Brannon Meyer, Tokai
Thank you to Xanthea Limberg, mayoral committee member for her response to my letter (“Water concern”, Constantiaberg Bulletin, May 18).
It does, however, raise my concern even more.
Her statement that re-establishing these systems to prevent “galvanic” corrosion to protect the bulk water supply pipelines from corrosion is to be implemented in the next few years with the assistance of “external service providers” is somewhat disconcerting.
I have never heard any spokesperson from the City tell us about the vandalism which could jeopardise the bulk water pipelines supplying the City and environs.
During my tenure with the City Council one aspect of my job description included electrolytic corrosion investigations and essential regular testing and inspections of all installations. This was included in my annual remuneration. There was no need for “external service providers”
Ms Limberg does not say how long or how many cathodic protection systems have fallen into disrepair leaving the bulk water supply pipelines unprotected.
I do not wish to be an alarmist but for argument’s sake, let’s say 70 separate groups of protective anodes were connected to the bulk water reticulation system supplying Cape Town and environs and they are now dysfunctional. Remember that at each location, the pipeline is being corroded continuously. Imagine the consequences if 70 bursts occurred within a short period due to the lack of essential regular monitoring and preventative maintenance being carried out. Who is going to jail or be fined if this happens?
I would therefore ask the following questions:
1. How many years ago did regular checking and testing of anodes stop taking place?
2. In which areas were sacrificial anodes installed?
3. Has the electrolytic corrosion protection of submerged structures in high security areas also fallen into disrepair?
4 Is there any other method of electrolytic corrosion protection other than sacrificial anodes on the bulk water supply pipeline still functioning?
5. What are the costs which will be borne by the ratepayers for the assistance of external service providers.
I do not wish to be unduly critical so I am quite willing to assist where I can.
City spokesperson, Hayley van der Woude, responds:
Sacrificial anodes which were installed on the pipelines between Steenbras Dam and Newlands in the vicinity of Firgrove and Ysterplaat around 1991, fell into disrepair approximately 10 years ago due to constant theft and vandalism of equipment.
In addition natural drainage units were installed on all steel pipelines where they cross or run in close proximity to railways around 1994, and a sophisticated impressed current system was installed on the 2,4 metre diameter pipeline from Faure to Philippi in around 2 000. These systems are also not currently functioning due to vandalism.
External service providers will be engaged in the reinstatement of the protection systems and design of effective security enclosures, however they will not necessarily undertake regular testing and maintenance functions. The cost of this design and reinstatement is still to be determined. We would gladly accept advice in formulating our plans for reinstatement of these protection systems.
Although these anodes are not currently in operation the City has achieved a massive reduction in pipe bursts through intensified proactive and reactive maintenance programmes, leak detection technology, and the rollout of pressure management systems to reduce the stress on pipework. Although the use of sacrificial anodes in areas where there is a risk of galvanic corrosion was found to be impractical due to the vandalism, an intensive focus on rehabilitating our network has reduced the burst rate from 63.9 bursts per 100 km of piping in the 2010/2011 financial year to 31 bursts per 100 km according to the latest statistics, saving millions of litres of water in the process.