Tampa Bay Water Assessment Pccp Pipeline Leaks Em

To proactively address its large-diameter Prestressed Concrete Cylinder Pipe (PCCP) for deterioration, Tampa Bay Water (TBW) completed a leak and gas pocket survey and electromagnetic (EM) condition assessment of the South-Central Hillsborough Regional Wellfield Transmission Main in April 2013. The results of the assessment were verified in 2014 to determine the remaining useful life of the pipeline, which is responsible for delivering 10 percent of TBW’s 24 million gallons of raw water per day.

Based on the EM inspection, only 0.5 percent (11 of 2,177) of pipe sections contained varying levels of distress; subsequent structural and finite element analysis determined that only a fraction of the distressed pipes warranted further consideration. In addition to the structural assessment, the leak and gas pocket survey identified only one small leak.

The results show the critical transmission main is in excellent condition and can be safely managed despite being nearly 30-years-old. Some PCCP users throughout the United States have experienced major failures as their assets approach 40 years of operation.

TBW maintains a large pipeline network that serves the Tampa Bay and St. Petersburg metropolitan area and includes approximately 80 miles of PCCP. The pipeline inspections were completed on 8 miles of 42-, 48- and 54-inch PCCP that convey wellfield supply to the Lithia Water Treatment Facility.

For the leak and gas pocket survey, SmartBall® technology was used as a forerunner for the EM condition assessment and provided TBW with an initial condition of the pipeline.

Early identification and repair of leaks can reduce Non-Revenue Water (NRW), but also helps determine the baseline condition of a pipeline, since leaks can be an indication that a pipeline might fail. In addition, locating and eliminating gas pockets reduces pressure on the pumps that are attempting to push water past a pocket. As pockets grow in size, they can significantly affect the flow of water and capacity of the pipeline if not released.

After the prescreening survey, TBW completed an EM inspection using PipeDiver®, a free-flowing EM tool that is able to accurately locate and quantify broken wire wraps in PCCP. The wire wraps in PCCP act as the main structural component; broken wraps are the main indication that this type of pipe will eventually fail.

TBW’s asset management program allowed them to prioritize and take the first steps in determining the remaining useful life of a critical asset. This will lead to more informed decision-making for the future management of this main through reinspection, monitoring or renewal.


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