Modern Mining January 2015

PLATINUM

As a result of the Optimisa- tion Plan, both the main and ventilation shafts have been shortened.

of mine. The net change in the project’s NPV is a positive R2,1 billion to R6,5 billion, the main contributors to this being the shorter timeframe to full production and the lower nominal capi- tal cost. Prior to the recent Merensky Reef intersec- tion, the previous major milestone passed during 2014 was the cutting of the first sta- tion/level on the ventilation shaft at a depth of 680 m in May. When Modern Mining visited the site at that point, the project was progress- ing well with the rate of advance on the shafts being targeted at 58 m per month, an objective which has since been met. The fact that the main and ventilation shafts are now expected to be completed well ahead of the original schedules is a considerable achieve- ment for Wesizwe given that the shaft sinking was at one stage running late as a result of the delayed delivery of Eskom’s phase one 20 MVA power supply to the site. However, an intense focus on shaft sinking performance has helped reverse the situation, as has the simple fact that – as a result of changes implemented as part of the Optimisation Study – the shafts are now shorter (by 30 m in the case of the main shaft and 50 m in the case of the ventilation shaft) than originally designed. The shortening of the shafts has been accommodated by the removal of the large underground primary crusher cham- ber originally planned and by bringing level development onto on-reef horizons. As part of the optimisation, a third shaft has been added to BPM’s infrastructure. This will be a 6 m diameter, 720 m deep shaft which will give extra capacity for men and materials and added ventilation capacity and current think- ing is that it will be raise-bored. The new shaft

will only be needed towards the end of the development phase, so it will probably only go out to tender in late 2016. Generally, BPM has experienced a good safety record but this was marred in October last year when a fatality was experienced dur- ing shaft-sinking operations – the first on the project. Ironically, the fatality occurred not long after the site had celebrated reaching the mile- stone of 500 000 fatality-free shifts. The main shaft will have a hoisting capacity of 255 kt/month of ore and 15 000 t/month of waste. An initial 230 000 tonnes a month will be mined from the Merensky Reef with the bal- ance coming from the UG2. Ultimately, once the Merensky reserves are depleted, the mine will become an exclusively UG2 operation – but this is not expected to occur until well into the mine’s 30-year life. The steel headgear of the main shaft, inci- dentally, is noteworthy as being – at 87 m – one of the tallest in the world. As has already been widely reported, it received recognition in the 2014 Awards of the Southern African Institute of Steel Construction, winning the Mining and Industrial Category of the competition. The structure consists of an A-frame designed to resist horizontal, vertical and wind loads. The top three levels of the A-frame form the sheave decks with the upper level at 72 m above the bank. There is a 14 m square centre tower between the bank and the underside of the sheave levels that accommodates six oper- ating floors. A 30-ton capacity electric overhead travelling (EOT) crane and its support structure tops off the headgear. To achieve a quick and safe completion of the steel erection, the main contractor – Louwill Bakgoni JV – planned and

The net change in the project’s NPV is a positive R2,1 billion to R6,5 billion, the main contributors to this being the shorter timeframe to full production and the lower nominal capital cost.

January 2015  MODERN MINING  35