What to Do After a Failure of PCCP: Forensic Evaluation of Pipe Failure in Green Bay

The Green Bay Water Utility (GBWU) proactively conducted an electromagnetic inspection in 2010 of three 36 in. diameter Water Transmission mains (about 25 miles total length) that deliver water between the Water Treatment plant and the distribution system. In December 2012 a pipe failure occurred on the 1974 pipeline. The repair identified the pipe that failed as one that was identified in the inspection as having broken wires but was not determined to be at a high risk of failure. The GBWU recognized the need to identify the cause of failure by conducting a forensic evaluation. GBWU also understood the criticality of these pipelines and the need to develop a plan for managing the maintenance of these pipelines based on a risk analysis. Our investigation included inspection of the failed pipe, petrographic analysis and testing of mortar coating, testing of prestressing wires and steel cylinder, soil corrosivity testing, and structural and failure risk analysis for pipes with broken wires. To assess the risk of failure of other pipes in the line, we performed external inspection and testing of a sample of pipes and evaluation of alignment soil and ground water corrosivity.

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