Diamond producer De Beers’ Limpopo-based Venetia mine has retained its ISO 14001 environ- mental certificate after the Venetia Limpopo Nature Reserve, which forms part of the Mapungubwe National Park, was audited in June.
Venetia mine environmental manager Gavin Anderson states that Venetia has audits twice a year, certified through professional services firm PwC, and adds that the mine is committed to conserving the surrounding environment and limiting its environmental impact.
“Environmental-impact assessments (EIAs) and environmental-management programmes are necessary to understand the physical impact the mine could have on the surrounding environ- ment,” he says, adding that De Beers has been conducting EIAs at Venetia since 1992 of its own volition.
He points out that conducting EIAs without being asked by a governing body to do so demonstrates the mine’s commitment to the natural environment.
Water Stress Monitoring
Venetia mine has been conducting plant moisture stress tests since 1992 to identify and under- stand the impact it has on its natural water source, notes Anderson.
He adds, however, that environmental regulation was not as strong or as regulated then as it is currently and that De Beers is committed to the environment on a global scale and, to a large extent, self-regulates its environmental actions.
“Plant moisture stress testing is done on the leaves of the large fever-berry tree because there are many of them in the area. “It is a good indicator to see if there are any changes in the moisture content of the soil,” he explains, adding that the large fever-berry tree shows stress before the rest of the vegetation in the area.
“We place one of the leaves inside a nitrogen chamber and apply pressure to it until the leaf releases the first drop of water. “We then take note of the pressure level at which the droplet was produced,” states Anderson.
He explains that if the water droplet is produced at less than 10 bar, the mine is not impacting on the environment, which means it can extract 300 000 m3 of water a month.
“If the droplet is produced between 11 bar and 20 bar we are impacting on the environment and we reduce our water extraction to 200 000 m3 a month,” he says.
Should a droplet be produced at a level higher than 20 bar, Venetia’s environmental management team further reduces extraction to 100 000 m3 a month and uses its off-channel storage dam in the dry season to substitute water from the well fields so that they do not impact further on the environment.
The off-channel dam, which holds 4.5-million cubic metres of water, is man-made and was built in the early 1990s.
“It has created its own eco- system and hosts crocodiles, hippos and tiger fish. “The water balance, from an operating philosophy, enables us to use the off-channel storage dam, which we fill up during the wet season, when we are putting too much stress on the natural environment,” he explains.
Legislation
When it comes to environmental conservation and mining, South Africa’s National Environmental Management Act has changed significantly over the last few years, states Anderson.
“Environmental management makes up one-third of a mine’s mining licence requirements and it is conditional to the mine’s water-use licence. “The natural resources belong to government.
“We, as a mine, need to demon- strate compliance and proactive management measures to show that we do not destroy or impact negatively on the environment,” he points out.
He adds that a company needs to demonstrate to the Department of Environmental Affairs that it is committed to and compliant with the legislation, which Venetia and other De Beers-owned mines, have achieved.
Meanwhile, Anderson notes that
Venetia has started to reprofile waste rock dumps, as mining legislation stipulates that the environment must be left in the same condition as it was found before mining began.
He explains that De Beers will not be able to restore Venetia to the same condition it was in before mining began.
“We opted for the predetermined-state option, so we have to commit to ensuring that our waste rock dumps, slimes dams and tailings dumps are covered with a growth medium,” he concludes.