ABSTRACT
While visual inspection technology is one of the predominant tools used in condition assessment, it has two major shortcomings: first, despite the inclusion of National Association for Sewer Service Companies (NASSCO’s) rating system, it is a qualitative system. Second, visual inspection technology is limited to observations above the flow. Most flows in buried pipelines have significant amounts of turbidity and are generally opaque. While most flow is not transparent to the naked eye, flows meeting these criteria are generally more slurry than fluid and have a consistent amount of particulate matter floating in suspension. While sonar is the only effective tool for “seeing” below the flow, there are a variety of techniques for obtaining quantitative information about the condition of a pipe in the headspace. Sonar videos are synchronized with a Closed-circuit television (CCTV) inspection, and the sonar video is overlaid on the flow, allowing a viewer to simultaneously see above and below the flow while watching an inspection video.
