Tag Archives: Shaft sinking

UMS gearing up for shaft sinking work at Karowe Underground

With a team comprising some of the most experienced professionals in shaft sinking, United Mining Services (UMS) says it is gearing up for the pre-sinking of two shafts for the Karowe Underground Mine Expansion Project (UGP) in Botswana.

Following the completion of the feasibility study for the Karowe UGP, UMS was appointed by Lucara Botswana Pty Ltd and JDS Energy & Mining Inc in October 2019 to engineer and design the shaft sinking of the production shaft (8.5 m in diameter), and the ventilation shaft (6 m diameter), both reaching a depth of approximately 750 m below surface.

Fully commissioned in 2012, Karowe is an open-pit diamond mine with operations until 2026. The UGP will extend Karowe’s mine life to at least 2040. At the end of 2020, Karowe’s total probable reserve stood at 53.9 Mt containing 7.4 Mct including stockpiles.

According to Lucara, the Karowe mine remains one of the best producing mines of high quality plus-10.8 ct diamonds, having yielded five of the 10 largest diamonds in recorded history. It is also the only mine to have recovered three diamonds greater than 1,000 ct.

Dr Pieter Louw, Group Executive Project Services at UMS and UMS’ Project Manager, says the company’s wealth of knowledge and expertise in shaft sinking played a key role in securing the contract, and that the company is bringing in the heavyweights in the industry for the project.

Louw, himself, has a long history in underground mining and shaft sinking, having worked for major players in the mining and engineering sectors. He was involved in the De Beers Venetia Underground Project feasibility study, as well as a number of other feasibility projects for mines that are now in development or have already started production.

Louw explains that the two shafts at Karowe will be blind sunk using conventional drill and blast techniques. The production and ventilation shafts will both have equipment installed to pre-sink to a shaft depth of 100 m, if required, to accommodate the main sink shaft equipment. The pre-sink phase also allows the sinking process to commence as soon as possible while the main sink infrastructure is being fabricated and installed.

The new underground mine’s production shaft will have an A-frame type headgear, which will hoist 21-t payload skips, and will have a single drum auxiliary winder for people movement, and a man/material winder with counterweight and a big cage to service the underground.

UMS has refurbished four winders, which will be going to the mine for shaft sinking, including two stage winders and two Kibble winders. The company also purchased and refurbished Scotch derrick winder cranes for the pre-sink.

Louw says that UMS is in the process of mobilising up to 170 people to site for the pre-sink, which is expected to commence at the end of August and will take between eight and 12 months to achieve changeover ready for the start of the main sink. The main sink will take another two years after that, ready for mine development to commence in 2024, and full underground operations in 2026.

To make sinking safer, Louw says that UMS has adopted different sinking methodologies and equipment to be used at Karowe.

“In the past, we used to sink with cactus grabs which needed people in the bottom,” Louw said. “We are now using vertical shaft muckers and are buying state-of-the-art jumbo drill rigs to drill at the bottom. We’re doing inline work as opposed to concurrent work with people working at the bottom.”

He adds that, as part of its safety management plan, UMS has established a training centre on site at Karowe that facilitates inductions and training of local operators on the various equipment. The company is constructing a mock-up training tower on the surface to train operators on vertical shaft muckers and will have a similar training simulator for excavator operators.

Louw says UMS is fully established in Botswana and has partnered with Botswana Investment and Trade Centre to ensure that the project work permits run smoothly. Furthermore, the UMS design engineers are registered with the Botswana certification boards and can sign off all engineering designs and drawings for the project.

OZ Minerals Board gives go ahead for shaft expansion at Prominent Hill

The OZ Minerals Board has approved construction of a hoisting shaft at the Prominent Hill copper-gold mine in South Australia, paving the way for a mine life extension and throughput expansion.

Prominent Hill mine began operation in 2009 as an open pit and is now an underground mine producing 4.5 Mt/y, moving to 4.5-5 Mt/y from 2022 via a trucking operation.

Coming with a pre-production capital expenditure of A$600 million ($436 million), the Wira Shaft expansion project will see the underground production rate increase to 6 Mt/y from 2025. At this point, the average annual copper and gold production is expected to be circa-54,000 t and circa-108,000 oz, respectively, some 23% more than expected in the current trucking operation.

The study leverages close to 100 Mt of mineral resources outside the previous Prominent Hill ore reserves of 38 Mt of underground material.

Sinking of the shaft is expected to commence in the March quarter of 2022. Mining and installation of underground and surface infrastructure is scheduled for completion along with commissioning of the Wira shaft at the end of 2024, with nameplate capacity expected in the first half of 2025.

The shaft design comprises a 1,329-m-deep, concrete-lined shaft with a diameter of 7.5 m. Construction of the shaft will be via conventional strip and line method, with the sinking period approximately two years.

The shaft mine expansion also enables generational province potential with further mine life extensions possible as 67 Mt of resource remains outside the shaft expansion mine plan, OZ Minerals says. Further, an exploration program has also identified that mineralisation remains open at depth beyond the current resource boundary, potentially accessible via the shaft.

Announcing the expansion today, OZ Minerals Chief Executive Officer, Andrew Cole, said: “We are thrilled to see a long and productive future for Prominent Hill with the Wira shaft mine expansion enabling access to areas previously thought uneconomic and opening up potential new prospects.

“Prominent Hill is a quality orebody and remains open at depth. The reliable performance of the operation and its consistent resource to reserve conversion rate were all influential in the decision.”

For the first time, the company has used a carbon price in determining the project valuation, a practice it plans to adopt in other OZ Minerals projects going forward, Cole said.

The company plans to reduce its underground loading fleet to eight vehicles, from nine after the shaft expansion, with its trucking fleet going from circa-14 to five, post-shaft.

Scope 1 emissions intensity per tonne of concentrate are also expected to drop from 0.47 t CO2-e/t to 0.28 t CO2-e/t after the shaft installation.

The pre-production capital of A$600 million, which was an increase on the A$450 million outlined in the November 2020 expansion study, enables transformation of the site in line with the strategic aspirations of OZ Minerals, it said.

Provisions have been included in site capital projections to support this transformation, including progressing underground fleet electrification, upgrading some of the existing infrastructure, remote operation capability and automation.

The company expanded on this: “A battery-powered mining fleet is part of the future vision as OZ Minerals moves towards its zero-carbon emission aspiration. For this study, diesel trucks were assumed. However, installation of enabling infrastructure is included in the Prominent Hill Expansion case to minimise future disruptions when the switch to an electric fleet occurs. This, implemented as part of the asset’s site-wide electrification aspiration, would contribute to a further reduction in Scope 1 emissions.”

A pilot study is also being undertaken to review a low-energy dry grinding option. The Prominent Hill Expansion Study is not directly connected to, nor dependent on this ongoing work, however, the work presents potential future cost reduction and other opportunities, OZ Minerals said.

UMS to start pre-sinking work at Lucara’s Karowe Underground Expansion project

Lucara Diamond Corp’s Karowe Underground Expansion project (UGP) in Botswana is moving ahead with mobilisation of shaft sinking teams commencing late in June, and pre-sinking activities scheduled in the September quarter.

The Karowe UGP, which is expected to extend the operation’s mine life to 2040, is in a fully-financed position, with the latest schedule expected to see underground production hit full production by the end of 2026.

The 2019 feasibility study for the project envisaged life of mine production of 7.8 Mct, a payback period of 2.8 years and an after-tax NPV (5% discount) of $718 million; all from $514 million in pre-production capital.

COVID-19 delays have pushed the project off the original schedule – both in terms of timeline and cost – but the company says it is now making headway towards a 2026 start to underground production.

Lucara said no “material variances” between the 2019 feasibility study and the current execution plan have resulted, despite the delays.

“Rather, during this period in 2020 and 2021, all critical path items were addressed and a concerted effort was placed on detailed design, engineering and procurement which have helped to significantly de-risk the project,” it said.

Out of the total capital budget, the company has spent $51.4 million on project execution activities through 2020 until the end of June 2021, including shaft and geotechnical engineering, procurement of long lead time and essential shaft sinking items, surface infrastructure and construction activities, bulk power supply power line engineering and procurement.

Mobilisation of the shaft pre-sink team has commenced with shaft pre-sinking on track to commence in the middle of the current quarter.

Detailed engineering and design of the underground infrastructure and layouts will commence this quarter and are expected to be competed in the September quarter of 2022, with no major changes from the 2019 study plan anticipated.

Underground mine development is scheduled to commence in the second half of 2024 with underground production ramp up starting in 2026. Full production is scheduled for the end of 2026.

At the same time, open-pit mining operations have been adjusted to limit the risk of production shortfalls during the ramp up of the underground mine operations commencing in the first half of 2026. The open-pit mine is expected to terminate in mid-2026, Lucara said.

Access to the underground mine will be via two vertical shafts, the production and ventilation shafts. The shafts will be concrete lined with the production shaft acting as the main air intake and the ventilation shaft as the exhaust.

The number of shaft stations and nominal elevations remain the same as the feasibility study, with the planned depth of the production shaft still at around 767 m. The final planned depth of the ventilation shaft has, however, increased marginally to 733 m, from 716 m.

A 7,200 t/d shaft operation using long hole shrinkage (LHS) mining will provide an additional 13 years of mine life to the Karowe operation after a five-year construction period. The 767-m-deep production shaft will be equipped with two 21 t skips for production hoisting and a service cage for man and material movement through the mine. This shaft will also serve as the main fresh air intake to the mine.

The pre-sink construction contract and shaft sinking equipment procurement were awarded to UMS Botswana and UMS South Africa, respectively. METS International Ltd, a subsidiary of UMS, was awarded the shaft engineering contract.

The company explained: “Detailed design and engineering work on the production and ventilation shafts is now 90% complete, and has resulted in the following changes to the 2019 feasibility study: i) production shaft diameter has increased from 8 m to 8.5 m, ii) ventilation shaft permanent headframe, hoists and internal conveyances have been removed, iii) parallel pre-sinking of both shafts, iv) ventilation fans and coolers to be located on surface, v) in-shaft grouting of water strikes changed from grout curtain installation from surface, vi) planned development of an additional sublevel to assist in drilling of drawbells, and vii) removal of 670L de-watering galleries.”

Increased schedule time related to shaft sinking has been a result of the increased production shaft diameter, time allowances for in-shaft grouting during sinking operations planned at known water strike horizons, holing through all shaft stations between shafts and additional ground support for underground stations/level breakouts, the company said.

UMS is in the process of mobilising crews to Karowe to initiate pre-sink works. Pre-sinking of the two shafts will run in parallel and start with mobile cranes and then transition to Scott Derrick cranes with the final depth of pre-sink at around 40 m below surface.

With the exception of an additional sublevel (340L) to assist with drill and blast of drawbells, the design, layout and infrastructure of the underground mine all remain aligned with the 2019 feasibility study, the company noted.

Temporary power for shaft sinking is required until such time as the upgrade bulk power supply infrastructure is commissioned in the December quarter of 2022. A three-phased ramp up of the generator capacity is planned to support the increasing power requirements related to the shaft sinking activities.

A power supply and services contract for the temporary generators has been signed with Aggreko International Projects Ltd. Mobilisation has been initiated with the generator pad established. Commissioning of Phase 1 is scheduled during the September quarter to support the start of pre-sink activities.

The Karowe UGP is targeting the substantial resources remaining below the economic extents of the open pit in the South Lobe.

The LHS method is planned to systematically drill and blast the entire lobe on a vertical retreat basis. In LHS, a significant proportion of the blasted muck is left in the stope during blasting and stoping to stabilise the host rock with only the swell extracted during the drill and blast phase. Mucking will take place from draw points from the 310L extraction level. Once the column is fully blasted, the stope will be drawn empty by mucking the draw points.

The bottom-up approach of the LHS mining method takes advantage of the higher value EM/PK(S) kimberlite unit at depth in the South Lobe at Karowe, and balances high initial capital costs with low operating costs while de-risking the project with respect to the geotechnical and hydrogeological aspects of the host rocks, according to Lucara.

A revised project cost and schedule has been developed that captures the detailed engineering and design work through 2020 until May 2021, incorporating all changes, improvements, and COVID-19 related delays. Overall capital expenditures, including contingency, have increased marginally by some 4%, to $534 million, driven by the increase to the production shaft diameter and additional mine development.

The schedule to 75% of full production has increased by 1.3 years, driven mainly by COVID-19-related delays to commence the shaft pre-sinking and additional planned time for shaft station break-outs and ground support, Lucara added.

During 2020, Lucara negotiated and signed a self-build agreement with the Botswana Power Corp (BPC) for the construction of two substations and a 29-km-long 132 kV transmission line from BPC’s newly established Letlhakane substation to the Karowe mine. The planned route follows an existing regional 400 kV line and then runs parallel to the existing 11 kV transmission line currently supplying bulk power to the Karowe mine.

The new power infrastructure will provide the required power for the current open pit, processing plant and the underground mine expansion. Commissioning of and handover to BPC is scheduled for the December quarter of 2022. Construction of substations is scheduled to commence this quarter and power line construction in the March quarter of 2022, the company said.

JDS Energy & Mining Inc is the engineering procurement and construction manager for the execution of the Karowe UGP and is currently building up the on-site project team in conjunction with Lucara’s owners team and working in close cooperation with the Karowe Diamond Mine operations team.

Efficient shaft revitalisation with remote-controlled demolition equipment

The benefits of robotic equipment have long been understood in mining applications, however common mining robots tend to be cumbersome and highly specialised – a great tool for drilling in large, open areas, but not much else, according to Raymond Ippersiel*.

Looking to apply mechanised solutions to ultra-deep, narrow-vein applications, some operations are employing a different kind of robot. Compact, highly versatile remote-controlled demolition robots are uniquely suited for the demanding conditions deep underground. These compact machines offer exceptional power-to-weight ratios – on par with classic excavators three times their size – while an advanced three-part arm provides unrivalled range of motion for drilling, scaling, breaking and bolting in any direction.

But there is a lot more these flexible, hard-hitting machines can offer modern mining operations. In addition to ultra-deep applications, the power and versatility of remote-controlled demolition machines makes them an ideal solution for support tasks such as shaft revitalisation and maintenance. Miners are finding employing a demolition robot not only speeds up progress in these situations, but also increases safety by taking on much of the physical work while keeping employees out of harm’s way.

Revitalisation versatility

Mining techniques have changed over the years, and productivity has decreased steadily since the 1960s. For many operations, returning to old shafts with more modern equipment can supplement production. However, getting these shafts in shape to meet modern safety regulations can be a difficult process requiring substantial work. Most are littered with rubble, collapsed supports and downed utilities, making the process of opening them up slow and dangerous.

In these types of situations, the versatility of remote-controlled demolition machines can minimise equipment and personnel requirements for highly efficient renovations. Armed with a suite of attachments, a demolition robot can perform almost any required task.

A breaker, for example, is used for scaling during initial refurbishment work, and a grapple is used to handle rubble and refuse to clear the bottom as well as assist in installing utilities. To dismantle old supports, steel or timber, a saw/grapple combination can be used. This reduces handling and cutting the steel to premium scrap lengths while working off a galloway.

With extensive equipment and attachment options available from innovative manufacturers, there is an opportunity to use demolition robots in just about every high-risk, heavy-labour maintenance situation, Raymond Ippersiel says

Primary and secondary blasting and rock bolting can all be managed with the drill attachments. Miners can then switch to a beam handler for erecting support ribs and installing wire mesh. These dexterous attachments can also be used for setting new services such as rails, pipes, or cables.

Finally, shotcrete attachments are also available.

More efficient maintenance

These attachments also make it easier for mines to maximise productivity for shaft and tunnel maintenance tasks. Replacing large crews with a small team and a demolition robot can result in a significantly more efficient process.

One operation was able to eliminate all manual labour in a shotcrete removal application and advance their maintenance schedule by months. They positioned the demolition robot on a platform that rotated around the core of a shaft boring machine. After the shotcrete was removed, they used the robot to pin and bolt new screening.

In addition to making shaft maintenance easier, demolition robots are increasing safety and efficiency for widening operations. They can be underhung from a galloway stage, hammer, drill and blast, drill and split and replace old clam buckets for mucking out.

The future of mining

With extensive equipment and attachment options available from innovative manufacturers, there is an opportunity to use demolition robots in just about every high-risk, heavy-labour shaft maintenance situation. The possibilities are only limited by the imagination.

*Raymond Ippersiel is a Training & Application Specialist at Brokk Inc. He has 10 years with the company and specialises in robotic demolition applications for the tunnelling, process and demolition industries

NexGen marries ESG and financials in Arrow uranium project feasibility study

NexGen Energy CEO, Leigh Curyer, says the company’s Rook I uranium project has earnt its place as one of the “leading global resource projects with an elite ESG profile” after the publication of feasibility study results on the project’s Arrow deposit in the Athabasca Basin of Saskatchewan, Canada.

The study was completed jointly by consultants including Stantec, Wood and Roscoe Postle Associates (now part of SLR Consulting), with other technical inputs completed by sub-consultants.

Financial highlights from this study included an initial capital bill of C$1.3 billion ($1.03 billion) repaid with a post-tax net present value (8% discount) of C$3.47 billion based on a $50/Ib uranium price. From years 1-5 average annual production was due to come in at 28.8Mlb of uranium oxide, with average production over the life of mine of 10.7 years of 21.7 MIb/y.
The company laid out plans for a 1,300 t/d mill processing an average feed grade of 2.37% U3O8.

Listed within the “top five feasibility study outcomes” was enhanced environmental performance, with NexGen saying an optimised facilities layout had reduced the project footprint by around 20% and lowered on-site personnel transportation and ore haulage.

Optimised shaft sizing, water usage through advanced water recycling, and plant engineering reflected elite environmental standards, it added.

“With respect to the proposed shaft, mine workings and underground tailings management facility (UGTMF) locations, geotechnical and hydrogeological testing validated highly competent rock with no significant alteration, no major structures, and low hydraulic conductivity,” the company said.

The mine plan at Arrow was based on conventional long-hole stoping using the 239.6 MIb of declared reserves, the company said.

“Geotechnical studies during the feasibility study re-emphasised the conventional long-hole stoping mining method, including the use of longitudinal and transverse stopes, 30 m level spacing, and the nominal stope strike length of 12 m to 24 m,” it said. “This represents an excellent stope stability range for underground mining in the highly competent conditions.”

Given the competency and conditions of the underground environment, all waste streams from the process plant are planned to be stored underground in the UGTMF, while process water streams will be treated on surface in the optimised effluent treatment plant, NexGen said.

The underground workings will be accessed by two shafts, with the production shaft supporting personnel movements, materials, ore, waste and fresh air. The production shaft was increased to 8 m in diameter (from 6.5 m in diameter in the prefeasibility study (PFS)) to optimise radiation and ventilation management, ensuring the mine is elite from a safety perspective, the company said.

“Additionally, the production shaft will have divided compartments, ensuring that fresh air and personnel entering the mine, remain isolated from ore being skipped to surface,” it added.

The exhaust shaft was ultimately decreased to 5.5 m in diameter (from 6.5 m in diameter in the PFS) and will be used for exhaust air and emergency secondary egress, NexGen said.

Like some other projects in the region, shaft freezing will be required to a point to secure the underground project, NexGen confirmed.

In terms of processing, NexGen said extensive test work and engineering had determined that proven technology in a conventional uranium processing flowsheet is most effective to produce uranium oxide from the Arrow deposit.

The main components of the processing plant are ore sorting; grinding; leaching; liquid-solid separation via counter current decantation and clarification; solvent extraction; gypsum precipitation and washing; yellowcake precipitation and washing; yellowcake drying; calcining and packaging; and tailings preparation and paste tailings plant.

Metallurgical testing resulted in supporting and refining process design parameters, with the process recovery of 97.6% confirming the predictable nature of the processing flow sheet, it said.

“The feasibility study also confirmed that all processed waste streams can be stored in the UGTMF and no surface tailings facility is required,” NexGen said. “The UGTMF is a reflection of NexGen’s industry-leading environmental design approach, contributing to the significant reduction of the project’s surface footprint, and representing an opportunity to implement best practice of progressive closure of tailings facilities during the operational phase of the mine.”

A feasibility study drill program validated the geotechnical conditions and favourable conditions for the UGTMF, with the study also optimising the geotechnical design, size and sequencing of the UGTMF included in the mine plan.

The study test work demonstrated paste fill strength met or exceeded all requirements set in the feasibility study design for a potential paste-backfill to be used for underground stope stability.

In terms of the timeline to production, NexGen said it planned to submit its Environmental Impact Statement in the second half of this year, along with relevant licences.

RUC Mining set for Newmont Tanami shaft lining and equipping contract

RUC Cementation Mining Contractors says its RUC Mining business has been awarded preferred bidder status for the shaft lining and equipping contract at Newmont’s Tanami Expansion 2 project in the Northern Territory of Australia.

Additionally, Newmont, last week, granted RUC Mining authority to proceed with long lead procurement RFQ process via a short-term contract to progress the works, the contractor said.

Back in November, RUC Cementation Mining Contractors and GR Engineering Services agreed to team up as part of a plan to construct surface infrastructure, as well as complete the shaft lining and equipping, for a proposed hoisting shaft at the Tanami Expansion 2 project. There was no mention of this agreement in the latest news from RUC Cementation.

“RUC Mining is excited to be engaged on the major project with global leader Newmont, the world’s largest gold producer,” it said. “Together we look forward to safely progressing the Tanami Expansion 2 project, delivering long-term value to both Newmont and RUC shareholders.”

Subject to finalisation of agreements, the contract award is expected this month, it said.

The Tanami Expansion 2 project is expected to increase the annual capacity of the processing site to 3.5 Mt/y, from 2.6 Mt/y, and extend the life of the mine beyond 2040.

Murray & Roberts Cementation achieves major safety milestone

The year has started strongly for mining services specialist Murray & Roberts Cementation, with a safety achievement of five million fatality-free shifts.

According to Mike Wells, Managing Director of Murray & Roberts Cementation, this landmark has been reached as part of a concerted corporate journey towards Zero Harm.

“This exciting milestone, which we reached in early January 2021, is the result of years of commitment by every member of the company – through multiple initiatives and programs,” Wells said. “This has included our unrelenting focus on the Major Accident Prevention program, as well as stringent risk assessments and the verification of critical controls in the field.”

Perhaps the greatest outcome of these efforts, he highlighted, is that the company’s safety leadership has succeeded in motivating and inspiring all employees in fully internalising safety principles. This has entrenched the belief that Zero Harm can indeed be achieved, with each employee returning home safely every day.

“We have seen a vital attitudinal change over the years, where success has bred more success and all our people take ownership of their safe work practices – both personally and collectively,” Wells said. “This builds a resilient safety culture, which has included a crucial commitment to doing work right the first time.”

Underpinning much of the success in safe working practices has been the increased investment in effective training strategies at the Murray & Roberts Training Academy at Bentley Park near Carletonville, South Africa. Here, the latest technologies and methods – supported by realistic mock-ups of mining environments – ensure workers are fully prepared for all working conditions.

“Our mining customers today regard the commitment to fatality-free operations as a given – not only for themselves but for their service providers,” Wells said. “We are proud to be able to demonstrate our success as part of the broader progress in this field by the whole mining sector.”

Over the years during which the five million fatality-free shifts have been achieved, Murray & Roberts Cementation has conducted a diverse range of projects across sub-Saharan Africa, including large shaft sinking contracts. Employee numbers over this time have averaged about 4,000, Wells said.

Anglo American pledges further investment in Woodsmith polyhalite project

Anglo American is to invest more money in the construction of its Woodsmith polyhalite mine in Yorkshire, UK, in 2021, following sound progress on the development in 2020.

In an investor presentation this week, Chief Executive, Mark Cutifani, announced the company will invest $500 million in Woodsmith next year, an increase on the $300 million it had previously committed to spending.

The improved funding commitment was, he said, a reflection of the good progress that was “ahead of expectations” and “to ensure that the critical path elements continue to proceed at the optimal pace and sequence”.

It was also revealed that the first drive of the 37 km tunnel from Wilton on Teesside was nearing the 12 km mark and that good progress was being made on preparing for further mineshaft sinking operations at the Woodsmith Mine site near Whitby, which are expected to begin in the new year.

Simon Carter, Chief Development Officer on the Woodsmith Project, said: “It’s been an incredibly challenging and busy time on the project recently, not least because of the adaptations and safety measures we’ve introduced to make sure that we can work safely during COVID-19. But, I am incredibly proud that the whole team has pulled together and enabled us to make such good progress. I’m delighted that we have been able to buck the trend of many businesses and expanded our workforce, providing important opportunities for people in the region in these difficult times.”

Anglo American has hired around 150 new people since it launched a recruitment drive in the autumn, with around 60 more expected to be hired in the coming weeks. Almost three quarters of these new workers have been hired from areas local to the project in North Yorkshire and Teesside.

The announcement of increased funding is expected to allow the project to recruit an additional 130 construction workers and dozens of additional management and administration roles next year, which will increase the size of the workforce to around 1,400.

The project involves the sinking of two mineshafts with Herrenknecht’s Shaft Boring Roadheader technology into the polyhalite ore over 1.6 km beneath the surface near Whitby, and the construction of a 37 km long tunnel to a new processing and shipping facility on Teesside.

When the mine is complete, extracted polyhalite ore will be hoisted up the mineshaft and transported underground on a conveyor belt, avoiding any impact on the countryside above, the company says. From there, it will be shipped around the world and sold to farmers as a natural low carbon fertiliser, certified for organic use.

Caledonia Mining heads for Central Shaft commissioning at Blanket gold mine

Caledonia Mining says it has fully equipped the Central Shaft from its base to the surface collar at the Blanket gold mine in Zimbabwe, with commissioning on track for the March quarter of 2021.

This milestone has been completed considerably below budget and within a time frame to underpin the company’s expectation of delivering production of 80,000 oz of gold in 2022, it said.

The Central Shaft project, which extends Blanket’s life of mine to the current time horizon of 2034, was initially slated to reach a depth of 1,089 m, however, was extended to 1,204 m.

Steve Curtis, Caledonia Chief Executive Officer, said: “Shaft sinking is widely regarded as one of the most dangerous activities in mining and I am proud to report that over more than five years the crew achieved 1,850 fatality free shifts to date with only two loss time injuries (LTI) and achieving more than one million LTI-free man hours worked since the last LTI.”

He added: “Central Shaft is one of the largest gold mining investment projects in Zimbabwe and will be transformational to our business: our target production is set to increase by 45% to 80,000 oz by 2022 while our long-term all-in sustaining costs are expected to drop to $700-$800/oz. Central Shaft will also position us to step-up our deep level exploration which, if successful, may extend Blanket’s life of mine, which is currently to 2034.”

The capital cost of the project to date is around $60 million, compared with initial sinking contractor quotes received of about $100 million. The shaft work was completed by Blanket crews with supervision from Sinking Engineering Mining Construction, Caledonia said.

BHP commits another $272 million for shaft lining at Jansen potash project

BHP has agreed to invest another $272 million in the Jansen Stage 1 potash project in Saskatchewan, Canada, following challenges encountered with placement of the shaft lining and more recent impacts from the company’s COVID-19 response plan.

Up until this point, BHP had committed to spending $2.7 billion on the project.

BHP said in its September quarter results: “As a consequence of the challenges encountered earlier with placement of the shaft lining and then the more recent impacts from our COVID-19 response plan, the board has approved additional funding of $272 million for the completion of the shafts, resulting in a total budget of $3.0 billion (previously $2.7 billion).”

This is expected to result in the excavation and lining of the 7.3 m diameter production (975 m deep) and service (1,005 m deep) shafts – sunk by DMC Mining using Herrenknecht’s Shaft Boring Roadheader – and the installation of essential surface infrastructure and utilities.

Back in August, the company said it would not decide on an investment in the full Stage 1 project until mid-2021, a delay on the February 2021 deadline it previously advised of. This was down to the shaft lining problem.

The current Stage 1 plan, which is 86% complete and has an expected capital outlay of $5.3-5.7 billion, involves building out initial capacity of 4.3-4.5 Mt/y of potash, with expansion optionality.

BHP added: “Jansen Stage 1 remains well positioned with attractive medium to longer-term commodity fundamentals, and is set to be a high-margin, low-cost, long-life asset, with multiple, basin-wide, expansion opportunities. As always, we will be disciplined about our entry into the market and it must pass our strict Capital Allocation Framework tests.”