Inspection Technologies to Keep the Pipeline in Service

The City of Glendale (City) operates the Arrowhead Effluent Reclaimed Distribution System (AERDS) Pipeline to convey reclaimed water from the City's Arrowhead Ranch Water Reclamation Facility (ARWRF) to various irrigation facilities and lakes within the Arrowhead Ranch development. The pipeline was constructed in 1987 and consists of 24,225 feet of bar-wrapped, thin steel cylinder covered internally and externally with cement mortar and includes 8,330 ft of 36-in., 3,110 ft of 30-in., 2,770 ft of 24-in., and 10,015 ft of 16-in. diameter pipe. The City experienced three localized failures on the pipeline in 1998 and 1999 after construction of the SR 101 near the pipeline alignment but has not experienced subsequent failures. To determine the pipeline condition after 25 years of service, the City initiated a pipeline assessment in 2013. Because the AERDS pipeline is critical to operation of the ARWRF (an end-of-the-line facility) and cannot be out of service, an innoviative step-wise approach was implemented utilizing appropriate technologies and modifications to operations to maintain flow. Information from each step was used to identify the next step inspections. This cost-effective approach has saved the City more than $400,000 and allowed the work to be completed without operations interruption. This paper will describe the challenges faced to keep the pipeline in service during the inspection by using indirect corrosion potential testing and a combined leak detection and video platform. To provide coverage for a critical portion of the pipeline under the highway the pipe was hot tapped for insertion of the inspection tool. The results of the interior assessments combined with indirect soil testing and sampling identified the areas for excavation and exterior testing. The nondestructive evaluation inspection of the pipe exterior with the impact echo and slab impulse technologies provided information on the condition of the pipe. This step-wise approach shows how the condition assessment can be completed with the pipe in service.