Remaining Useful Life Assessment of Buried Iron Water Mains: Case Studies Using Integrated Diagnostic Methods (C2026-00066)

Anil Chikkam, mehrooz zamanzadeh, Aaron Ulmer, Tara Wockenfuss, Edward Larkin

This paper presents two case studies focused on the assessment of remaining useful life (RUL) for aging buried water mains using a multi-disciplinary diagnostic approach. The first case involves a 6-inch cast iron main, over 70 years in service, located in non-corrosive soil (>3,000 Ω-cm; 0 points per AWWA C105). Despite the presence of corrosion-related bacteria and localized internal corrosion at the 6 o’clock position, the pipe remains structurally sound. Magnetic flux mapping, ultrasonic wall thickness, and microstructural analysis yielded an estimated RUL of approximately 85.6 years.
The second case examines a 24-inch ductile iron main buried in aggressive gypsum-based soil ( <1,500 Ω-cm; 10/10 AWWA points). Severe external corrosion was found at the 3 and 9 o’clock positions, with up to 46% wall loss. SEM/EDS analysis confirmed sulfur enrichment and calcareous deposits, suggesting corrosion initiated prior to cathodic protection (CP) installation and was later mitigated. Based on wall loss and service history, the estimated RUL ranged from 24.3 to 25.2 years.
These case studies demonstrate the importance of integrating soil corrosivity, non-destructive testing, and metallurgical analysis for accurate RUL estimation and proactive infrastructure planning in diverse environments.