Quarry Southern Africa May 2018 - Page 7

NEWS The regular desilting of return water ponds and dams is becoming increasingly important. water than usual,” says Vine. “It is therefore vital that they operate optimally and do not have their capacity constrained by excess silt.” He highlights the environmental risk of tailings spilling out of ponds and perhaps even out of the boundaries of the mining lease area – something that mines work hard to avoid due to the stringent legal requirements. “The regular desilting of return water ponds and dams is more and more important as we begin to appreciate the proper value of water on our planet, and especially in relatively dry countries like South Africa,” he says. “Not only should mines ensure there is enough capacity to receive and retain excess water during the rainy season, but there is also the need to store as much as possible for the dry season.” He argues that purchasing treated municipal water to ‘top up’ their requirements is less of an option for mines due to the rising cost of water and the growing competition for water among stakeholders like communities, industry and agriculture. Applying a regular dredging programme need not be onerous, he adds, and can avoid a situation where silt or slimes threaten the water retention and water-holding capacity of ponds and dams. Integrated Pump Rental has locally designed, engineered and manufactured the SlurrySucker dredge unit for precisely this purpose, and offers the technology on a rental or turnkey contract basis for mine pond maintenance. “There are even conditions under which a mine may find it worthwhile to procure its own SlurrySucker for permanent and ongoing use on desilting operations,” says Vine. “The equipment can be moved easily by road trailer and commissioned within a day. The operation of the equipment is conducted by just one person, and we provide all the necessary training, support and maintenance required,” he adds. During the rainy season in South Africa’s mining regions, checking the capacity of process water return ponds to monitor whether silt build- up is jeopardising the dams’ performance, and this is increasingly critical. “Managing the water balance on mines is more demanding as mines work to be more self- sufficient, and to draw less water from municipal sources,” says Lee Vine, managing director at dredging and dewatering specialist Integrated Pump Rental. “Process water ponds therefore need to be carefully monitored and regularly dredged to prevent too much sediment from accumulating.” More sediment means less water storage capacity, which can affect the efficient running of the process plant as well as create a potential environmental hazard if heavy rainfall leads to tailings over-topping the pond. Exacerbating the risk of insufficient water storage capacity is the widely held opinion that rainfall is becoming increasingly variable due to climate change factors. “In many areas, this means that summer rains will include a higher number of heavy downpours within relatively short periods of time. And this will place an increased load on these ponds to contain more Dredging the ponds Process water ponds need to be carefully monitored and regularly dredged to prevent too much sediment from accumulating. QUARRY SA | MAY/JUNE 2018 _ 5