Execution of Data-Driven Surgical Rehabilitation on a 36-Inch Concrete-Lined Steel Pipe

Helix is a unique water district with history dating back to 1885 serving a nearly 50 square mile service area that includes the cities of La Mesa, Lemon Grove, and El Cajon, the communities of Spring Valley and Lakeside, and other areas of unincorporated San Diego County. The district operates a 5.8-mile-long 36-inch pipeline that is part of an aqueduct transporting raw water from the regional water wholesaler, San Diego County Water Authority’s raw water system, to downstream treatment facilities. The 36-inch concrete-lined cylinder pipe line was inspected in early 2017, and the inspection flagged a number of localized areas with distress. Since most of the distress appeared to be externally induced, there were no internal visual indicators available to help facilitate subsequent repairs. As such, the repair efforts required a multi-stage approach where initial verifications efforts drove future verification and repair decisions. Initially, pipe tally listings and heat-color map representations of the pipes were used to locate areas of distress. While this allowed verification and rehab efforts for distressed areas nearby manholes, areas further away required a different approach. This paper discusses the challenges involved with location and verification of the distressed areas, the unique techniques implemented to resolve the challenges, and the drivers for selecting the optimal rehabilitation type. Factors that were considered were accessibility of the above ground terrain, nearness of infrastructure such as overhead busy roads, and the severity of the identified distress. The paper concludes with a cost comparison and overview of lessons learned which the authors believe will benefit other aqueduct operators.