Sustainability Report 2006/07Maintaining supply of Melbourne’s high quality drinking water
Melbourne Water distributes safe, high quality drinking water that consistently meets stringent requirements. To ensure the continuous supply of high quality water, the supply system is managed according to the Hazard Analysis and Critical Control Point (HACCP) system, which focuses on quality management from catchment to consumer.
This year, we supplied 411,747 million litres of drinking water (444,365 million litres in 2005/06) to City West Water, South East Water, Yarra Valley Water and Western Water. They delivered water to homes, businesses and other consumers.
Melbourne Water met its water pressure requirements for 2006/07. Monthly targets must be met and 99.6% compliance is required overall for the year. We also met compliance requirements for drinking water in regard to microbiological standards, disinfection by-products and turbidity of the drinking water, but we did not meet the target for aluminium, which relates to aesthetic characteristics not health impacts.
Our target was not met when, during the treatment process, a higher than normal dosage of aluminium was added to the source water at the Yan Yean treatment plant to deal with increased turbidity. The aluminium levels were well within the Australian drinking water guidelines and did not have any impact on customers.
After months of record drought conditions the storm event on 27 June 2007 caused turbid inflows to the Upper Yarra Reservoir. In the week following, the turbidity of the water supplied from the reservoir began to increase and stayed high for a number of weeks. By mid-July, a boil water notice for the Yarra Valley townships was issued because the water from the Upper Yarra Reservoir is unfiltered and there was the potential for the treatment process to be affected by the turbidity.
By late July, the turbidity in the reservoir had reduced and in August the boil water notice was lifted. Melbourne Water approved the installation of five small media-filtration plants to enable effective treatment of the water if required in the future. Further information on the incident will be reported in next year’s Sustainability Report.
Melbourne Water successfully renewed its Major Hazard Facility licence at both the Winneke Water Treatment Plant and the Eastern Treatment Plant in accordance with the Occupational Health and Safety (Major Hazard Facilities) Regulations 2000. The licence was issued by the Victorian Workcover Authority and is necessary due to the quantity of dangerous goods, such as liquid chlorine, stored on these sites. Detailed safety cases were prepared to address the hazards and controls in place to ensure the risk of a major incident occurring was reduced as much as was reasonably possible.
Our retail water partners
Melbourne Water worked closely with the retail water businesses on several projects to maintain or improve water supply to consumers. One of the most significant projects was the cleaning of the Winneke-Preston Water Main. Yarra Valley Water and City West Water were involved in planning and implementing the cleaning of the 31-kilometre water main.
The project required the main being isolated, emptied and valves removed to allow the installation of the cleaning equipment. During the cleaning, water for Melbourne’s northern and western suburbs was supplied from Yan Yean and Silvan reservoirs.
(See Our relationships).
More information on water quality and Melbourne Water’s public health report can be found in Melbourne Water’s 2006/07 Social and Environment Report.
Case study
Harnessing new technology to reduce leaks
During 2006/07, Melbourne Water joined with Sydney Water, Yarra Valley and City West Water to bring an innovative leak detection system developed in the United Kingdom to Australia to test it under our own conditions.
In Melbourne, the retail water businesses and Melbourne Water work together to detect and repair leaks as quickly and effectively as possible. However, until now, there was never an easy way to check for leaks in large trunk water mains.
The Sahara system is designed specifically for detecting leaks on large water supply mains, without the need to take them out of service to be tested. This means that the tests can be done without any impact on supply to consumers or water quality.
The system was used to check seven Melbourne Water trunk mains along a distance of some eight kilometres. The results were impressive, with 10 leaks identified that would not have been detected otherwise.
The system uses a highly sensitive detector unit, which is inserted into a pipeline at a tapping point and is then carried along the pipe by the flow of water. A processor inside a van identifies any leaks immediately and pinpoints the exact location to within a few millimetres. The magnitude of the leak is measured by an acoustic system.
Depending on the configuration of the pipe lengths, up to 2000 metres can be surveyed in one pass and a leak as small as a few litres per hour can be detected. This assists in determining which leaks need urgent attention. It could also mean the difference between being able to repair a minor leak and having to completely replace a pipe, which was damaged by leaks that have gone undetected.
As part of an active leak detection program, Melbourne Water and the retail water businesses are now considering continued use of the Sahara, or an even more effective system if available, in 2008/09. Presently, the Sahara system is not available in Australia due to licensing arrangements.