Tucson Water's Homegrown Condition Assessment of PCCP

On February 5, 1999, a 96-in. diameter pipeline failed catastrophically, funneling 38 million gallons of water through a half-mile square residential area in just 90 minutes, causing extensive property damage and resulting in 12 homes being condemned. The City vowed to the community that it would begin performing annual inspections of this and similar pipelines. Within months of the catastrophic failure, Tucson began networking with other agencies that operated and maintained similar pipeline infrastructure. By February 2000, Tucson implemented its own condition assessment program, named the Pipeline Protection Program (PPP), and it evolved to become one of the more advanced predictive and preventive maintenance programs for prestressed concrete cylinder pope (PCCP). Beginning with routine internal visual pipeline inspections, internal electromagnetic surveys, and hydrophone arrays and quickly advancing to acoustic fiber optics (AFO), Tucson has managed to avoid any catastrophic failures, yet had a very close call when it identified a recent incipient failure of a 96-in. pipeline. Alerted by Tucson's AFO system, the 96-in. pipeline had all the potential to surpass the damage and destruction experienced in the $5 million 1999 failure. This technical paper shares some of the biggest challenges faced when building and implementing a condition assessment program for large-diameter pipelines and highlights successes, including how Tucson's most recent investment in AFO paid off big for Tucson.