Concrete Bar-Wrapped Cylinder Pipe (C303) Condition Assessment and Verification Increases Reliability of TRA's Water Delivery

The Trinity River Authority of Texas (TRA) recently completed a comprehensive condition assessment of 8.8 miles of 30-in. bar-wrapped pipe (BWP). The assessment utilized an inline free-swimming acoustic tool, an inline free-swimming enhanced electromagnetic tool, transient pressure monitoring, and nonlinear finite element analysis (FEA) of the steel cylinder corrosion and broken bar wraps. This project is one of the first and perhaps most comprehensive assessments of a BWP transmission main in the industry. The pipeline is a critical link in the reliable delivery of drinking water to five cities in the Dallas-Fort Worth Metroplex, and it had been slated for replacement due to its age, previous failures, inability to be shut down for repairs, and the need for additional capacity. However, as the future projected water demands decreased, the additional capacity that was driving the immediate replacement of the pipeline was not necessary. TRA decided to evaluate the possibility of keeping the pipeline in service by performing a comprehensive hydraulic, leak, and condition assessment. The inspection and FEA analysis found that the majority of the pipes (93%) are in good structural condition and 6% of the pipes in fair condition, leaving only 14 pipes (1%) that need to be addressed in the near term. To confirm the efficacy of the condition assessment strategies, TRA excavated three test pits and performed external evaluation of the pipe at locations where damage was reported. This paper will present the inspection results including the leaks, gas pockets, broken bars, and cylinder corrosion detected during the field inspection work. Based on these results, TRA successfully deferred a $25 million capital replacement project by managing the pipeline as individual, 36-ft pipe assets.