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wateronline.com ■ Water Online The Magazine $4,441.22. Ninety-five percent of the main breaks during the period cost less than $10,000. Managing Assets To The Lowest Life Cycle Cost The criteria are then inserted into Tacoma Water's life cycle cost model (shown below), which evaluates each of the 56,000 main segments in the distribution system to determine the optimal time for replacement. For each main segment, a remaining economic life is generated, indicating estimated time until the annual risk cost of operating a main is equal to the annualized cost of the asset's replacement. Optimal replacement timing is determined to be the age at which the annual risk cost of the asset (shown in orange) is equal to or greater than the annualized replacement cost of the new asset (shown in blue). The annual risk cost of the new asset is represented by the brown line. The intersection of the orange and blue lines indicates the optimal time for replacement. Operating an existing water main beyond this intersection means the utility is taking excess risk. Whereas replacing the main prior to the intersection means the value of the asset will not be fully realized. Incorporating Condition Assessment The output from the economic model provides a prioritized list of main segments based on their remaining economic life. As the prioritized list was generated using a generalized failure curve developed from the maintenance and repair histories for their respective material class, further analysis is conducted to ensure the replacement of the main segments is warranted. To confirm the replacement recommendations, Tacoma Water utilized non-invasive acoustic condition assessment technology to conduct condition assessment testing on cast iron and asbestos cement water mains. The assessment technology was selected based upon the short time by which the analysis was completed and the ability of the technology to conduct analysis without service interruption to customers. By combining the output of the economic model with condition assessment technology, Tacoma Water is provided with quantifiable data that can be used to develop business case justification for main replacement projects. In addition, and perhaps even more important, is that replacing main segments can be deferred if the condition assessment indicates replacement is not warranted at this time. In doing so, our rate payers are able to realize more value from existing assets rather than replacing assets too early. Through the use of asset management principles by implementation of the SAMP and use of condition assessment technology, Tacoma Water is able to optimally time the replacement of our water mains. In so doing, Tacoma Water will have reduced the capital budget for the main replacement program from $18 million during the 2011/2012 biennium to $9 million in the 2015/2016 biennium. Case Study 16 Ryan Flynn has worked for Tacoma Water since 2006. As a senior principal engineer with the distribution engineering section, Flynn is responsible for the main replacement program and serves as the lead for the distribution main strategic asset management plan. Tacoma Water's life cycle cost model. Pipe breaks can be prevented if the right data is collected before they happen.