Joburg can be saved from rising acid mine drainage – but only if private and public stakeholders join forces and work fast.
THE government has just 20 months in which to put the infrastructure in place to deal with acid mine drainage in the Witwatersrand area.
The large void beneath the Wits area is filling with water
Acid mine drainage refers to the water that drains over the surface of acid-bearing rock which has been exposed through mining, becoming toxic as it rises to the surface of disused mines and makes contact with air. It threatens the health of rivers and people who come into contact with that water.
The Witwatersrand stretches 50 kilometres from Krugersdorp on the West Rand to Boksburg on the East Rand. Mining started 124 years ago on the Rand, in 1886, but from the 1950s mines across the region started closing down. In 2008, the last remaining operational mine, East Rand Propriety Mines (ERPM) in Boksburg, closed its operations.
ERPM had maintained the water level at 1 200 metres below the surface, pumping 40 million litres of water every day from below ground. The company was in the unfortunate position of having to pump the accumulated water from the remaining disused mines across the Witwatersrand.
Pump water out
While they were operating these mines, mining houses had infrastructure in place to pump the water out. But as the mines closed down and pumping ceased, the underground voids created from mining operations began filling – and continue to fill. Accumulated water flowed into adjacent mines, gradually filling up the entire void.
When ERPM closed, the acid water carried on rising into the void; now, the rising water has covered ERPM’s pump, which is 600 metres below the surface.
The void, created by the removal of 1 300 million tons of rock - yielding over 12 million kilograms of gold - will be completely filled in about two-and-a-half years - just 30 months. But disaster can be avoided if we move quickly.
“The solution to the problem is relatively simple, however, and involves the establishment of pumping stations to pump the water to the surface for basic treatment,” says professor Terence McCarthy, from the school of geosciences at Wits University. He delivered a lecture at Wits last week, entitled “The decanting of acid mine water in the Gauteng city-region”, as part of the Gauteng City-Region Observatory series of lectures.
He indicates that the problem is universal but doesn’t usually occur within a major metropolitan area. McCarthy confirms that at present, the water level is at a depth of about 600 metres below the surface, but it is rising at about 15 metres each month.
“At this rate, the void will be completely filled in about two-and-a-half years from now,” he warns.
The acid water contains sulphuric acid, minerals and metals. “The water that accumulates in the mine void is acidic and contains high concentrations of dissolved sulphate and heavy metals and is toxic and corrosive.”
Decanting water
The acid water will rise and flow out of mines at low points along the reef. These low points are along Main Reef Road and the M2 in Joburg. Already, the void in Krugersdorp has filled up and the contaminated water is flowing out, into streams and watercourses in the area.
Mining companies have closed down, leaving disused mines behind
“Decant will occur because the mine void and openings connected to it such as shafts and collapsed areas occur at a variety of elevations and water will flow into the void in higher areas and decant at low points,” says McCarthy.
The lowest large opening is at the Cinderella Shaft of ERPM in Boksburg, but because water is restricted in its flow laterally, the water level will stabilise at different levels, resulting in multiple decant points.
The first decanting of acid mine water in the city will occur in low basements and the underground cables in Newtown, and possibly also at the disused mine in Gold Reef City, which McCarthy is particularly concerned about as he feels it is a great heritage site, demonstrating to visitors what early mining on the reef looked like.
Solution
But McCarthy says the solution to the problem is relatively simple. It involves establishing two pumping stations – one in Germiston and another in Florida – which will pump the water to the surface, maintaining the water in the void at 250 metres. Treatment plants will need to be established at the pumping stations, and the treated water will be pumped into nearby streams and rivers.
“It must be accepted that pumping will have to continue indefinitely. Initially, this will involve considerable financial outlay to establish the pumping and treatment facilities with an ongoing cost to maintain the pumping and water treatment.”
He explains that much of the expense of the plants will not be new, as the government has for decades been paying pumping subsidies to mines to cover the cost of pumping water from the defunct mines.
But he stresses that time is of the essence, saying there is now a window of opportunity in which steps must be taken to prevent the situation getting out of control. In 20 months, the water will reach the 300m mark, and so “it is essential that steps be taken immediately to start preparing the pumping and treatment infrastructure”.
The Department of Water Affairs has agreed to install one new pumping station and upgrade a sludge treatment operation, to save Johannesburg from rising acid water.
Payment
The question is which parties should pay for the rescue operation – mining houses or the government. McCarthy argues that the government should pay, as it has benefited from tax collected from the companies and their employees. But civil society activists say the companies have benefited from the mining operations and have not acknowledged the damage caused to the environment.
But over the years mining companies have closed down and many no longer exist.
Yet there is good news despite the gloom. In time, probably over 20 years, the quality of the water will gradually improve and become drinkable, making it a profitable operation, says McCarthy.
“However, we have no idea how long this will take and could extend over many decades or longer.”
Read more: http://www.joburg.org.za/index.php?option=com_content&view=article&id=5977&catid=88&Itemid=266#ixzz16ve2NgXA
THE government has just 20 months in which to put the infrastructure in place to deal with acid mine drainage in the Witwatersrand area.
The large void beneath the Wits area is filling with water
Acid mine drainage refers to the water that drains over the surface of acid-bearing rock which has been exposed through mining, becoming toxic as it rises to the surface of disused mines and makes contact with air. It threatens the health of rivers and people who come into contact with that water.
The Witwatersrand stretches 50 kilometres from Krugersdorp on the West Rand to Boksburg on the East Rand. Mining started 124 years ago on the Rand, in 1886, but from the 1950s mines across the region started closing down. In 2008, the last remaining operational mine, East Rand Propriety Mines (ERPM) in Boksburg, closed its operations.
ERPM had maintained the water level at 1 200 metres below the surface, pumping 40 million litres of water every day from below ground. The company was in the unfortunate position of having to pump the accumulated water from the remaining disused mines across the Witwatersrand.
Pump water out
While they were operating these mines, mining houses had infrastructure in place to pump the water out. But as the mines closed down and pumping ceased, the underground voids created from mining operations began filling – and continue to fill. Accumulated water flowed into adjacent mines, gradually filling up the entire void.
When ERPM closed, the acid water carried on rising into the void; now, the rising water has covered ERPM’s pump, which is 600 metres below the surface.
The void, created by the removal of 1 300 million tons of rock - yielding over 12 million kilograms of gold - will be completely filled in about two-and-a-half years - just 30 months. But disaster can be avoided if we move quickly.
“The solution to the problem is relatively simple, however, and involves the establishment of pumping stations to pump the water to the surface for basic treatment,” says professor Terence McCarthy, from the school of geosciences at Wits University. He delivered a lecture at Wits last week, entitled “The decanting of acid mine water in the Gauteng city-region”, as part of the Gauteng City-Region Observatory series of lectures.
He indicates that the problem is universal but doesn’t usually occur within a major metropolitan area. McCarthy confirms that at present, the water level is at a depth of about 600 metres below the surface, but it is rising at about 15 metres each month.
“At this rate, the void will be completely filled in about two-and-a-half years from now,” he warns.
The acid water contains sulphuric acid, minerals and metals. “The water that accumulates in the mine void is acidic and contains high concentrations of dissolved sulphate and heavy metals and is toxic and corrosive.”
Decanting water
The acid water will rise and flow out of mines at low points along the reef. These low points are along Main Reef Road and the M2 in Joburg. Already, the void in Krugersdorp has filled up and the contaminated water is flowing out, into streams and watercourses in the area.
Mining companies have closed down, leaving disused mines behind
“Decant will occur because the mine void and openings connected to it such as shafts and collapsed areas occur at a variety of elevations and water will flow into the void in higher areas and decant at low points,” says McCarthy.
The lowest large opening is at the Cinderella Shaft of ERPM in Boksburg, but because water is restricted in its flow laterally, the water level will stabilise at different levels, resulting in multiple decant points.
The first decanting of acid mine water in the city will occur in low basements and the underground cables in Newtown, and possibly also at the disused mine in Gold Reef City, which McCarthy is particularly concerned about as he feels it is a great heritage site, demonstrating to visitors what early mining on the reef looked like.
Solution
But McCarthy says the solution to the problem is relatively simple. It involves establishing two pumping stations – one in Germiston and another in Florida – which will pump the water to the surface, maintaining the water in the void at 250 metres. Treatment plants will need to be established at the pumping stations, and the treated water will be pumped into nearby streams and rivers.
“It must be accepted that pumping will have to continue indefinitely. Initially, this will involve considerable financial outlay to establish the pumping and treatment facilities with an ongoing cost to maintain the pumping and water treatment.”
He explains that much of the expense of the plants will not be new, as the government has for decades been paying pumping subsidies to mines to cover the cost of pumping water from the defunct mines.
But he stresses that time is of the essence, saying there is now a window of opportunity in which steps must be taken to prevent the situation getting out of control. In 20 months, the water will reach the 300m mark, and so “it is essential that steps be taken immediately to start preparing the pumping and treatment infrastructure”.
The Department of Water Affairs has agreed to install one new pumping station and upgrade a sludge treatment operation, to save Johannesburg from rising acid water.
Payment
The question is which parties should pay for the rescue operation – mining houses or the government. McCarthy argues that the government should pay, as it has benefited from tax collected from the companies and their employees. But civil society activists say the companies have benefited from the mining operations and have not acknowledged the damage caused to the environment.
But over the years mining companies have closed down and many no longer exist.
Yet there is good news despite the gloom. In time, probably over 20 years, the quality of the water will gradually improve and become drinkable, making it a profitable operation, says McCarthy.
“However, we have no idea how long this will take and could extend over many decades or longer.”
Read more: http://www.joburg.org.za/index.php?option=com_content&view=article&id=5977&catid=88&Itemid=266#ixzz16ve2NgXA
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