Pretoria - Land and homeowners in the Centurion area should treat all pipe leaks as a matter of urgency before the concentration of water ultimately leads to the formation of sinkholes.
A simple and inexpensive way residents can test for leaks in their pipes is to open their meters and close off all the taps in the house.
Should the water meter keep running even after the taps have been closed, then homeowners should promptly fix the leak, said Professor SW Jacobsz from the Department of Civil Engineering at the University of Pretoria.
Jacobsz said that there were caves in the Centurion area which formed a long time ago and had reached an equilibrium. However, he said with more and more people moving into the area and developing on the land, the stormwater was redirected and ended up being concentrated in certain parts, and ultimately lead underground into cavities.
“Sinkholes shouldn’t be a problem, but almost 95% of the time they are triggered by leaking pipes. This is why it is important for residents to check for leaks and (fix) them as soon as possible.
“Another issue is that infrastructure deteriorates over time so it would be crucial for those looking to purchase old homes to ensure that they conduct geotechnical investigations, which can be expensive but would help to determine the severity.”
Jacobsz said with thousands calling Centurion home, it would be too expensive and improbable to move out of the area completely. However, he urged people not to buy property without the confirmation of a geotechnical investigation.
Meanwhile, a report by the Council for Geoscience painted a worrying picture that sinkholes would not be dealt with in one fell swoop, taking into consideration the history and activities by man, which was aggravating the situation.
The entity said about 25% of Gauteng was dolomitic, and this also affected other parts of the country including Mpumalanga, Limpopo, North West and the Northern Cape, all of which were also underlain by dolomite in certain areas.
The report said sinkholes often occurred with little warning, however, cracks in walls or settlement of the ground were often the early signs of impending sinkhole formation.
To date, they reported that at least 39 people were known to have died over the last 50 years in South Africa due to the formation of sinkholes, with an estimated cost of the damage caused by sinkholes being in excess of R1 billion.
They said what aggravated the formation of sinkholes in places, particularly in areas such as Centurion, was that new developments were taking place on the edge of the dolomite ground, which raised the question as to whether dolomite stability investigations were required especially during construction.
The council said dolomite stability investigations were required where dolomite bedrock was present up to 60m below ground surface in a non-dewatering scenario and 100m below ground surface in a dewatering scenario.
A total of 2 500 sinkholes and subsidence events have been recorded in South Africa to date, the majority of which have occurred in Gauteng’s far West Rand, areas south of Pretoria and the East Rand.
“Given sufficient time and the correct triggering mechanisms, instability of sinkholes and subsidences may occur naturally but currently it is expedited by the magnitude of man’s activities.
“The primary triggering mechanisms in such instances include the ingress of water from leaking water-bearing services, poorly managed surface water drainage and groundwater level drawdown,” the report said.
Pretoria News