The local geological structure at Narrabri has been influenced by the presence of the Boggabri Ridge. The strata strike north-south and dip westwards at less than 5°. The stratigraphic sequence developed at the mine site includes the following units, described in descending order:

- Pilliga Sandstone – coarse grained quartz sandstone up to 60 m thick, which crops out in the western parts of ML1609 and EL6243;
- Purlawaugh Formation – up to 140 m thickness of thinly bedded sandstone and siltstone, with subordinate claystone and coal;
- Garrawilla Volcanics – up to 40 m thickness of alkali basalt flows with thin intervening mudstone and clastic rocks, unconformably overlying Triassic rocks where it is present;
- Deriah Formation – sporadically developed, lithic sandstone up to 15 m thick;
- Napperby Formation – siltstone, sandstone/siltstone laminate and fine- to mediumgrained quartz-lithic sandstone to 140 m thick;
- An intrusive basalt sill is present 30-35 m above the base of the Napperby Formation and is 15 to 20 m thick;
- Digby Formation – lithic, pebble conglomerate, typically 12-24 m thick, overlying the Black Jack Group; the boundary between the two being a low angle unconformity;
- Black Jack Group – consists of lithic sandstone, siltstone, claystone, coal and minor tuff; thickness is up to 70 m in the western part of ML1609 and less than 40 m thick in the east where the sequence is partially overlapped by the Digby Forma ........

Narrabri Mine has approval to use longwall mining methods to extract up to 11 Mtpa of ROM coal from the Hoskissons Seam within ML 1609.

The approved underground mining area encompasses a total of 20 longwall panels ranging in length between approximately 1.8 km and 4.0 km, depending on seam conditions and site constraints, and ranging between 295 m and 400 m wide.

The longwall design will be based on proven technology with an emphasis on reliability of equipment. The principal components of the system will include:
- Double-ended ranging drum shearer rated at 4,500 tph with full horizon control;
- An armoured face conveyor rated at 4,500 tph with provision for single tailgate drive and dual maingate drives;
- Beam Stage Loader rated at 5,000 tph; and
- High capacity two leg and four leg chocks shields with shearer initiation, base lift and high set functions.

Access to the underground mining area is via three drifts from the box cut. The box cut is located in the Pit Top Area. A conveyor to transfer ROM coal to the surface is located in one of the drifts. The other drifts allow for employee, machine and material access and services including ventilation, water and electricity.

Mining operations are undertaken 24 hours per day, seven days per week.

Narrabri Stage 3 Extension
Longwall mining methods and equipment would continue to be employed for the Project.

Longwall mining involves the ........

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