Ergo’s surface tailings retreatment

MINE CLOSURE

DRDGOLD subsidiary Ergo Mining has begun reclamation – at a R3.8 million setup cost – of the 4L25 mine dump, which holds 2.7 Mt of mining waste.

The reclamation of this dump is integral to sustaining production at Ergo and would free up a considerable land patch.

The dump is within the 4A8 reclamation area, less than 5 km from Johannesburg’s central business district, near Ergo’s City Deep milling and pumping plant.

With an average grade of 0.308 g/t, the 4L25 dump is estimated to contain some 850 kg of gold. 4L25 slimes will be recovered at a rate of up to 300 000 t per month over a period of 10 to 12 months, with supplemental tonnages coming from the 4L2 dump, whose reclamation is ramping down. This will sustain City Deep’s production levels for a further 12 months, until the larger 4L3 and 4L4 reclamation sites begin. 4L25 slimes will be reclaimed by a remotecontrolled, high-pressure water gun positioned on top of the dump. It will be combined with 4L2 slimes, and then pumped via a 40 km pipeline to Ergo’s metallurgical plant at Brakpan for gold recovery.

Reversing gold mining’s environmental impact

Besides sustaining City Deep’s production for longer, 4L25’s reclamation forms part of the extensive land rehabilitation programme DRDGOLD is executing under its ‘rolling back gold mining’s environmental legacy’ banner. The partially reclaimed dump will now be removed completely to liberate some 37 ha of land for rehabilitation and sustainable land use.

Further, remnant material from other clean-up sites will be reclaimed and trucked to the 4L25 site, and the newly installed pumping and piping infrastructure there will also relay this to the Brakpan plant for processing. This will clear additional land for rehabilitation and sustainable use.

High volume and low risk

The retreatment business is high volume and low risk. Vast quantities of material are processed monthly through the plant in order to recover gold from old mine dumps at a recovery rate that varies depending on the material being treated. As each old dump or dam is depleted, others are brought on stream. Teething problems are inevitable during the commissioning of new dumps and decommissioning of exhausted reclamation sites, and these can negatively affect recovery rates in the short term. Excessive rain can also affect recovery rates, although DRDGOLD has taken the appropriate measures to better manage weather-related issues in future.

Ergo, one of the world’s largest gold surface tailings retreatment facilities, owns the rights to treat around 100 sand dumps and slimes dams on the Witwatersrand. Some of these are currently being treated.