Expanding NASSCO's PACP 5 Rating to Triage Concrete Sewer Interceptor Pipe for Rehabilitation

Out of sight, out of mind has been the normal approach in thinking (or not thinking) about buried underground sewer infrastructure until there is a collapse in the street, the public is impacted, and the unseen now is revealed. Beginning in the early 1990s, the City of Albuquerque (now the Albuquerque Bernalillo County Water Utility Authority, or Water Authority), experienced this very phenomenon, the sudden and seemingly random collapse of large diameter sewer pipelines in various areas of their collection system. A careful evaluation of these collapses pointed to the aging unlined concrete pipe whose useful life had been reached, or exceeded. The prediction by staff was that these collapses were just the beginning of more to come unless steps were taken to rehabilitate or replace high-risk pipe segments. This paper describes the efforts undertaken by the Water Authority to identify and properly rank high-risk sewer pipe before they collapse.