Central Highlands Water (CHW) operates a distribution network in which has significant portions of asbestos-cement (AC). However, these assets account for 58% of recorded leaks and bursts between 2020 and 2025, representing a disproportionate share of network failures relative to their extent. Smaller diameters, particularly 100 mm and 150 mm mains, are the most affected and together contribute around 70 per cent of failures within their respective size groups, driving a significant portion of the unplanned maintenance activity.
To better understand the condition trajectory of the AC cohort, a deterioration model adapted from Davis et al. (2008) was implemented and informed by local failure data. The modelling indicates that many mains at 200 mm diameter and below are approaching the lower bounds of residual tensile capacity. As structural capacity declines, the likelihood of failure increases and burst events become more frequent. Larger diameter mains generally retain greater structural margin; however, the same degradation mechanisms remain active and their risk profile is expected to evolve over time.
The implications for the organisation are multi-dimensional. Operationally, AC failures generate a disproportionate share of reactive maintenance demand, placing sustained pressure on labour, plant and operational budgets. Historically, AC mains have contributed on average 175 more bursts per year than all non-AC materials combined, contributing to ongoing service and customer impacts.
From a safety and compliance perspective, intact AC mains present low public health risk; however, failure and excavation events introduce additional controls associated with asbestos-containing material. As failure frequency increases, so too does the complexity and cost of field operations.
Collectively, the evidence indicates that ageing AC watermains are becoming a dominant driver of reactive workload and risk within the CHW network. These findings support the need for risk-informed renewal planning and targeted management strategies for legacy AC assets.