Khwezela North is located in the Witbank Coalf ield where f I've coal seams are present. These consists of, from bottom, the No 1 Seam, sequentially to the No 5 Seam at the top and all contribute to the resource and reserve base. At Navigation pit, all seams, with the exception of the No 3 Seam, to a greater or lesser extent, have previously been mined underground, with the select portion of the No 2 Seam mined most extensively. The No 4, 2 and 1 Seams currently contribute to the colliery’s export product.

Washouts have been intersected in the north where the coal seams have been eroded by palaeo-rivers, with the resultant channels filled with clastic sediments. The edges of the washouts are irregular due to differential compaction. Northeast – southwest trending floor rolls are also encountered.

Both the No 1 and the No 2 Seam occur, separated by the No 1 Seam parting (P1). The floor to the No 1 Seam consists of a thin carbonaceous shale band, which conformably overlies a reworked tillite of the Dwyka Formation. The No 1 Seam is present over the majority of the Navigation area and has been previously mined via underground workings (bord and pillar). It averages 1.27 m thick but reaches a maximum thickness of 2.63 m.

The P1 is variable in thickness, ranging from zero to 4.20 m with an average thickness of 1.74 m.

The No 2 Seam is present across the entire Navigation area; the select portion of the seam ( the Number 2 Seam Select, S2S) has been previously mined by underground mining. The No 2 Seam is generally 7.12 m thick (varying from 4.63 to 9.60 m) and consists of a number of distinct quality zones or sub-seams with the better quality coal occurring in the lower portions of the seam. The uppermost zone, the Number 2 Seam Roof Coal (S2RC), is generally poorer in quality with shaley partings. The underlying Number 2 Seam Top Coal (S2TC) has a maximum thickness of 1.08 m, only averaging 0.21 m, and consists of dull coal. The S2TC is occasionally separated from the S2S by a gritty, carbonaceous shale parting (P2S). The S2S occurs at the base of the No 2 Seam and has a high proportion of bright coal.

The No 3 Seam consists of good quality coal but is thin (average thickness of 0.30 m) and is therefore not currently economic.

The No 4 Seam is present across most of the Navigation area, but due to a regional erosional event, it is truncated to the west of the Navigation Pit. It averages 3.99 m thick and is subdivided into the Number 4 Seam Top (S4T) and Number 4 Seam Select (S4S) sub-seams. The S4T is on average, 0.95 m thick and the S4S is 1.59 m thick. The S4U is separated from the No 4 Seam by a shaley parting that ranges between 0.15 and 3.86 m thick. The S4U has an average thickness of 1.63 m and consists of virgin coal with a relatively low Calorific Value (CV1) of 19 MJ/kg and is therefore not considered economic.

The No 5 Seam has been affected by weathering and erosion and, as a result, is poorly preserved in the Navigation area. It is generally present in the south and south-eastern portion of the area (as both virgin blocks and pillars in previously mined areas) These previously mined areas have extraction rates of up to 67%. It averages approximately 1.75 m thick.

The Navigation pit is an opencast operation with a pre-strip operation allocated to a truck and shovel fleet. The overall stripping ratio is low compared to other similar opencast operations. The main operational risks are the potential spontaneous combustion in the old workings and local subsidence effects.

The primary mining equipment includes a dragline, hydraulic shovels, haul trucks, overburden drills and a coaling drill and is supported by the necessary ancillary equipment.

The mine design is planned to maximise the use of the dragline excavating the interburden material between the No 2 and No 4 Seams. The remaining material above the No 4 Seam and the No 5 Seam, which is a combination of soft and hard overburden, is excavated with a truck-shovel fleet. This process material allocation allows the pre-strip and No 5 Seam to be in advance of the dragline operation whilst allowing the maximum use of the dragline, which is the most cost-effective method of interburden removal. The large degree of underground workings dictates that buffer blasting is required; the dragline is the most effective for this.

The material excavated by the truck-shovel in advance of the dragline is then trucked around the pit and placed on the spoils or on the available spoil dump areas at the beginning of the pit. The access to the coal and for the dragline relocation will be through highwall ramps to the No 4 Seam elevation and by a lowwall ramp to access the No 2 and No 1 Seams. Pit access will be not be optimal due to the small space available, but this access can be repositioned later, if necessary, as the deposit is shallow.

The overall equipment fleet is not constrained by capacity, but by the sequencing of the equipment, limiting its capacity. Within the Khwezela equipment allocation, there is more equipment available from the Bokgoni and Umlalazi operations, as these are now mothballed.

The Navigation Tip consists of a 1200x1200 mm static grizzly above a primary bin. The -1200 mm material is extracted via an apron feeder and fed onto a vibrating grizzly with an aperture size of between 80-100 mm. The grizzly oversize is fed into a jaw crusher and crushed to -350 mm. The material is then fed into a single rotary breaker for reduction to between 80-100 mm. The crushed material from the rotary breaker joins the vibrating grizzly undersize material and conveyed to the RoM bunkers which were previously used to receive railed and trucked RoM coal. Rotary breaker waste is fed to a 300 t rock bin for disposal back to the pit.

The Navigation CHPP replaced the Landau CHPP in 1992, processing coal from the Kromdraai Pit. The same infrastructure is now used to process the RoM from the Navigation Pit instead. The plant consists of two identical modules, A and B. The wash plant has had modifications, which will be described, but the major change has been the change in feed coal from the now-depleted Kromdraai Pit to the Navigation Pit. This is planned to extend the life of the reserves by eight years.

The Coal Handling Preparation Plant (CHPP) has a nameplate throughput capability of 6.0 Mtpa (nominal), but this has never been achieved due to a lack of RoM. The best feed-to-plant (FTP) achieved was 5.64 Mt in 2012. The plant was originally conceived as a two product plant, with two stages. The second stage cyclone plants were replaced by using Three-Product Cyclones (TPC) instead of the original 610 mm first stage cyclones.

The Navigation processing plant feed consists of a single conveyor t ........