A Review of the Challenges to Large-Diameter Water Pipeline Maintenance Inspections

Regular inspections of water pipelines are crucial for ensuring effective pipeline operations and planning necessary maintenance. Failing to adequately inspect a pipeline may have catastrophic results, such as a rupture of a major transmission pipeline or perhaps merely a leak in a relatively low-pressure distribution pipe. Regardless, many pipeline failures could have been avoided with regular maintenance inspections. However, most pipelines are buried and not given much thought when it comes to the maintenance of water system infrastructure. When they are considered, many owners who have not regularly performed maintenance inspections lack an understanding of the complexity that goes into the planning and execution of inspecting large-diameter water pipelines. The Central Arizona Project (CAP) is one of the largest aqueduct systems in the United States and has some of the world's largest diameter water pipelines in its inventory. Some of the challenges CAP has experienced while planning and executing large-diameter water pipeline inspections include how to isolate the pipeline from the rest of the system, steps to dewater the pipeline, lock-out/tag-out requirements, personnel access locations, ventilation, handling of debris in the pipeline, rescue/response procedures, communications with the inspection team, lack of as-built drawings, operational impacts, customer impacts, assessment tool selection, contractor support, public outreach, and stakeholder consideration. This paper addresses several challenges faced by utility owners and operators in conducting maintenance inspections of large-diameter water pipelines.