Styldrift I project
Styldrift I, which is an underground mine, lies about 5km from the North shaft of BRPM and is located within the boundaries of the Styldrift and Frischgewaagd farms, one of the last known blocks of shallow Merensky reef deposits. At steady state the mine will produce 230 000 tonnes a month, increasing RBPlat's production to 350ktpm.
In the latter half of 2015 the RBPlat Board made a strategic decision to align construction activities on the Styldrift I project and subsequent deferment of the ramp-up due to the material reduction in PGM prices experienced at the time. This approach required the implementation of a revised mining and construction plan.
The plan focussed on developing key shaft infrastructure on 600, 642 and 708 levels as well as the decline clusters on 600 and 642 levels to the north and south in order to accelerate the establishment of stoping sections. This would enable the mine to sustainably deliver 50kt per month and afford Styldrift the flexibility to effectively respond to market developments and align its ramp-up accordingly.
Towards the latter half of 2016 the progress made at Styldrift as well as basket price improvements allowed the company to commit to the next phase of expansion at Styldrift which will ramp up the mine to 150ktpm over a period of two years. This first phase of expansion makes allowance for all key underground and surface infrastructure which would be required to meet a 230ktpm production level and includes:
- an overland belt back to the BRPM concentrator complex
- all underground silos
- associated belt conveyor systems
- required water handling and pumping facilities
- stores and two ventilation shafts
Trackless bord and pillar methods will be employed in the thick Merensky resource areas with mining heights varying between 1.8m and 2.0m. The narrow Merensky reef area will be mined using a conventional breast mining layout.
A mining optimisation study completed in the fourth quarter of 2012 resulted in a change of scope, which was approved by the RBPlat Board in February 2013. The major changes approved included:
- Reducing mining bord widths from 13 metres (m) to 8m
- The use of ore transport in footwall drive by means of trucks was replaced with on-reef strike conveyors
- Shaft depths were increased by 18 metres to mitigate the geotechnical risk associated with UG1 strata intersecting key life of mine excavations.
Power and water supplies have been secured for the life of mine from Eskom and Magalies Water. There is good access to both BRPM and Styldrift I via modern roads and the infrastructure necessary to conduct mining is in place.
Twin vertical shaft system
Access to the underground workings at Styldrift I will be via a twin concrete-lined vertical shaft system, comprising a 10.5m diameter Main shaft and a 6.5m diameter Services shaft, sunk to a depth of 753m and 723m, respectively. Footwall infrastructure, mainly for the transporting of ore to the shaft will be developed approximately 25m below the Merensky reef horizon. Two 22-tonne rock skips will be used to hoist the ore to the surface via the Main shaft. A second footwall network will be developed at 690m level, at the base of the UG2 horizon, for potential concurrent exploitation of the UG2 reef.
The shaft system will be linked to the up-dip and down-dip on-reef roadway clusters on both the reef horizon and the footwall level. A network of on-strike haulages will underlie all sections for the transportation of ore to the Main shaft.
Styldrift shaft positions relative to key life of mine excavations
Merensky footwall infrastructure
Situated 25m below the Merensky reef horizon, the Merensky footwall will be the main artery of the mine. Apart from travelling ways, all footwall infrastructure will be mechanically developed. This infrastructure includes tipping points on the reef horizon, from which ore will be sent via box holes to the trucking haulage points 25m below. Fifty-tonne diesel-powered trucks will then transport the ore to ore passes feeding an underlying conveyor belt system 18m below. The conveyor system will include the main conveyor belt decline and an adjacent auxiliary decline.
The configuration of the Main shaft allows for:
- a single deck personnel and material cage compartment with capacity to transport 185 people
- a cage counterweight compartment
- two Merensky reef skip compartments, each designed to accommodate a 22-tonne skip
- two future UG2 skip compartments, each to accommodate a 13-tonne skip.
The Services shaft will comprise a personnel and equipment cage compartment with capacity to transport 22 people, as well as a cage counterweight compartment.
Four winders will be used during the project construction phase and three during the production phase. The height of the Main shaft headgear is 58.6m and the Service shaft 41.3m.