Defect-Level Condition Assessment of Sewer Pipes

Closed-circuit television (CCTV) inspections are essential in keeping sewer pipe performance at a desirable level. A sewer pipe condition score is usually assigned to each pipe based on the type, quantity, and extent of defects observed through CCTV inspections. Although the impact of different factors on the condition score has been considered in several studies, the effect of these factors on the underlying defects has yet to be investigated. The aim of this study was to investigate the effect of various potential influencing factors on the prevalence of eight defect categories (gas attack, material damage, infiltration, roots, debris, total joint, structural, and dipped pipe) in the transmission sewer network of Auckland, New Zealand. A cleaned data set with the defects identified through recent CCTV inspections of 2,780 sewers was gathered and linked to various physical and environmental factors. Results identified insightful and statistically significant relationships between defect categories and factors that provide new insights into the drivers of deterioration processes in sewer pipes.