65B - PROPOSED WATER AND SEWER RATE ADJ

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City of Santa Ana, CA I WATER RATE STUDY Other Factors Other water distribution system factors are sometimes used for pipeline condition analysis if the data is available. These data sources may include the use of customer complaints for identifying areas of the system that may be deficient in water pressure or quality. Another data source may include results of hydraulic modeling analysis; again indicating possible capacity deficiencies, pressure / surge issues, or water quality indicators. These data sets were not available for this study. However, the City may decide to include these factors in future analysis efforts as their Asset Management system matures. Probability of Failure Analysis (PoF) The Probability of Failure (PoF) criteria (factors) are used to assess the likelihood that a particular asset will fail. This is done by considering the physical properties of the asset itself as well as its surrounding environment and /or operational history. Three criteria were used for evaluating the likelihood of failure of the City's water main segments. These criteria include Cohort Rank, Pipe Vintage (age), and Repeated Failures. The following section describes the approach taken to select and prioritize pipe segments for replacement or rehabilitation. This approach is based on identifying, from the analysis above, the factors which have the most tangible effects on pipe deterioration and assigning weightings to these factors to reflect their relative importance. Cohort Rank Some materials have been shown to be more prone to failure than others. Likewise, the older the asset is, typically the more likely it is to fail. Often it is the combination of these considerations that impacts the asset's life expectancy. By combining pipe material and vintage (installation year), groups of similarly performing pipes can be identified. These are considered pipe "cohorts." An evaluation of the City's pipe data on materials, age, breaks, etc. was performed to identify likely pipe cohorts. This evaluation included trends as observed in the source data and also general past performance knowledge of similar materials in similar environments. Not all pipe segment records in the GIS database provided complete or accurate date attributes. The City is encouraged to investigate further to identify these missing data. This might be accomplished by reviewing appropriate asbuilt drawings, or assuming attribute data based on neighborhood construction periods or adjacent pipe attributes. This effort was beyond the scope of this investigation. Once the missing data is identified, these pipe segments may likely acquire lower Cohort ranks. Based on a review of the GIS data, the Number of Breaks per Mile by Decade Pipe Installed and Material analysis appears to provide the best insight into grouping of similar pipe performance. The following pipe cohorts have been identified for this analysis and were assigned a priority PoF ranking: • Cohort 5, High PoF Score: 1970s / 1980s Ductile Iron Pipe and High Pressure 36" MWD Transmission Line • Cohort 4, Med -High PoF Score: Asbestos Cement Pipe installed before 1940 • Cohort 3, Med PoF Score: Cast Iron Pipe installed before 1960 • Cohort 2, Med -Low PoF Score: Cast Iron Pipe Installed after 1960 • Cohort 1, Low PoF Score: Asbestos Cement Pipe Installed after 1940 BLACK & VEATCH I Appendix B'. Water CIP Prioritization Prst r�ss 65B -119 107