United Wambo is a 50:50 joint venture between neighbouring mines operated by United Collieries Pty Limited (United) and Wambo Coal Pty Limited (Wambo).
United is owned 95 per cent by Abelshore Pty Limited, a wholly owned subsidiary of Glencore Coal Pty Limited (Glencore) and 5 percent by the Construction, Forestry, Maritime, Mining and Energy Union (CFMMEU), which is managed by Glencore. Wambo Coal Pty Limited (Wambo) is a subsidiary of Peabody Energy Australia Pty Limited.
Summary:
Geology
Regionally, the predominant geological feature is the Sydney Basin, formed via igneous rifting and crustal thinning resulting in the deposition of Permian and Triassic aged sedimentary sequences. Within the UWJV Project area Permian sediments form the Wittingham Coal Measures of the Hunter Coalfields. The coal measures generally plunge in a west to south-westerly direction and outcrop to the east of the Project area near the Hunter River.
The Wittingham Coal Measures comprise the economic coal seams interspersed with overburden and interburden consisting of sandstone, siltstone, tuffaceous mudstone and conglomerate. Quaternary alluvial deposits unconformably top the Permian sediments. These deposits consist of silt, sand and gravel in the alluvial floodplain of the Wollombi Brook. To the east of the Wollombi Brook is a sequence of aeolian sands, known as the Warkworth Sands Formation, that form a thin capping on the underlying Permian bedrock Additionally, the Triassic Narrabeen Group also unconformably overlie the Permian sediments. The Narrabeen Group, which formed from uplift during the Triassic, comprises fluviatile deposits that form the ridges and a high plateau within the Wollemi National Park, west of the Project Area. Surficial weathering, typically present as a thin heterogeneous layer of unconsolidated material overlying fresh bedrock occurs across the project area.
Locally, the predominant stratigraphic units that occur within the Project area and nearby surround, include:
1. Quaternary sediments
- Localised presence along North Wambo Creek, 4-7 metres thick comprised of clays, sandy silts, with localised occurrence of medium grained sand.
- Along Wollombi Brook and the Hunter River flood plans – commonly comprises two distinct depositional units, the surficial alluvium and productive basal alluvium. Typically constrained to within 400 metres of the creeks and is between 7 – 19 metres thick.
2. Triassic Narrabeen Group
- Comprises quartz-lithic to quartzose sandstone, conglomerate, mudstone and siltstone with rare coal. Does not occur within the project area but 500 metres west
3. Permian Newcastle Coal Measures
- Formally known as the Wollombi Coal Measures, present in the south-west of the Project area. Generally less than 15 metres thick and deeply weathered comprised of tuffaceous claystone, tuff, siltstone, sandstone, conglomerate, and minor coal. Coal within the Newcastle Coal Measures generally contains stone and is not considered of economic quality within the region
4. Permian Wittingham Coal Measures
- comprise coal seams interbedded with siltstone, sandstone and shale (known as the interburden) and up to 450m thick at the Project Area.
The Wittingham Coal Measures outcrop approximately 8km to the north and east of the Project area where recharge via rainfall infiltration occurs. The coal seams also subcrop in localised zones along the Hunter River and Wollombi Brook, where they are recharged by the overlying alluvium. Recharge also occurs via leakage from the overlying Triassic Narrabeen Group. The coal measures form unconfined groundwater systems at outcrop, becoming confined as they dip towards the south-west.