As yet the only obvious infrastructure failure which could have contributed to reports of pollution in the vlei, is a vandalised low-flow stormwater to sewer diversion in the Big Lotus River. Low-flow diversions are installed in chronically polluted stormwater ways, normally in catchments where land invasions and illegal development are prevalent; as these normally have a very noticeable effect on water quality. These low-flow diversion works function to channel polluted stormwater straight to the sewer infrastructure, where it will flow to the nearest waste water treatment works.

In the case of land invasions, sometimes it is not legally possible for the City to provide services such as toilets, or at the very least - provision of services is delayed until budget becomes available to provide services on unlawfully occupied land. This leads to pollution of storm drains, which flows into the natural water bodies around Cape Town. Low-flow diversion schemes are normally effective at minimising chronic pollution; however when water flows in the river increase above the capacity of the diversion chamber, pollution can still get past.

The most likely explanation for pollution currently is therefore a combination of both the recent rains and the vandalised low-flow diversion. However, further testing is still underway to try and eliminate other source possibilities. The vandalised low-flow diversion was repaired on 24 September 2020.

While the City’s Catchment, Reticulation, Scientific Services and Biodiversity Management teams are conducting their investigations, mitigation measures currently underway or commencing shortly are as follows:

1. Litter in the waterbody is being cleared by the LitterBoom River wardens
2. Bio-enzyme dosing to continue at strategic locations in the Big Lotus River catchment
3. Biodiversity Management who manage the Zeekoevlei section of the Nature Reserve have been communicating with concerned interest groups
4. River maintenance operational teams are undertaking routine clearing of accumulated silt and vegetation from sections of the Big Lotus Canal
5. Appropriate warning signs to inform the public have already been installed on site

Tests conducted on Friday, 25 September 2020, indicate significant sewage pollution in the northern portion of the vlei, most likely reflecting the lingering effects of the vandalised low-flow diversion, and as such, the Zeekoevlei Reserve will remain closed for now. The City apologises for any inconvenience caused, but commits to keeping interested and affected parties informed. Further testing has been planned.

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