THE PLANNING AND EXECUTION OF INTERNAL INSPECTIONS OF LARGE DIAMETER PCCP WATERLINES-A CASE STUDY

摘要

The City of Phoenix is undertaking a comprehensive eight year program to inspect its entire 150-mile system of pre-stressed concrete cylinder pipe (PCCP) water transmission mains. This system serves over 1.4 million people over an area of more than 500 square miles. This paper illustrates in detail the numerous steps involved in planning and performing an internal inspection of a PCCP transmission main. A 40-year old, 4-mile long, 66-inch diameter pipeline is used as a case study. The specific steps and their related challenges include: Identification and development of individual inspection scenarios; risk assessment and the development of an inspection prioritization plan; the use of computerized hydraulic modeling to predict, mitigate, and address possible impacts of having portions of the system out of service; planning and coordination with planned shutdowns of pipelines and water production facilities related to concurrent capital improvement projects; development of detailed shutdown and startup plans providing step by step procedures for the isolation, dewatering, inspection, filling, and disinfection of the pipeline; intensive coordination efforts with City Engineering, Construction Management and Operations personnel; implementation of a valve management and exercise program well in advance of the shutdown of the pipeline; alternative methods for dewatering of the pipeline; the use of Job Order Contracting (JOC); identification and mitigation of field challenges; public involvement strategies; planning and execution of the actual electromagnetic and visual/sounding inspections; and lessons learned. The pipeline was placed back into service on the scheduled date and with no complaints from the public.