The City of Cape Town’s Roads and Stormwater Department is embarking on a groundbreaking project to improve the quality of stormwater entering the City’s bathing areas.
A pilot project has been initiated in the Three Anchor Bay and Rocklands areas to test three technologies that are designed to either disinfect or divert polluted stormwater before it enters the sea. This project forms part of the City’s overall Inland and Coastal Water Quality Implementation Plan and Implementation Strategy.
Jeffares Green, the consulting engineers on this project, initially undertook a study that assessed the quality of stormwater entering the bathing beaches in Cape Town and assessed various technologies for stormwater treatment and disinfection. Three pilot projects were then initiated and designed to test the following technologies under local conditions:
- Diversion of the summer low flows to sewers (Three Anchor Bay North)
- Granular chlorine disinfection (Three Anchor Bay South)
- Ultraviolet disinfection (Rocklands)
Construction of the necessary infrastructure, which commenced mid-February 2012, will take four to five months. Once the infrastructure is in place, the technologies will be monitored for a year and then conclusions will be drawn as to the effectiveness and suitability of the technologies. In particular, the impact of the chlorine disinfection on the marine life in Three Anchor Bay will be evaluated by an independent marine biologist.
A comprehensive Environmental Impact Study including a full public participation process was carried out prior to launching the project. Approval in this regard was issued by the Department of Environmental Affairs and Development Planning (DEADP) in three separate Records of Decision dated January, March and July 2010.
It is believed that this is the first time in South Africa that such technologies have been trialled to treat municipal stormwater. This is considered to be a state-of-the-art approach by international standards. If the pilot trials are successful, the technology could be rolled out to other areas in Cape Town where contaminated stormwater needs to be disinfected before entering the sea.
It is important to note that the City takes the approach of first trying to eliminate the source of pollution before considering such end-of-pipe treatment solutions, but this type of treatment would be useful when it is not practically or financially feasible to locate or eliminate the source of pollution, as is the case in the Three Anchor Bay area.
The project at Rocklands will involve the construction of a building between the two existing buildings at the traffic lights and the installation of screening and ultraviolet disinfection equipment inside the building. The chlorine disinfection equipment will be installed at Three Anchor Bay and will consist mainly of underground tanks (a small raised structure, located near the road, will house the equipment). The low flow diversion infrastructure at Three Anchor Bay will be located near the parking lot and will consist of the manhole and small rising main, both buried below the ground.
Work will be undertaken on the pavement in some areas, but there will always be some access for pedestrian movement along the promenade. The site workings will be fenced off from the public at all times.
“I am excited to be part of such a unique project, which will inform the standard for similar interventions in Cape Town,” said the local Ward Councillor, Beverley Schafer.
