SECTION 2
Development of Asset
Management Framework
2.1 Development of Risk-Based Asset
Management Framework
As part of the master planning effort, WES developed a risk-based asset management framework to augment its current asset management practices. With this new framework, operations and maintenance (O&M) activities and capital investments are evaluated and ranked by priority in terms of risk posed by an asset’s failure. Risk is measured in terms of the consequence, which is evaluated by the impact on levels of service, and in terms of likelihood, which is the possibility that the asset will fail.
The level of service categories defined for WES are: • Health and safety of the public and employees • Financial impact
• Public confidence
• Environmental compliance • System reliability
Likelihood of failure was evaluated based on physical condition of the asset, performance, external and internal physical factors affecting the asset, O&M protocols, and reliability history. The consequences of failure categories are assessed individually as negligible, low, moderate, or severe. The likelihood categories are rated as negligible, unlikely, possible, likely, and very likely to contribute to asset failure.
With this approach, the likelihood and consequence scores are combined to determine a risk score for each asset. The relative order of risk established by this evaluation is used to guide decisions about operating and maintenance activities, rehabilitation and replacement of system components, and establishing priorities for capital improvement projects.
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2.2 Recommendations
To ensure WES receives the most value for the resources invested in this risk-based approach, the following recommendations are offered:
• Undertake detailed condition assessments of those interceptor segments and subbasins having unacceptable risk, giving priority to those with highest risk.
• Incorporate condition assessments into planned maintenance activities.
• Update risk scores based on the most recent condition and performance assessments. • Revisit consequence scoring at periodic intervals, no greater than every 5 years, but
more frequently as demographics, customer issues, and regulations change. • Update asset hierarchy as new assets are added to the system and when assets are
removed from the system.
• Use computerized maintenance management system (CMMS) and geographical
information system (GIS) to store consequence and likelihood data, and retrieve the data to perform periodic analysis when preparing capital improvement program (CIP) and revising O&M protocols.
• Incorporate a risk-based approach into operational and business processes and train staff in its use.
• Expand the risk-based approach to treatment facility assets.
2.3 Existing System Characterization
CCSD #1 is served primarily by gravity-flow sewage collection systems that terminate at the Kellogg Creek Water Pollution Control Plant (WPCP). Pump stations provide service to areas at the edge of the gravity flow basin boundaries. In total, CCSD #1 includes fifteen pump stations and approximately 1.6 million linear feet of collection system pipeline. The existing collection system is briefly characterized in Figures 2-1, 2-2, and 2-3 in terms of pipeline diameter, construction material, and year of installation based on WES data. As shown in Figure 2-1, most the collection system pipelines are 8 inches in diameter.
FIGURE 2-1
Summary of CCSD #1 Collection System Pipelines by Diameter
0 200,000 400,000 600,000 800,000 1,000,000 1,200,000 1,400,000 4 6 8 10 11 12 15 16 18 20 21 24 27 30 33 36 42 45 48 54 72 84
Pipe Diameter in Inches
Q u antity of Pi pe i n Li ne ar Fe et
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The currently available inventory of CCSD #1 collection system pipeline materials accounts for approximately 40 percent of the existing system. As shown in Figure 2-2, the majority of the inventoried system is made of concrete pipe. Based on general system knowledge, CCSD #1 staff indicates that most of the un-inventoried portion of the system is probably constructed of PVC.
FIGURE 2-2
Summary of Inventoried CCSD #1 Collection System Pipelines by Type of Construction Material
0 50,000 100,000 150,000 200,000 250,000 300,000 350,000 400,000
ACP CCP CIP CSP DI HDPE NCP PE PVC RCP RPVC STL
Type of Pipe Material
Qua n ti ty of Pi pe in Li ne ar Fe et
ACP = asbestos cement pipe; CCP = concrete culvert pipe; CIP = cast iron pipe; CSP = cement sewer pipe; DI = ductile iron; HDPE = high density polyethylene; NCP = concrete pipe; PE = polyethylene; PVC = polyvinyl chloride; RCP = reinforced concrete pipe; RPVC = reinforced PVC; STL = steel.
The construction history of the collection system is summarized by linear feet in Figure 2-3. As shown, nearly a third of the system was constructed in 1974. The primary elements of the system were constructed from 1971 to 1976, including approximately 80,000 feet of
interceptor sewer lines. Since that time the system has been expanded incrementally to accommodate community growth.
FIGURE 2-3
Summary of CCSD #1 Collection System Pipeline by Construction Year
0 100,000 200,000 300,000 400,000 500,000 600,000 Un k n o w n 19 70 19 72 19 74 19 76 19 78 19 80 19 82 19 84 19 86 19 88 19 90 19 92 19 94 19 96 19 98 20 00 20 02 20 04 20 06 20 08
Pipeline Construction Year
Pi pe li ne in Li ne ar Fe et
2.4 Data Development Needs
Inventory data to support the modeling of the collection system were found to be available and of high quality for the portion of the system analyzed. Invert and ground elevations,
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Flow monitoring data should continue to be gathered to support future refinements to the system model and to gage potential increases in RDII over time.
The asset management information compiled during the pump station and conveyance elements of the master plan project should be incorporated in the GBA software system. GBA can then be used as an asset management tool. Condition assessment should be used to establish a base reference index score that can then be used to establish
replacement/repair priorities.
Land use data in the Hoodland area was not as complete as the Metro database used in the rest of the service area. Area contributing sanitary sewer flow for existing and future land use conditions would enhance the ability to predict future existing and future peak flow for the design storm conditions.
