The Kriel Colliery reserves are situated on the northern margin of the Highveld coalfield. Sediments of Vryheid and Dwyka formations underlay the area which was deposited on a glaciated Pre-Karoo basement consisting of Rooiberg felsites. The Vryheid formation is essentially an interbedded succession of sandstone with lesser gritstone, siltstone and mudstone, which contains five coal seams of the Highveld coalfield.

No. 4 seam
The No. 4 seam is found in most of the area and it is unmined in areas that have undergone weathering or been burnt by dolerite. The seam has thicknesses that vary from 3 to 6 m, but is remarkably consistent at approximately 4.9 m in thickness. The coal is commonly dull-lustrous, with a few bright bands, and has an average calorific value of 21 MJ/Kg. The top third of the seam contains inferior coal interbedded with bands of shale, carbonaceous shale and coaly shale10.

No. 5 seam
The No. 5 seam is found on certain parts of Kriel Colliery as shown in Figure 2. Figure 6 shows the No. 5 seam which is of interest to mine. The whole seam (No. 5 seam upper and lower) has an average thickness of 1.8 m. It contains a parting of carbonaceous shale which divides the seam into two parts. The parting has an average thickness of 0.2 m. No. 5 seam upper is sporadically developed and generally has less thickness of approximately 0.5 m. No. 5 seam lower is more consistently developed and has a thickness of approximately 1.1 m.

Kriel Colliery is an open cast (strip and benching) and underground coal mining operation (board and pillar mining using a continuous miner) located to the west of Isibonelo Colliery.

Board and pillar mining is typically used for flat or gently dipping bedded ores or coal seams. Once the coal seam has been accessed, the ore is mined utilising a regular grid of mining tunnels and involves progressively excavating panels into the coal seam whilst leaving behind pillars of coal to support the mine. The coal is then removed in a regular pattern while the rooms are mined out through the tunnels by drill and blast methods or a Continuous Miner and deposited onto a conveyor. The open chambers remaining following coal removal is referred to as a stope. The remaining coal contained within the pillars may be won at closure by a retreating system, starting at the farthest point from the stope access, allowing the roof to collapse and fill in the stope. This allows a greater recovery as less ore is left behind in pillars.

Anglo American Inyosi Coal: Kriel Colliery (Kriel) supplies coal to Eskom’s Kriel Power Station. Kriel Colliery intends to extend their mining operations in order to meet the Power Station’s coal requirements.

A coal Beneficiation Plant (also known as a Wash Plant or Coal Processing Plant) is required to meet the quality specifications of the power station. The quality of coal from current operations is higher than that of future operations and thus the plant is required due to the quality of coal required by the power station. The plant is to produce first washed coal in 2016 and is planned to continue until 2039. The footprint of the proposed plant and discard disposal facility is estimated to be approximately 150ha however this figure is subject to change.

Raw and product coal from underground and opencast operations will be conveyed to the wash plant, thus no trucking will take place. Coal will be stockpiled before entering the plant, while discard will be placed in a new waste dump facility. Two discard dumps, with a whaleback design and with capacities of 4 million tonnes and 26 million tonnes respectively are planned.