Deep South African mines will continue to have production problems in the future. This article illustrates one current problem. Creamer's Mining Weekly provides a good amount of free content.
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Driefontein takes ton-a-quarter knock in interests of safe pillar project
NEWSSouth African gold miner Gold Fields has put safety first by halting a high-grade pillar-extraction project that will result in a loss of nearly a ton of gold a quarter at its Driefontein operation until a solution is found.
The company plans to overhaul the design of its mining model for the Driefontein 4 shaft pillar-extraction project after geological instability was recorded in and around the shaft barrel.
Driefontein is the group's largest operation, having produced 1,15-million ounces of the company's 4,1-million ounces of gold during its 2006 financial year.
The redesign, which will focus on alternative-access solutions in the event that the shaft barrel collapses, will delay extraction and will also result in a decrease in gold output from the mine over the next two quarters.
South African operations head Brendan Walker reports that Gold Fields is now budgeting about 7,5 t or 240 000 oz of gold from the mine in the December quarter, rising to around 7,8 t or 250 000 oz by the June quarter. In the September quarter some 8 t or 257 500 oz was produced at the mine, which was down on the 8,9 t or 285 100 oz produced in the June quarter.
The decision to hold back on the project has no relation to the tragic loss of five miners at AngloGold Ashanti's TauTona mine, where pillar extraction was also being undertaken, or to the fact that labour unions have raised serious concern about future pillar-extraction projects.
Walker believes a safe solution will be found as the instability is centred on the shaft barrel and not in the ground where extraction is planned.
At present the shaft itself remains an important access way, which means that alternative access has to be developed should the shaft area have to be sacrificed.
“There is time deterioration in the shaft which gives us an indication of possible collapse. We want to ensure that we have alternative access points,” Walker explains.
He says previous pillar extractions have been possible using the shaft system, but the new ground being targeted has some unique geological features that are affecting the shaft and, thus, alternatives are required.
However, CEO Ian Cockerill stressed that, while the company was assuming that a solution would be found, it would only proceed once it was convinced that the projects were safe. This could also mean lower levels of extraction from the area.
“It has already meant taking a drop in production, which we don't enjoy, but safety has to come first,” Cockerill told Mining Weekly exclusively, revealing that will lose about 300 kg a month or nearly a ton of gold a quarter.
“My underlying philosophy is that, if I am not prepared to work in an environment, I cannot expect others to work in that environment.
The company reported nine deaths in the quarter, with 38 miners having lost their lives during the 2006 financial year.
Cockerill says its internal plan will be subjected to critical external review and that a full monitoring system will be introduced to ensure that the reality of mining is consistent with the models. “If there is any inconsistency, we will stop and step back, which is what we have done with the 4 shaft project,” Cockerill avers, stressing, though, that he is convinced that the company has the expertise to mine pillars in a responsible and safe way.
“We have to find a way to go into this area safely efficiently and making sure that we keep the energy-release rates as low as possible. But it is still a very unpredictable science,” Corkerill admits.
He says the redesign will not only give attention to the issue of access, but also the rate of extraction.
Gold Fields is working on the assumption that it is unlikely to find a design that meets the original extraction plan. The management at Driefontein has, thus, been mandated to look elsewhere to try and make up some of the shortfall from the loss of the high-grade area. |
