Redeveloping Phoenix's PCCP Assessment Program: A Pragmatic Approach

The City of Phoenix (City) owns and operates over 150 miles of Prestressed Concrete Cylinder Pipe (PCCP) water transmission mains. Between 2001 and 2008 the City conducted the first large diameter assessments on their most critical pipeline in the 15-mile Val Vista Transmission Main, as well as on 15 miles of opportunistic pipelines which were taken out of service concurrently with water treatment plant shutdowns, valve maintenance, or a catastrophic failure. Because these pipelines were shutdown and dewatered, both manned and unmanned electromagnetic, visual/sounding, acoustic monitoring, and destructive testing were completed to collect assessment data. While at the time many of the technologies employed were emerging in the PCCP assessment industry, they were economically practical and within the City's pipeline assessment budget. After a three-year break from condition assessment on their large diameter water pipelines, the City has decided to reinitiate their program. In 2011 the City started a three-year program to perform condition assessment on their large valves and 32 miles of their highest risk pipelines according to pipe vintage, service areas, and easement locations. The intent of this program is to collect baseline data on these pipes, determine the cause of deterioration, and prepare City staff for conducting this type of assessment work in the future. The 32 miles requiring condition assessment are comprised of 10 individual pipelines delivering water from five water treatment plants across nearly 500 square miles. Each pipeline requires an individualized shutdown and dewatering plan, limited to low-demand months and tailored around the City's schedule for water treatment plant shutdowns and other capital improvement projects. Further, the City seeks to maximize the use of local and City staff, while performing condition assessments which yield an optimal balance between cost and actionable information. To achieve this goal, the City is seeking to integrate into its assessment program purchased equipment and low to no-mobilization services, including pressure surge monitors, corrosion surveys, continuity testing, visual and sounding inspections, and acoustic methods. This paper will thoroughly detail the pragmatic execution plan that the City will utilize for this three-year program and beyond. Purchased and low to no-mobilization cost methods that City staff can self-perform for collecting PCCP condition assessment information are emphasized throughout this paper.