In the comparatively dry climate of the South African Highveld, wind-borne dust and sand have always been a significant irritation, especially to residents of the industrial and mining centres of Johannesburg. The main sources of the dust and sand, at least from an historical perspective, have been the dozens of largely exposed mine dumps that line the famous Main Reef outcrop – from the East Rand to the West Rand. However, over the last decade, concerted initiatives have been undertaken by one particular company to drastically minimise the impact of this environmental nuisance on those living in the shadows of the city’s historical mine dumps.

Since 2008, JSE- and NYSE-listed gold producer DRDGold has invested R600-million in its environmental management programme, the main focus of which has been dust suppression and vegetation strategies in its main areas of operations. This investment represents significantly more than all the dividends the company has distributed to its shareholders in the same period. Moreover, that figure was almost equivalent to DRDGold’s market capitalisation in August as at this year, when its share price fell to just R1.53 per share.

“I do not know of another mining company in South Africa that has spent the equivalent of its market cap on environmental containment measures,” DRDGold CEO Niël Pretorius tells Mining Weekly.

Of course, the nature of DRDGold’s operations has necessitated a strict environmental management regime. The company’s main activity, at least since the mid-2000s, is the retreatment of the old sand dumps and slimes dams that are spread between Springs and Randfontein. This asset base, which covers an area of some 1 200 km2, includes access to between 750-million tons and 900-million tons of gold-bearing material – sand and slimes – with a grade of between 0.28 g/t and 0.29 g/t of gold.

The actual reclamation of the gold-bearing material involves one of two processes: high-pressure water-jetting or loading using front-end loaders. It is the latter process, particularly, that can produce a significant amount of dust in the immediate vicinity and can be a major environmental headache.

Pretorius admits that, during the first three months of a reclamation project, it is very difficult to contain the dust generated by the operations. “The only method to address dust being blown from reclamation sites is watering down, and this is only partially successful in the early stages, particularly if there are strong winds. In the early days, when a lot of reclamation was taking place in the industrial areas to the south of Johannesburg, we had to resort to employing car cleaners in the immediate vicinity to wash down cars covered with the dust. Companies such as panel beaters had to be compensated for work impacted on by excessive wind-borne dust.”

Pretorius elaborates that, while dust mitigation is certainly a difficult objective, what has made the task doubly challenging is the fact that communities now live in much closer proximity to the dumps than in previous decades. At the company’s main installation at the Crown Complex, on the Central Rand, the number of people living within a 2 km radius of the site has grown from just 6 000 in 1960 to 680 000 currently. As it is impossible to stop such urban growth, the company has had to improve its measures to reduce inconvenience and the nuisance factor.

The company has also had to pursue a high level of engagement with neighbouring communities through its Dust Forum initiative. This forum, which sits every quarter, includes representatives of the Department of Mineral Resources, the Department of Water Affairs and Sanitation, municipalities and the community. While the forum may not always be well attended, says Pretorius, the opportunity for transparency and open discussion on aspects of environmental management is very much there.

Although it is difficult to control dust during operations, DRDGold seems to have perfected the art of dust management once dumps have been fully reclaimed by means of vegetating the rehabilitated area. In fact, the company spends R15-million each quarter on vegetating its main installation at Crown. The vegetation predominately consists of several local grass species, including Eragrostis teff (Teff), Eragrostis curvula (weeping love grass), Cynodon dactylon (Bermuda/couch grass), Lucerne SA standard (properly inoculated) and Hyparrhenia hirta (thatch grass).

Interestingly, the method of vegetating mine dumps to control dust was first perfected by John Phillips, a professor of biology at the University of the Witwatersrand, in 1932. Before that, dust suppression methods ranged from tipping large rocks on dump sites to spraying dump surfaces with various substances, such as molasses, salt and hygroscopic materials, as well as covering them with a sludge made from black vlei soil.

The positive impact that the vegetation strategy is having on dust emission levels is evidenced by the drastic reduction in dust exceedances over the past three years. While a total of 182 dust exceedances were recorded in 2012, only 31 of the 1 500 measurements, or just 2%, recorded in the 2015 financial year exceeded the limit.

DRDGold has four main reclamation areas, including Crown, City, Knights and Ergo, and is currently reprocessing seven historical tailings dams within those areas.

Pretorius elaborates that the company has practically vegetated or is in the process of vegetating the GMTS, Homestead, Diepkloof and Mooifontein tailings dams in the Crown Complex, as well as the Rooikraal, Brakpan, and Daggafontein tailings on the East Rand. He adds that the flagship fully rehabilitated site is the Homestead tailings dam, in the Crown complex. “We have prioritised the rehabilitation process on the basis of impact and how much dust nuisance the sites cause to the surrounding communities.”

The company has come a long way since getting its first capital vote for dump vegetation eight years ago, says Pretorius. “While there is still some dust coming off the dumps that we haven’t vegetated yet, we are definitely starting to see the fruits of that decision. Give it another two to three years, and there will be hardly any dust coming off the rehabilitated sites.”