The City of Cape Town has done a drastic U-turn, saying effluent water can be used by developers to mix concrete, but it’s still leaving it up to them to make that call as “Day Zero” looms.
This despite a former civil-engineering lecturer saying there is no need to use potable water for that purpose and for the City to claim otherwise suggests it has been misled or misinformed.
The flip-flop comes just weeks after City officials said at a public Ward 54 meeting in Sea Point that potable water “must” be used for concrete (“Developers allowed to use potable water,” Atlantic Sun November 2). In a response to an inquiry last month, Xanthea Limberg, mayoral committee member for informal settlements, water and waste services, and energy, said that potable water had to be used for concrete.
“Potable water must be used for mixing cement as using lower-quality water can adversely affect the structural integrity of the concrete.”
However it seems that wasn’t set in stone, because now Ms Limberg is saying the City is aware that treated effluent and borehole water can, in some cases, be suitable for cement mixing, albeit under rigorous quality-control.
“The characteristics of this water would have to be continuously evaluated to ensure the structural integrity of the concrete, and water may need to receive additional treatment before use. We are, however, encouraging all developers to please explore whether these options are feasible for any of their projects.
“Furthermore, the treated effluent supplied by the City is much cheaper than potable water.”
She added: “The discretion to use treated effluent or borehole water on concrete and stabilised bases remains with the developers at this stage. The City cannot yet assume liability by prescribing its use until more detailed testing takes place.”
The City said treated effluent could be used for various construction-related activities, including some road construction, dust control, washing retarder off concrete, compaction, trench backfilling and cleaning construction equipment.
Ms Limberg repeated calls for the public to save water, saying daily consumption was still too high.
“Our data shows that there are still people who are exceeding the consumption target of 87 litres per person per day.
Isa Jacobson, a Sea Point resident who was at last month’s meeting, said the City needed a policy shift and new developments should incorporate grey-water systems.
“We can’t continue to behave as if there is going to be rainfall. We need to know that the City is looking after our water supply. We need regulation and policy on it,” she said.
“They can’t just keep chasing after us when there is no onus on developers. It begs the question as to how they continue to get away with it.”
In a letter sent to the Atlantic Sun, Professor Mike de Kock, a former civil-engineering lecturer at UCT and an honorary life member of the Concrete Society of South Africa, also said the City should stop developers from using potable water.
“The City management has either been misled or is poorly informed. The claim that potable water is necessary for construction work is incorrect. Borehole water, which is not muddy, is perfectly adequate for mixing concrete and building work, as is water out of the river.
“The City should stop builders using potable and require builders and ready-mix concrete manufacturers to switch to using borehole and run-off water immediately. There is very little preventing the City from establishing boreholes at strategic points in the city and charging builders for water.”
Professor De Kock agreed that there needed to be a policy shift.
“You cannot afford to waste our lifeblood on something like mixing concrete.”
He added that as long as the water was clear it would be good enough to mix for concrete. He also said that the testing only took a matter of days, saying it wouldn’t be such a difficult thing for developers to do.
Ms Limberg stressed that there were several projects on the cards to push back “Day Zero” when taps will run dry. “We are on track with our first set of augmentation plans: the first seven projects. These are Monwabisi, Strandfontein, the V&A Waterfront, and Cape Town Harbour desalination plants; the Atlantis and Cape Flats aquifer projects; and the Zandvliet water recycling project that will collectively produce an additional 196 million litres per day between February and July 2018.”
In addition, she added, the City had 12 projects in an advanced stage of planning that are ready to proceed if required. “These projects will help extend Day Zero.”