Asset planning for water reticulation systems - the PARMS model

Abstract

Traditionally water reticulation systems have been operated so that pipeline repair/renewal occurs on a reactive basis, based upon the number of failures, the consequence of failure and the cost. Planning for future replacements and the costs associated with these has been based upon a best guess of pipe lifetimes, which have generally been very conservative, when compared to the actual pipe life obtained. Factors such as the required level of customer service, trade-offs between repair and renewal, or operating practices such as pressure reduction or shut-off block reduction have not been widely considered, except when they are required under the water authorities operating licence. To allow long-term strategies to be implemented for the repair/renewal of water pipelines, a Pipeline Asset and Risk Management System (PARMS) is being developed. This planning model has been designed to allow a range of “what if” scenarios to be analysed to determine their effects on water authorities’ long-term costs. This model is based upon whole of life costing and includes data on externality and customer impact costs. It analyses the failures of individual pipe assets, rather than the traditional practice of predicting failure of pipe cohorts, currently used by many authorities. This paper discusses the application of the PARMS planning model to allow selection of pipeline repair/renewal, and briefly analyses the influences that a range of customer service or operating decisions can have on a water authority’s capital and operational expenditure.