Introduction
City West Water (CWW), manages a water supply network providing drinking water, sewerage, and recycled water services to its customers in Melbourne’s central business district, inner and western suburbs. Each year City West Water supplies about 93 billion litres of drinking water and transfers approximately 94% of sewage and trade waste collected to the treatment plant in Werribee, with the remaining going to the treatment plant in Altona.
The Challenge
The water supply network comprises 16 pressure zones supplied from various sources. The average pressure across the network is close to 60m, however this varies significantly depending on zone characteristics such as elevations, demand and hydraulics.
One of the areas within the Yuroke Supply Zone was identified with excessive pressures of up to 115m. This area supplies water to over 2,000 customer properties. Traditionally design pressures of reticulation networks are limited to 100m to minimise the risk of leaks and pipe bursts. Reduced pressure compromises supply and water quality, excessive water pressure leaves pipelines vulnerable.
City West Water required a solution to enable them to effectively reduce the excessive pressures, customer complaints and improve performance while ensuring value for money in terms of whole life cost, safety and durability of the pipeline.
The Assessment
Previous measures undertaken included throttling sluice valves and installing pressure reducing valves (PRV’s) on approximately 15 customer assemblies. However, this did not provide a permanent solution, customer complaints continued and the pipeline integrity risk remained.
Investigations made apparent that a permanent solution was required for a wider effected area and that City West Water would need to monitor the network performance and respond quickly to any potential issues.
Additionally, a risk-based strategy was needed to evaluate capability and improve performance, balancing reactive demands against proactive development for the lifecycle of the asset. Detection Services teams provided solutions aimed at achieving organisational long-term goals and effectiveness through alignment of the required infrastructure assets to meet the changing needs of our customers and the environment.
The Solution
To allow the development of a logical and fully justifiable solution, the City West Water Non Revenue Water (NRW) Management team worked with Detection Services teams to develop a decision making strategy. This resulted in the solution to create a pressure management area (PMA). This addressed two main business needs, firstly reducing the pressure and risk to pipeline structure while addressing the customer complaints of excessive pressures, secondly allowing for district metered area (DMA) to monitor network performance.
The solution required a primary supply and a secondary supply to the area for added security. DMA’s are used to facilitate minimum night flows and water loss data allowing City West Water to better understand system losses and to more effectively target non-revenue water.
Upon completion of the meter and PRV construction, a pressure reduction test and fire flow test were undertaken, to confirm the integrity of the DMA boundaries and that the DMA was sufficiently supplied during a fire event – both with successful outcomes.
The results from the establishment of the PMA were a 34% reduction in leakage, 43% reduction in bursts and minimum night flow monitoring now provides the necessary data to determine water loss. The performance data collected and transmitted twice daily from this DMA, and the other DMAs created in the region, provide high resolution information that is otherwise unavailable in the 16 large water supply zones. This allows City West Water to effectively manage the infrastructure, increase productivity and performance while ensuring value for money in terms of whole life cost, safety and durability.
The approach adopted for City West Water showcases how Detection Services asset management strategies, investigations and solutions allow customers to achieve best practice alignment and maximise the value of their assets across their lifecycle.
