WCL Wongawilli Colliery contains three coal seams of potential economic extraction. These are the Bulli Seam, Wongawilli Seam and Tongarra Seam.

Wollongong Coal Wongawilli Colliery is located in the Southern Coalfield, which is the southern portion of the Permo-Triassic Sydney Basin and contains the Illawarra Coal Measures of Late Permian Age. Overlying the Illawarra Coal Measures are sandstones, shales and mudstones of the Narrabeen Group, which in turn are overlain by the Hawkesbury Sandstone, a massive quartzose sandstone unit. The Wianamatta Group, stratigraphically above the Hawkesbury Sandstone, is the top most unit in the Southern Coalfield.

Bulli Coal
The Bulli Coal is the most extensively worked coal seam in the Southern Coalfield, from outcrop mines on the coastal margins to current inland mines of South 32 and Glencore. The seam produces a hard coking coal usually needing beneficiating to two products (coking and energy) to obtain a marketable low ash coking coal. In the southern areas of the Coalfield the Bulli Seam has been worked extensively in the former Mt Kembla, Tom Thumb and Kemira Collieries and to a lesser extent at Wongawilli Colliery. The seam is poorly developed to the south / southwest in Wongawilli Colliery.

Wongawilli Coal
The Wongawilli Coal is generally about 9 to 11m thick across the Coalfield and consists of interbedded bands of (usually) kaolinitic brown mudstone (with occasional thin pyrite or siderite lenses) and coal plies. In the southern part of the Coalfield the lower section of the seam is economically mined but deterioration from thickening and increasing numbers of stone bands in the working section occurs northward in the Coalfield. The interval between the Bulli Coal and the Wongawilli Coal has an average of around 23m in the Wongawilli lease area.

Tongarra Seam
Occurs from about 16m below the American Creek Seam and has a potential economic mining section which is restricted to the upper split. The Tongarra Seam consists mainly of carbonaceous shale and mudstone bands with thin coaly plies and averages about 6.5m in thickness. In the southern part of the coalfield the Tongarra Seam has two splits, separated by shale and/or sandstone. The upper split varies in thickness from 0.94m to 3.58m and consists mainly of coal and coaly plies separated by carbonaceous shale and mudstone bands. The lower split is consistently thinner; varying from 0.15m to 0.89m but usually contains proportionally more coal plies than the upper split. The seam was mined in the Huntley and Avondale Collieries which have both closed.

Events involving difficult geological conditions and financial issues saw the WWC go into care and maintenance in July 2014.

The WWC (Wongawilli Colliery) recommenced operations in August 2016 under the contractual operation of Delta SBD. Delta used the split and lifts bord and pillar method and mined the Wongawilli Seam until going into administration at the end May 2017.

Operations at WWC resumed in August 2018 but ceased in March 2019 due to frequent roof falls making operations riskier and less economical. WLC has submitted an application for an extension to the current mining approval. Currently, the application is under review by the department. WLC has also evaluated different mining sections to resume the mining activity.

The Coal Resource estimation is based on the mined product being sold into the global coal market as an unwashed coking coal. No beneficiation plant exists for the washing of the ROM product on site. Previous operations involved inline crushing of the mined product to nominally -50mm material. The majority of the previous production has been sold to WLC’s major shareholder for beneficiation in India where all of the material is utilised either within the coke making industry, power generation or other industrial processes. Long term planning will see the construction of a washing facility off site to produce coking and thermal coals.