Tarrant Regional Water District's Risk Management Plan for Prestressed Concrete Cylinder Pipe

The Tarrant Regional Water District (TRWD) operates two, 120 km long, large diameter prestressed concrete cylinder pipelines in north central Texas to daily supply water to over 1.5 million people. Both pipelines have suffered from failures due to corrosion, hydrogen embrittlement or inadequate thrust restraint, with about 800 pipe segments damaged. A model was developed to determine remaining strength of the damaged pipe. About 100 pipe segments, most of which have been replaced, were found to be damaged enough that they could fail and about 250 more were found to be damaged enough that further deterioration would put them at risk of failure. To prioritize their replacement, the District will use a fuzzy risk model. TRWD is attempting to balance the high cost of mitigating all damaged pipes with the potential cost of consequential damages due to a failure by modeling the risk. This paper will discuss the path TRWD is taking to further its model development of risk management of the pipeline.