The City of Cape Town would like to assure residents that it is doing everything possible to miminise the environmental impact of a significant sewer overflow into Zeekoevlei, part of the False Bay Nature Reserve.
To guard against the risk to human health, the vlei has been temporarily closed for recreational activity until further notice. Environmental regulators have been informed of the incident.
The main cause of the overflow is not yet clear, however various factors could be contributing to some degree. The City is currently using temporary pumps at the inlet works of the Cape Flats Wastewater Treatment Works while permanent pumps are in for repairs. Three of the four permanent pumps have experienced mechanical failure due to dumping into sewers. These screws were replaced in 2018, and without the illegal dumping of items such as bricks into the sewer system, these screws should last for at least 15 years. Recent hard rains, that filled our dams by nearly 15% in one week, most likely put significant pressure on this temporary fix. Currently, everything from plastic to nappies to large objects like steel drums and gas cylinders can be seen jammed into the remaining screw pump. These will be cleared as soon as sump levels drop.
The City has also observed that the overflowing manhole in the reserve is significantly damaged. How this occurred, is not yet clear, but it could potentially have also been a contributing factor to overflows.
Further investigations are planned to identify the extent to which possible new and undiscovered points of stormwater ingress, and its infiltration into sewers in the catchment, are playing a role.
While these investigations are under way, a number of additional temporary pumps are being sourced in order to divert sewage away from the vlei as far as possible, and will be monitored closely as these efforts may not be sufficient to prevent the overflow entirely should high rainfall events be experienced again.
It is expected that one of the screw pumps at the inlet works will be returned to service by 17 July 2021. For now, the City has stopped the flow of wastewater from the damaged manhole into the vlei by building a coffer dam with sandbags, the contents of which will be pumped out and into the existing cut-off drain, which then by-passes both the vlei and the wastewater treatment works and flows into the outlet. However, the effectiveness of this intervention measure could be compromised when the next rainfall arrives and will be continuously monitored. The City will also be monitoring the water quality in the vlei and investigating what remedial measures can be undertaken to mitigate the damage.
The City intends to engage with concerned interest groups and stakeholders to keep channels of communication open as the situation develops.
The City sincerely regrets the current situation but would like to highlight this as an example of the impact of using sewers illegally. Sewers should only be used to dispose of human waste, toilet paper and grey water. The City asks residents to please help spread awareness throughout their communities.
Source: City Of Cape Town