volume 1 - Halifax Regional Municipality

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Halifax Water Integrated Resource Plan Appendices As noted previously, the first stage of the IRP analysis was carried out for the initial and intermediate alternative resource plans. It explored the A, B, C (monolithic) level for all asset systems (i.e. water, wastewater and stormwater) and all components within each system (e.g. distribution mains). In reality, the risk of failure has significantly different impacts depending upon which asset system or component is under consideration. For example, the failure of a single sewer pipe, while inconvenient, does not have a widespread or generally high impact. In contrast, the failure of a major water transmission main will have a significant and widespread impact on water supply. Since asset renewal resources are constrained, it is appropriate to have a higher level of asset renewal for those assets that are “high risk” and a lower level of renewal for those whose failure poses a “low risk”. An asset component-by-component risk analysis was conducted to determine the acceptable levels of asset renewal for each component. This was the second stage of the asset renewal program analysis and was undertaken for the intermediate plans creating a single optimized component asset renewal strategy. The risk analysis was based on methodology originally developed by the City of Edmonton 7 to assess the risks of failure associated with all municipal assets – not just water, wastewater and stormwater infrastructure. The failure impact of each asset component was assessed on the basis of best professional judgment by the study team (Halifax Water and consultants). A high (red), medium (yellow) and low (blue) coding scheme was used. The meaning of failure impact was understood to be “the impact of the failure of the system component (e.g. distribution main) on the ability to meet the asset system (e.g. water system) LOS”. Accordingly, the failure of a major WSP would have a high impact on the ability to meet the LOS for service outages while the failure of a single distribution main would have a relatively low impact on the LOS from a systemwide perspective. The failure severity is defined as “the impact of a single failure x the failure amount”. The failure amount is in turn related to the likelihood or probability of one or more components failing. This has most relevance to asset systems with multiple components such as distribution mains or sewers. For example, water transmission mains have a high failure impact. If it were determined that due to condition, age and other factors that multiple mains have an elevated probability of failure, then the overall failure severity would be high. Condition data are limited and hence decisions in this IRP rely on the knowledge of asset age and an estimate based on industry norms of expected remaining life. This was, in fact, the basis of the scoring for the failure severity for each asset component. Two metrics derived from Table 2.2 for water assets and Table 2.4 for wastewater and stormwater assets were applied – average weighted asset age at the 7 Edmonton Bridges the Gap – A Risk Analysis Approach to the Municipal Infrastructure Gap, S. AbouRizk et al., Summit, Jan/Feb 2005 Revision: 2012-10-29 Integrated Resource Plan –Appendices F-17 October 31 2012 Page 196 of 272
Halifax Water Integrated Resource Plan Appendices end of the planning period compared to the age at the beginning of the planning period and the fraction of the assets at the end of the planning period above design life. These two metrics in conjunction with the failure impact was used to qualitatively rate failure severity. Table 2.5 presents the scoring methodology. Table 2.5 Asset Component Failure Severity Score Failure Severity Score Colour Code 0-150 151-350 351-600 Table 2.6 presents the results of the asset risk analysis for the water assets. Table 2.6 Water Asset Component Risk Analysis Asset Design Asset Life (Years) Failure Impact Failure Severity Index Under Current Conditions Failure Severity Under A Level Renewal Conditions Failure Severity Under B Level Renewal Conditions Failure Severity Under C Level Renewal Conditions Preferred Asset Renewal Level Distribution Mains 75 low 150 100 125 150 C Transmission Mains 75 high 350 250 300 350 A Meters 20 low 50 50 60 75 C PRVs Civil - 50 M&E - 20 low 50 50 60 75 C Valves 75 low 50 50 60 75 C Revision: 2012-10-29 Integrated Resource Plan –Appendices F-18 October 31 2012 Page 197 of 272
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VOLUME 1: INTEGRATED RESOURCE PLAN
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Halifax Water Integrated Resource P
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Page 177 and 178: FINAL 1 2 3 4 5 6 7 10 13 16 17 18
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Financial Model 40-4 3.511 Stokil (
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Financial Model 40-4 2.075 Beaver C
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Financial Model 40-4 2.848 Storage
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Summary of Capital, Operational and
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Asset Renewal Costs Halifax Water I
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Asset Renewal Costs Stormwater Asse
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Statement Concerning Halifax Water
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Statement Concerning Halifax Water
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volume 1 - Halifax Regional Municipality

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