Using Life-Cycle Cost Analyses (LCCA) to Evaluate Large Diameter Water Pipeline Maintenance Strategies

The Central Arizona Project (CAP) operates and maintains two (2) 21-ft (6.4 m) diameter steel pipes as part of the aqueduct system that delivers almost 2 billion gallons of Colorado River water per day, to Maricopa, Pinal, and Pima Counties in central and southern Arizona. The water is delivered to municipalities, industries, Native American communities, and agricultural users; over 5 million people (more than 80% of the population of Arizona) are provided water by the aqueduct system. The approximately 350 mi (563 km) long aqueduct system is composed of about 300 mi (483 km) of open channel canals, about 10 mi (16 km) of tunnels, and roughly 40 mi (64 km) of pipelines. The system traverses rugged mountains, desolate deserts, and highly populated urban areas as it conveys water from Lake Havasu at the western edge of the state to just beyond the southern boundary of the San Xavier Indian Reservation south of Tucson. As the aqueduct spans the state, it crosses several natural waterways. To facilitate not interrupting the natural waterways, the open channel canal transitions to a closed conduit and proceeds beneath the watercourse. Depending on the location within the aqueduct these pipelines range in size from 13-ft (3.9 m) to 21-ft (6.4 m), and include steel, monolithic concrete, and prestressed concrete pipelines. These large diameter water pipelines can be considered “forever assets”—there is no real service end-of-life, but there may be an economic end-of-life; for pipelines that is when it is more economical to replace the entire pipeline rather than continue to perform scheduled and unscheduled maintenance and/or repair. This paper examines the evaluation and results of a life-cycle cost analysis (LCCA) performed by CAP in attempting to determine the most cost-effective strategy in maintaining not only the two large diameter steel water pipelines but apply the maintenance strategies analyzed to CAP’s other pipelines.