|Decision-Support Tools for Predicting the Performance of Water Distribution and Wastewater Collection Systems (EPA/600/R-02/029)
Water and wastewater infrastructure systems represent a major capital investment. Utilities must ensure that they are getting the highest yield possible on their investment, in terms of dollars and water quality. Accurate information related to equipment, pipe characteristics, location, site conditions, age, hydraulic rates, and water quality is critical to industry and municipalities to enable the most cost-efficient operation, maintenance, and rehabilitation of existing systems. This report summarizes information on European efforts to optimize operation, maintenance, and rehabilitation activities related to water distribution and wastewater collection systems.
The report includes descriptions of:
A review and analysis of European research and product literature related to the use of models for rehabilitation management suggests that modeling applications are not widely used in Europe. Each model presented in this report has been applied in selected urban or rural water services but not on a large national scale.
UtilNets is the most comprehensive model. It has the capability to model pipe failures, water quality, and rehabilitation scenarios. However, it is only in the prototype development stage. The concept of modeling the impact of pipe failures on water quality and using that information for rehabilitation planning has not yet been put into practice. Only the EPAREL/EPANET and UtilNets models have integrated a water quality module.
Data collection costs associated with using models are high. Accordingly, water services must avoid the collection of unnecessary data. The minimum data elements required by the models to develop a prioritized list of pipes based on risk of failure include pipe material, pipe age, section length, number of breaks or bursts, and diameter. Additional information (such as location, date, and nature of last break; type and cost of rehabilitation options; and type of customers who would be affected by a service interruption) is necessary if managers are to assess the impact of different rehabilitation scenarios.
Spatial analysis plays an important role in rehabilitation planning because the research shows that a significant number of failures appear in geographic clusters. However, only four of the models (AssetMap, Gemini VA, KureCad, and UtilNets) employ an integrated geographic information system user interface.
A review of three case studies and European research papers revealed that the practice of using performance indicators as a management tool is not widespread or standardized across European countries. Only Britain is using a well-defined and nationally standardized approach. However, even in Britain, the costs of additional data collection versus the benefits of additional system serviceability has not been studied.
The performance indicators used in the case studies varied considerably but could be grouped into indicators of network type and size, customer service, water distribution system effectiveness and reliability, wastewater collection system effectiveness and reliability, environmental impact, and infrastructure construction and rehabilitation cost effectiveness. The performance measurement system in Britain was found to be the most developed and could serve as a model for the U.S.
Although all of the case studies provided examples of how performance indicators could be used for intra-system and inter-system comparisons, only Britain’s Office of Water uses performance indicators to approve rehabilitation plans and price rate changes. A private water authority must demonstrate, using performance indicators, how its rehabilitation plans will improve the distribution or collection system’s serviceability to customers.
Based on the finding of this study, it is recommended that a Web-based survey of industry, state and local government officials, and academic and professional groups be developed. The purpose of the survey would be to select the most important performance indicators, create uniform definitions, and verify the core data elements necessary to support the selected indicators. The results from the Web survey could serve as a basis to convene an expert steering committee to provide direction to the development, fielding, and use of the database. Once uniform definitions are developed, volunteer water authorities should be solicited to collect the data necessary to develop a statistically significant database of infrastructure performance indicators.
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