1. Asset inventory
Description: This measure gauges a utility’s efforts to assess assets and asset conditions, as the first steps towards building a comprehensive asset management program.
Example calculations:
- Inventory coverage (percent): 100 X (total number of critical assets inventoried within a reasonable period of time (e.g., 5-10 years) ÷ total number of critical assets). A utility will need to first define what it considers to be a critical asset and a complete inventory will involve understanding the following for each:
- Age and location;
- Asset size and/or capacity;
- Valuation data (e.g., original and replacement cost);
- Installation date and expected service life;
- Maintenance and performance history; and
- Construction materials and recommended maintenance practices.[1]
- Condition assessment coverage (percent): 100 X (total number of critical assets with condition assessed and categorized into condition categories within a reasonable period of time (e.g., 5-10 years) ÷ total number of critical assets). Condition categories could include: unacceptable, improvement needed, adequate, good, and excellent to reflect expected service levels and accepted risks.
2. Asset (system) renewal/replacement
Description: This measure assesses asset renewal/replacement rates over time. The measure should reflect utility targets, which will vary depending on each utility’s determinations of acceptable risks for different asset classes. Decisions on asset replacement typically factor in internally agreed-upon risks and objectives, which may differ by asset class and other considerations. For instance, a utility may decide to run certain assets to failure based on benefit-cost analysis.
Example calculations:
- Asset renewal/replacement rate (percent): 100 X (total number of assets replaced per year for each asset class ÷ total number of assets in each asset class). For example, a two percent per year replacement target (50-year renewal) for a particular asset class could be identified as the basis for performance monitoring.
— or —
- Asset (system) renewal/replacement rate: 100 X (total actual expenditures or total amount of funds reserved for renewal and replacement for each asset group ÷ total present worth for renewal and replacement needs for each asset group). This is a QualServe Indicator.[2]
3. Water distribution/collection system integrity
Description: For drinking water utilities, this measure quantifies the number of pipeline leaks and breaks. Distribution system integrity has importance for health, customer service, operational, and asset management reasons. For wastewater utilities, this measure examines the frequency of collection system failures. When tracked over time, a utility can evaluate whether its failure rate is decreasing, stable, or increasing. When data are maintained to characterize failures by pipe type and age, type of failure, and cost of repairs, decisions regarding routine maintenance and replacement/renewals can be better made.[3]
Example calculation (drinking water utilities):
- Leakage and breakage frequency rate (percent): 100 X ((total number of leaks + total number of breaks) ÷ total miles of distribution piping per year). (Note: leaks and breaks are distinctly different events.) This is a QualServe Indicator.[4]
Example calculation (wastewater utilities):
- Collection system failure rate (percent): 100 X (total number of collection system failures ÷ total miles of collection system piping per year). This is a QualServe Indicator.[5]
4. Planned maintenance
Description: Planned maintenance includes both preventive and predictive maintenance. Preventive maintenance is performed according to a predetermined schedule rather than in response to failure. Predictive maintenance is initiated when signals indicate that maintenance is due. All other maintenance is categorized as corrective or reactive.[6]
Example calculations:
This measure can be measured in different ways. Calculating costs may be preferable to encourage business decisions based on total cost; however, the reliability of costs is uncertain. Hours are likely to be less variable than costs, but not all utilities track hours. Thus, cost and hours ratios are desirable, where possible.
- Planned maintenance ratio by hours (percent): 100 X (hours of planned maintenance ÷ (hours of planned + corrective maintenance)). This is a QualServe Indicator.[7]
- Planned maintenance ratio by cost (percent): 100 X (cost of planned maintenance ÷ (cost of planned + corrective maintenance)). This is a QualServe Indicator.[8]
More information on resources for this attribute-related measure can be found in the EUM Resource Toolbox.
[1] From the U.S. General Accounting Office, Water Infrastructure: Comprehensive Asset Management Has Potential to Help Utilities Better Identify Needs and Plan Future Investments. GAO-04-461. March 2004. Available: http://www.gao.gov/new.items/d04461.pdf.
[2] From AWWA and AwwaRF, Selection and Definition of Performance Indicators for Water and Wastewater Utilities, p. 53. 2004. Note: This material is copyrighted and any reprinting must be by permission of the American Water Works Association.
[3] Ibid., p. 70.
[4] Ibid., p. 61.
[5] Ibid., p. 70.
[6] Ibid., p. 65.
[7] Ibid., p. 66.
[8] Ibid., p. 66.