PCCP Sanitary Sewer Force Main Evaluation and Management - A Case Study

In March 2003, the Middlesex County Utilities Authority (MCUA) experienced a rupture of their 2.59-meter (102-inch) diameter prestressed concrete cylinder pipe (PCCP) Sayreville Relief Force Main. A previous failure of the pipeline in 1983 was due to hydraulic surges exceeding the design strength of the pipe caused by power loss to the pumping station. The 2003 burst was the first PCCP failure in the MCUA system attributable to environmental degradation of the pipeline. Subsequent to the pipeline burst, MCUA has pursued a proactive condition assessment and pipeline management program to mitigate the potential for future pipeline failures. The 2.59-meter (102-inch) diameter PCCP Sayreville Relief Force Main is approximately 5,700 meters (18,700 feet) in length and was constructed of pipe manufactured by the Interpace Corporation around 1977. The pipes were constructed utilizing high strength “Class IV” prestress wire that has a history of susceptibility to hydrogen embrittlement failure. Comprehensive failure investigation, condition assessment and monitoring programs are being implemented for the Sayreville Relief Force Main. Failure investigation of the March 2003 event concluded that the most probable root cause of the pipeline failure was environmental deterioration of the pipe caused by reactions with acidic soils in combination with failure of the hydrogen embrittlement sensitive wire. Environmental testing is being conducted to determine if the soils are aggressive to PCCP along the entire pipeline alignment. Internal inspections of the entire pipeline have been conducted utilizing visual and sounding methods in combination with P-Wave™ non-destructive electromagnetic testing to detect and quantify existing wire breaks. A SoundPrint® acoustic emission monitoring system has been installed to allow continuous monitoring of wire break events in the pipeline. Structural analysis of the PCCP under actual field loading conditions is being performed using the electromagnetic testing results as baseline wire break data. The structural analyses will be routinely updated with the acoustic emission wire break event data. Results of the structural analysis will be used to set criteria for rehabilitation or replacement of individual distressed pipe sections.