Diamond major De Beers’ US$2 billion cash injection to transition its Limpopo-based Venetia mine from a surface operation to an underground mine has in 2019 entered its sixth year of development.
This will represent a significant year for the mine as it completes sinking of its new production shaft.
At this point the next major target moves into sight as 2020 becomes the final push needed to start delivering underground carats from early in 2021, Venetia Underground Project head SAILESH SAHU tells LAURA CORNISH.
This article first appeared in Mining Review Africa Issue 1, 2019
The Venetia Underground Project is an impressive undertaking. It remains the largest investment spend for both De Beers Group and its largest shareholder Anglo American in South Africa.
The dedication required by the project teams to execute the project has required steadfast commitment considering the first underground diamonds are scheduled to be recovered nine-years after it was granted board approval back in 2012.
As the Venetia Underground Project moves into its sixth year of development, it is tracking well.
The project remains within budget and is not only on track to deliver its first diamonds in 2021 but also is scheduled to gain access to the second ore body earlier than previously planned, aligned to optimised production planning in the open pit operation.
The Venetia project comprises two primary ore bodies – K01 and K02 – which have to date been mined on surface.
Because the ore bodies extend well below surface, the transition will enable De Beers to continue mining the two kimberlites underground – to depths of between 800 m and 1 000 m.
To achieve this, De Beers’ shaft sinking contractor Murray & Roberts Cementation was awarded the contract to sink two vertical shafts as well as a surface decline.
Supporting underground and surface infrastructure is also required. Once complete and fully operational, the Venetia Underground Project will extend the lifespan of the mine by at least another 20 years to 2045.
At steady-state production, 5.9 Mt of ore will be treated in the existing process plant to produce around 4.5 million carats annually.
The underground infrastructure however has been designed to deliver up to 8 Mtpa of ROM material and should this tonnage volume be considered; De Beers will need to expand/upgrade its existing process plant.
Current project status
For now, Venetia remains an active open pit operation where diamonds are produced from the K01 pit using a split shell open pit configuration.
The K02 open pit reserve was depleted at the end of 2017 enabling underground development to access the ore body from underground workings which is the first carat production to be delivered in 2021.
“Delivering a project with relatively long timelines such as in Venetia Underground Project benefits from a flexible approach and this has enabled De Beers to continually evaluate options to optimise timelines, integration and ultimately business value,” notes Sahu, who took up the project head position in August 2018. He has an Engineering degree and an MBA from Wits University.
Depletion of the K01 open pit, which was a year ago set to continue producing diamonds until 2023 to a depth of 465 m, has been brought forward quite substantially and will conclude in 2021/2022 now.
“We have incorporated new infrastructure and mine design options to bring the K01 underground ore body into operation from 2022,” he continues.
This specifically entails the delivery of raise bore shaft and underground in-pit decline which will enable faster access to the two ore bodies.
“Piloting work for the raise bore shaft is scheduled to start next year,” says Murray & Roberts Cementation project executive designate Japie Du Plessis. The raise bore shaft will serve the purpose of a temporary hoisting arrangement.
“In 2020 the in-pit decline will be ready and will then enable us to meet our earlier production targets from underground operations,” Sahu adds.
Reviewing progress made on the vertical shaft and ‘top-of-mine’ decline over the last 12 months, Du Plessis notes that both vertical shafts now extend just below 940 m in depth.
“We remain on schedule to hit shaft bottom at 1 065 m at the end of 2019 for our production shaft, followed shortly thereafter by our service shaft,” he outlines.
“The supporting surface infrastructure, including winders, bulk air coolers, change houses and lamp rooms is also well underway,” says WorleyParsons RSA project director for large mining project Peet Greyling.
Bringing world-class standards to Venetia Underground Project
One of the biggest standout features for the Venetia Underground Project is the Canadian shaft sinking methodology that Murray & Roberts Cementation is applying to the vertical shafts, which has never been done in South Africa before.
It is designed to deliver optimal safe working conditions in what is traditionally recognised as one of the hazardous mining development processes.
The process is new in South Africa but is internationally common practice and Murray & Roberts Cementation has adopted it from its Canadian sister company.
In essence, it entails harnessing sling-down Jumbo drill rigs that nest in the sinking stage. These jumbo drill rigs need only one driller per boom to be on the shaft floor to operate the rig and to change drill rods.
The use of vertical shaft muckers, housed in the stage to clear the broken rock, have replaced cactus grabs. Because the muckers are capable of maneuvering the kibbles into position quickly and accurately, the need for the human element in this dangerous task is eliminated.
Cactus grab cleaning by comparison requires the kibbles to be manually handled by those on the shaft bottom to move it into position.
All activities throughout the sinking cycle are handled sequentially, meaning no two jobs will take place above one another simultaneously.
With fewer people working in the shaft and exposed to the contact area, safety risks are automatically reduced – significantly.
The drill rigs can drill a burn cut round, which improves the advance and reduces the fly rock that typically causes damage in the conventional method. They also have greater drilling precision which reduces overbreak and conversely eliminates the need for any secondary breaking.
With the blasting of a smoother shaft barrel, concrete usage is also substantially reduced. The use of emulsion provides a better blasting break, which will in turn make the task of the cleaning crew easier.
“This methodology has been highly successful at the Venetia Underground Project and has delivered on its primary objective to improve safety.
Further to this, our development rates have been on track which has successfully achieved more than 300 m since the end of 2017,” Du Plessis highlights.
Employee training is another area the Venetia Underground Project should be acknowledged for. Together with Murray & Roberts Cementation (at its Bentley Park training facility in Carletonville), De Beers has conducted thorough training exercises for employees. Sahu confirms that in addition to this the company is investing in the establishment of a training facility on site at Venetia.
“Training is an essential part of transitioning our mine to an underground operation and we want to ensure that all open pit employees who are fit and willing to work underground are given the opportunity to do so.” Sahu says.
The final component in delivering a world-class mine is the incorporation of new technologies that again offer safety enhancements and optimised production performance.
At this stage Sahu and his team are evaluating automation technology options which for now will include driverless trucks.
“We want to ensure that the technologies we adopt have been proven to work and will build these into the mine moving into the future. Capitalising on our mine design flexibility we will accommodate relevant automation technology that are beneficial to Venetia and its stakeholders”
Moving forward, the remaining two years to take the VUP into production is a critical period and requires ongoing commitment to ensure it continues to stay on track. 2020 will see the project peak in terms of development – increasing the on-site workforce from around 1 300 at present to around 2 000 from late 2020 through 2021 (excluding stay-in-business development and underground operational workforces).
The three lead project teams have developed a sound working relationship and Sahu, Du Plessis and Greyling are confident that together the project will continue to deliver according to its schedule. Based on its performance to date, this will undoubtedly be a flagship project for De Beers – in terms of both development and production.