News24

Sinkholes threat to houses in Gauteng

2011-10-05 22:07

Johannesburg - Gauteng authorities have warned of an increasing risk of dolomitic sinkholes opening up around Johannesburg, which has cost 38 lives in the last 50 years.

"The dolomitic situation is satanic," says Gauteng MEC for local government and housing, Humphrey Mmemezi.

"[Residents don't realise] it comes during the night... People can wake up and the section [of the township] is not there."

Greg Heath, an engineering geologist at the Council for Geoscience (CGS), says dolomite forms a loose belt around Johannesburg and makes up a quarter of the province. It stretches from Westonaria in the west to Centurion in the north and Thokoza in the east.

At least 2 600 sinkholes have been recorded.

"The damage they have caused to development and infrastructure is estimated at a very conservative R1.5bn.

Unstable land


"At least 38 people have died as a result of sinkholes and the number will increase if people do not move off unstable land," says Heath.

About 110 informal settlements exist on dolomitic land in Gauteng.

Heath says sinkholes are almost always man-induced and develop when communities move into an area with water-bearing services. In townships and informal settlements, leaking taps or burst pipes could trigger dolomitic erosion, which expands underground cavities.

In areas of mining or farming, dolomitic ground could become unstable through changes in the water table.

Two weeks ago, part of a street in Centurion collapsed as a sinkhole opened up. The 7m x 5m hole stretched over a lane of Jean Avenue, revealing water pipes and a dark depth below.

In Westonaria, an ever-growing sinkhole the size of a small dam and about 100m deep, lies a metre away from a tee-off at the local golf course.

Excuse


In Thembelihle, an informal settlement near Lenasia, protesting residents who want electricity infrastructure were told they need to relocate as the dolomitic land beneath their shacks is unstable.

Many residents are refusing to move, even though new housing developments are available for them at Lehae and Vlakfontein. They believe dolomite is being used as an excuse for removing informal settlements.

Heath says with an increasing population and a limited amount of land, the government will have to review dolomitic areas and assess the risk of erosion.

"We can't always avoid dangerous ground, but [the question is] how can we use it? People have gravitated towards Johannesburg [and surrounding areas]. We have to use what land we've got."

Unpredictable

Geologists can work out where "good" dolomite and "bad" dolomite lies.

"Good" dolomite is more stable and may allow development while "bad" dolomite is filled with voids and should be avoided.

Heath says dolomite is unpredictable over short distances and extensive surveys are needed to map it.

Engineering geologists and geotechnical engineers use a gravity surveying machine to determine the density of underground materials. A team then drills percussion boreholes at small intervals to survey what is up to 100m below.

The downside of this technology is that it is slow and expensive, costing about R250 per metre.

With few other options, the provincial government has mandated the CGS to help with surveys on populated dolomitic land.

Immediate intervention

Besides Thembelihle, seven areas in Gauteng have been prioritised for immediate intervention.

They are Khutsong and Bekkersdal on the West Rand; Bapsfontein informal settlement, Thokoza, Vosloorus, Katlehong on the East Rand; and the Centurion CBD in Tshwane.

Most have been targeted because of leaking and deteriorating infrastructure.

In Bapsfontein, the abstraction of dolomite groundwater by farmers is causing sinkholes. In Centurion, anticipated development in the CBD will increase the risk of dolomitic exposure.

Precautions have been taken for part of the Gautrain, which runs through Centurion, traversing about 16km of dolomitic ground.

The CGS's risk management strategy involves precaution, monitoring and working with property owners and developers.

For established properties, gutters and aprons - a ground covering of concrete or other material surrounding a property - are used to protect underlying dolomite from water erosion.

Water-bearing services are also monitored periodically for leakages. If a leakage is found, it should be repaired quickly.

Mmemezi has urged residents to be responsible with taps, pipes and buckets, or face the consequences.

"If they don't care and ignore our warnings, they'll be buried."

Comments
  • Yoni - 2011-10-05 22:27

    "...an increasing risk of dolomitic sinkholes opening up around Johannesburg, which has cost 38 lives in the last 50 years." This is laughable. Only 38 deaths in half a century? How many people die on our roads as a result of fraudulent driver's licences PER WEEK? How many people die weekly as a result of alcohol-fuelled violence? Still, is alcohol and cars now going to be banned?

      Siener2 - 2011-10-06 07:23

      Exactly. More people die from choking on their food. This is all just PR to prepare us for the R millions that will now be wasted on extensive geological and geophysical surveys. All to prevent another 38 deaths over the next 50 years.

      LiraShea - 2011-10-06 08:17

      Ermm... is there something wrong with you two? Would you like to buy property in that area and live there without concern? I think, you're missing the point here.

      Daniel - 2011-10-06 08:27

      Did'nt you read what the man said.........."It's SATANIC !! Lucifer comes to Gauteng,or is he in hospital with flu ?

      bling bling - 2011-10-06 09:23

      whahahahahahaha.....@ Daniel......yeah they blame lucifer for everything.....my goodness he is more powerful than god.....he is proving it daily.....causing sink holes....stealing the christians...his following is growing huge...and the churches are becoming empty......hmmmmm.......I wonder why!!!!...

      Alpha - 2011-10-07 10:50

      @bling bling: Maybe its the other why around: He is moving more freely and becoming stronger because the churches are empty.

  • gaharaa - 2011-10-06 00:16

    Yeah, SABC10. Seems the white man foresaw the destiny of the country the ANC seems to produce and decided to save the non whites the trouble of having to dig so many graves. Thoughtful if you ask me. Besides, the less you have, the less you have to fix. Come now you dumb@ss. Let go of your inability to compete in civility and allow those that want to make something of themselves do it. White, non white, transparent, what ever. Just because you can't progress doesn't mean that no one else is.

  • pitbull - 2011-10-06 03:30

    "The dolomitic situation is satanic," says Gauteng MEC for local government and housing, Humphrey Mmemezi. HAHAHAHAHAHAHAHAHAHAHAHAHA!! This bunch don't believe in God, but they believe in Satan. Dolomite isn't Satanic, it is holey!!! Beware where you build your house. There is a verse in the bible that says "a wise man who built his house on the rock", not on sand. The ANC, which is built on quicksand, will crumble and fall as its foundations, crack and sink.

      Siener2 - 2011-10-06 07:16

      @ pitbull: Dolomite is rock. It just happens to be rock that will slowly dissolve if exposed to water, especially acidic water. So in this case following the advice of that bible verse would not have helped much.

      DEVILS SON - 2011-10-06 07:42

      hahaha satanic, f@cking classic, prejudice bastards dont realise they protect satanism in the constitution, sooo stop blaming what does not exist and stop building townships on dolomite and next to the god damn jukskei, its not satanic its stupidity

      bling bling - 2011-10-06 09:30

      hahaha.....I love it.....yes yes...blame lucifer...he is showiong his powers.....he is more powerful than god....for if god was stronger he would stop him.....WHAT A LOT OF BS!!!!......hehehe....just goes to show how stupid ppl are .....FFS!!!!

      RonJ - 2011-10-07 11:24

      Does that mean that the ANCYL racist blacks who come in the night to murder white families are also 'satanic' ??? Must be

      Gandalf - 2011-10-07 15:18

      What News 24 says: "The dolomitic situation is satanic," says Gauteng MEC for local government and housing, Humphrey Mmemezi." What BusinessDay says: "He (Mmemezi)said residents are not educated and don’t understand geology. "They think dolomite is satanic," Mmemezi said.

  • IrishLuck - 2011-10-06 08:07

    This is probably a run-up to the removal of people from these areas to change the voting percentages elsewhere. Look at the informal settlement in Bapsfontein before the last election, the people were moved to prop up the ANC candidate in Delmas. Jerrymandering the borders sinkhole style.

  • GypseyAnn - 2011-10-06 08:24

    "The dolomitic situation is satanic," says Gauteng MEC for local government and housing, Humphrey Mmemezi. Good grief, what does satan have to do with all of this? LOL :)

      gaharaa - 2011-10-06 19:17

      Maybe he also believes that hell is a big hole in the ground.

  • Ascendo Tuum - 2011-10-06 08:26

    I used to play on the Westonarea Gold Mine golf course in the late 80's, early 90's. In many places there were noticeable and quite sizeable cracks in the ground. One of the holes was blocked off due to sinkholes. If your ball went over the fence, it stayed there.

  • ProsAndCons - 2011-10-06 08:32

    The sinkhole in Centurion is right outside the Moose Pub. It is a Moose se gat.

  • Badballie - 2011-10-06 09:48

    all it will take is one big earthquake and the entire area will collapse into the mine shafts below it, Sinkholes due to Dolomite and mining operations have been a reality in Gauteng since the second world war. Dolomite is also very porous so the rising mine water problem is also causing further instability and deterioration of the dolomite mass.

      chris.faurie - 2011-10-06 10:08

      You are correct!

      skull - 2011-10-06 10:50

      And the ANC were warned about the rising mining water and to date hasn't done a thing about it, all they care about is making themselves rich. The ANC supporters really needs to open their eyes they are so stupid to think if the white man takes over that they (white government) will again impose apartheid. This is Bad for all and may cost many more lives of all races in the future, so yes I am blaming this in the Government as these points were raised long ago and still they ignore it until the day God decides now is the time for depopulation.

  • kalabafazi - 2011-10-06 10:00

    "Many residents are refusing to move, even though new housing developments are available for them at Lehae and Vlakfontein" Just wait till a sink hole develops under their ass, then you'll see 'em move quickly enough.

      Ockert - 2011-10-07 09:14

      down ? and in the night only.

  • Gamerforlife - 2011-10-06 10:28

    "Anya, it's a giant worm! They're sinking cities with a giant worm!" Quoted Marcus Fenix from Gears of War.... ROTFLOL

  • kozikan - 2011-10-06 11:11

    if you dont listen then you must feel!!!!!

  • Dumba1234 - 2011-10-06 11:46

    " It's satanic, it comes in the night" - How did these people become MEC's etc with mess like this coming out of their mouths. What is in their brain that they can utter stuff like this. Bwaaahahaaaaah

  • sikabopha - 2011-10-06 11:50

    yoni and siener2, did you guys do comprehension at school? you are true examples of scatterbrains

  • zackie - 2011-10-06 12:00

    sinkholes is one way to remove illegal shacks..

  • Technoshy - 2011-10-06 15:17

    looks like a good place to deposit a certain hospitalised youth leader hehe!

  • Jonny Doe - 2011-10-06 15:47

    I wouldnt build my house anywhere on those dolomites. As a geologist I can tell you that there are very extensive cavities there. Sterkfontein cave (which is a huge cave system filled mostly with water) is in the those dolomites. If youre interested, go read up on the Transvaal Supergroup Dolomites (yes, i said transvaal)

  • news.moler - 2011-10-06 16:31

    Oi! where is my comment????

      Totman - 2011-10-06 22:11

      Oi! It is gone down with the editors Bells.lol.

  • Gaina - 2011-10-06 19:51

    Give Malema a house there.

      Face - 2011-10-07 09:29

      Imagine the headline: One hole was swallowed by another!

      Shaz - 2011-10-07 10:52

      WAHAHAHAHA!!!! @Face... you just made my whole YEAR!!!

  • Woofix - 2011-10-06 21:33

    Sinkholes as a result of dolomite ground structures!!! Wat jy waaaar kry!!?? It is only the potholes in the roads that reach maturety!!!

      Kiepies - 2011-10-07 10:10

      Brilliant and not even all patchwork in hell will stop it as they cannot even do this properly, let alone build new roads At present its try and dodge one hole and next moment you hit another which is a few metres from the one you tried to dodge...

  • Totman - 2011-10-06 22:14

    I red once JHB is the biggest city in the world that is not next to the coast, a river or a lake. If it goes on like this it will be the biggest city in one massive pothole. ;)

  • kingv - 2011-10-06 22:21

    There is R2.1Bn missing from public works in 1 year and they say nothing, sinkholes cause R1.5Bn damage in 50years and they call it satanic. Somehow i think they got the stories mixed up.

  • Deon - 2011-10-07 07:07

    When water is "free", our black brothers believe every tap should be left running at all times. Must remind them somewhere in their primitive psyche of "home", i.e. the virgin savannah where fountains and rivers used to flow free before being clogged with their s**t. I say, roll on sinkholes, let the idiots who do not want to move stay there and let nature take its course in clearing idiots from our gene pool of civilised intelligence.

  • neo_acheron - 2011-10-07 09:03

    "The dolomitic situation is satanic"-- Yeah the earth is swallowing you because of your sins agains the Dalai Lama! LoL WHAT NEXT? The sky has an evil eye that burns people? Or no, no... The sharks in the Cape work for the madam and they are out to sabotage tourism?!? WTF! My parrot has more brains than these morons.

      Thinkr - 2011-10-07 14:39

      Dont forget the very real study they were going to commission to ascertain why lightning strikes people, or something like that (it was a few months ago)

      umlaut - 2011-10-07 15:15

      If we can only get your parrot to speak in parliament or to stand for elections- we need some good leadership in this country.

  • capetownphotographer - 2011-10-07 10:00

    Dig deeper or fill them with all the useless crap we import from China #OccupySouthAfrica

  • kaapenaar - 2011-10-07 12:46

    satanic? really!? hahahahahahhahahahhahahahahahaha

  • Kiepies - 2011-10-07 12:53

    Sink and GAT maar aan!!

  • HJS - 2011-10-07 13:49

    Let those who refuse to move STAY, once the sinkhole appears, no need to then do anything. Dear Mother Earth will swallow them, and hope she does not choke.

  • nosiphom - 2011-10-07 14:42

    A few years ago, half of the N14 north after the Jean Avenue off ramp disappered undergorund and many people in Centurion have woken up to huge ditches in their front yards. I am shocked that many people commenting here take htis as a big joke, it isn't!

  • Lionel - 2011-10-07 15:13

    What about all the needless deaths on our roads? Where is the ANC when it comes to law enforcement? Joke.

  • Jason Borne - 2011-10-12 08:43

    All evil actions committed by human beings are Satanic inspired!! So if people are killing people - of course it is Satanic. Bling Bling, you obviously don't ever read the word of God! The almighty can control the weather and the oceans if he so desires! Yet being stupid is human! Satan has great influence on people even the stupid ones... Unfortunately the reason people live in informal settlements mostly, is because they are here illegally!!

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