Modern Mining June 2019

REGIONAL FOCUS: WEST AFRICA

by hydraulic excavator and trucks will be employed. The project scale suits 120-t – 200-t class excavators in a backhoe configuration matched to 95-t class mine haul trucks. The main M5 pit is 2 km long and averages 430 m wide and 200 m deep at the southern end. The pit has been designed so the southern higher grade portion can be mined indepen- dently of the northern portion of the pit. Both the northern and southern pits will be mined in two stages, an initial starter pit and then a cutback to final limits, in order to target higher grade earlier in the schedule and defer waste. In addition to the open-pit resources, the M1 South deposit has a steeply dipping, high grade zone that extends to a depth of more than 500 m and is suitable for exploitation by underground mining methods using conven- tional jumbo development with long hole open stoping, progressing upwards from the base of each lift. Stope filling will use a combination of cemented aggregate fill, cemented rock fill and development waste rock depending on whether or not the fill needs to be exposed to mine adjacent stopes. The deposit has been divided into four lifts each of four or five levels. Within these lifts stoping progresses upwards from the base of the lift. The final level in each lift is mined as a pil- lar recovery beneath the lift above, or the open pit in the case of lift 1. The crown between the underground mine and the open pit is mined after the completion of the other stopes. The ore from the mining operations will be treated in a process plant with a nameplate throughput of 2,2 Mt/a, with an availability of 8 000 hours per annum and a nominal capacity of 275 t/h. It will be fed predominantly from the M1 and M5 deposits, with only small volumes of material supplied by the M3 pit. The plant design is simple but robust and broadly comprises the following: primary jaw crushing; a crushed ore stockpile and reclaim system; SABC mill grinding, pebble crusher and classification; gravity recovery; leach feed thickening; leaching and adsorption; elution, electrowinning and smelting. A heavy fuel oil (HFO) power station will be constructed at the process plant by an independent power provider (IPP) under a build-own-operate transfer (BOOT) agreement. The power station will be fitted with three heavy-duty HFO generator engines and one standby generator to maintain supply in the event of a shutdown of one of the engines. The Tailings Storage Facility (TSF) will comprise a four-sided paddock storage facility located 1,5 km north-east of the process plant

using a 5 % discount rate, the project generates a pre-tax NPV of US$612 million and an IRR of 83 %. Post-tax, the NPV is US$444 million and the IRR 62 %, with a post-tax payback period of 14 months following commissioning. The mine will deliver an average annual pro- duction of 217 000 oz of gold over the first five years of mine life and 153 000 oz of gold over the 10-year life of mine (LoM), with the average all-in sustaining costs (AISC) being US$523/oz in Years 1 to 5 and US$633/oz over the LoM. Year 1 production will be 301 000 ounces of gold at an AISC of just US$497/oz. The mine will recover 1,53 Moz over its life with the LoM recovery being 92,9 %. The majority of the mineral resources suit- able for open-pit mining at the project are within 200 m depth from the surface and of a lode-style mineralisation. The material to be excavated will be predominantly free dig from surface with blasting required deeper in the oxidation profile. Given these conditions, conventional open-pit mining techniques using drill and blast with material movement

Raw water for the mine will be sourced from the Nakambé River and stored in the 1, 5 million cubic metre Water Storage Facility (WSF), which is seen here.

Layout of the Sanbrado gold project.

36  MODERN MINING  June 2019