City of Phoenix Superior Pipeline PCCP Investigation and Assessment

The City of Phoenix is currently in a multi-year program to investigate 150 miles of prestressed concrete cylinder pipelines (PCCP). The failure of a 60-inch pipeline focused the efforts of the investigation to a pipeline known as the "Superior" pipeline. The Superior pipeline is a 2.2-mile long, 29-year old pipeline that ruptured on October 3, 2006, resulting in extensive damage to the surrounding community. The pipeline was immediately shutdown and the failed section of pipeline was repaired. However, the condition of the remaining pipe and the potential for additional failures was a concern. To identify wire breaks, Pressure Pipe Inspection Company (PPIC) conducted Remote Field Transformer Coupling investigations. In addition, visual and sounding investigations were conducted by Openaka of Branchburg, New Jersey to identify internal defects. These investigations identified pipe segments that were in need of immediate repair prior to putting the pipeline back in service. This information provided baseline wire break information for the subsequent investigations. Prior to putting the pipeline back into service, 11,700 linear feet of fiber optic was installed by Pure Technologies allowing the City to acoustically monitor wire breaks in real time. This information was critical as the pipeline needed to be back in service to meet the high demand for water during the hot Phoenix summer. Real time wire break monitoring allowed the City and Brown and Caldwell to slowly resume the operation of the pipeline to prevent another failure. Monitoring of the pipeline was conducted from February 2007 through January 2008 and the pipeline was found to be extremely active with an initial average of three wire breaks occurring each day. This paper focuses on the investigations conducted and conclusive results relative to: 1) Benefits of multiple technologies for PCCP investigations, 2) Calibrated vs. non-calibrated curves for electromagnetic analysis, 3) Real time data collection through fiber optics to monitor pipeline conditions, 4) Verification of fiber optic results using electromagnetic analysis, 5) Pressure and surge monitoring.