Gold miner AngloGold Ashanti expects to resume underground ore mining at the Obuasi gold mine, in Ghana, by mid-October.

Underground mining activities at the mine were voluntarily suspended following a sill pillar failure in May.

A detailed review of the mining and ground management plans has since been conducted by a cross-functional internal team and supported by independent third-party company Australian Mining Consultants (AMC).

Following this review, a comprehensive series of protocols has been introduced to supplement existing operating procedures.

The full suite of procedures ahead of the mining front now include the existing systematic probe drilling procedure; extensive use of technology, including cavity monitoring systems and cavity auto laser systems; and will be augmented with visual inspections to confirm the position and status of backfill in previously mined areas.

A new paste-fill plant has been commissioned and its reticulation system is expected to be completed by the end of this year.

These protocols, which have been integrated into the mine operating system, will be bolstered by scheduled audits to ensure the accuracy and diligence in probe drilling, and the intended implementation of the revised plan.

AMC will continue its review of future mining areas.

For the remainder of this year, underground ore will be used only to replenish the run-of-mine stockpile.

Gold production from underground ore sources is, therefore, expected to resume only in January and the ramp-up to the full mining rate of 4 000 t/d is expected to be achieved by the end of the first half of 2022.

Meanwhile, during the review period, underground development and work related to the Obuasi Redevelopment Project continued to progress, with Phase 2 construction substantially completed at the end of June.

Phase 3 of the project, which relates principally to extended capital expenditure to refurbish existing infrastructure around the KMS shaft, as well as to service the mine in deeper production areas, has progressed and will continue as planned through to the end of 2023.

AngloGold's revised production guidance for this year remains unchanged and assumes no gold production contribution from Obuasi for the remainder of this year.

It is estimated that the supplementary operating procedures introduced following the review will add about $10/t to $20/t to the mine’s operating costs, or about $50/oz.

In 2022, Obuasi is expected to produce between 240 000 oz and 260 000 oz of gold at an all-in sustaining cost of about $1 250/oz to $1 350/oz, and with cash costs of $900/oz to $1 000/oz.

AngloGold expects the mine to reach an annualised production rate of 320 000 oz/y to 350 000 oz/y by the fourth quarter of 2022.

Production is likely to remain at that level until the Phase 3 development is completed in the fourth quarter of 2023.

Production from 2024 to 2028 is anticipated to average 400 000 oz/y to 450 000 oz/y at an all-in sustaining cost of $900/oz to $950/oz.