News agency, Cape Town, South Africa
Wednesday May 22nd 2019

City seeks to clean up stormwater flowing out to beaches

Stormwater channelled out to sea is one cause of water pollution at city beaches, but the City of Cape Town is embarking on an innovative pilot project – possibly the first of its kind in South Africa – to clean up the discharge flowing into to the city’s bathing areas.

Following an Environmental Impact Assessment (EIA) the project in Three Anchor Bay and Rocklands area in Sea Point tests three different technologies under local conditions to determine how best to clean up the stormwater entering the sea.

  • To the north of Three Anchor Bay the summer low flow stormwater is being diverted to sewers
  • At Three Anchor Bay south granular chlorine is being used to disinfect stormwater, and
  • At Rocklands in Sea Point, ultraviolet disinfection is being used to treat stormwater.

Construction on the projects began last month and once complete, the technologies will be monitored for a year to test their effectiveness.

The City states on its website that “it is believed” that this is the first time such a trials using various technologies would be conducted in South Africa in what “is considered to be a state-of-the-art approach by international standards”.

Should the trials be successful, the technology could be implemented in other areas. This would be particularly useful for stormwater systems running through highly urbanised areas such as Sea Point where it is difficult to prevent pollution at source and numerous contaminants are washed off the hard surfaces such as roads and pavements.

The City’s news release coincides with the latest Inland and Coastal Water Quality Report for the January 2011 to December 2011 period which notes that the quality of water at inland rivers and vleis, as well as at beaches in False Bay has improved, but the water quality along Atlantic ocean beaches, such as those at Sea Point, has deteriorated in comparison to the previous year.

The monitoring of 40 bathing beaches in False Bay from Miller’s Point to Kogel Bay shows a 95% compliance with water quality guidelines as stipulated by the Department of Water Affairs.

The coastal bathing areas are tested every two weeks to check for levels of faecal bacterial contamination discharged into the ocean via river and stormwater outlets.

Two tests are conducted: The stringent 80th percentile test where 80% of samples must contain 100 or less indicator organisms such as e.coli per 100ml, and the 95th percentile test where 95% of samples must contain 2000 or less indicator organisms per 100ml.

In False Bay 98% of all samples complied to the 95 percentile test while 95% of all samples complied with the more stringent 80 percentile test.

This was in improvement on the January 2010 to December 2010 period when only 83% complied to the 80th percentile test and 78% complied to the 95th percentile test.

However, a slight deterioration was evident from results obtained at the 28 sampling points along the Atlantic coastline stretching from Silverstroom beach in the north to Scarborough beach in the south.

On the Atlantic side 79% of tests complied with the 80th percentile quality guidelines while 89% complied with the 95th percentile measurement.

The figures for January 2010 to December 2010 were 93% and 100% respectively.  – Steve Kretzmann

Tags: Coastal Water Quality Report, Environmental Impact Assessment, rocklands, Sea Point, Three Anchor Bay

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