Leeuwpan coal mine is in the Delmas coalfield, on the western border of the Witbank coalfield. Leeuwpan, in the Victor Khanye local municipality in Mpumalanga province,
is 10km south-east of the town of Delmas, 80km east of Johannesburg and 70km south-east of Pretoria. It lies alongside the R50 hard-topped secondary road and is serviced
by a rail track that includes a rapid load-out station.
Leeuwpan is an opencast operation with various reserves, in various pits, mined simultaneously. Current mining operations are on the OJ, OL and OWM reserves with the introduction of OI reserves. OJ was depleted in 2018. The OI box-cut was completed in September 2018, with first coal expected in Q1 2019. The mine uses trucks and shovels for mining-related operations. We estimate that the mine will be in production until 2031, with the mining right lapsing in 2040. Leeuwpan supplies both domestic and export markets. The mine is equipped with a rapid rail load-out station, which is the preferred means of coal offtake, although road transport is accommodated.
Leeuwpan has two dense medium separator (DMS) plants that beneficiate export thermal coal and a crush-and-stack (CS) plant that handles selectively mined thermal coal, mainly for the local market. The second DMS plant, commissioned in 2016, is operated by Fraser Alexander (FA DMS). The original DMS plant produced a 5 700kcal/kg product whose market ended in Q4 2018, necessitating the change to a 5 200kcal/kg product. The FA DMS, on the other hand, was geared to produce a 5 200kcal/kg product. The CS produced a 4 200kcal/kg product. All three plants produce mainly thermal coal.
Leeuwpan has 4 152 boreholes in the mining right covering 4 269 hectares, but only 2 215 falls in the resource blocks. These boreholes were drilled in various campaigns and not all boreholes are reliable, so only 871 have been used in geological modelling. All Measured Resources at Leeuwpan are currently at 100m x 100m drill spacing.
|Date range||Company||Material notes|
|Up to 1988||Southern Sphere||262 borehole records exist for this period. Leeuwpan was sold to Kumba in 1988|
|1988 – 2006||Kumba Resources||Exploration began in 1990. Box-cut commissioned in 1992. Ceded rights to Exxaro Resources in 2006|
|2006 – 2018||Exxaro Resources||Ongoing exploration campaigns focused mainly on operational de-risking drilling programmes|
Two coal seams have been identified at Leeuwpan: top coal seam (TC) and bottom coal seam (BC). BC correlates with the number 2 seam of the Witbank and Highveld coalfields and TC correlates to the number 4 and 5 seams. BC qualities are generally higher than TC qualities.
The coal seams at Leeuwpan are primarily interbedded with sandstone, shale and carbonaceous shale. The coal was deposited on glacial sediments of Dwyka tillite which, in turn, were deposited on dolomite of the Transvaal Supergroup. A significant amount of magma intruded as concordant sills of dolerite in the Karoo strata in the Delmas area. Associated with the dolerite intrusion are numerous thin dolerite dyke structures that transgress the stratigraphy. Factors controlling geological and quality continuity are mainly surface weathering, significant variation in seam thickness due to an undulating tillite floor, faulting associated dolerite activity and dolomitic basement, and devolatilisation and weathering due to dolerite intrusions (sills and dykes).
The average total seam thickness at Leeuwpan is 10.9m, with an average raw calorific value of 20.1MJ/kg, raw volatile matter of 18.7% and raw ash content of 31.4% (adb). These qualities require beneficiation for export-quality products.
Operation resource evaluation
Samples are named and numbered as per the standard task procedure at Leeuwpan (STP-LP-PO.003) which states that: samples should be numbered on the BH core using a wax marker in a different colour to that of the lithology code. The number of samples is recorded on the log sheet as per STP-LP-PO.002. Numbering of the sample tag is written in the order of reserve BHID/sample number, example, MN971/2.
Samples are split on the lithological contact, if needed, use a chisel and hammer to ensure a clean break. Each sample is put in an individual bag with all contents represented in that interval, ensuring no contamination occurs between materials to be sampled. Should there be any unwanted material in the bag, a comment is made on the sample sheet. Once the sample is in the bag, a tag is attached. Two sample tags are written on plastic sample tags using a permanent marker. One sample tag is placed inside the bag and the second on the outside of the bag when sealed with a cable tie.
In 2014, Bureau Veritas was awarded the coal quality analyses contract for sample preparation and analyses. Raw RD is firstly determined, the sample is then crushed to -12.5mm and the 0.5mm fraction is screened out. Raw analysis is done on the +0.5mm -12.5mm material and float-sink analyses performed at float RD: 1.4, 1.5, 1.6, 1.7 and 1.8. Proximate analysis, CV and Sulphur are performed on each fraction. All sample preparation is done in accordance with ISO 3909 parts 1 to 5.
Bureau Veritas is SANAS-accredited for analytical work and participates in monthly local and international round-robins.
|Thickness cut-off (thickness and extraction height considerations)||Quality cut-offs (adb)||Geological loss|
|<2m (2014 model)
<1m (2015 model and onwards)
|Data datum||Cape LO29|
|No drillholes used for resource estimation||2 293 of 4 152 in the database|
|Validation||Conducted using queries in acQuire and Excel|
|Data compositing and weighting||Minex|
|Model||Previous model date||2016|
|Last model update||2018|
|Geological modelling software||Geovia Minex|
|Estimation technique||Growth algorithm|
|Grid mesh size||20m x 20m|
|Scan distance||2 000m|
|Model build limits||Upper: limit of weathering and topography/collar
|Model outputs||Roof, floor and thickness grids generated for structure
Raw quality grids
Wash quality grids
|Changes to modelling process||None|
|Category||Type of boreholes||Borehole spacing||Structurally complex areas||BH/ha|
|Measured||Cored boreholes with applicable coal qualities||0 – 100m||Resource blocks limited by faults, dolerite sill breakthrough and devolatisation. Geotechnical risks associated with faulting, dykes, sill and weathering – infill drilling||
|Indicated||Cored boreholes with applicable coal qualities||100 – 200m||Resource block limited by devolatisation and coal depth – infill drilling||0.6|
|Inferred||Cored boreholes with applicable coal qualities||200 – 1 000m||Resource block limited by devolatisation – infill drilling||0.2|
|Category||2018 (Mt)||2017 (Mt)||Differencein tonnes (Mt)||Difference
|Reason for changes|
|Measured||101.07||118.19||(17.12)||(14.49)||Mining depletion, disposals based on RPEEE and movement of resources from inside to outside LoM|
|Indicated||2.59||0.00||2.59||New information at OI West|
|Total Resources||107.26||121.88||(14.63)||(12.00)||Reporting methodology due to re-digitalisation of reporting strings|
|Probable||6.19||3.25||2.94||90.46||New information for OI West|
|Rounding of figures may cause computational discrepancies|
|All changes more than 10% are explained|
|Mining method: OC – underground|
|Figures reported at 100% irrespective of percentage attributable to Exxaro|
|Tonnages quoted in metric tonnes and million tonnes is abbreviated as Mt. Coal resources quoted as mineable tonnes in-situ and refer to remaining resources after 31 December 2018 and 31 December 2017|
|Coal Resources reported on a mineable in-situ (MTIS) basis|
|Coal Resources quoted inclusive of Coal Reserves|
Minex is used to model the coal seams and estimate in-situ Coal Resources at Leeuwpan. Coal resource block sizes vary, and boundaries are determined by farm boundaries, coal qualities, coal thicknesses, infrastructure and geological structures. The model generates grid surfaces for the upper and lower boundaries of the coal seams from borehole intersection points. The grid surfaces of the top of a seam and bottom of the seam are then subtracted from each other to estimate the thickness of the seam. The washability qualities associated with each sample are also converted from point to grid data using the same Minex growth technique. The method gives smooth surfaces which replicate the regional trends of geology, while reflecting local anomalies.
|Geological data||Data validated and signed off by competent person||Yes|
|Geological model||Geological model considered and signed off||Yes||Seam depth, seam thickness >1.8m, dry ash-free volatiles >26% air-dried CV >15MJ/kg, ash <50%. Coal qualities reported on an air-dry basis|
|Structural model||Structural model considered and signed off||Yes|
|Mining||Mining assumptions considered and defined||Yes||OC|
|Assurance||Minimum tier 1 assurance (Exxaro governance)||Yes||2018|
|Economic evaluation||Concept-level exploitation with economic and mining assumptions, including geotechnical and geohydrological assumptions||Yes||Life-of-mine exploitation study|
|Environmental||Reasonable demonstration that environmental approvals can be obtained within the context of local, regional and national governmental legislation||Yes||Current required approvals in place, except for OI West where IWUL had been granted for infrastructure. Approval for mining is pending|
|Tenure||Formal tenure must be demonstrated. Reasonable demonstration that a mining right approval can be obtained within the context of local, regional and national governmental legislation||Yes||Mining right valid to 2040|
|Infrastructure||Assumptions used should be reasonable and within known/assumed tolerances or have examples of precedence||Yes||Current infrastructure|
|Market||A potential market for the product with a reasonable assumption that this market is sustainable||Yes||Current coal supply agreement|
Operation reserve estimation
Scheduling of reserve is determined using mine scheduling applications from XPAC, the same software used to develop the LoMP schedule.
There is no difference between resource grids and reserve grids. Grid validation for Leeuwpan is conducted by checking for negative thicknesses, ensuring contact integrity and checking energy ratios to ensure progressive increase down the wash tables.
At Leeuwpan, the Measured Resources are all converted to Proved Reserves, except for UB, where it is a Probable Reserve because of low volatiles and absence of a market for this quality of coal. Indicated Resources are converted to Probable Reserves as is the case for OI West.
|Average thickness cut-off||0.5m on all seams except S5, which is 1m|
|Mining loss||25% for S5; 5% for all other seams|
|Contamination||5% on DMS plants and 1% on CS plant|
|Mining recovery efficiency||5% (CS); 5% (DMS bypass)|
|Planned average slope angles||45 degrees. For highwall stability, soft material is mined at least one strip ahead of hard material and coal-mining activities|
|Practical plant yield||90% DMS; 90% FA DMS, slimes loss on DMS of 9% and on FA DMS of 15%|
|Strip ratio cut-off||N/A|
|Environmentally sensitive areas||OJ (environmentally sensitive areas such as wetlands)|
|Social||Socially sensitive areas in the mining right (eg graveyards) are excluded from reserves in the reserving process|
|Geohydrological||Pit floor was taken into consideration to minimise water handling in the pit face|
The OI west portion of the Coal Reserve is still classified as Probable as Leeuwpan is still awaiting approval of the integrated water use licence (IWUL). Geological challenges (eg seam floor undulation and presence of sill and dykes) are addressed through proactive infill drilling and mine planning.
DMS bypass project to improve plant throughput on RoM with in-spec raw qualities. Leeuwpan is running a number of operational excellence initiatives to improve productivity, including:
The Leeuwpan integrated operations centre is intended to increase operational throughput by optimising the value chain. Having an across-the-board view of operations, it will be possible to make timely decisions for better control of interruptions across the value chain.