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January 2015
MODERN MINING
35
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.