Identificationof Critical Water Supply Assets

ReportNo WSAA 57


June 1993




Themanagement of water supply assets requires managers to make many decisionsunder circumstances with significant uncertainty. Such decisions includeprioritising asset renewals, formulating appropriate maintenance policies,inspection and condition monitoring programs and so on. With limited resourcesand increasing standards of service, effort needs to be put where it is of mostbenefit.


Criticalityis a tool developed to assist managers in asset management, to improve and giveconfidence to their decision-making.


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


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


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


Proceduresand examples for applying the analytic model are presented. Although the SydneyWater Board has been used (by necessity) as the source of information and data,the methodologies and modelling are widely applicable with only minoradjustments required to factors and parameters to reflect circumstanceselsewhere.


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


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