STYLDRIFT PROJECT

From exploration to development

In 1970 three exploration holes were drilled by Johannesburg Consolidate Investments Co. Ltd (JCI). After a 20-year hiatus, drilling continued from 1990 to 2001, during which time 48 boreholes were drilled. In 1980 JCI undertook additional exploration campaigns at Styldrift and intersected UG2 for the first time.

Drilling campaigns started on Frischgewaagd in 1970 and between 1992 and 1998, nine boreholes were drilled on the property. Between 2005 and 2008, a total of 111 boreholes were drilled on Styldrift. During this period pre-feasibility studies (focusing on Merensky Reef extraction) were undertaken on both Frischgewaagd and Styldrift.

The Styldrift shaft complex lies about 5km from Boschkoppie's North Shaft. The feasibility study on the Styldrift Project was approved in September 2008 by the JV partners and bulk earthworks started in March 2009 and extend over a 17-hectare footprint.

The project will process Merensky ore via a new twin shaft system which is being sunk to a depth of 740m. Mining will be undertaken through a combination of mechanised room and pillar and conventional mining methods.

The Styldrift Project scope

• All preparatory civil and earthworks necessary for the commencement of shaft sinking
• Sinking of the twin vertical shafts and associated underground shaft system infrastructure
• Development of all planned underground capital infrastructure necessary for production ramp-up
• Procurement of all capital or other equipment necessary for the construction and permanent condition of the mine (underground and surface)
• Construction of a concentrator plant for the processing of ore from the Styldrift Merensky Phase 1 Project

Project infrastructure

Utilities

Power and water supplies have been secured for the life of mine from Eskom and Magalies Water respectively. Both the Boschkoppie mine and Styldrift Project have modern access roads, and the necessary infrastructure to conduct mining successfully.

To reduce dependency on the existing Magalies water supply, all excess water produced by mining operations at Styldrift will be pumped to the BRPM concentrator complex and reused for ore processing.

A 1.2km gravel road will provide a link between the project site and the existing access road during the construction phase, and will be upgraded to a permanent tarred road. A second gravel road will form a service link along the conveyor service corridor and connect the BRPM complex to the Styldrift mine.

Twin vertical shaft system

Access to the underground workings will be via a twin, concrete-lined vertical shaft system comprising a 10.5m-diameter Main shaft and a 6.5m-diameter Services shaft, blind sunk to a depth of 740m and 705m 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.

Twin vertical shaft system

Merensky footwall infrastructure

Situated 25m below the Merensky reef horizon, the Merensky footwall is the main artery of the proposed 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 boxholes 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.

Mining method

The orebody lends itself to a combination of mechanised Room & Pillar and conventional breast stoping. The mechanised mining method will be bord and pillar. Each trackless mining section will consist of 9 panels and 8 pillars. The primary extraction layout was originally designed to be 13m wide rooms separated by pillars which are 12m wide and 12m in length, however the bord widths are currently being reviewed. Ventilation holings are mined between panels within the mining sections and are 6.5 metres wide. Regional (17 metres wide) pillars will separate the mining sections. On reaching the stope limit, partial secondary pillar extraction will be undertaken using remote controlled equipment resulting in 12m by 4m crush pillars being left in secondary mining areas. The secondary crush pillars are designed to fall within the width/height ratio of 1.8:1 and 2.5:1. In the very thick reef areas, where reef thickness reaches 3.2 m these secondary crush pillars will be increased to 12m by 6m.

Both primary and secondary extraction may be adjusted locally in areas where poor ground conditions exist.. This may involve reduced primary bord widths and/or selective secondary extraction.

Shaft infrastructure

The shaft infrastructure comprises a main shaft with a diameter of 10.5m sunk to a depth of 740m and a services shaft with a diameter of 6.5m sunk to a depth of 705m below surface The configuration of the Main shaft allows for the following:

• 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.

The concentrator capacity at Styldrift will be 2.76 million tonnes per annum. Surface earthworks for the Styldrift Project began in 2009. Ramp up is planned for 2015 and steady state production anticipated by 2017. At steady state, the Styldrift Project will increase the BRPM production to 430,000 tonnes per month with in excess of 400,000 ounces of platinum concentrate per annum being produced by the BRPM JV.

3D rendering of the main and services shaft headgear

Project schedule

The feasibility study on the Styldrift Project was approved in September 2008 with the development of site infrastructure commencing in March 2009. With the project ahead of schedule, shaft sinking commenced in the fourth quarter of 2010. The Main and Services shafts had reached a depth of 219m and 152m respectively by December 2011.

The pre-sink of the two shafts commenced in October 2010 and was completed in April 2011. The process of converting the two shafts from pre-sink to full main sink was completed in July 2011 and the reef is anticipated to be intersected by the first quarter of 2013.

Underground mine first production is anticipated during the second quarter of 2015 and steady-state expected to be reached during the second quarter of 2017.

The Styldrift II shaft area will be the subject of pre-feasibility study in 2012.

For further information, please see the project review (PDF - 88KB) from Report 2011.