Isaac Downs is located in the northern part of the Permo-Triassic Bowen Basin containing principally fluvial and some marine sediments. The economic seams are contained in the Late Permian Rangal Coal Measures which are approximately 100 m thick. The Rangal Coal Measures are underlain by the Fort Cooper Coal Measures and overlain by the Late Permian to Early Triassic Rewan Group. The transition from the Rangal Coal Measures to the Rewan Formation is 15 to 60 m above the first major seam of the Rangal Coal Measures. The Fort Cooper Coal Measures comprise typically tuffaceous sandstones, siltstones, mudstones and coal seams. The transition between the Rangal Coal Measures and the Fort Cooper Coal Measures is generally clearly marked by the Yarrabee Tuff - a basin-wide marker bed comprised of weak, brown tuffaceous claystone. The first coal seam of the Fort Cooper’s is the Girrah Seam which is 25 metres or more below the Vermont Seam within the Project area.

Alluvium occurs along the Isaac River. The alluvial sediments comprise a fining-upward sequence of unconsolidated sand, silt, clay, gravel, and lithic fragments. The alluvium may extend to a distance up to 750 m from water courses. However, the lateral extent of alluvium may be highly variable.

In the Project area, the Rangal Coal Measures dip to the east to north east (2 to 6 degrees) and include interbedded sandstone, siltstone, and lesser amounts of carbonaceous mudstones, coal, and tuff. A weathered zone extends to 15 m to 30 m below ground level. Typically, the Leichhardt Coal and Vermont Coal Seams occur as a singular package, in very close proximity, with splits in some areas up to 30 m.

The mine will utilise an open cut mining technique where strips and blocks will be mined in succession, thus allowing waste from one strip or block to be dumped into a previously mined out area. Waste from an initial strip or boxcut will be dumped into an out of pit dump (ex-pit spoil) to the west of the pit area.

Under the BFS mine planning scenario, the initial Isaac Downs box cut will be established where the coal seam is close to the surface topography using an excavator and truck operation at low strip ratios. Subsequently, the dragline will be ‘walked’ from Isaac Plains to Isaac Downs and a standard Bowen Basin dragline operation will be established from north to south, supported by excavator and truck pre-strip operations.

A series of mine stage plans has been developed for the Project, showing the progression of mining activities at each stage. These stage plans have underpinned the assessment and management of Project impacts during and post operations. The Project open cut mining will involve the following activities:
- clearing of any vegetation;
- stripping and stockpiling of topsoil;
- drilling and blasting of pre-strip overburden;
- removing the pre-strip overburden using truck and shovel fleets and/or dozers;
- drilling and blasting of overburden;
- overburden removal by dragline;
- coal mining using excavators;
- progressive rehabilitation of overburden emplacement areas.

The coal will be mined using front end loaders and excavators and placed into rear dump trucks for haulage. The haul trucks will transport the coal along the strip or terrace, up a coal ramp out of the pit, then along a haul road to a ROM coal stockpile area located near the pit. The coal will be dumped onto a stockpile, from where it will be loaded onto road trains (or similar) for transport to the IPM CHPP.

ROM coal will be hauled on a purpose built, dedicated haul road to the adjoining IPM to the north, where it will be processed at the IPM coal handling and preparation plant (CHPP), before loading onto the IPM rail loop for railing to the Dalrymple Bay Coal Terminal (DBCT) for export. The Project will utilise approved capacity at the CHPP. Coal mined at Isaac Downs will transition from coal mined at IPM, with mining equipment and a similar workforce transferred from IPM to Isaac Downs. IPM operations will recommence once production from Isaac Downs declines in the later years of Isaac Downs operations.