MEDIA RELEASE
NO. -61/ 2010
02 FEBRAURY 2010


The recently approved mid-term adjustment budget provides for an amount of R54, 2 million for upgrading of water networks.

The City regularly receives complaints from suburbs where a number of pipe bursts have occurred, stating that the pipe system is rotten and must be replaced. Even though this is generally not the case, it is a reality that pipelines sometimes do need to be replaced to reduce the risk of pipe bursts occurring. Therefore the City is acting proactively to replace pipes as far as the budget allows - to date in the first six months of the current 2009/10 financial year, some 21km of pipe has already been replaced.

Even though residents blame ‘old, rotten’ pipes for pipe bursts, the most common reason for pipes bursting is actually related to ground movement. Pipes are more likely to burst in areas where clay and cohesive soils are found, where inadequate compaction had taken place when the pipes were laid, or where certain types of trees were incorrectly planted over or too close to water mains, in which case the root system dislodges the pipe itself as it grows.

The City’s 11500 km pipe network comprises rigid materials such as cast iron and coated steel. In the more recent past, internally bitumen coated fibre cement pipes were used and these days the most common material for use in suburban streets is the more flexible UPVC pipes that are able to withstand small movements without fracturing or bursting.

“The other main reason for bursts can be high internal water pressures, particularly at night, which physically burst the pipes at a weak point. Pipes in the City’s network are sized to be capable to overcome the friction of water in the pipes, so that even at the peak periods in the morning and again in the evening, there is sufficient water for everyone,” said Justus.

As water is normally gravity fed from the service reservoirs on the hills surrounding the city, the water pressure in the pipe network will rise substantially once the majority of people have stopped taking water, sometime to more than twice the daytime working pressure.

To overcome this, the City started a programme some years ago for the installation of major pressure reducing valves that work in whole suburbs to adjust the water pressure as it rises. The first of these, the largest in the world at the time, was installed almost 10 years ago in Khayelitsha and another major scheme was installed in Mitchells Plain in 2008.

Several other smaller scale pressure management projects are currently underway in Lwandle, Delft, Fisantekraal and Gugulethu. Commissioning of the Atlantis project will take place shortly. ”Pressure reduction devices will continue to be installed throughout the city, where these projects will show beneficial results. A start needed to be made and this has initially been focused in those areas where water losses have been the highest and where we can best put into practice our Water Conservation and Water Demand Management Strategy, Justus said.

He added that these pressure management devices not only reduce the incidence of pipe bursts and save the City’s valuable water, but have a beneficial effect for the local residents as well, as it reduces leaks and bursts at their own residences. The Khayelitsha pressure management scheme for example is saving an estimated one million litres of water an hour which would have otherwise gone down the drain through leaks and bursts.

The City’s water reticulation performance is measured against international benchmarks and reported monthly at the Utilities Portfolio Committee meeting. Pipe replacement initiatives recently undertaken have improved the burst incident performance from 60bursts/100km/year down to 50 bursts/100km/year. Continued budget allocations are going to be required to maintain this progress to reach the acceptable standard of 20 bursts/100km/year.

All burst pipe incidents are captured at the Technical Operations Centre. Reports are generated per district/sub-council/street/suburb, as required. This information is confirmed by operational response teams and processed at local level for action. Burst incidence criteria are applied and this in turn informs the replacement program.

Whilst a database for bursts is maintained, the planned replacement program is at present informed by the reactive burst incident record, and is also governed by the available remaining capital budget allocation. A metro-wide, pro-active (planned) program for pipe replacement is not yet available; however the proposed Integrated Asset Management Plan will address this shortcoming. “Pipes which have reached the end of their useful life are however being replaced,” said Justus.

The majority of pipes requiring replacement are 100 mm diameter, and these are replaced at an average cost in excess of R1000/m. Approximately 6km was replaced in 2006 and this figure has grown to 46km being achieved in 2008/09 financial year. As mentioned before, some 21km of pipe has already been replaced in this financial year.

Justus said that budget reductions in the second half of the year caused by the general economic downturn may however prevent similar replacement rates as last year, being achieved in the future.


END

ISSUED BY:
COMMUNICATION DEPARTMENT
CITY OF CAPE TOWN


MEDIA QUERIES:
ALDERMAN CLIVE JUSTUS
MAYORAL COMMITTEE MEMBER FOR UTILITY SERVICES
TEL: 021 400 4865 CELL: 083 628 4136