Modern Mining January 2017

GOLD

have to bring Dynamite Hill into operation.” Truter notes that there have been some slope failures in the Nkran pit. “To counter this, we’ve now become the first mine in Ghana –- indeed in West Africa, as far as I know – to install a slope stability radar (SSR), which we’ve sourced from an Australian company, GroundProbe. The SSR monitors movement on a millimetre by milli- metre basis. The information is transmitted to our geotechnical office which analyses the data and can then alert personnel in the pit if any slippage is expected – and even give a very accurate estimation of when it might happen and the volumes involved. We demonstrated the system recently to Ghana’s Chief inspector of Mines and he was hugely impressed.” Moving to the process plant operation, Truter says the facility – whose basic design was com- pleted by PMI before Asanko’s involvement – has performed extraordinarily well and is now achieving gold recoveries of around 94 %, which is above feasibility study estimates. “As I’ve mentioned, the plant is now exceeding its design capacity,” he observes. “Interestingly, the mills – which PMI bought and we inherited – were over-designed and have been more than capable of keeping up with the higher tonnages we’ve been putting through the plant. Where we did have a bottleneck was with the crusher circuit. So we’ve recently commissioned a mobile crusher– a Sandvik UJ440i. This can

roughly doubling to 470 000 ounces a year. Our combined resources for Nkran – including sev- eral satellite deposits – and Esaase amount to 7,94 Moz at a grade of 1,71 g/t and our reserves are 5,25 Moz at 1,68 g/t. The reserve grade at Nkran is 2,21 g/t as opposed to 1,41 g/t at Esaase but Esaase is the larger deposit, accounting for around 56 % of our total resource ounces.” Phase 1 is a conventional open-pit, CIL operation. The mining is in the hands of mining contractor PW Ghana, highly experienced in gold mining in the West African region (includ- ing at Obotan, where it worked for Resolute). PW’s trucking fleet consists of mainly new Cat 777s working with a mix of shovels and excavators, among them a new 300-ton shovel which arrived on site earlier last year. Commenting on the mining operation, Truter says that Asanko was ‘over-mining’ quite sub- stantially until recently. “We’re currently a single-pit operation so – to derisk this – we took the decision to build up a strategic stockpile of over 1 Mt on the ROM pad. We’ve achieved this objective, which means that we’ve been able to cut back the mining rate. We’ve also put in a twin ramp system to avoid bottlenecks in the pit and have multiple working faces avail- able at various elevations to manage water ingress and any pit slope instability. The maxi- mum rate at which we can mine at Nkran is 3 Mt/a, so to reach our target of 3,6 Mt/a we

A recent photo of the Nkran pit, the main source of the Phase 1 ore.

The SSR monitors movement on a millimetre by millimetre basis.

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