ment meetings were also conducted regularly. Coordination meetings identified critical tasks to be completed prior to the inspection. Access locations were confirmed for fitness, rental equipment was secured, and it was established that the utility would also perform a visual inspection of the interior of the pipeline. Fieldwork commenced in January 2017, with crews inserting the inspection tool into the pipeline at a blow-off vault. Over 11 days, 16 sections of pipe, totaling 9,100 m, were inspected. One critical deliverable from PICA was providing inspection data within 48 hours of each inspection, identifying any "imminent failures". By locating high-risk areas, the utility would be able to perform rehabilitation work while the pipeline was already dewatered and out of service. Overall, the aqueduct was found to be in very good condition. However, PICA identified several sections that would benefit from immediate rehabilitation. Personnel entered the pipeline and mobilized to several of these locations to verify the inspection data. Cement mortar was chipped away and ultrasonic probes were used to document the changes in steel cylinder wall thickness. When analyzing the data, utility staff established baseline criteria for actionable levels of pipe wall loss and the associated confidence level. All pipe anomalies showing 50% wall loss or greater and a moderate or higher confidence level were physically inspected for verification by entering the pipe, chipping away the interior mortar lining and using a handheld ultrasonic thickness gauge for data validation. Once it was confirmed that PICA’s data was accurate, they relied on this to prepare drawings and specifications for the cost-effective rehabilitation of the aqueduct. With the inspection data verified, the utility extended the shutdown of the pipeline to address these areas. In total, 21 m of the 90 mm bar-wrapped pipe were replaced, and seven internal repairs with steel patches to address local corrosion pits had to be done. At the same time, two new access manholes were installed,
along with a manway upgrade. The inspection and repair work cost the utility $1.56 million, which is approximately 5% of the total cost if they had to replace the entire aqueduct. Chris Garrett is with PICA Corporation. For more information, visit: www.picacorp.com
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