Regional geology
All of the known coal deposits in South Africa are hosted in sedimentary rocks of the Karoo Basin, a large retro-foreland basin that developed on the Kaapvaal Craton and filled between the Late Carboniferous and Middle Jurassic periods.

The Karoo Supergroup is lithostratigraphically subdivided into the Dwyka, Ecca, Beaufort and Stormberg groups, succeeded by the Drakensburg Formation (SACS, 1980). The coals range in age from Early Permian (Ecca Group) through to Late Triassic (Molteno Formation, Stormberg Group) and are predominantly bituminous to anthracite in rank, which is a classification in terms of metamorphism under the influence of temperature and pressure.

The coal deposits of the Witbank Coalfield are restricted to rocks of the Vryheid Formation, which ranges in thickness from 70m to over 500m, being thickest in the northeast and east of the preserved outcrop area, to the south-southwest of the town of Vryheid, where the basin was the deepest.

The coal seams, from the base upward, include the No.1, No.2, No.3, No.4 and No.5 Seams. The No.1 Seam is best developed in the northern part of the Witbank Coalfield, where it is between 1.5m and 2.0m thick.

The No.2 Seam contains some of the best quality coal. Its average thickness is 6.5m in the main- central part of the Witbank Coalfield and thins to approximately 3.0m towards the west and east.

The No.3 Seam is poorly developed and is usually less than 0.5m thick. It is, therefore, not generally economically extracted.

The No.4 Seam varies in thickness from approximately 2.5m to 6.5m. In places, the seam is divided into the No.4 Lower, No.4 Upper and No.4 A Seams, separated by sandstone and siltstone/mudstone partings. The seam usually contains dull to dull lustrous coal.

The No.5 Seam has been extensively eroded over large areas, and where present has an average thickness of 1.8m, being between 0.5m and 2.0m thick The seam is generally a high quality, low phosphorus coal, and is a source of blend coking and other metallurgical coal.

Local geology
At Moabsvelden, the typical Witbank Coalfield seam sequences of No.1 to No.5 Seams are present, but in a somewhat compressed manner. This has resulted in the Moabsvelden area being characterised by a thicker than usual sequence of the lower most seams which represents a combination of the No.4U and No.4L, No.2U and No.2L and No.1 Seams. The thinner uppermost seam at Moabsvelden represents the Witbank Coalfield’s uppermost No.5 Seam.

This has resulted in a specific seam nomenclature being adopted for Moabsvelden which is somewhat different to the more conventional Witbank Coalfield nomenclature. Instead the thicker lower seam complex has been termed as the Bottom Seam and the top thinner seam as the Mid Seam. In turn the Bottom and Mid Seams have been divided into plies identified by using geophysical log data with relation to the in-seam partings. These plies are well developed and extend across the Moabsvelden area.

The Bottom Seam sequence, representing plies SBA (0.51m), SBB (3.39m), SBC (4.41m), SBD (3.44m), SBE (3.79m) and SBF (1.34m) (each corresponding in turn to the No.4U and No.4L, No.2U and No.2L and No.1 Seams) are the most widely distributed across Moabsvelden which was intersected in most of the drillholes, except for those drilled in the south-western corner where a palaeo-high was intersected. The Bottom Seam shows remarkable lateral continuity with respect to internal partings and thin individual layers which has been confirmed by the geophysical logs. The average thickness of the Bottom Seam is 18.80m.

The No.4 Seam is split into the No.4 Upper and No.4 Lower, which are on average 4m thick each and are not separated by a distinguishable parting, but rather by coal quality. The No.4 Seam sequence is gently undulating and is at its deepest in the centre and southeast of Moabsvelden.

The No.4 Seam sequence is separated by the No.2 Seam by a 2.5m shaly sandstone parting. The No.2 Seam is split into the No.2 Upper and No.2 Lower by a 0.79m thick intra-seam parting. The No.2 Lower is generally thinner than the No.2 Upper, and both seams thicken towards the north. The No.2 Seam sequence is gently undulating and is at its deepest in the centre and southeast of Moabsvelden.

The No.1 Seam is on average less than 1.5m thick and is separated from the No.2 Seam by a thin shale parting. The floor to the No.1 Seam shows the same undulating nature as the overlying seams and does not display signs of major faulting though a dolerite intrusion associated with potential faulting showing less than 10m displacement has been modelled on the west of Moabsvelden.

The Mid Seam, or ply SM which corresponds to No.5 Seam, is situated approximately 11m above the No.4U Seam and is limited to the central part of Moabsvelden. The Mid Seam dips towards the east, reaching a maximum thickness of approximately 55m. In the northern and western areas of Moabsvelden the No.5 Seam has been eroded away. The coal seams are underlain by Dwyka Group tillites which range in thickness from 1m to 20m and are in turn underlain by basement dolomite and chert formations of the Malmani Group which typically display karst features.

Moabsvelden is proposed to be a typical deep open cast mining operation utilising the rollover methodology. As the coal seams on Moabsvelden do not outcrop, an initial boxcut will comprise a large volume of waste material prior to the commencement of coal production. The mining philosophy therefore aimed to minimise the total volume of waste material and therefore cost and time to first commercial production.

On completion of the mid-burden roll over, construction for the low-wall ramp access will commence on the northern side of the cut. The existing ramp has been designed to be extended 200m westwards into the cut which will ultimately form the first cut in pit MV2. Production access for both pits MV1 and MV2 will therefore be via the newly excavated low-wall ramp.

RoM coal will be trucked from Moabsvelden using 75t payload road trains to the respective 5-Seam and new 350tph coal processing facilities on Vanggatfontein, approximately 7.5km from the RoM stockpile on Moabsvelden.

Mine design parameters
Numerous considerations were measured in selecting the boxcut position, including:
- the northern high sensitivity wetland, with an initial 150m offset;
- power line location on the eastern boundary;
- positions of the dolerite intrusions in the geological model;
- potential upside to include possible joint ventures to extract surrounding Coal Resources later in the mine’s life; and
- startup risk, including pre-strip volumes and qualities.

The initial box-cut has been planned in an east-west orientation at a length of 600m and to a depth of 70m to the floor of the No.1 Seam, with the access ramp extending toward the west. Box cut waste and coal total volume amounts to 7.15Mbcm, of which the ramp contributes 1.02Mbcm. The ramp has been designed at 10% to intersect the floor of the No.2L seam at the western end-wall of the initial cut, with an initial cubby with ramp to be constructed to expose 200m linearly over the 90m wide box cut. The cubby will then be pushed back towards the ramp in 200m increments, during this process the ramp will be extended progressively.

After construction of the box cut, two strips of No.5 Seam will be exposed, to allow for roll over on the first. The current design only allows for one 50m off set bench on the No.5 Seam horizon (45m cut width + 5m offset for drills), the next bench above the No.5 Seam will be on a 15m off set to allow for a safe operation on the No.5 Seam bench.

Pit MV1 will mine southwards for approximately five cuts before the Pit MV2 boxcut construction commences. The initial MV1 access ramp therefore forms part of pit MV2, and the development of MV2 will essentially be a ramp pushback. A new low-wall access ramp will then be constructed from the north which will provide access to MV1, splitting it roughly into two 300m pit sections. Once the western boxcut is complete, the pit will be producing from two ramps serving four sections of the pit. For the MV2 pit, the low-wall ramp will be split again to service both sides of the dolerite intrusion effectively.

Mining will take place in three different pits. Pit MV1 will mine southwards for approximately five cuts before the Pit MV2 boxcut construction commences. The MV2 cut will be a pushback of the existing MV1 ramp with access to pit-bottom then achieved via a low-wall ramp. The northern MV3 pit has been designed to commence in mid-2026 with MV1 pit depleted in 2030. From 2031 onward mining will be conducted on the remainder of the MV2 and MV3 pits.

The northern pit is to commence mid-2025, with the eastern pit finishing in 2029. From 2030 onwards mining is conducted in the remainder of the western and northern pits.

For the full east-west boxcut development, access will be from the existing boxcut low wall ramp. Here care will need to be taken not to back fill the area required to access this extension. This low-wall access will be further extended to service the planned north pit (MV3) boxcut as well. The boundaries of the MV3 pit, planned in the north-western quadrant of the property, are defined by the property boundary and the wetland buffer zone. The pit will be accessed through a dedicated boxcut from Year 11 and will supplement production from both the MV1 and MV2 pits up to closure of the mine.

Pit RoM will be stockpiled on the basis of quality. The low quality plies will undergo a full wash, with the best quality coal simply crushed and sized. Mid-range quality coals will be split into a full wash portion and a crush and screen portion, providing for the blended end product to meet the desired 4,800kcal/kg NAR (22.0MJ/kg AD) product.

Based on a 22.0 MJ/kg product from the Moabsvelden plant, the crushing section would receive the RoM coal where it would be crushed to a -40mm size and then screened. The coarser oversize -40mm would be fed through a 350tph cyclone for further beneficiation. Bypass on the good quality coal would be increased in a similar manner to which the current Vanggatfontein CHPP operates.

The -1mm+150 micron fines, representing 6% of the plant feed would report to a spiral circuit, with the -150 micron ultra-fines reporting to the filter press plant via an 18m thickener.

Pit RoM will be stockpiled on the basis of quality. The low quality plies will undergo a full wash, with the best quality coal simply crushed and sized. Mid-range quality coals will be split into a full wash portion and a crush and screen portion, providing for the blended end product to meet the desired 4,800kcal/kg NAR (22.0MJ/kg AD) product.

Prior to the selection of the 4,800kcal CV (22.0MJ/kg AD) product, the proposed processing method had been based on a 19.6/19.0 MJ/kg product to Eskom which had been the basis of preliminary discussion with and presentations to Eskom. The change in product will simply require a modification to the DMS wash density setting within the CHPP.

Based on a 22.0 MJ/kg product from the Moabsvelden plant, the crushing section would receive the RoM coal where it would be crushed to a -40mm size and then screened. The coarser oversize -40mm would be fed through a 350tph cyclone for further beneficiation. Bypass on the good quality co ........