Tag Archives: AMC Consultants

Strandline kicks off Coburn open-pit development with dozer mining units

Strandline Resources says rapid construction of its 100%-owned Coburn mineral sands project in Western Australia has facilitated commencement of open-pit mine development (starter pits) two months ahead of schedule.

After successful early mobilisation of the mining contractor (MSCS) in April 2022, construction of the temporary tailings storage facility is almost finished, and pre-strip mining will commence from next week, it said.

Mine development will now run concurrently with finalising the construction of the processing and supporting infrastructure, which remains on-budget and on track for first production of heavy mineral concentrate later this year.

The Coburn definitive feasibility study, released in June 2020, outlined a mine life of 22.5 years at a mining rate of 23.4 Mt/y.

Detailed mine planning optimisation by AMC Consultants, using the latest infill drilling data, has resulted in an enhanced pit design for the first two years of the mine plan, which contains less overburden (lower strip ratio) and potentially reduced mining costs compared with assumptions contained within this study, the company noted. The strip ratio has reduced from an average of 0.7 to 0.5 over the first two years of the mine plan, due primarily to optimising and scheduling more ore closer to surface on the eastern side of the deposit.

The three dozer mining units, in the meantime, have been delivered and assembled on site, ready to be moved into position for mining first ore later this year. These dozer units were designed and constructed by Piacentini & Son and form a key part of Coburn’s efficient dry mining methodology, capable of receiving, screening and pumping ore from the mine to the processing facilities at an average rate of 3,100 t/h, based on two units in operation at any one time, Strandline says. The in-pit dozer mining units are designed to be frequently relocated as the mine progresses through the mine plan.

Commissioning of the sub-systems associated with the wet concentration plant and hybrid power station is expected to commence from July as construction verification works ramps up, the company added.

Strandline Managing Director, Luke Graham, said commencement of pre-strip mining represents another important milestone for the project, ensuring the company remains on track for first production of heavy mineral concentrate in the December quarter this year.

“Construction continues to advance strongly with commissioning of the wet concentration plant and hybrid power station set to commence next month,” he said.

Capstone prepares Cozamin for introduction of paste backfill, dry-stack tailings

An updated Technical Report on Capstone Mining’s Cozamin copper-silver mine in Zacatecas, Mexico, has shown the potential for a mine life extension to 2031, and a plan for dry-stack tailings and underground paste backfill. At the same time, the company says it is studying the use of “innovative mining techniques and enhanced pillar recovery” to make the most of existing reserves and resources.

The updated life of mine plan released outlined average annual copper production of 51.2 MIb (23,224 t) of copper and 1.6 Moz of silver production over 10 years at average C1 costs, including the 50% silver stream, of $1.02/Ib of payable copper. From 2021 to 2027, average annual production is slated to be 58.8 MIb of copper and 1.7 Moz of silver.

The company said a planned ramp-up to 3,780 t/d, or 1.38 Mt/y, by the end of March quarter is on track, with a new section of ramp to open the one-way traffic circuit to debottleneck the mine (pictured) completed in early December 2020, ahead of schedule.

Reserves increased by 39% and now stand at 14.1 Mt, relative to April 30, 2020. Contained copper and silver increased by 37% and 49%, respectively, with around half of this increase due to recovery of high-grade pillars using paste backfill, Capstone said.

The miner said “tailings management transformation” activities were progressing on schedule at site, including feasibility-level design and studies in support of permitting a filtered (dry stack) tailings storage facility.

“This conversion from a slurry tailings impoundment aligns with industry leading socio-environmental best practice for tailings management,” the company said.

Meanwhile, a prefeasibility study (PFS) for an underground paste backfill system was completed in December.

The study indicates a paste backfill system will allow ore extraction containing over 100 MIb of copper and 3.1 Moz of silver between 2023 and 2031, which would have otherwise been left as unmined pillars. The PFS design has a capital cost estimate ranging from $41-$45 million and an increase in operating costs of around $7.50/t of ore mined. Capstone says its management has approved the paste backfill project and work has commenced on procurement of long lead items.

The proposed paste backfill system includes a tailings filter plant, a paste mixing plant, twin boreholes to deliver paste underground and an underground distribution system. The system is expected to be commissioned starting in the December quarter of 2022, with ramp-up completed in the March quarter of 2023.

PFS design of these facilities was completed by Paterson & Cooke in December 2020 and a feasibility study is underway with completion expected in April 2021. Mine planning was completed by Cozamin, with design support provided by a geotechnical consultant, and paste backfill operational guidance provided by AMC Consultants.

Within the latest release, Capstone also flagged the initiation of its “Impact23 Growth” project, which has identified areas of exploration excellence, innovative mining techniques and enhanced pillar recovery at Cozamin.

“By 2023, the goal is to further extend mine life, increase environmental and safety standards, and improve operational efficiencies at Cozamin, utilising mineral resources already discovered in addition to testing new targets,” the company explained.

Included among the options are the innovative mining techniques for resource to reserve conversion flagged at the start of this story.

Capstone says a study will be initiated this year to assess alternative mining techniques with the objective of lowering costs and dilution to convert resources to reserves from the indicated resource base. The current mining methods are longitudinal longhole open stoping and AVOCA, with possible alternatives to be studied including cut-and-fill, drift-and-fill and longhole open stoping with ore sorting technology.

Brad Mercer, Capstone’s SVP and Chief Operating Officer, said: “The life of mine plan announced today maximises extraction of the orebody’s high-grade core by deferring stoping in this area until the paste backfill plant is in operation in 2023. Projected production averages nearly 60 MIb of copper per year for seven years at first quartile costs.

“The Impact23 Growth project that we are kickstarting today is aiming to demonstrate in a 2023 technical report how Cozamin can sustain these levels of performance well into the 2030s.”

Darren Pylot, Capstone’s President and CEO, added: “After 14 years in operation, the best years of Cozamin are ahead. The mine is world class with sustainable low costs and leading safety and environmental performance entrenched throughout the organisation. The growth initiatives are supported by an entrepreneurial fabric at Capstone, as we embrace innovation and technology to create high impact value for our shareholders.”