Pretoria - The City of Tshwane has limited funds to work with in repairing at least 41 problematic sinkholes in the metropolis.
It was responding to complaints by some residents, who said it was taking too long for the sinkholes to be repaired.
Mayoral spokesperson Sipho Stuurman said their repair teams had not stopped the work on the sinkholes and were making progress although it could take as long as nine months due to the large extent, bulk earthworks and specialised repair methods.
The City spent R30 million to repair five sinkholes in the previous financial year (2020/2021). Stuurman said they were already working on the large sinkhole at 1 Pierre van Ryneveld, near the intersection of Dan Pienaar and Len Beyers streets, in Centurion. It was first reported in June 2018.
It is 50m in diameter and affects three properties. Investigations found it was caused by water leaks.
Stuurman said in the current financial year (2021/22), the City had an allocated budget of R28.5m. The work to repair all the sinkholes will carry on from one financial year to another.
"The sinkhole repair works follow the priority listing, but based on funding availability, duration and scope of repair, lower ranked sinkholes may sometimes be repaired before the higher priority sinkholes. Where there are savings in the current year, these will be used to repair other sinkholes as per the priority listing. Sinkholes do not remain in a constant stability condition into perpetuity, conditions may worsen or improve over time.
“The status of sinkholes and the repair priority listing is a dynamic process that requires regular updates, taking into consideration the occurrences of new sinkholes, existing sinkholes that reactivate, increase in size or become unstable, existing sinkholes that have been repaired or backfilled and are stable, as evidenced by ongoing monitoring, and the fact that once every quarter sinkholes go through assessment.”
He said sinkholes on municipal property, caused by municipal services and or affecting municipal services or infrastructure, were the responsibility of the municipality to repair.
However, where sinkholes had occurred on provincial or state property, caused by state or municipal services and or affecting municipal services or infrastructure, there was a joint responsibility between the municipality and affected department to repair.
According to the list, the second most prioritised sinkhole was in Lyttelton Manor at the corner of Clifton Avenue and Potgieter Street. It was reported in October 2019 and found to have been caused by a water leak.
The sinkhole affected area, approximately 20m by 12m and 8m deep, and was growing. Clifton Avenue was closed to traffic because the sinkhole was “growing” towards the northern and southern sides, affecting the southern corner of school grounds.
According to experts, water and electrical services had to be diverted. Stormwater diversion could not be carried out. Although geo investigations and repair methods were completed, further investigations were required based on recent reports of houses cracking and would be done as a separate incident.
Third on the list were sinkholes in Irene on Alexander Street. The first one was reported in March 2018 on the intersection of Queen Street. It was 11m by 6m and 5m deep and encroaches towards private property.
Subsidence formed approximately 1m by 6m long on western side of the sinkhole, the City said.
In December 2019, a new sinkhole, approximately 1.5m by 2.5m deep, formed on fibre cables caused by sewer leak.
These would be followed by another sinkhole approximately 7m diameter and 12m deep that was reported in June 2021. It is 7m west of an existing sinkhole and affected the driveway on 29 Alexandra Street and western boundary wall of erf 3/324.
This one was caused by water seepage from cable ducts, water leak at connection to meter, sewer leak.
The fourth on the list was the sinkhole in Lyttelton Manor at 1011 Kruger Avenue, first reported in January 2019 and later in December.
The sinkhole was 20m by 10m and 6m deep. It was eroding at depth and encroaching towards a roadway.
It was caused by poor backfill on property and subsequent water leak.
“Services are diverted and the area is being monitored for further expansion. It affects private property, municipal services and a sidewalk, with possible expansion into a roadway. Kruger Avenue must be closed off due to undercut of roadway by the sinkhole. All affected services like water, electricity and stormwater must be diverted. Geo investigations can only be done once the roadway is closed off and a detour is in place,” said Stuurman.
Although numerous sinkholes were in Lyttelton, Irene and Valhalla, some sinkholes were found in Erasmia at 237 Sesmylspruit Street, Jeffsville, Phomolong and Itereleng informal settlements, and in Lyttelton Manor, Laudium soccer grounds and Nellmapius Drive in Doornkloof.
Pretoria News