The project is located on the north-western flank of the Bowen Basin, a sedimentary basin comprising Permian to Triassic age geology. In the vicinity of the project site, the Bowen Basin geology has been folded, forming a broad syncline that plunges and opens to the north. The project site is located on the western limb of the syncline.

Subsequent magmatism has resulted in the formation of localised intrusions of igneous rock within the Bowen Basin sediments. The Bowen Basin sediments are typically overlain by more recent Triassic and Cainozoic age deposits. These deposits (and the upper profile of the Bowen Basin sediments) have been extensively modified by long periods of weathering.

The stratigraphy of the project site and its surrounds includes the following (in descending order):
• Localised alluvium associated with North Creek (not present within the project site);
• Cainozoic sediments, including the Suttor Formation, associated colluvium, weathered sediments, and residual soils;
• Triassic sediments of the Rewan Group;
• Permian coal measures, comprising the Rangal Coal Measures (including the target Leichhardt seam) and the underlying Fort Cooper Coal Measures; and
• A localised Cretaceous granitoid intrusion.

Alluvium is not present within the project site. The distribution of alluvium is limited to localised deposits associated with North Creek and its floodplain. The floodplain alluvium thickness is variable, and ranges from a few centimetres at the edge of the floodplain to approximately 3 m thick on the banks of North Creek. The creek channel is incised into the floodplain alluvium and there is typically a thin covering of bed sands present in the creek bed. Alluvium is not present outside this localised area.

The Cainozoic sediments are a weathered profile of sandstone, mudstone, other sediments and residual soils. The Cainozoic sediments are characteristically fine-grained, clay-bound and poorly consolidated. The Cainozoic sediments are widely distributed over the project site and its surrounds. The Cainozoic
sediments underlie the alluvium (where present). Elsewhere, the Cainozoic sediments are typically located at the ground surface. The Cainozoic sediments are between 5 m and 18 m thick within the project site. The Cainozoic sediments are up to approximately 30 m thick in the vicinity of North Creek east of the
project site and in the elevated areas to the north-west of the project site.

The Permian coal measures include the Rangal Coal Measures and the Fort Cooper Coal Measures. The Permian coal measures comprise a sedimentary sequence with interbedded coal seams. The coal seams include:
• The Leichhardt seam targeted by the project and the surrounding mines, including Millennium Mine, Daunia Mine, Poitrel Mine and Moorvale Mine; and
• The Vermont seam targeted by the surrounding mines.

The Permian coal measures underlie the alluvium, Cainozoic sediments and Rewan Group (where present). Within the project site, the Permian coal measures are located at depths of between 100 m to 440 m.

The Permian coal measures dip to the north-east. As they dip, the thickness of the coal measures and the depth of the coal seams increase. The thickness of the Permian coal measures ranges from approximately 70 m in the western part of the project site to approximately 150 m in the north-eastern part of the project site. The depth of cover above the Leichhardt seam increases from approximately 110 m in the west of the project site to 450 m in the northeast of the project site.

A Cretaceous granitoid outcrops 5 km to the south-east of the project and comprises gabbro, leuco-diorite, diorite and granodiorite.

Carborough Downs is an underground longwall and bord & pillar operation mining, located 25km east of Moranbah in the heart of the Bowen Basin.

The mine produces metallurgical coal sold to meet the growing needs of international steel demand.

Carborough Downs Coal Mine (CDCM) is an operating underground longwall and bord and pillar mine located approximately 15 km east of Moranbah Township in Central Queensland. CDCM commenced bord and pillar mining in 2006 and longwall mining in 2009 and produces export coking and Pulverised Coal Injection (PCI) coal. The CDCM EA prescribes a maximum coal extraction rate of 5 Million tonnes per annum of Run-Of-Mine (ROM) coal. At the current mining rate, the CDCM will be operational until 2027.

Carborough Downs South Extension Project involves the extension of the Carborough Downs Coal Mine (CDCM) underground bord and pillar mining operations into the project site.

The project will provide access to approximately 8.9 Mt of mineable coal and will extend the life of the CDCM mining operations by approximately 5.5 years. Without the project, the coal resource in the project site will likely be sterilised and the economic benefits of mining the resource will be forgone.

Mining in the project site is scheduled to commence in mid-2022, subject to obtaining the relevant approvals. The project mining operations will involve extracting a total of approximately 8.9 Mt of Run of Mine (ROM) coal over a period of up to 11 years.

Bord and pillar mining in the project area will be undertaken using the existing CDCM bord and pillar mining equipment and the same mining method. The project will target the same Leichhardt coal seam as the existing CDCM underground mining operations.

The bord and pillar mining method involves dividing the target coal seam with underground roadway excavations. The coal seam is initially excavated along mined roadways (called ‘main headings’). The main headings are intersected at regular intervals by connecting roadways (called ‘cut-throughs’). Collectively, the main headings and cut-throughs are the bords. The cut-throughs are typically mined perpendicular to the primary headings creating a block-like array (or panel) of coal pillars bounded by the bords. Bell outs (small, fan shaped coal excavations) are also created at the ends of the bords to maximise coal extraction.

Mining is carried out by a continuous miner (cutting machine) that loads coal onto a shuttle car which transports and loads the coal onto an underground conveyor belt system. Once a bord is excavated to the required distance, the continuous miner moves to the next mining area and roof support is installed in the previous bord. The coal pillars support the overlying strata as the bords are mined and remain in place after the completion of mining.

PROJECT MINE LAYOUT
The width of the roadways (bords) will be 6 m. The final coal pillars will be 24 m by 24 m of solid coal. The coal extraction height will vary between 4.6 m and 6.0 m.

The project bord and pillar mine layout has been specifically designed with sufficient roadway and pillar strength to ensure that there will be no caving and the underground workings will be stable and safe. Consequently, the bord and pillar mining will not result in any significant surface subsidence above the underground workings.

An overland conveyor transfers raw coal from the underground mine for processing on site at a modern Coal Handling and Processing Plant (CHPP). The Carborough Downs CHPP operates seven days a week and is capable of processing 1,000 tonnes per hour.

The mine produces predominantly coking coal with PCI coal as a secondary product.

Coal from the underground workings is transported via overland conveyor to a ROM coal stockpile north-west of the conveyor drift portal. ROM coal is then transported from the ROM stockpile by an overland conveyor to the CHPP. ROM coal is washed at the CHPP. Product coal is transported from the CHPP via an onsite rail loop and train loading facility. Product coal is railed to the Dalrymple Bay Coal Terminal, for export.

Two export products will be produced from the Project, a low ash coking fraction (HCC) and a pulverised coal injection fraction (PCI). An overall yield of approximately 77% is predicted, of which approximately 63% is expected to be HCC and 14% PCI. After processing, the product coal will be stockpiled at the existing CDCM product coal handling facility and loaded onto trains using the existing rail load-out.

Rejects and dewatered tailings produced from the washing of coal at the CDCM CHPP are stored in the Dry Rejects Emplacement Area.