Down to the Wire: The Evolution of a Utilities' Large Diameter Force Main Asset Management

Middlesex County Utilities Authority (the Authority) was established in 1950 to provide regional wastewater management for 36 municipalities in three counties of central New Jersey. A critical system asset includes the 102-inch diameter prestressed concrete cylinder pipe (PCCP) Sayreville Relief Force Main (SRFM), which runs approximately 3.5 miles from the Sayreville Relief Pump Station to the Edward J. Patten Water Reclamation Center. The SRFM was commissioned in 1982 and experienced a catastrophic failure shortly after in 1983 as a result of a pipeline surge following a power outage. Twenty years later in March 2003, the SRFM experienced a second catastrophic failure for similar reasons. At the time of the second failure, the Authority engaged with a local engineering firm to design a surge relief system for the SRFM, and with Pure Technologies, a Xylem brand, to provide a forensics investigation on the failed pipe, as well as perform inspections and structural analysis to determine condition of the pipeline. The investigation identified manufacturing defects in the PCCP, corrosive soils, and a high deterioration rate on the SRFM. This led the Authority to develop a first of its kind, innovative asset management program to effectively manage this critical, high risk PCCP asset. The presentation will discuss the evolution of the inspection methods deployed, structural analysis, live monitoring, proactive repairs, and long-term management solutions made on the SRFM under this asset management program over the past 18 years. The full length of the SRFM is inspected on a routine basis using Visual and Sounding techniques, as well as by an Electromagnetic technology scan. The Visual and Sounding inspection identifies pipes in a state of incipient failure, documents defects in the pipe's concrete core, and evaluates the condition of pipe joints. The Electromagnetic inspection identifies broken prestressing wire wraps in the PCCP. Each induvial pipe is documented with its respective Visual, Sounding, and Electromagnetics findings using updated record laying sheets established during the inspections.
Additionally, Pure Technologies performs structural analysis per the American Water Works Association (AWWA) standards on the SRFM pipe classes and finite element analysis modeling, which determines the structural consequence of the broken prestressing wire wraps. The structural analyses are used to determine intervention limits to initiate pipe repairs. Since the 2003 failure, the Authority has used the asset management program to implement proactive, fully structural repairs on 39 of the 1,003 pipes in the SRFM. Another critical component to the asset management program includes live monitoring of each individual pipe in the SRFM for broken prestressing wire wraps. With the high deterioration rate on the SRFM, the system allows for continuous monitoring of the broken wire wrap activity in between the scheduled internal inspections. The monitoring began with a surface-mounted system (SMS), which included email alerts and a website that provided the break summaries in a Pipe List format. The SMS system was replaced in 2008 with an acoustic fiberoptic (AFO) cable installed inside the SRFM. The AFO system provides a more accurate and reliable real-time monitoring and alerts of the wire breaks as they occur, and the website was updated to a GIS based platform called the HUB. The HUB is a customized website that displays an interactive GIS based map showing each individual pipes in the SRFM with its respective as built records, inspection data, broken wire wrap summaries, an interactive finite element analysis model, and many more features to be discussed. The AFO system and HUB is a powerful asset management tool for the Authority and Pure Technologies, allowing live monitoring of the SRFM, tracking historical data and repairs, and identifying broken wire wrap activity of interest that may escalate a pipe for repair.
As the only known wastewater AFO system installed in the world, the Authority has been at the forefront of current PCCP management strategies. In combination with a robust inspection program consisting of Visual and Sounding, and Electromagnetic inspections, structural evaluations, and Remaining Useful Life Analyses (RUL), the Authority has been able to anticipate pipe lengths requiring intervention in order to prevent another catastrophic failure. Furthermore, the proactive approach has allowed the Authority to manage their capital spending program by repairing the pipes based on their structural limits and condition, so the known damaged pipes are repaired before they become a problem, and the Authority is able to bid out the repair work and plan it in conjunction with their utility's operation. Based on current deterioration rates, on average, the Authority repairs two to three pipe sticks per year. The SRFM program serves as an example for other water and wastewater utilities who can learn and benefit from the lessons learned through their experience and innovation.