Identification of Critical Water Supply Assets

This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.

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Report no. UWRAA 57

June 1993

Synopsis

The management of water supply assets requires managers to make many decisions under circumstances with significant uncertainty. Such decisions include prioritising asset renewals, formulating appropriate maintenance policies, inspection and condition monitoring programs and so on. With limited resources and increasing standards of service, effort needs to be put where it is of most benefit.

Criticality is a tool developed to assist managers in asset management, to improve and give confidence to their decision-making.

The adopted Criticality model is based on Loss Potential which combines both severity (or consequences of failure) and failure risk (likelihood of failure) to give a criticality value or ranking for any asset. The units of measure for criticality are probable cost/year.

The severity component of criticality accounts for all failure consequences ie. Direct costs (including repairs, value of water lost, cost of alternative supply, loss of revenue) and indirect costs (such as consumer disruption, third party liability, traffic disruption, environmental penalties, image impacts). Where possible, methods and procedures for estimating these costs have been developed; for some components, given our present state of knowledge, subjective assessment or ranking only is possible.

Many authorities are developing predictive failure models for their pipeline assets, however, much work remains to be completed before such models can be used with confidence. For the present, simplified models for estimating failure risks for pipeline and other assets have been developed.

Procedures and examples for applying the analytic model are presented. Although the Sydney Water Board has been used (by necessity) as the source of information and data, the methodologies and modelling are widely applicable with only minor adjustments required to factors and parameters to reflect circumstances elsewhere.

Recommendations are made for further model development activities, including trialling of the model on actual failure events and the establishment of suitable databases(nationally accessible) to collect and record necessary information.

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