City of Cape Town: Zandvlei in need of dredging

The City of Cape Town has received the final assessment reports from specialist consultants on the proposed remediation interventions for Zandvlei, located in the False Bay Nature Reserve. The City is studying the reports, and notes the recommendations and considerations related to the imminent dredging of Zandvlei. photo

Specialist consultants were appointed in June last year to advise the City on the proposed dredging of Zandvlei to improve the water quality for recreational use, and practical remediation options to address pollution in the catchment.

The study included hydrodynamic modelling to evaluate the sedimentation patterns, tidal influences, projected climate change implications, and dredging scenarios.

The reports state that Zandvlei hosts inorganic and organic sediments and that fine sediments contain the greater part of contaminants and nutrients contributing to the poor water quality. Of critical importance is to also address the sources of pollution from the catchment to ensure the ongoing health of Zandvlei’s ecosystem, and to reap the benefits of dredging in the long-term.

“According to the experts, the dredging of Zandvlei would have an overall beneficial effect on the water quality of the estuary,” said the City’s Deputy Mayor and Mayoral Committee Member for Spatial Planning and Environment, Alderman Eddie Andrews.

“However, there are several considerations the City needs to take into account, among which available funding and how we can use the budget that we have to achieve the best possible outcome. In this sense, the reports are very useful as the consultants also advise us on an incremental way forward as far as dredging is concerned.”

The reports recommend the following dredging scenarios:

  • Contaminated sediment is spread over the entire Zandvlei, and the ideal is to dredge the whole waterbody to the same depth – this would cost an estimated R202 million for dredging, dewatering and hauling to a disposal site,
  • If funding is limited, the priority area to be dredged must be the upper part of the estuary as it has a higher rate of sediment, the highest nutrient loading in the sediments, and higher rates of pollutant build-up than the lower parts of the vlei,
  • The dredging of the tidal channel will improve water exchange in the estuary with tidal driven ocean water and should be implemented in conjunction with dredging of the upper part of the estuary, etc.

Next, the City will begin with the necessary statutory processes related to dredging, among which an Environmental Impact Assessment and Water Licence.

It is foreseen that these processes will start in the 2024/2025 financial year.