Modern Mining January 2019

ZINC

time as the bulk mining contractor (although some early access road construction and pre-stripping was carried out by a local contractor, Roux Mining). VZI could not have made better choices, as both compa- nies have high reputations in their respective fields. ELB has a long and impressive track record of deliver- ing capital projects in the mining and power sectors while Moolmans is one of Africa’s biggest – and cer- tainly most professional – mining contractors. Interestingly, the concentrator incorporates – for the first time in Africa and the first time globally on a zinc project – Staged Flotation Reactor (SFR) technology from one

the SA Institution of Civil Engineers. Fraser Alexander is operating and managing the TSF on behalf of VZI. The mining operation takes place on top of Gamsberg mountain, which hosts the Gamsberg deposit. It is an oval-shaped inselberg which rises about 220 m above the surrounding plain. The mine plan allows for three pits which, over time, will develop into a single super-pit. The total amount of material moved as of early December 2018 was 84 Mt with 68 Mt of this being pre-stripping. Ore production thus far has totalled 1,1 Mt. While open-pit mining will be the basis of operations for many years, there is under- ground potential at Gamsberg which would see the Gamsberg East underground resource (32,27 Mt of ore at 9,83 % Zn) – and possibly the depth extension of the Gamsberg North

of ELB’s many international partners, Canada’s Woodgrove Technologies Inc. Among the ben- efits of the SFR technology are a smaller plant footprint, a major reduction in power and air consumption (compared to conventional flota- tion plants) and reduced wear and maintenance costs due to lower impeller tip speeds. The plant, which is operated under contract by Minopex (part of the DRA group), boasts a high-tech control room which allows opera- tors a panoramic view of the flotation section of the facility. Mention should also be made of the highly-automated assay laboratory which has been supplied by IMP and makes use of robotics. ELB undertook the construction of the plant using, for the most part, companies within the ELB Engineering group, specifically ELB Construction (ELBCON), its construction arm, and B&W Instrumentation & Electrical, its elec- trical and instrumentation (E&I) specialist. The civils work was contracted out to Murray & Dickson and Teichmann. The tailings from the plant are discharged to a 117-ha HDPE-lined Tailings Storage Facility (TSF), which was designed and built by Liviero Civils in conjunction with Knight Piésold to accept 3,55 Mt of tailings a year. A change from the spigot deposition method outlined in the feasibility study to cycloning resulted in sig- nificant cost savings due to lower earthworks quantities and a smaller lined footprint while the concrete decant penstock was designed to incorporate precast concrete members to act as sacrificial formwork, enabling faster construction. The innovative features of the TSF led to it being named as the ‘Most Outstanding Geotechnical’ project in the 2018 awards of

The control room allows excellent views of the plant.

Gamsberg located in biodiversity ‘hotspot’ With Gamsberg being located in a unique and fragile environment which ranks as a global biodiversity ‘hotspot’, VZI has put a major effort into ensuring that the inevitable environmental impact of the project is kept to a minimum. To explain all the initiatives it has undertaken would take an entire article in itself but suffice it to say here that VZI’s environmental spe- cialists have worked with a wide range of experts to design and implement a process to ensure the necessary protection, preservation and ultimate restoration of the Gamsberg site. Among other measures, some 80 000 plants and 360 000 seeds have been collected and moved to the specialised facilities of the Karoo Desert National Botanical Garden to allow disturbed areas to eventually be replanted. In addition, a biodiversity offset programme offsets nearly 23 000 ha of land. The water system is a closed-circuit while the waste dumps and tailings facilities have been designed to reduce atmospheric pollution and to ensure run-off is prevented. VZI also points out that the open-pit operation was redesigned to reduce its size, effectively ‘sterilising’ 10 million tons of ore. „

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January 2019 _ MODERN MINING _ 51