The surface geology of the HVO, MTW and Ashton coal leases is dominated by outcrops of the Jerry’s Plains and Vane Subgroups which form the Whittingham Coal Measures. The main rock types of this subgroup include sandstone, siltstone and conglomerate, which occur with subordinate coal and tuffaceous claystone.

HVO is located on the asymmetric southerly plunging Bayswater Syncline. The Auckland area is located on the western flank of the Camberwell Anticline and dips more steeply than the western limb of the Bayswater Syncline. The West Pit is located on the eastern flank of the Muswellbrook Anticline. The Barrett seam outcrops in the east of the Auckland area on the Camberwell Anticline.

The sedimentary pile in the Sydney Basin has asymmetrical thickness distribution. The thickest accumulations are along the easterly-dipping Hunter-Mooki Thrust Fault System suggesting that subsidence was greatest along that fault. The sedimentary sequence thins to the west due to the sediments onlapping into the basement rocks in the west. The Hunter Coalfield is a district- scale north-eastern subdivision of the Sydney Basin. The Permian coal bearing stratigraphic section occurs within the Whittingham Coal Measures.

HVO uses dragline and truck and shovel methods, and is operational 24 hours a day, seven days a week.

Coal is loaded using a combination of loaders and excavators with haulage to the ROM hopper undertaken using rear dump trucks. The operations are supported by additional equipment including dozers, graders and water carts.

All pit end-walls have benched and battered designs based on the existing operation with allowances made for increasing depth of mining. The design provides for mining roadways and catch benches.

Coal loss and dilution factors are also applied and vary by the equipment type uncovering the various coal seams (i.e. excavator/truck versus dragline). Typical roof and floor coal loss thickness ranges from 5-25cms. Typical roof and floor waste dilution thickness ranges from 3- 7cms.

HVO comprises three separate previous mines namely Howick, Hunter Valley and Lemington Assets which included the following:
- The Lemington Mine, which began production in 1971, was acquired and merged into HVO in 2001.
- Coal production began at the Howick Coal Mine in 1968 in what is known as the West Pit at HVO. In 2000 the Howick Coal Mine became part of Rio Tinto's Hunter Valley Operations as a result of the merger with Hunter Valley Mine.
- The Hunter Valley No. 1 Mine began production in 1979.

The HVO site area is approximately 20 km long (North to south) and 10 km wide. HVO is divided into HVO North (HVON) ........

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