The weed harvester for Marina da Gama at work in 2018.
City officials say they are unaware of fish die-offs at Zandvlei.
Responding to criticism about pollution levels in the vlei Xanthea Limberg, the mayoral committee member for water and waste, said the City’ scientific services drew samples monthly from ten points across the vlei and Marina da Gama, checking nutrient levels and doing algal analysis. The last measurement was taken on Monday April 12.
Ms Limberg said she was unaware of fish die-offs in the marina, while Marian Nieuwoudt, mayoral committee member for spatial planning and environment, said the City needed more information about aquatic deaths, but there had been no big fauna die-offs in the Zandvlei Nature Reserve.
Asked about contamination by sewage spills over the past two years, Ms Limberg said the vlei could potentially be affected by a sewer problem, such as an overflow or pump-station malfunction, in the Sand River catchment, which reached Wynberg/Kenilworth and included the Constantia and Tokai areas.
There were as many as 300 sewage spills a day across the City, she said.
Ms Nieuwoudt said that the past four monthly readings in Zandvlei had shown E coli levels that complied with national thresholds.
Ms Niewoudt said it would take the cooperation of City departments and the public to achieve the objectives of the 2010 estuary management plan for the Zandvlei estuary. An updated 2018 plan was in draft form and would show the progress made since 2010.
The City of Cape Town's Inland Water Quality Report 2019, she added, gave a full review Cape Town’s major water bodies over a five-year period.
"The report looks at the specific water quality parameters monitored on a monthly basis within Zandvlei, as well as the larger Sand River catchment, and also provides a valuable perspective of Zandvlei within the greater Cape Town context," she said.
These reports can be found on the City’s website here and here.
Ms Niewoudt said a manually operated weir had been installed in the stormwater infrastructure of the Sand River canal to reduce the impact of sewage spills
"This weir is designed to contain any effluent in the event of an emergency from where it is pumped out, preventing it from entering the Sand River canal and thereby the Zandvlei recreational waterbody," she said.
The weir had been in use since January last year and would continue to be used until something more permanent could be installed, she said.
Ms Limberg said officials were working on a formal, detailed response to the petition to save Zandvlei.