The coal seams of interest in the Illawarra Coal Measures are the Bulli, Balgownie and Wongawilli Seams. At Russell Vale, the Illawarra Coal Measures are overlain by the Narrabeen Group, the thick sequences of Triassic Hawkesbury Sandstone and in parts, the Wianamatta Group.

The Wongawilli Seam is on average around 27m below the Bulli seam at Russel Vale. The Wongawilli Seam has a typical total thickness of 8 – 11 metres over the project area and is characterised by a series of kaolinitic mudstone partings in the seam. The basal part of the seam contains the highest proportion of coal and is typically targeted in underground mines in the area including Wongawilli and Dendrobium (South32 Limited).

Depth of cover to the Wongawilli ranges from 200-320m in the Wonga East area, increasing to 400- 450m in the west. Most of the variation in depth of cover arises from the surface topography.

The Wongawilli Seam dips towards the north-west at less than two degrees in the Wonga East area as shown. The dip direction swings to the west in the Wonga West area towards a broad syncline structure known as the South Bulli Syncline. In the eastern portion of the tenement boundary the coal seams outcrop on the escarpment.

There are several dykes that traverse the south-eastern project area mostly orientated in a WSW-ESE direction while occasional dykes (mostly trending NE to NW) are located to the west. Numerous dykes have been encountered in previo ........

The Russell Vale mine utilises the bord and pillar mining-technique, an innovative mining method with no or negligible subsidence and consequent environmental impact. As part of the approval process for re-starting Russell Vale, Wollongong Resources formally committed not to use longwall mining methods, which causes surface subsidence. As part of its commitment, Wollongong Resources has abandoned its multimillion-dollar longwall equipment.

Bord and pillar is a more expensive mining technique when compared to longwall mining but has been adopted by Wollongong Resources for its minimal environmental impact and to protect water catchments across Sydney and the Illawarra’s from subsidence and water loss.

The proposed method is bord and pillar with the pillar size being dictated by surface constraints and previously mined upper seams. There is to be no subsidence as the mine operation will be below a major water catchment area. Mining recovery will range from 30 to 40 percent.

Mains headings and panel insert headings will be developed by conventional cut and bolt mining equipment.

The plan does not utilise longwall mining or pillar extraction. The main development works, and Place Change panels are all designed as first workings with the coal pillars to be long-term stable with the appropriate factor of safety to ensure negligible subsidence of the overlying surface. Pillar dimensions are assumed to be one tenth (1/10) the depth of cov ........

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