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To decant, or not to decant? That is the question

Written by  MARA KARDAS-NELSON - M&G Sunday, 14 November 2010 07:24
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Concerns that Johannesburg and the Cradle of Humankind will soon be flooded with acid mine drainage (AMD) have been central to discussions on polluted mine water for months, with the public being worked up into a frenzy about the CBD sinking and South Africa's heritage being wiped out.

While a media storm has been created around these predictions, fuelled by worried activists and a reactionary government, estimations of both sites flooding are not as concrete as one might think. Some scientists and government officials note that Johannesburg will with no uncertainty be the next target, advocating action, while others claim the city faces a very minimal threat. Similar opinions surround potential affects on the Cradle.

So, who's right?

The answer lies in a muddled pool of conflicting data. No one disagrees that both sites have been or will be affected in some way, but to what extent remains heavily debated.

Polluted water is indeed rising within Gauteng's Central Basin, which houses Johannesburg. It is currently 530m below the surface, increasing between 0,3 and 0,9m a day. While the Department of Water Affairs (DWA) originally estimated that water would hit the Jo'burg streets in early 2012, the current interministerial task team has reportedly pushed that date back on AMD to 2014.

The DWA has pegged the so-called environmentally critical level at 400m below the surface. That means that if the water rises above this, groundwater will be affected, decant inevitable, and the effects exponentially worse than if the water is kept at bay. Speaking to Agence France-Presse in July, the department's Marius Keet promised that pumping would take place so that "[AMD] will not decant in the city of Johannesburg".

According Gerrit van Tonder of the Institute for Groundwater Studies (IGS) at the University of the Free State, the suggestion to pump at 400m is based on "a wrong conceptual model used by [the Council for Geoscience (CGS)] ... the seriousness of the acidic mine water decanting at 57 mL [or 57-million litres] a day close to Boksburg is by far exaggerated and so are estimations about the poor quality of the water that will decant. I'm not saying it's not going to [happen], but it's not going to decant in February 2012. And it will be manageable."

The IGS estimates that water will not reach the surface until June 2014 at the earliest.

Pumping could in fact worsen the situation, said Van Tonder. "Pumping at a fixed level of 400m below Boksburg will create, (a) mixing, (b) water turbulence, (c) structural erosion and also (d) seismic activities," he explained. Pumping could "most probably cause serious earthquakes in the Central Rand ... All of this poses a problem much more serious than the supposed decanting of acid water."

Rather than removing water from the filling void, "you must get rid of the oxygen, and the way to get rid of oxygen is to fill up the mine", says van Tonder. Iron pyrite mixing with oxygen is a crucial part of the creation of acid mine drainage.

The institute noted that those who are in favour of pumping at 400m are "mostly non-hydro geologists", such as government officials, academics specialising in other fields, and activists, while those against the pumping are "mostly hydro geologists".

Van Tonder says that DWA and individual members of the task team have refused repeated requests to meet with the IGS.

Earthquakes have been sited as a potential impact of the basin filling, shaking building structures. According to mine consultant Garfield Krige, who predicted Gauteng's 2002 Western Basin decant, "it's known that when you fill up a basin, or anything that contains water ... there may be several nasty earthquakes because you're putting pressure on rocks that weren't under pressure".

"You will have earthquakes, but it's not comparable to [those] along a fault line," he continues. "In all likelihood it's going to be similar to the mining related tremors we used to have."

Additionally, Krige says, "there is theoretically a chance that the foundations of buildings could impacted, but it's not going to happen overnight. It's going to take tens, maybe hundreds of years".

Lesley Stoch of the North-West University at Potchefstroom was commissioned by Absa and Standard Bank to assess whether reports of their CBD buildings being affected were correct. According to his research, neither site is threatened. "The Central Basin is level, like a lake. Water will come out at the lowest point, which is not in the CBD," he says. "It might affect properties in the south of the city, which are lower ... but definitely not the CBD."

Where the decant occurs is of significant concern. According to Krige, "it's going to decant in the Klip River catchment, so the drainage is going to be towards the Vaal River, and the water will enter the Vaal Barrage dam." The Klip runs through Soweto, home to 1,3-million people, while 10-million users pull from the Vaal dam daily. Because of this, Central Basin decant "is going to be even more significant than the Western Basin," says Krige.

Figuring out exactly what will happen, and where it will happen, is made difficult by a lack of transparency and access to data, according to Frank Winde of North-West University at Potchefstroom. While the Department of Mineral Resources began looking at re-filling of empty voids years ago, this data is "currently embargoed by the [CSG], labeling the unfinished project "work in progress". That may put the CGS in an advantageous position for the current DWA tender on the issue. I also agree with Trevor Manuel that there are private interests at play in sensationalising the issue." In August, Manuel was quoted as saying that "private-sector interests" were driving debate on AMD, particularly in Johannesburg, and that a "rational debate" was needed to properly assess the situation, adding "the idea that there will be acid mine drainage running through the streets of Johannesburg next week, and that we should all walk around in gum boots, is completely ridiculous."

AMD in the Cradle: The devil is in the dolomite

Just as there are a flurry of questions over whether, when, and how Johannesburg will be aaffected by acid mine drainage , scientists are sparring regarding the Cradle of Humankind. While there is no denying that polluted mine water originating from the Western Basin decant has made its way into the World Heritage site, whether the caves have already been affected -- and to what extent they may be in the future -- is up for debate.

The large amount of dolomite housed within the Cradle is central to differing opinions. Dolomite is a type of rock commonly found across South Africa, and specifically Gauteng. "Dolomite is calcium carbonate, basically. It's easily soluble, and also holds huge volumes of water," explained Carin Bosman, former director of Water Resource Protection and Waste at the Department of Water Affairs and Forestry. While dolomite already dissolves easily, "the acid dissolves [it] much faster."

Phil Hobbs of the Council for Scientific and Industrial Research, who has been assessing groundwater quality in the Cradle for over a year, noted that "acid mine drainage is only one of the threats to the area ... One of the other, bigger threats is treated waste water effluent out of the municipal waste water works."

Ironically, the mix of sewage water and acid mine drainage may in fact have a positive effect. Because of dilution, "to a certain extent the municipal waste water is helping to mitigate the impact of the ... mine water," Hobbs explained. In addition to the dilution effect, "nutrients [from the sewage] capture the metals [from AMD]... [these metals] help to coat and armour the dolomitic strata, in other words helping to protect it from further dilution, meaning that less dolomite will be dissolved."

Based on his data, "for the majority of the fossil sites [of which there are 14], there are only five that have a risk rating of moderate or higher ... most are all low to very low," Hobbs says. "One can never say never, but it is extremely unlikely that [the north and north east part of the Cradle] will ever be threatened by any source, be it AMD, be it anything else."

Krige notes that due to the large amount of limestone within dolomite, the rock helps to neutralise the water by raising the pH. But while that's "obviously a good thing because it purifies the water, just because it isn't polluted doesn't mean [the Cradle's] not impacted. For every mL of mine water that hits dolomite, about 300 litres of void is created…a lot of this…could be under the N14 road [connecting Pretoria to Springs]. There is a danger that this could collapse."

For Francois Durand of the University of Johannesburg, studying amphipods, or blind shrimp who live in the Cradle, demonstrates the effect of AMD on the natural environment. "As you approach the mines from the Cradle, the composition and the quantity of the insects in the water becomes impoverished," he says. "There are less and less and fewer and fewer, until you get to Robinson Lake [in the West Rand] where it's devoid of life."

Amphipods aren't the only organisms at risk. "If the surface water is compromised, the bats will die, and that will have an effect in the [cave] ecosystem as well, and things above ground will die," says Durand. "If both the ground and surface water are affected, the entire ecosystem will collapse." Amphipods also act as a key food source. "[Insects] that live on the banks of the rivers, actually take up heavy metals, so it is made accessible to the rest of the food web."

Amphipods are "endemic to Gauteng and Limpopo," he continues. "You don't get them anywhere else. If they disappear here, they disappear off the face of the earth."

While Durand says that the Cradle has not been heavily affected impacted yet, he suggests that the worse-case scenario must be protected against, given the importance of the site to South Africa's tourism industry and heritage. "I am a socialist ... with respect to our heritage. It belongs to everybody equally," he says, noting, "this isn't just South African heritage, this is world heritage."

This article made possible through funding from the Open Society Foundation for South Africa's Media Fellowship Programme




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The Federation for a Sustainable Environment’s ongoing role in addressing the sewage pollution in the Vaal River

‘People the same as pigs’ in the VaalBy Sheree Bega | 16 Oct 2020 Foul: Pigs root in sludge in Emfuleni municipality. (Photos: Delwyn Verasamy/M&G) Clutching her one-year-old son, Monica Ndakisa jumps onto a brick to avoid the sewage that runs like a dark stain across the passage in her home.  “We’ve lived like this for years,” she says pointing to one of the culprits: her blocked toilet, which causes sewage to pool into nearly every room of her home in Sebokeng hostel in the Vaal. “The smell is too terrible.” It’s worse outside. Her small garden is submerged in a sickly, grey sewage swamp. To stop the human waste from seeping inside, Ndakisa has built a concrete barrier at her front door. But it’s futile. “My five-year-old son was in the hospital for two weeks with severe eczema and they told me it’s because of all this sewage. It makes us cough all the time. It’s so depressing to live like this.” Samson Mokoena, of the Vaal Environmental Justice Alliance (Veja), shakes his head. “It’s chaos. You can’t allow people to live in such conditions. The government is playing with our people.” Ndakisa’s neighbour, Maphelo Apleni, has used pipes to divert the stream of sewage from his garden. “It never stops,” he says grimly. “We have a municipality [Emfuleni] that doesn’t care about us.” Mziwekaya Mokwana points at a sewage-filled furrow clogged with litter where pigs are feeding. “This is no better life,” he says. “People are the same as pigs here.” Sewage in Vaal River system  Last month, the human settlements, water and sanitation department said it would take at least another three years to minimise and eventually stop the sewage flowing into the Vaal River system. In a recent presentation, it states how “design treatment capacity is at its limit, housing development investments are delayed and there are negative environmental and health impacts”. Ageing infrastructure is to blame for sewage spillages, coupled “with a lack of operation and maintenance investment” as well as theft and vandalism.  It will cost about R2.2-billion “to have a sustainable impact on the Vaal River catchment within Emfuleni local municipality”. The department’s plan aims to safeguard infrastructure; repair the bulk network to eliminate spillages, key and critical pump stations and rising mains; refurbish wastewater treatment works “in an attempt to comply with discharge licence conditions”; and achieve operation and maintenance requirements. But Maureen Stewart, the vice-chairperson of Save the Vaal (Save) is sceptical. She says there is no political will to tackle the crisis. “These problems go back over 12 yearsand reached crisis proportions when the system collapsed in 2018. The result is some 200 million litres of raw or partially treated sewage entering the Vaal River and its tributaries daily.” Stewart warns that it’s an ecological disaster that also affects agriculture and has serious health implications for people living above and below the Vaal Barrage Reservoir, which is 64km long and used to supply Johannesburg with water but is now too polluted to do so.   She says the Emfuleni municipality has been under Gauteng’s administration since mid-2018 and, despite promises, the status quo remains — unbridled sewage pollution of the Vaal River and Emfuleni.  “The Ekurhuleni Water Care Company (Erwat) was appointed to take over in 2019 and were given funding and spent R179-million. Their contribution was to unblock pipes and remove 50 tons of rubbish from the system. This opened the pipes but, as the pump stations and the three wastewater treatment plants remain dysfunctional, there has been no improvement. Raw sewage continues to flow into the Vaal River and into the streets of Emfuleni.”  Monica Ndakisa sweeps overspill from her toilet. There was a “glimmer of hope” when Minister, Lindiwe Sisulu, visited the Vaal in January this year, assuring Save that action will be taken and that funds are earmarked in the 2020-2021 budget.  “It seems her enthusiasm has not filtered down to her department,” says Stewart. “After Erwat’s contract was not renewed, the department stated they would undertake the repairs by appointing their own contractors. Tender documents have been languishing on someone’s desk at the department since July.” Sputnik Ratau, spokesperson for the department, says the government has committed resources towards solving the sewage problem in the Vaal.  “Government sent state institutions to assist Emfuleni local municipality (ELM) in this regard; these include SANDF and Erwat. Recently, the department finalised the scope of all that needs to be done to solve the sewage problem. There are 26 work packages that will be advertised in the coming weeks for competent contractors to take part in solving the sewage challenge in the Vaal.”  The department, says Ratau, aims to have a “busy festive season” working with the appointed contractors. “In the 2020/21 financial year, the department has committed R911-million towards solving this challenge. The total investment by the department in 2020/21 financial year is R1.2-billion in the Vaal; this includes the building of additional wastewater treatment capacity and associated pump stations.” Maphelo Apleni installs pipes to drain sewage out of his garden. Before the end of the financial year Module 6 in Sebokeng water care works will be launched, “subject to no community unrest disrupting construction”. The department, Ratau says, has to take all necessary precautions to ensure that section 217 of the constitution is followed as far as procurement is concerned.  “Thus the departmental checks and balances had to be followed to the letter to ensure compliance with procurement processes. This unfortunately caused delays but was necessary.” Within the next month the department aims to advertise for all the contractors “that can assist in this challenge”. Ratau says commitment dates, including start and completion dates, “will be sent not only to Save but all interested stakeholders once the contractors are appointed. The department cannot preempt this before the appointments are made.” He says that R7-billion is required to “solve the pollution challenge in ELM. This needs to be coupled with operations and maintenance, which is a function of ELM at local government level”. Save is once again taking the government to court to enforce legislation to ensure infrastructure is repaired within phased completion dates and that sufficient funds are made available for ongoing maintenance and operation of the system by the municipality, supervised by the high court.   Veja’s Mokoena is glad the department is taking over the Vaal clean-up. “This situation was supposed to be fixed a long time ago. So much money has been squandered at the municipal level.” Rand Water’s delay Eight months. That’s how long it took Rand Water to release public water quality records for the Vaal Barrage system to a team of aquatic specialists investigating the ecological health of the river system.  In January, Aquatic Ecosystems of Africa submitted a Promotion of Access to Information Act (Paia) application to Rand Water for access to its water quality analysis data for the Vaal Barrage and downstream since 2015.  Nothing happened, it says, until Tshepang Sebulela, the Paia compliance officer from the South African Human Rights Commission (SAHRC) intervened late last month.  New pipelines are being installed in the Vaal. In an email to Rand Water, Sebulela noted how the multiple requests for records by Aquatic Ecosystems and the Federation for a Sustainable Environment have allegedly been ignored, which in terms of Paia are deemed refusals.  “The SAHRC is greatly concerned by a large number of public institutions who provide such important services to the public who refuse to meet their basic legislative obligations,” he wrote. The records landed in the firm’s inbox on 2 October.  Aquatic Systems’ Simone Liefferink says sourcing surface water system data is becoming increasingly difficult. “It’s disturbing the data is not adequately managed, readily accessible to the public and private sectors who pay tax and other water charges for effective catchment management to be implemented.”  Rand Water did not explain the reason behind the delay.  That the information was provided in a PDF format of almost 2 000 pages “frustrates and delays” its interpretation, says Liefferink.  She and her partner, Russell Tate, began their investigation after a major fish kill in the Vaal River in mid-2018. That September they testified at the HRC’s inquiry into the contamination of the Vaal River that high levels of ammonia from the wastewater treatment works was wiping out life in the river system. A snap-shot analysis of the data provided by Rand Water shows high levels of E coli, ammonium and ammonia — key indicators of sewage pollution. Average E coli counts soared from 12 705 colony-forming units per 100ml in 2010 to more than 107 000 in 2018 and 66 923 in 2020.  “The contributing factor is clear — dysfunctional sewage treatment conveyances and treatment plants. More disturbing is the long-standing deterioration of the system that ever increases the loss of biodiversity and other essential ecological functions and human services. Yet this matter is still not treated with extreme urgency,” says Liefferink. HRC’s long-awaited report It’s taken nearly two years for the Human Rights Commission to release its report into the Emfuleni sewage crisis. “Their report has not yet been taken to parliament, nor has it been published. Why?” asks Save’s Stewart. Buang Jones, the Gauteng manager of the HRC, says the provincial report has been finalised.  “It’s with the commissioners now for final adoption and approval. Once it’s been approved, it will be shared with implicated parties and they’ll have 10 days to comment. This is a countrywide issue and the report seeks to address broader challenges when it comes to river pollution and wastewater management,” he says.  Read the original article here.


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