The burst pipe that flooded Meredale in southern Johannesburg with 80-million litres of water in July was the result of corrosion and a 41-year-old bad weld, Rand Water said on Friday.
Rand Water chief executive Simo Lushaba said the pipe that burst developed a leak along a seam that had been welded in 1964.
The pipe, carrying water to the West Rand, did so under 8,9 bars of pressure. The average car tyre is inflated to two bars.
Over the years, corrosion had thinned the walls of the pipe from 8mm to just 3mm. The welding was also substandard by today’s benchmarks.
Lushaba said water in the pipe started seeping out at 1.30am on July 5, which was when Rand Water’s control centre noticed a dip in water pressure. Calls from residents started coming in from 2.45am. Technical teams were on-site by 3.15am.
Lushaba said an independent metallurgical consultancy, T Brady and Associates, had found that once the water found the weakness in the bottom part of the pipe, it literally exploded.
Water jetting out of the pipe gouged a 5m-deep hole through the floor of the valve chamber in which the burst occurred, resulting in a wall of water cascading into 35 or 40 houses in Meredale.
The pipe that burst, a conical reducer with one end smaller in diameter than the other in order to connect pipes and valves of different sizes, was manufactured on the site of its installation by making numerous longitudinal cuts in the pipe, pressing the resulting petals together and welding them.
”The ejection of a large piece, significantly larger than the cross-sectional area of the pipe, accounts for the rapid discharge of large volumes of water and the extensive flooding which ensued.”
Turning to the cost of the disaster, Lushaba said the water alone had cost about R300 000. This was R50 000 more than first estimated.
In the immediate aftermath of the flood, Rand Water spent R417 803 providing food and temporary shelter and restoring power, water and sewerage. The figure also included eight courtesy cars for people whose vehicles had been damaged, and accommodating two families at a nearby hotel.
The cars, barring one awaiting parts from France, have also been repaired and returned to their owners.
Five household claims totalling R106 808 have been settled. Ten homeowners’ claims have also been settled, costing a further R223 386.
Rand Water’s insurers have also accepted a claim of R521 601 to pay 47 more claimants’ insurers.
Another R600 000 will go to City Parks and the Johannesburg Roads Agency (JRA) to rehabilitate the site and rebuild damaged roads.
As a step in that direction, Rand Water planted 101 trees in the area, worth R47 000, on Arbor Day, September 3.
Replacing the burst taper cost R16 800 and was done within 24 hours.
A 6m section of pipe damaged by the leak was being replaced this week and a further 6m section will be replaced next week.
Lushaba said this was the first accident of this kind in Rand Water’s 103-year history and he is determined that it will not be repeated.
An audit after the burst found three more reducers of the same design as at Meredale. They are at Meyershill and Elands Park in southern Johannesburg and along Van Buuren Road in Bedfordview.
All will be replaced by June next year.
In the meantime, all are being braced to prevent a similar blow-out. The welds are also being X-rayed and the thickness of the metal determined, Lushaba said.
Rand Water is already spending about R200-million a year maintaining its 3 800km network of pipes.
Staff are also being retrained on inspection procedures.
Lushaba said Rand Water is grateful to Johannesburg’s emergency services, City Power, Pik-it-up, City Parks and the JRA for assistance. Others thanked were the media, the Mondeor Dutch Reformed Church and the police’s counselling services.
Speaking on behalf of the affected residents, community leader Tico Mokhoko said: ”Overall, the community is happy with the progress.” — Sapa