https://www.miningweekly.com

Mine dumps not a perpetual rehab challenge

24th April 2015

By: Ilan Solomons

Creamer Media Staff Writer

  

Font size: - +

JSE- and NYSE-listed surface gold miner DRDGold has dismissed the public perception that mine dumps continuously present rehabilitation challenges even after they have been removed.

“This is not the case and we have to continuously stress this point to the public through our stakeholder engagement platforms,” said DRDGold Ergo Mining’s operations director Jaco Schoeman during his presentation at black-owned training and conferencing company Intelligence Transfer Centre’s fifth yearly EnviroMining conference, held in Johannesburg last month.

He noted that DRDGold owned most of the mining dumps from Randfontein, in the West of Gauteng, to Springs, on the East Rand, which all comprise Ergo’s mining operations.

DRDGold’s assets cover an area of about 62 km from the east to the west and 25 km from the north to the south, in the Witwatersrand, in Gauteng, and include access to about 750-million tonnes to 900-million tonnes of tailings deposited across the western, central and eastern sections of the Witwatersrand.

“Our liability assessment is set at about R400-million and I estimate that we can reduce this by about 50% once the dumps have been removed,” Schoeman pointed out.

He explained that DRDGold rehabilitates the dumps, with an environmental footprint of 1 200 km², by removing the dumps’ soils – including the subsoils – and undertaking radiation evaluations to ensure that the sites are below the required radiation limits.

If high radiation levels are detected, more soil is removed from the site until bedrock was reached, after which the area was vegetated, Schoeman noted, adding that such a process removed the material that created acid mine drainage (AMD). The sites are then monitored for about five years to ensure complete rehabilitation.

He stated that the biggest environmental challenges DRDGold faced, as a surface miner operating in urban areas, were dust and water resources.

Dust is produced when a new rock face is opened and when old dumps have not been vegetated.

DRDGold has, therefore, spent R225-million on vegetation and environmental programmes over the past five years.

Schoeman noted that the mix of the vegetation and the consistancy of water supply to irrigate the vegetation were very important to ensuring successful site rehabilitation.

He admitted that Ergo required “an enormous amount of water” – about 2 Mℓ of water per hectare a year to establish vegetation at mine dumps and 1 Mℓ per hectare a year thereafter to maintain the vegetation.

Ergo’s operations used good-quality potable water within the 24 Mℓ/d limit it consumed for vegetation and reclamation purposes, Schoeman added.

“We acknowledged that this was not a good practice from an environmental perspective and it was also expensive . . . Therefore, going forward, we aim to reduce potable water use and to use it only for potable water purposes and not mining-related activities.”

The average annualised figure, which could vary because of seasonality, for AMD generated in the Witwatersrand’s Central, Eastern and Western basins is 166 Mℓ/d.

He noted that the State-owned Trans-Caledon Tunnel Authority’s (TCTA’s) AMD treatment plant in the Central basin neutralised the water and the plant’s sludge was deposited into Ergo’s Brakpan tailings dam, while the neutralised water was released back into the water system in the area.

However, as a result of the high levels of calcium sulphate and calcium carbonate in the AMD circuits of the TCTA and Ergo, the company can use only up to 8 Mℓ/d of treated AMD water – high levels of calcium sulphates in pipelines cannot be chemically removed and have to be removed physically.

Schoeman explained that accepting more than 8 Mℓ/d of such AMD would have resulted in “major financial costs” for Ergo, potentially putting the company “out of business in the long term”.

Ergo also uses local municipal wastewater circuits and is developing its R22-million Rondebult Wastewater Treatment Plant, which the company expects to start pumping water by the end of next month, on the East Rand.

The plant’s 7.5-km-long pipeline is in place, and it will use sand and carbon filtration systems. The sand filtration system will remove the various types of solids in wastewater and, after it has been treated, an activated carbon filter will absorb the organic matter in the wastewater.

Once the wastewater has been processed, it will be pumped to Ergo’s reclamation sites.

Schoeman pointed out that water manage- ment was a “key concern” for DRDGold, with 70 km of pipe in the Witwatersrand transporting water to its metallurgical plants to prevent water spillage.

Although the mining industry accounted for only about 8% of South Africa’s total water use, the industry impacted significantly on the quality of water in the national system, he added.

Edited by Martin Zhuwakinyu
Creamer Media Senior Deputy Editor

Comments

The content you are trying to access is only available to subscribers.

If you are already a subscriber, you can Login Here.

If you are not a subscriber, you can subscribe now, by selecting one of the below options.

For more information or assistance, please contact us at subscriptions@creamermedia.co.za.

Option 1 (equivalent of R125 a month):

Receive a weekly copy of Creamer Media's Engineering News & Mining Weekly magazine
(print copy for those in South Africa and e-magazine for those outside of South Africa)
Receive daily email newsletters
Access to full search results
Access archive of magazine back copies
Access to Projects in Progress
Access to ONE Research Report of your choice in PDF format

Option 2 (equivalent of R375 a month):

All benefits from Option 1
PLUS
Access to Creamer Media's Research Channel Africa for ALL Research Reports, in PDF format, on various industrial and mining sectors including Electricity; Water; Energy Transition; Hydrogen; Roads, Rail and Ports; Coal; Gold; Platinum; Battery Metals; etc.

Already a subscriber?

Forgotten your password?

MAGAZINE & ONLINE

SUBSCRIBE

RESEARCH CHANNEL AFRICA

SUBSCRIBE

CORPORATE PACKAGES

CLICK FOR A QUOTATION