Overview
Stage | Production |
Mine Type | Open Pit |
Commodities |
|
Mining Method |
|
Processing |
- Wash plant
- Desliming
- Centrifugal concentrator
- Filter press plant
- Dewatering
- CHPP
- Spiral concentrator / separator
- Dense media separation
|
Mine Life | 2033 |
Source:
p. 548
Company | Interest | Ownership |
Peabody Energy, Inc.
|
100 %
|
Indirect
|
Wilpinjong Coal Pty Ltd.
(operator)
|
100 %
|
Direct
|
The Wilpinjong Coal Mine is owned and operated by Wilpinjong Coal Pty Ltd, a wholly owned subsidiary of Peabody Energy Australia Pty Limited.
Summary:
The Wilpinjong Mine is located in the Permian Illawarra Coal Measures on the northwest margin of the Sydney Basin. This coal measure is around 115m thick in the area, where the dominant lithologies are mudstone, siltstone, sandstone, coal, carbonaceous mudstone and tuffaceous claystone. The coal seams of interest at Wilpinjong include the Moolarben seam and the Ulan seam.
The Wilpinjong mine accesses the Ulan Seam, a 15m-thick seam that is hosted at the base of the late Permian aged Illawarra coal measures. The paleoenvironment is a protected swamp environment on the stable Carboniferous granite basement. The Ulan seam consists of ten plies, including plies of good quality coal, high ash coal, stony coal and partings of claystone, carbonaceous claystone, tuffs and other non-coal lithologies. The working plies at the Ulan seam are inter-bedded with clay stone and siltstone horizons. The seam is shallow and sub crops in the deposit area.
The Coal Reserves reported are high volatile bituminous in rank. The various coal products making it marketable for thermal use in domestic electricity generation and export.
Peabody classifies the Wilpinjong property as a coal deposit with low geological complexity based on the following factors:
• The Ulan seam is laterally continuous and can be correlated using geophysical logs across large distances with high confidence;
• The seam is relatively flat lying (1 to 3 degrees), gently dipping towards the north-northeast;
• There are no major faults in the area;
• The Ulan seam is currently mined across the area at two other mining operations.
The Moolarben seam consists of three plies, of which the lower half of the basal ~0.50m thick ply (M4) is currently being mined. The other plies – M1, M2 and M3 all exceed 40% in ash and have yields of less than 50% and are not considered mining targets. The Moolarben seam has not been mined in the local area in the past.
The Ulan seam ranges between 11 and 22.5 m in total thickness, however the mineable coal plies have a combined thickness of 5.7 to 9.0 m. The seam consists of a number of coal and stone plies that are correlated across the Wilpinjong resource area and into adjacent mines and projects. From these plies, Wilpinjong Coal Mine is currently using selective mining and washing, with some bypass to produce both domestic and export thermal coal products.
The overall confidence in the geological interpretation of the deposit is high. This is due to low variability (both structural and coal quality) as evidenced by the laterally consistent seam dip, lack of structure and relatively homogeneous coal quality (ply by ply basis).
Two areas of relatively high variability are around intrusions (dykes, sills and plugs) and palaeochannels (adjacent to Triassic age ridges and hilltops). In these areas a multi-faceted exploration approach has been utilized to increase confidence in the geological interpretation; including ground mapping, geophysical surveys and associated validation drilling.
The surface geology of the Wilpinjong Mine is dominated by subcrops of the Illawarra Coal Measures. This unit overlies the Shoalhaven Group, which crop out immediately south of Wilpinjong. The coal measures are overlain by the Narrabeen Group, which forms the cliff-lines and plateaus to the north and south, the ridges that protrude out from these plateaus and outliers such as those adjacent to the Slate Gully area. In places, the Illawarra Coal Measures are concealed beneath younger alluvial deposits, particularly those that occupy abandoned channel-fill, referred to on site, as “palaeo-channels”. Quaternary alluvial deposits also flank Wilpinjong and Cumbo Creeks.
In the Wilpinjong Coal Mine area, the shallow nature of the coal seam, combined with flat topography has resulted in extensive interaction between the base of weathering and the coal seam, to the extent that in some areas the seam has been completely oxidised. In addition, several extensive paleochannels have been identified adjacent to ridgelines that have deeply incised the coal seam. Locally, dips are relatively flat (1 to 3 degrees), with strata dipping to the north-northeast.
The Moolarben seam consists of three plies, of which the lower half of the basal ~0.50m (1.6ft) thick ply (M4) is currently being mined. The other plies – M1, M2 and M3 all generally exceed 40% in ash and have yields of less than 50% and are generally not considered mining targets. The Moolarben seam has not been mined in the local area in the past.
The Ulan seam ranges between 11 and 22.5m (36 to 74ft) in total thickness, however the mineable coal plies have a combined thickness of 5.7 to 9.0m (18.7 to 30.5ft). The seam consists of a number of coal and stone plies that are correlated across the Wilpinjong resource area and into adjacent mines and projects. The Ulan seam has minimal stone partings in the north west of the project with midburden partings opening up to the east.
The Ulan Seam is broken up into the A, B, C, D, E, F and G plies. These sections are selectively mined and campaign washed or bypassed at the CHPP to produce product coal at a specific ash point for both domestic and export thermal coal products. Some coal plies are mined across the whole site including A12, B1, B23, D1, D2, E1 and G. Other coal plies are mined only in certain pits (eg. C1 and D0 taken in Pit 6). The plies of the D seam (D0, D1, D2, DD2) are mined selectively or combined depending on the coal quality of the mining block. Several smaller splits occur either approximately on an north-south orientation (such as the G floor coal ply) or an east-west trend (such as B1 splitting away from B23). Generalised coal quality trends area also present across Wilpinjong for different coal plies in similar north-south and east-west orientations that the structure of the seams follow.
The rank of the coal seams is high volatile bituminous (ASTM D388 ‘Standard classification of Coal by Rank’), based on the volatile matter (daf) content of the coal plies, which is generally in the range 35 to 44%. The average volatile matter content of the Ulan seam plies ranges from 11 to 35%. For the plies that are less than 40% ash ad, the volatile matter content is between 20 and 35%. The low volatile matter content of parts of the Ulan seam is largely a function of the high inertinite content of the dull coal plies. The basal ply of the Moolarben seam is 32% ad. The air-dried moisture content of the Ulan seam averages 2.9% ad and is around 2% for high ash plies, and ranges from 2.5 to 3.5% ad for the coal sections. The basal section of the Moolarben seam has an average air-dried moisture content of 3.8% ad. The total sulphur content of the majority of coal plies is <0.5% ad. Certain plies are known to be locally higher in sulphur content (e.g., E and G plies) with values generally in the range 0.5 to 1.2% ad; and isolated analyses over 2.0%. The calorific value of the raw coal closely follows that of the ash content. On an air dried basis, coal that is less than 28% (ad) ash yields greater than 24 MJ/kg (ad) (5730 kcal/kg).
The surrounding ridges of resistant Triassic strata have combined with the thick seam and shallow dips resulting in an extensive area of shallow coal that is amenable to open cut mining. These ridges are generally within National Park and are excluded from mining.
No major faults have been identified within the Wilpinjong Coal Mine area, however, some minor faulting (<5m vertical throw) produces normal faults with a few meters throw or small thrust faults producing localised seam rolls that have limited impact on the current mine’s coal recovery.
Summary:
Conventional open cut mining methods are used at the Wilpinjong Coal Mine, with a low strip ratio allowing for relatively rapid pit advance.
The design of spoil/truck dumps takes into consideration the following parameters:
• Overall Slope Angle should not exceed 37° (crest to toe angle).
• Lift heights should be ~20 m to 30 m dump lifts with standoff distances of ~10 m to 15m for successive lifts.
• Lift heights greater than 30m require specific Job Safety Analysis (JSA)
• Dump height should be consistent with the natural stability of the material being dumped. In general, the higher the dump face, the greater the risk the dump face has of collapsing under the influence of the vehicle tipping.
• The surface of the dump shall be free draining and comply with dumping procedures.
• Seepage from the dump and natural groundwater inflow should be drained to sumps, and ponding at the toe of or within the in-pit dump should be kept to a minimum.
• The dump designs and slopes are such that the run of water reports to the site sedimentation dams. • Reduced bench heights minimising the potential dump instability especially in weak material dumping spots.
• Maintain a minimum berm, safety windrow or stop log at the tip face of ½ wheel height of the largest vehicle using the dump thereby increasing the Factor of Safety (FoS).
• Where the base of the dump is subject to the influence of water or mud, recognise the requirement to dump short of the tip face;
• Where cracks appear tip short and seek supervisory and geotechnical advice, especially where cracking may be more severe than minor tension cracks due to dump settlement.
Out-of-pit waste dumps are comprised of either:
• 20 m lifts with ~35-37 batter angles and a 10 m standoff between the crest and toe of successive lifts, or
• 30 m lifts with ~35-37 batter angles and a 15 m standoff between the crest and toe of successive lifts.
• Lift heights greater than 30m require specific Job Safety Analysis (JSA)
Mining Process
The general sequence of open cut mining is as follows:
1. Vegetation clearance and removal (including mulching).
2. Topsoil/subsoil stripping by scrapers and/or dozers. Stripped topsoil is used directly in progressive rehabilitation or is placed in stockpiles for later re-use.
3. Drilling and blasting of overburden, with some waste rock ‘cast blast’ into the adjacent mined-out strip.
4. Dozer pushing of blasted overburden into the adjacent mined-out strip to expose the target seam, or removal with excavator and haul truck.
5. Drilling and blasting plus ripping of coal/parting material.
6. Mining of exposed coal seams by excavator and loading into haul trucks for transport directly to the ROM dump hopper or ROM pads.
7. Interburden/parting material is then drilled and blasted, ripped, pushed or excavated and hauled to expose the underlying working coal sections.
8. Coarse rejects and tailings from the CHPP are selectively placed within mine voids, waste rock emplacements and approved tailing storage facilities.
9. Hauled overburden/interburden/parting material is strategically placed within mine voids and associated waste rock emplacements to develop the final landform.
10. Progressive landform profiling and rehabilitation of mine voids and waste rock emplacements. In some areas, temporary rehabilitation is undertaken to stabilise landforms until further mining operations are carried out in the future.
ROM coal is either hauled directly to a ROM dump hopper and conveyed to the CHPP for processing, or delivered to ROM pads and later rehandled to the ROM dump hopper using a front end loader and trucks.
The existing capacity of the ROM pads is over 2.5 million tonnes (Mt). Due to previous spontaneous combustion events on ROM pads that contained coal held on-site for an extended period, WCPL has put in place a risk identification system, whereby coal stockpiles that have a higher propensity to spontaneously combust are closely monitored (including physical inspections at daily intervals and/or use of thermal probes to identify areas of heating). In addition, after select ROM coal types have been stockpiled on-site for a designated period, they are prioritised for washing in the CHPP.
Flow Sheet:
Crusher / Mill Type | Model | Size | Power | Quantity |
Sizer
|
|
|
|
|
Summary:
ROM coal is reclaimed at a rate of up to 1,600 tph from ROM Dump Hopper 1 and up to 1,400 tph from ROM Dump Hopper 2 to Sizing Station 1 and 2 respectively, via a feeder breaker. The broken coal is then screened, and if oversized, further crushed in separate sizers. Sized coal less than 50 millimetres (mm) is transferred to either a raw coal stockpile or a product coal stockpile (bypass coal). Raw coal is reclaimed from the raw coal stockpiles and is fed to the coal preparation plant at up to 1,400 tph.
Processing
- Wash plant
- Desliming
- Centrifugal concentrator
- Filter press plant
- Dewatering
- CHPP
- Spiral concentrator / separator
- Dense media separation
Flow Sheet:
Summary:
ROM coal from the open cut pits at the Wilpinjong Coal Mine is transported via internal haul roads for direct dumping to the ROM hopper, or rehandled from a main or satellite ROM pad to the dump hopper.
Sized coal is washed in the raw coal and desliming screens, with fine coal/slimes (less than 0.7 mm) fed to the fine coal circuit, washed medium coal (greater than 0.7 mm and less than 2 mm) fed to the medium coal washing circuit and washed coal (greater than 2 mm) fed to the coarse coal circuit.
The fine coal circuit separates coal fines from slimes and comprises cyclones, spirals, centrifuges, a screen and a tailings thickener.
Tailings are pumped from the tailings thickener to the tailings filter press, which then dewaters the material to allow it to be conveyed to the reject bin.
The medium coal and coarse coal circuits comprise dense medium cyclones to separate the coarse rejects from the washed coal.
The fine and coarse reject ........

Reserves at December 31, 2021:
Category | Tonnage | Commodity |
Proven
|
71 M tons
|
Coal (thermal)
|
Probable
|
5 M tons
|
Coal (thermal)
|
Proven & Probable
|
76 M tons
|
Coal (thermal)
|
Measured
|
103 M tons
|
Coal (thermal)
|
Indicated
|
25 M tons
|
Coal (thermal)
|
Measured & Indicated
|
128 M tons
|
Coal (thermal)
|
Inferred
|
6 M tons
|
Coal (thermal)
|
Commodity Production Costs:
| Commodity | Units | 2015 | 2014 |
Cash costs
|
Coal (thermal)
|
USD
|
22.8 / ton
|
24.4 / ton
|
Financials:
| Units | 2021 | 2020 | 2015 |
Sustaining costs
|
M USD
| | |
2.6
|
Growth Capital
|
M USD
| | |
5.1
|
Revenue
|
M USD
| ......  | ......  |
|
Pre-tax Income
|
M USD
| ......  | ......  |
|
After-tax Income
|
M USD
| ......  | ......  |
|
EBITDA
|
M USD
| ......  | ......  |
110.6
|
Operating Cash Flow
|
M USD
| ......  | ......  |
|
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