Setting Pipeline Rehabilitation Priorities to Achieve "Best" Results — A Case Study Using Condition and Criticality Criteria

In these days of fiscal frugality, utilities struggle to get financial resources for pipeline rehabilitation. Once resources are dedicated, it is critical that they achieve the "best" results possible based on multiple objectives and criteria. These criteria reflect the often competing interests of different utility departments (e.g., planning, engineering, operations and maintenance), and they must consider the expectations of the utilities' customers and outside stakeholders, including the business community, regulatory officials, and environmental groups. Add politics and the media to this scenario, and the decision making process becomes complex. This paper presents a method of developing, applying, and defending a decision making process that is technically sound, practical to apply, and reflects the values and objectives of stakeholders both within and outside of the utility. The method sets rehabilitation priorities based on available information related to condition (probability of failure) and criticality (consequences of failure) criteria that are developed and weighted through a stakeholder's involvement process. The results provide a framework for setting priorities for immediate rehabilitation action items as well as priorities for collecting additional information in areas where it is needed to support better decisions. In coastal Wilmington, North Carolina, the need for sewer rehabilitation became a focus of the media and politically charged after several force main failures and system stoppages resulted in a series of sanitary sewer overflows (SSOs), one of which impacted beach areas on a holiday weekend. Quickly responding, the city initiated a priority-setting process using the methodology described herein that affirmed the importance of several sewer rehabilitation projects already ongoing and identified a number of high priority rehabilitation and condition assessment efforts to be started immediately. Several of the condition assessment efforts have been completed using techniques including zoom camera inspections in priority gravity sewers and ultrasonic thickness testing of several ductile iron pipe and prestressed concrete cylinder pipe force mains. These results demonstrate the successful application of this method in a politically-charged and high profile environment. The details of this case study are described in more detail later in this paper.