure, the depth of the basement from the surface through many sedimentary epochs and the deformational episodes of the basement rock. The Palaeozoic granite basement rock underlies the Sydney Basin sedimentary rocks. At Metropolitan Coal the total depth of Sydney Basin sedimentation is 2.3 km.

Surface lineaments are linear features in the surface landscape, preferentially eroded, that may be the surface expression of an underlying geological structure, fault or dyke or simply a result of surface joint sets. Lineaments are identified from aerial photography, LiDAR and from digital topographic sets. Lineaments mapped by Metropolitan Coal are shown on Figure 5. Additional LiDAR mapping was conducted by Metropolitan Coal in July/August 2019 to identify any new linear features within the Longwalls 305-307 35° angle of draw and/or predicted 20 mm subsidence contour. The 2019 LiDAR review confirmed the existing lineament mapping analysis.

A strike slip fault, F0008, with up to 1.2 m vertical displacement occurs over Longwalls 20-27, and this fault extends partially through Longwall 304. This fault is associated with a surface linear that aligns with the Eastern Tributary and then passes east of the Woronora Reservoir full supply level dissipating into the landscape. Longwall 20 through 27 were extracted through this feature directly under the Eastern Tributary with no moisture evident at seam level and no change in mine water balance during the seven years of extraction in the area. At the time of writing, Longwall 304 extraction had not intercepted F0008 projected extents.

Longwalls 305-307 extraction will occur from north to south. Longwalls 305-307 will be extracted using retreating longwall mining methods for secondary extraction of a panel with a 138 m void width. The longwall panel will be formed by driving two sets of gate roads (the tailgate and maingate roads). Each gate road requires two roadways (headings) to be driven parallel to each other. The two roadways will be used for ventilation purposes, with one of the roadways utilised as a transport road and the other roadway used to convey the coal that will be mined back to the main conveyors. Construction of development main headings and gate roads are mined using continuous miners.

The dimensions of the headings will be approximately 5.2 m wide and 3.2 m in height. The headings are connected approximately every 120 m by driving a cut-through from one heading to another which forms pillars of coal along the length of the gate road. The tailgate and maingate roads are separated by the 133 m wide longwall panel (measured between roadway centrelines). The maingate roads and tailgate roads are then linked together by driving an installation road and bleeder road at the top end of the longwall panels. Run-of-mine (ROM) coal will be conveyed by the maingate conveyor to the main conveyor which will carry coal to the surface of the mine.

Coal extracted from the underground mining operations is transferred by conveyor to the ROM coal stockpile at the surface facilities. ROM coal is crushed, screened and washed at the CHPP.

The CHPP is located in the major surface facilities area (Figure 4) and comprises crushers, screens, dense medium cyclones, spirals, flotation cells, separators, filters and thickeners to process the coal and separate coal reject materials.